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contact: craig er oochi a t outlook dotty com
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updated: March 16th, 2018
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My "Background Radiation" Graphs
March-April 2011 (10 uR/hr ~ 35cpm with my Medcom Geiger counter, 16cpm with my M4011 and SBM-20 G-M tube devices)
* These early graphs are based on averaged uR/hr readings, using a Radex 1503 Geiger counter with an SBM-20 tube. I would repeatedly wait out the 1503's internal 2.7 minute averaging cycle, note the reading, then average those averages. The 1503 will not display CPMs.
22nd: That peak is probably no more significant
than the next. I was only taking 2.7 minute counts (+/- 7.2cpm or +/- 2uR),
but went to 10.7 minute averages on the 24th (+/-3.6cpm). (I was using
twice the "standard error", based on the square root of the assumed total
26th: * Those large dots are 100 minute averaged readings made with my "Inspector" Geiger counter (sealed inside a thin "ZipLoc" plastic bag). Note that the last dot is double, the lower blue dot being the count with beta radiation blocked. The smaller black dots are 26.66 minute Radex RD-1503 (SBM-20) averages, taken over a period of about 30 minutes, expressed in "Inspector" (LND-7317) nominally "equivalent" (for gamma) CPMs, for which totals, the standard error is +/-2.6cpm.
* It appears that the large black dot, 5-day whoop-de-do on this graph is all about beta radiation --the stuff I wait for to go away before testing my air filters for residuals. There was no rain until until the 25th, so the invasive beta (radon daughters, presumably) might have been driven out of all the sand around here by our sunny warm days of late. (The 26th was especially warm, but also windy and dry.)
* On the 25th I ran inside and outside tests which included using my old Radex-RD1503 Geiger counter. Like in the past, I saw no increase when I took it outside (actually getting a slightly lower reading), whereas the Inspector, with its mica window, reads about 11% higher in the same location. This is most likely because the RD1503 is less sensitive to beta radiation.
* It started raining again while I was running the outside RD-1503 count, but there was no effect upon the last 5 readings^. Nor did the rain and steady drizzle of the 25th seem to affect the "Inspector's" readings.
^ The RD-1503 has neither a long count timer nor a data port, so I have to take a reading every 3 minutes in order to build up a longer average --than I can get from its native 160 second cycle. However, it still seems stable and in calibration, so I'll use it for my outside counts. (The exercise will do me good :-)) My purpose in this is to possibly get an earlier warning, should fall-out or volatilized gamma emitters from the beach begin accumulating. (We're fairly close to the bay and Pacific ocean.)
* Note that the last big dot is double. The lower blue one is the Inspector's average with beta blocked. Laying the beta blocked "Inspector" Geiger counter on the ground gave nearly the same reading: 36.33cpm. Removing the beta shield ran it up to 44.37cpm (off the chart, but that's mild, compared to some of the beta CPMs we read about elsewhere after "rain-outs" (or "rain-ups" --not sure).
* Having reverted to placing my old Radex-RD1503 Geiger counter out in the yard (34 inches above ground) for a 26.66 minute averaged count, I'm multiplying the indicated "uR/hr" by 3.5 for a rough "Inspector" Geiger counter equivalent.
* I deal with our radon CPMs to some extent when I do air filter readings, recording the initial value and their signature rate of decay.
28th: * No Radex outside check (small dot) today.
29th: * I ran the outside Radex Geiger counter (SBM-20
tube) check twice, once open, again with 1/8" aluminum shielding: no difference
that was anticipated, since past outside versus inside Radex checks showed
very little difference. After a series of bench tests with potassium chloride
and varying aluminum shielding, it appears that the Radex behaves as if
it has about .009" of aluminum shielding (over an imaginary mica window).
impression I get is of very weak (under 100KeV) beta at 34 inches off the
ground --which changes my gnotion of what "half value layer" (HVL) means
with respect to beta. I thought that the intensity of beta electrons was
only "depopulated" to 50% by an HVL (at whatever associated KeV), but that
the energies of the remnant beta stayed the same. (Obviously, gamma behaves
on the depopulation model, since passing light through a 0.3d (50%) neutral
density filter does not change its color, and since useful gamma
spectrometry can be performed on the radiation escaping (say) the large
cadaver of an ocean creature, or the living body of a "nuclear medicine"/imaging
Was able to install a Russian SBM-20 G-M
tube in my failed Medcom "Inspector" Geiger counter. I've got about 43%
of the Inspector's original gamma sensitivity, plus I've lost the ability
to detect alpha and soft beta radiation --but I can once again do automatically
timed counts plus participate on-line with
*9th: We selected two remote locations for 30 minute monitoring counts: 4.7 miles in from the mouth of Coos Bay (EBR = Empire Boat Ramp) and two miles south of the mouth (SB = Sunset Bay). We'll check these high tide spots throughout the year. (See 2015 entry, just below.)
*27th: Resumed doing periodic air filter monitoring, but drawing about 4.4 cubic meters of air over 15 minutes --instead of the old 10 cubic meter standard. The buildups in the filters were weak, with 50% more CPMs (at about 2x background) in the draw taken 2 inches off the ground, than in the filter drawn at 12 feet above ground level. Of necessity, only a 10 minute initial reading, then another 40 minutes later, were taken. Consequently, the possible errors were large, but the decays were: to 69% (2 inch high draw) and to 43% (12 foot high draw) over 40 minutes.
*28th: Tested the two air filters of the 27th, finding their gamma and hard beta radiation to be indistinguishable from the background level.
*5/25/2015: Have mostly discontinued the remote 30 minute counts in favor of 2.7 minute averaged roving beach wanders (with our dog Sammy). A shirt pocket Geiger counter (Radex RD1503) is set to audible, so the ear sensitivity to anomalies adds considerably to the nominal +/-16% sigma/standard deviation of the display (which is checked periodically). Have added Bdrf = Bastendorff (just north of Sunset Bay).
6/9b: * I don't know what these peaks are about, but that 24 hour average is a whopping 17.7 standard deviations ("sigma") over the 15.77cpm norm here (at least: the way I figure it). As shown below, the day's 60 minute averages, 10 minute averages and one minute counts are no slouches either. (*Click* on them to enlarge the images.)
Hour-long averages on June 9th, 2015
(I'm guessing this is a rounded running average.)
Hour-long averages on June 10th, 2015
(This appears to be an hour-by-hour straight average, based on a different output of GeigerGraph data.)
Hour-long Averages, June 1st through 9th, 2015
6/10c: The high count experience here seems to have been isolated to my station. Judging by the period of hours that it appeared to last, I speculated that I was picking up radiation from a neighbor who'd been given a radioactive tracer injection (ie: "nuclear medicine"), although I have no confirmation of that.
6/11: * Okay --I'm stumped. Assuming this is about a neighbor who's been given a medical dose of a radioactive tracer substance, a second day of high CPMs suggests that it can't have been 6 hour half lived technetium-99m (which is rapidly eliminated from the body). Possibly, the tracer was iodine-131, but for all I know, my elevated CPMs were caused by something else altogether.
* I compared my regular Geiger counter to one which use to match its counts fairly well (long term averages), and found it about 5% higher now. Since my graphs have otherwise been looking consistent, I'm saying that the 2nd Geiger counter was 5% low --for some reason.
* I did a 4 loop "beach wander" today, since there's so much in the (Ene) news about ocean contamination, but my readings were normal --and I was listening to the beeps as I walked. (I saw the same bands of --what I take to be-- small, dead, paper thin jelly fish --as before.)
6/16: How to log and graph such a rough and casual reading is a problem. Tentatively, I'll average the displayed range of readings and "round up" to the nearest 10% --as looked at and informed by the audible beeps.
* As of 10/10/2015 I standardized on Co-ordinated Universal Time, or "UTC" --which is similar to GMT", but sans any DST changes. I should have been doing since March of 2011. (We need to don pirate costumes and form a rabid, single issue political faction which is hell bent on abolishing our absurd Daylight Saving Time clock changes --!-- Arrrrrr!)
* As of 10/31/2015, logging here has been within our normal
range, with isolated peaks (ie: no preceding build-ups nor follow-on
decays) as follows:
~33cpm peak at 17:30 hours on 10/2
~34cpm peak at 20:49 hours on 10/9
~34cpm peak at 09:33 hours on 10/10 (Switched to UTC time-dates)
~33cpm peak at 06:13 hours on 10/25 (10 minute avgs reached 20cpm 4 times --otherwise isolated.)
~33cpm peak at 00:19 hours on 10/26
November - 2015: * As of 11/30/2015, and except for a double-peaked 10 minute running average excursion on the 30th (to 22cpm, but 1 minute peaks did not reach 33cpm), logging here has been within our normal range, with isolated peaks (ie: no preceding build-ups nor follow-on decays) as follows:
~The log for the day of 11/2 was somehow lost.
~The 10 minute running average reached my reporting threshold of 20cpm at 08:30 hours on 11/4.
~The day's 24 hour average was 15.64cpm on 11/10 (The 7-day average ending 1/31/2014 was 15.77)
~The 10 minute running average reached 20cpm at about 01:39 hours on 11/15.
~The 10 minute running average reached 20cpm at about 16:15 hours on 11/17.
~33cpm peak at 10:30 hours on 11/18
~On 11/20 I started saving images of the daily graph (to the default directory for GG-5b).
~The 10 minute running average reached 22cpm at about 17:00 hours on 11/20.
~35cpm peak at 10:46 on 11/22.
~The 10 minute running average reached 20cpm at about 05:30 hours on 11/24.
~The 10 minute running average reached 23cpm at about 20:00 hours on 11/24.
~The 10 minute running average reached 20cpm at about 09:30 hours on 11/25.
~33cpm peak at 12:51 hours on 11/25.
~34cpm peak at 23:50 hours on 11/26.
~The 10 minute running average touched 20cpm 3 times on 11/29.
~The 10 minute running average touched 20cpm 3 times on 11/30 --once to 22cpm, but no 33cpm 1-min peaks.
* I'll continue to base percentages on year 2014 being 100% (15.77cpm).
* Why do the 1 and 10 minute averaged levels of 33-34cpm and 20cpm repeat so often? This has to be some sort of an event with an irregular but frequent recurrence. I checked the USGS "Real-time earthquake map" (via the R-G Oregon Live Link) and tallied 9 small earthquakes spanning the past 30 days --within a radius of about 130 miles (land and ocean). None of them came even close to the UTC timed peaks on this page.
* Perhaps I can get some regional magnetometry to match up.
* We've recently had a few frog drowning rainfalls, but with no marked
effect upon the gamma counts that I can see. Perhaps if I compared rainfall
rates to the rolling 10 minute averages, I could
see some match-ups.
* As of 4/1/2016, logging here has often been below our normal
range, with isolated peaks (ie: no preceding build-ups nor follow-on
decays) as follows:
~ 5th: The 10 minute running average reached 20cpm at about 22:10 hours.
~ 5th: 33cpm peak at 21:58 hours. (A brief decay, but no build up. Saved the graph.)
~ 7th: Found the logging program stopped. Rebooted the OS.
~12th: The 10 minute running average reached 20cpm at about 12:15 hours.
~19th: 36cpm peak at 04:23 hours. (No build up, brief 10m avg plateau at 18cpm.)
~20th: The 10 minute running average reached 20cpm at about 06:00 hours.
~21st: The 10 minute running average reached 20cpm at about 12:00 hours. (isolated)
~21st: The 10 minute running average reached 20cpm at about 18:30 hours. (isolated)
~22nd: 33cpm peak at 03:04 hours. (The average over the past 3 days: 15.51 = 98.35%)
~23rd: This day's average fell to 14.98cpm = 95% --the 3rd such low this year.
~24th: Only got the last 12 hours of this period (forgot to restart the logging program in the morning).
~29th: The 10 minute running average reached 20cpm at about 15:45 hours.
~30th: The 10 minute running average reached 20cpm at about 10:50 hours. (isolated peak)
~30th: The 10 minute running average reached 21cpm at about 11:20 hours. (isolated peak)
~31st: The last 7 days averaged 96.8% of this station's 2014 baseline (100% = 15.77cpm).
* As of 5/1/2016, my counts have been trending back up toward our
range, with isolated peaks (ie: no preceding build-ups nor follow-on
decays) as follows:
~ 2nd: The 10 minute running average reached 20cpm at about 04:30 hours.
~ 7th - 8th: I found the GG-5 logging program off. Rebooted the operating system.
~10th: 32cpm peak at 14:30 hours. (From graph only. GG-5's SS overwrote data after the 3rd day.)
~14th: The 10 minute running average reached 20cpm at about 06:40 hours.
~15th: 32cpm peak at 01:46 hours.
~17th: 32cpm peak at 00:42 hours, and again at 02:30 hours.
~22nd: The 10 minute running average reached 20cpm at about 16:15 hours.
(I don't know why the 10 minute count is so often 20cpm.)
~30th: The rest of April was "low" to "average" with no one or ten minute peak reaching levels of note.
* As of 6/1/2016, my counts have been trending back up toward our
range, with peaks (one of which appeared to be a build-up and decay)
~ 1st: 33cpm peak at 20:24 hours (UTC).
~ 3rd: The 10 minute running average reached 20cpm at about 10:00 hours.
~ 6th: 32cpm peak at 16:30 hours.
~ 8th: The 10 minute running average reached 21cpm at about 00:30 hours.
~ 8th: 33cpm peak at 03:52 hours.
~10th: The 10 minute running average reached 20cpm at about 15:00 hours.
~10th: 33cpm peak at 22:17 hours.
~11th: 32cpm peak at about 10:45 hours.
~13th: 34cpm peak at 06:06 hours.
~13th: The 10 minute running average reached 20cpm at about 13:15 hours.
~14th: 32cpm peak at 11:17 hours.
~14th: Another 32cpm peak at about 14:30 hours.
~17th: The 10 minute running average reached 20cpm at about 12:45 hours.
~20th: Found my logging program stopped and data lost for the day. Rebooted OS.
~21st: 32cpm peak at 19:25 hours.
~21st: The 10 minute running average reached 20cpm at about 19:40 hours (almost a decay from that 32 peak,
but looks more like a coincidental stand-alone). Saved graph and SS.
~23rd: The 10 minute running average reached 20cpm at about 06:45 hours.
~24th: 33cpm peak at 06:22 hours.
~25th: 32cpm peak at 13:20 hours. (Saved SS & graph. Submersion tests today.)
~28th: A 33cpm peak at 15:24 hours, surrounded by a brief build-up and decay --which amounted to a 10 minute
running average peak of 21cpm at about the same time. Although these peaks, alone, are barely
remarkable, a "build-up and decay" is unusual enough to take note of (if not graph).
~30th: The 10 minute running average reached 20cpm at about 22:05 hours. (Today's average reached 100.1%)
~31st: The 10 minute running average reached 20cpm at about 08:15 hours. (Today's average reached 102.4%. )
* My notices of higher peaks were growing rather lengthy --now that "background" radiation counts are returning to the 2014 baseline average (15.77 = 100%), I've arbitrarily raised the bar --to a whole count of 22cpm for 10 minute running averages (140% of baseline), and to a one minute count of 33 (209% of baseline).
* G-M tube mid-level energy gamma efficiency might only be about 2%, but G-M tubes will continue to count up into Cosmic energy levels (well above scintillator levels) so G-M tubes might have good response to muons (flux ~ 1/cm^2/minute, they carry charge & are some 200x the mass of an electron, so the shielded noise count seems about right, given the profile of an LND-7317 G-M tube). An argument against: they're relativistically fast enough to only be perceptually present --and don't hang around long enough to ionize G-M tube gas. (Muons collide with and get amplified by lead shielding due to secondary splatters --to the extent that counts can go up with over 100mm of shielding.)
~ 9th: The 24 hour run ending today averaged 101.8 percent.
~10th: 33cpm peak at 12:32 hours (UTC).
~11th: The 24 hour run ending today averaged 101.8 percent.
~18th: A 33cpm peak at 06:50 hours.
~18th: A 33cpm peak at 07:17 hours.
~22nd: Found my logging program stopped and data lost for the day. Rebooted OS. Due to the increasing
frequency of my logging program crashes, I'm scheduling OS reboots every 8 days now.
~30th: Above times UCT/GMT. No further threshold crossing peaks to report, as of this (PST) morning.
~21st: Lost data, so only the late night and early morning 10 hours,
which I "corrected" by +2.1%, based on a
recent day-to-night averaging comparison.
~22nd: 33cpm peak at 05:16 hours (UTC). (Isolated)
~31st: Above times UCT/GMT. No further threshold crossing peaks to report, as of this (PST) morning.
* One gets the impression that there was some kind of an event spanning the 17th through the 19th. / The solar notations are from my readings/interpretations of Dr. Tony Phillips' daily descriptions at Spaceweather.com.
* Some are of the opinion that solar winds and other activity "sweep away" a lot of the primary cosmic rays (from deep space), the secondaries of which (mostly muons near sea level) make up half or more of the "background radiation" that Geiger counter type monitoring stations tally up.
* If I get another distinctive looking graph, I'll compare data again.
High altitude counts (see Space
Weather) show a marked increase of 10 to 15%, which is attributed
to our Sun having entered a quiet period --the solar wind being less able
to sweep away incoming cosmic primary rays. Peter Daly's Australia
based station has seen just this much of an increase, but my station
cleaves doggedly near its long term average of 15.61cpm (= "100%" and approximately
an indicated "0.10 uSv" [on a Geiger counter so calibrated in otherwise
meaningless Cs-137 gamma "dose" units]).
~ 1st: 37cpm peak at 15:16 hours (always
~ 2nd: 33cpm peak at 21:04 hours (isolated).
~ 8th: No other threshold crossing peaks as of this morning (PST).
~ 8th: 34cpm peak at 21:03 hours (isolated).
~ 9th: No threshold crossing peaks today, but between 08:00 and 16:00 hours (UTC) the average hit 117.8%!
I'm not aware of any special reason for it. Here's a 2 day graph (click to enlarge):
~ 14th: 36cpm peak at 06:13 hours (isolated).
~ 25th: 33cpm peak at 11:12 hours (isolated).
~ 31st: No other threshold crossing peaks as of this morning (PST).
~ 22nd: 35cpm peak at 17:35 hours (isolated).
~ 28th: No other threshold (33cpm) crossing peaks as of this morning (PST).
~ 12th: 34cpm peak at 17:13 hours (isolated).
~ 13th: 35cpm peak at 07:05 hours (isolated).
~ 16th: No other threshold (33cpm) crossing peaks as of this morning (PST).
* The May 18, 2017 edition of Space Weather (use their archives retrieval utility, top right of page) carries an article describing the recent discovery that very low frequency radio communications to our nuclear submarine fleet also resonate the Earth's magnetosphere, forming a belt around the Earth. That belt appears to be offering protection to satellites (and space farers?) against "killer electrons" --presumably born of primary cosmic rays. That outcome is an accidental byproduct of (what I gather to be) near 24/7 radio transmissions since the 1960s, so we might not have ever been able to study the Earth's normal deployment of its magnetic field and radiation belts.
What I want to know: if high energy electrons (beta
radiation) can be "killers" of space electronics, then tell me more about
--which carry the same negative charge, move at relativistic speed, are
over 200 times more massive than electrons, might constitute half of our
normal "background radiation" near sea level, and much more at higher altitudes.
How is it that the health-physics people assign muons the same biological
impact as gamma and X-rays? (Somehow, they're alleged to shed/impact very
little energy per foot of travel.)
* It looks like 1800 tons of "spent" fuel rods are going to be sequestered indefinitely a little more than 100 feet back from the high tide line as the San Onofre nuclear power plant in California gets fully decommissioned. At least it will be out of the poorly protected pools, but this stuff must be kept safe for thousands of years, since spent fuel is a far worse radioactive hazard than fresh rods. If I read the news correctly, the outer containers, made of 5/8" stainless steel (instead of the European standard of 20 inches), will only be half buried --perhaps due to the water table. (Stainless steel deteriorates in a watery environment, which is why maritime hardware is made of bronze.) Be my guess that, with the rising sea level, corrosion will make the containers and their contents un-moveable, long before a permanent nuclear waste repository has been completed. Are property values within a 50 mile radius already dropping?
* An item --from the Bulletin of the Atomic Scientists. (But they missed citing the Fukushima detonations!)
* For those of you following my graphs, feel free to email me when an item on this page is out of place, out of date, gone missing or wrong. I normally update my graphs at 8 day intervals or within 24 hours of an event.
* My (steep slope roof) sheltered, sealed and desiccated outside monitoring station humbly emulates those used in Germany. While I have a bench setup for the consistent (if not accurate) reading of beta and gamma from samples and air filters, I attempt to avoid counting beta (and I can't count alpha) radiation with my outside station or my "walks", since that would only serve to inconsistently mess with the totals --having more to do with wind and rainfall than any presumed artificial radiation content. (If my outside count goes up, I'll do some air readings again.)
* A 5 year-long string of inquiries^, tests, monitoring methods, 3 Geiger counters, discussions and reading parts of Glenn F. Knoll's book: Radiation Detection and Measurement --at first led me to subtracting an apparent "noise" component from my counts, only to finally go back to whole count averages.
* I'm satisfied (now) that the G-M tube noise component (what remains after shielding out all that one can, which is about half of a normal "10 uR/hr" count here) --is largely the secondaries and tertiaries from cosmic (sky) radiation. I've read that the cosmogenic stuff is about 80% muons (near mean sea level, and I'm at MSL+90 feet here) --to which health-physics assigns the same biological impact as ordinary gamma rays (despite their speed, charge and mass).
* Counting efficiency is near 100% for higher energy beta (electrons), so I'd expect muons, which carry the same charge plus they have 200x the mass, would also count well --but they are said to shed little ionizing energy as they travel --at relativistic speeds.
* What this comes down to: all I know for sure is *click* *click* *click* and how much the click count rate varies.
* Consequently, I revised the several (noise subtracted) 2016 graphs I'd made, bringing them in line with the whole count graphs of recent years and all graphs since.
* I've also dispensed with specifying "standard deviation" and multiples/probabilities there-of. The count is made up of disparate components and I just don't know how valid it is to base that on a simple, total count.
** My thanks and a shout-out to Dr. Martin Bleher of Germany's Federal Office for Radiation Protection (Bundesamt für Strahlenschutz). He addressed those long standing questions of mine. Dr. Bleher could, of course, only speculate on their own G-M tube "noise" components, and although he didn't directly state as much, I gathered that they log all the clicks, which are then presented to the public as so many (current) uSv/hr "dose rate" units --without distinctions or speculation as to the actual components. (I wrote a polite note back to him with these inferences of mine, which he has not corrected.)
* I've been aware of G-M tube noise specifications for years, but they've always been ambiguously given as a (rather hefty) upper limit (when shielded with 50mm of lab lead --perhaps with some interior aluminum as well to soak up "bremsstrahlung" secondaries). However, I previously couldn't get satisfactory answers about noise from those I've contacted, nor did I trust my own methods for detecting "noise" (which appeared to be quite high in my tests as well).
~ I suspected there was more to "noise" than the lead shielded remainder value --and more to it than internal G-M tube contamination, because I got another 22% reduction by submerging a Geiger counter to a depth of 2 meters here in Coos Bay's bay. (I included 8 pounds of lead shot in my simple pressure vessel --not intended as shielding, but for ballast, plus whatever radioactive contamination my cheap lead shot might be contributing^.)
^ Technicians doing professional lab work use only quality, clean, radioactively quiet lead bricks for building their "lead castles" --into which their samples and ultra sensitive scintillator probes are placed. Lead shot (for loading shotgun shells), on the other hand, is surely the worst grade of lead (blended with antimony) that you could use --but: it's cheap, widely available, packs well, and (in thick plastic "freezer" bags) is easy to work with. (Be sure to buy it all in the same pellet size, such that it always packs the same --for consistently effective shielding.) Perhaps lead shot is good enough for shielding the amateur's G-M tube.
* My noise inquiries entailed postal letters, email and web site
feedback utilities. I contacted several "ask a scientist" venues (including
Firmi Labs, nice response), the Nuclear Physics Department of the University
of California Berkeley campus (which invites such questions, but no response
after 4 tries), Bundesamt für Strahlenschutz (a nice response years
ago, and now again [thanks!]), two university campuses here in Oregon (one
very nice response from a department secretary), several Geiger counter
manufacturers and dealers, and (of course) the groups and "web people"
which the monitoring community is close to: Safecast, Radiation Network,
Fairewinds, Energy News, "Anti-Proton", Citizen Scientist League, Robert
Hart ("Hardhack"), LND (indirectly), Aware Electronics, and others --with
several good (if somewhat contradictory) responses.
* I'm continuing with the daily monitoring of 1 minute counts and 10 minute running average counts, archiving any unusual daily automatic graphs (via an off-line, beta edition of GeigerGraph-5). Each morning I look at a graph display to see if there've been significant departures or trends away from my station's (January 2014) base line average of 15.77cpm.
~ These past two years I went from 33cpm to 32cpm and back up to 33cpm again --for the 1 minute "alert level" that I've set into my data logging. I visually (and more sensitively) look for trends and my 10 minute alert level (now 22cpm). Since there's a "Poisson distribution" of counts around my station's long term average, one might expect to see isolated, one minute long, 32cpm counts to occur every day by random chance alone. (although I no longer (2016) cite graph excursions as so many standard deviations/"sigma", I've done the mean/variance calculations for a large number of counts and their distribution agreed fairly well with the statistical Poisson assumption.)
** As of October 10th, 2015 --and being ever so weary of accommodating DST changes to my radiation and astronomy date stamps, I standardized my computers to "UTC": "Co-ordinated Universal Time", which (I think) is the same as GMT minus any DST happy horse-shit. (All USA clocks should run on UTC or some other single time standard --as they did across the old Soviet Union.)
* My radiation charts are updated at 8 day intervals, or within 24 hours of an event.
* Per my corrections of January, 2014, "100%" was set equal to an outside station average of 15.77cpm (using a glass M4011 G-M tube), then corrected again to 15.61cpm (due to a net 1% long term contradiction between the Spread Sheet and the "Report" logging of the software I'm using). It works out that the graphs' continuity has not been affected.
* This "100%" represents the long term averaged count for my outside station. It would correspond to (about) 36cpm from a typical, "pancake tube" (LND-7317) equipped Geiger Counter (say: a Medcom brand "Inspector") --placed in a steep roofed, plastic sealed shelter, at a meter off the local ground^. It also represents about 16cpm from an LND-712 equipped Geiger counter, or an indicated "10uR/hr" (10 micro-Rem per hour), or "0.10 uSv/hr" (micro-Sieverts per hour) --from any Geiger counter with a (meaningless, but roughly cross-Geiger counter equalizing) indicated "dose" display.
^ I've several times compared long period averages between my outside station and a test bed location in my office, getting the same results (meaning: they were within an expected narrow range of statistical departure). Were we to suffer significant fall-out from a radiological event, no doubt the steep roof of the outside station's shelter would shed particles faster than the roof of our house, but both would provide an alert.
* There's pretty good agreement among monitoring stations along the west coast of the United States, per this June, 2017 "uRAD" monitoring map:
* Note that typical "survey" Geiger counters and their Geiger-Mueller tubes are commonly calibrated and/or rated at 1000 uR/hr (using a cesium-137 source at a specified distance), and were originally intended for such high level readings as might be encountered during triage after a radiological accident or attack. We (in the monitoring community) use these Geiger counters at background levels because they're affordable and practical (if used methodically). Again: their "dose" indications would only be meaningful when reading Cs-137 contamination at a specified location --but: uR/hr and uSv/hr allows us to roughly compare readings between a diversity of such instruments (much as I'd prefer the station specific base line percentages that I'm using).
* So: what are we actually reading? By isolating a geiger counter
in a meter-high, desiccated, gamma radiation transparent plastic housing,
CPM (or "dose") readings will hopefully be minimally affected by natural
local or fall-out beta and alpha radiation --which should be separately
attended to via the methodical (if however humble) readings of soil samples
and forced air filters. That being the case, and at such low background
levels as I've been reporting for 5+ years, perhaps over half of the counts
are due to secondaries and tertiaries from cosmic/sky radiation
--which might be mostly "muons" --which are some 200x the mass of electrons
and carry the same charge (ouch!) (ouch?).
* For our radiation counts, we'd expect them to be within the square root of the total count --about 68% of the time (that is to say: within plus or minus one "standard deviation"^ for 68% of the time), which total count you'd then divide by the number of minutes in the period counted --for the average CPM. Notice how the red line excursions appear to be something like 3 times wider than the 10 minute averages. The square root of 10 is about 3.16.
^ However: I've stopped referencing standard deviations (or so many "sigma") since gathering that these counts are made up of very different components ("NORM", cosmogenic, plus any "fall out" that we worry about). All I know for sure are my count totals, what I'm using for Geiger counters, and how/where they're located. I strongly suspect that I'm not alone in this and that very few people have a good handle on what drives their low level "background" counts.
* The several kinds of averaged graphs I've generated (manually and with graphing programs) all look different. I don't like any of them, so I might as well stay with what I've been doing (takes 5 manual operations), despite its tendency to miss events and produce statistical artifacts. Again: I see the maximum CPM for each day, I investigate the spread sheet and report on those which reach 33cpm or higher --so as not to miss anything egregious.
* 33cpm might seem rather high (4.4 "deviations" --from whatever) --but there are 43,500 minutes counted each month, and it's turning out there's (seemingly) about a 1 in 10,000 chance of a count running that high on the (valid or not) basis of the above described statistical noise. Usually, I find that in the 10 minute period surrounding such an event, the peak is isolated --and that the period's average isn't otherwise elevated.
* Never mind the oddly pointy and square topped shapes of the 10 minute graph line --per:
* Try to avoid line graph displays which attempt to pretty-fy the results with such as 3-D effects, gradient color backgrounds, garishly colored fat lines and grids. Simple, jumpy, black-on-white radiation graphs are hard enough to interpret as it is.
* Peter Daley of Australia has made me aware that the risk of food contamination extends to serious, gamma emitting particles --aka: "hot particles" or "fuel fleas", for which a common Geiger counter could be a life saver. There are accounts of such particles to be found across the Internet, some of them active enough to affect a basic Geiger counter several feet away. (I'm talking a steady, penetrating, "this can of tuna for sure, not that one" count of hundreds or thousands of CPM.)
Thankfully, such occurrences are extremely rare. I've seen nothing but normal "backgrounds" here after 5+ years of daily monitoring (plus a neighbor who came home loaded with radiation from medical imaging). For a long while I made an effort to discretely carry a compact Geiger counter, especially when I went grocery shopping.
* If you decide to do that, I suggest minimal beeping/clicking and no theatrics. If the alarm sounds, switch straight to silent mode and mutter something about "damned cell phones" --but locate, and remove the hot item, mark it poisonous, write down (or photograph) any identification on the food item, what radiation reading at what distance, the manager's name, date, time --then attempt to interest the store's management and the hazmat crew of your local fire department.
* Unless you have a nearby lab to properly test it, I don't suggest that you purchase the food item, since it then becomes your responsibility --to competently and securely isolate the item, preserve and document its "chain of possession", and make certain that matters are properly attended to by the proper authorities.
* More on Peter Daley's resources, which include a volume of advice and links concerning radiation and food. Good starting points are:
The Food Lab: http://sccc.org.au/archives/2861
* So: a Geiger counter does not, of course, have the sensitivity or discrimination to pronounce any food stuffs as being safe to eat. Neither can a Geiger counter condemn a food or beverage item --unless it's plenty hot --way hotter than the (mostly beta) CPMs you get in close proximity to (say) potassium chloride (dietary "salt substitute").
* Proper food monitoring requires spectrometry on the (often incidental) gamma radiation involved, which takes honorable equipment, handling methods, lab discipline, and learned, seasoned experience.
* Gamma emitters seem (to me) to be the only practical isotopes for an amateur with a Geiger counter to check for. Beta radiation is nearly all blocked by the moisture content and even the food's own bulk. When desiccated and/or thinly sliced, the available (and natural) potassium sourced beta count of many foods increases considerably, but that can swamp any count you're getting from serious traces of other polluting radio nuclides.
* Be very careful not to contaminate your Geiger counter when checking samples, when the air is not clean, and when at the beach (wind, spray, alluvial sand, salt air). Bagging it in a Ziploc is a good idea (but place a packet of freshly charged desiccant inside with it, or at least open and let the bag/counter breath after its back home, warmed up and safely stored).
The Green Party (USA) has been opposed to nuclear power plants for years --never having bought into the greenwashing of nuclear energy. Currently (January, 2017) there's a new push (and a big puff piece on PBS) to rehabilitate nuclear power, this time reviving the 50 year-old notion of using corrosive, flammable, liquid sodium instead of water. (A sodium cooled test plant underwent our nation's first nuclear power meltdown.)
The Solar Flare Threat
3/21/2015 update: Have we made it through the worst of this solar cycle? I sure hope so.
3/06/2014 update: Here's a *link* to a 3/4/2014 Wall Street Journal article by Rebecca Smith --which might display in full the first time you access it --but which might subsequently fade out. Apparently, this is the WSJ's new way to game us into subscribing), with more recent information on the availability of replacement EHV transformers. We do have a domestic manufacturer who can build the big ones (400 tons each! --similar to the largest stones in ancient megalith monuments), but it takes months to complete and deliver one. A recent delivery from an overseas source took about 2 years. (Hat tip to Majia for this information.)
3/15/2013: Either the 2012-2013 solar maximum will be unexpectedly tepid, or it will come as a delayed "double peak". Watch the video at NASA Science News. Prevailing opinion favors a repeat of the double peaks we've seen in the last 2 solar cycles. (That video also reference a double peak during solar cycle #14 [early 1900s], but I didn't see one in the record that I looked at.)
If we do get a double peak, the second one might have us weathering a series of "X-Class" flares and coronal mass ejections ("CMEs"). Whether one of them smacks the Earth and shuts down some of our power grids is a game of "Russian roulette".
11/17/2016: Well: we got a "double peak", but we made it through anyway, and seem to be in the clear for some long while again. Never-the-less, I think --
It's vital that our political leaders understand and address the following points. (Good luck on getting through to them, but one recent presidential candidate pledged to phase out nuclear power: the Green Party's Dr. Jill Stein.)
* Nuclear power plants, despite that they might end up literally bursting with thermal energy, were designed such that they're unable to power their own cooling pumps --in the event that there's a local failure of the power grid. On-site diesel-electric backup power then takes over to run the pumps, controls and instrumentation.
* I know that's hard to believe, so rather than simply discounting my concerns here, please confirm it for yourself. Google on "station blackout". Newer designs use steam power to run turbine driven water pumps, but they still require electricity to open valves and turn those pumps on, which is supplied by only hours of battery power.
* Because the spent fuel pools (SFPs) were only meant to hold 1/4th or 1/8th of what was eventually crammed into them, there was no provision to supply them with emergency backup power at all.
* To be very clear about this: there was originally (and still?) no provision to connect the diesel backup generators to the SFP's cooling pumps --!! The plan was to simply let the water in the pool coast up --near to the boiling point (which might take as little as 24 hours), and to then replace boiled off water by means of manually deployed fire hoses. (Sweetjeez!)
* The SFPs are crammed with old fuel rod assemblies because there's no place to store nuclear wastes, and because the operator/owners of nuclear power plants are too cheap to use "dry cask storage".
* There are several deadly important things to understand about "spent" fuel pools and rod assemblies:
~ Their radioactivity is far more deadly than fresh nuclear fuel rods.
~ There's serious question as to whether their sometimes 40 year-old liners can stand the strain of boiling water.
~ If the zirconium cladding on the fuel rods gets hotter than 1800 degrees Fahrenheit, it oxidizes with steam and water, releasing explosive hydrogen. Above 2000F, the oxidation process turns into a furiously burning fire which destroys the rod, releasing its radioactive contents.
* As to keeping a reactor's containment cool after a shut-down, months of mechanically forced water cooling are required --but the U.S. Nuclear Regulatory Commission originally (pre-Fukushima) only required that nuclear power plants be independently capable of supplying diesel-electric backup power for 72 hours, plus 4 hours worth of battery backup power --to cover any delay in getting their diesel engines to turn over.
~ The Fukushima Daiichi power station reactors had 8 hours of battery backup power. They used every bit of it.
~ The NRC might have recently started upgrading that requirement to 8 hours of battery and more on-site diesel fuel. The recent near nuclear disaster at New Jersey's Salem nuclear power plant established that they had a store of 7 days worth of diesel fuel on hand.
~ While SFPs might require mechanical/forced cooling for a year, I don't know how long mechanical cooling is required to remove residual heat from a normally shut down, intact reactor in order to maintain "cold shutdown". The damaged reactors in Fukushima have required months of cooling.
~ Backup power will continue to be available at a nuclear power plant if more diesel fuel can be delivered to the power plant, if the diesel generators remain operable, and if operator personnel can be persuaded to remain at their posts. (The regular Fukushima crew initially fled, but was successfully ordered to return. The head of TEPCo has stated that, in the event of a fuel fire, he'd have no way of ordering his crews to face certain death in order to mitigate the situation.)
*** A report by the Oak Ridge National Laboratory stated that over the 40-year licensing term of a nuclear power plant, solar flare activity adds up to a 33 percent chance of it experiencing a long term power loss: a risk significantly greater than that of earthquakes and tsunamis --!
* Federal government studies have suggested that extreme solar flares could result in regional blackouts lasting months or even years, since critical power grid components like EHV (extremely high voltage) transformers are made in places like India and we have scant spares here in the United States. There are more than 300 aging, vulnerable EHV transformers in substations across this nation and the existing over-seas manufacturers of these transformers currently have a 3-year backlog of standing orders.
* A severe solar storm might destroy hundreds of transformers world-wide, leaving vast populations without water, sewers, hospitals, TV/radio broadcasts, fire and basic safety services. Military escorts would have to bring in fuel tankers through the ensuing chaos from our strategic reserves, since the pumps which normally transfer gasoline and diesel fuel wouldn't be operating, nor would refineries be making more.
* I understand that nothing material has been done to provide for the recovery of our power grid.
* As of 1/22/2012, the prediction was for a long, quiet series of solar cycles, following the 2013 maximum. Since our nation has already passed up years of opportunity to prepare for a solar flare disaster, and since it would take about 3 years to prepare if we'd started in 2013, there were only two meaningful things to be done.
1) Shut down all nuclear power plants (before a solar flare strikes).
2) An executive order which would establish a national emergency force and plan to provide for a year's worth of backup power. Under National Guard protection and execution, helicopter deliveries of stockpiled fuel, replacement diesel generators, and replacement operating and management personnel would be made available to all of our nuclear power plants, once it becomes apparent that blackouts are imminent.
Let's not face that choice again.
Key government and military officials must think about, and publicly discuss --how dangerous it is to continue operating our nuclear power plants --while our good luck holds.
Sources: John Kappenman of Storm Analysis Consultants and Metatech Corporation, as commissioned under Executive Order #13407, NASA Planetary Sciences Director James L. Green (See the February issue of Sky & Telescope), National Research Council Chair Daniel N. Baker (Space Physicist),
* Against all the above bad news about nuclear power plants, there's good news in that solar and wind power alternatives are coming on line with a kilowatt-hour operating cost that's significantly lower than nuclear power plants (aside from the inability to estimate the costs for disposal --since no such disposal site exists).
* Hopefully, the solar and wind industry will get away from the retail level co-generation of power, myriad complex demark/interfaces (since power must be reliably taken off when lines are damaged), loading home owner roofs with panels (fire and storm insurance is bound to become a real problem), locating noisy windmills near communities --and turn instead to distributed, professionally managed, renewable energy power plants.
* Retail energy storage (say: via electric car batteries) also strikes me as being hare-brained, hazardous and unreliable. I'm reminded of 1950s notions that homes of the future would be equipped with nuclear powered hot water heaters. Even professionally managed, large scale energy storage can be expected to present dangerous consequences, should something go amiss. I don't have answers here --except that alternatives to both nuclear and fossil fuel generated power must be found.
* I started it by default of anyone else doing this work for my part of Oregon (which I found hard to believe) --and until a new Radiation Network private station appeared in Florence in 2014, I remained the only entity, public or private, doing and posting regular monitoring along the Oregon coast.
* I no longer make much of an effort to popularize my own monitoring numbers --which (to date, and thankfully) have been steady and mild. I worry about giving people false assurances, and should my numbers go up, I'd worry about spreading false alarms. However, it would be wrong to stop keeping and posting this record --as long as my equipment holds up.
* Although I've been monitoring each day and watching the minute-by-minute log for spikes, my manually composed graphs over the first quarter of 2015 were no longer continuous --just representative --for an assortment of reasons: We stopped paying Charter Communications $55/mo for Internet access (something which once cost $10). Trundling down to our library for a short period of access meant higher priority traffic came first. Also, I became discouraged. The CPMs barely change --which is good news, of course, but also: I didn't know what I was counting, and I couldn't get definitive answers.
* I created this Web page (thanks, NeoCities!) after the system at www.RadViews stopped loading my graphs. I've dedicated our old Dell laptop to Geiger counting/logging 24/7. Both the computer and the outside Geiger counter (a GMC-200) have battery back up, allowing reliable and continuous 24 hour averaging with minute-by-minute logging and spike alarming.
* Sunshine Coast Computer Club,
Peter Daley's SCCC web site based monitoring, record keeping and public presentations are exemplary. More-over, he backs up his monitoring with the demanding work of gamma spectrometry on consistently captured and prepared samples. I hadn't previously included his monitoring station because it's in Australia --the other hemisphere (from here). However, his graphs are the only data I've been able to find for comparing and possibly corroborating my own. (Be sure to click on and enlarge his graphs for legibility.)
* Greg's Lab:
Greg's Lab has been everything that the EPA's RadNet and other private monitoring networks should be --but often aren't: map based "at a glance" clarity, with the basis of the displayed radiation levels clearly explained. His pages have been simple, concise, with all aspects freely and publicly accessible. Greg reports the total averaged CPMs (all of RadNet's KeV gamma energy bands added together) for each of the California stations he tracks. This is more comparable (trend-wise) to our private Geiger counters --were they to be monitoring air filters --so actually there's little or no comparisons to be made. Another factor is that Geiger counters tally a much broader range of gamma energy than RadNet's scintillator sensors. Unfortunately, and as of this edit (12/27/2016), Greg's automated web page isn't working. The next best thing for the region Greg covered (and the only thing for all the other states) is EnviroReporter's web site.
At Michael Collins' EnviroReporter web site you can easily get at all of the EPA-RadNet station graphs --and in their original 9 channel format.
* Radiation Network:
* At "Message", Mineralab/Radiation Network owner Tim investigates and posts what I consider to be honest and rational reports about unusual readings across his network. (Yes: he has identified what appear to be actual radiation alerts.) Unfortunately, very few alerts are attended to with follow-ups. I understand that a comprehensive "Alert Log" is being developed for a future version of RN.
* Perhaps the strongest feature of RN is its "All Station Average" graph:
* Radiation Network's stations report in "CPM": counts per minute, which makes a lot more sense than uSv/hr or uR/hr when the source is not known. Unfortunately, different Geiger counters have different sensitivities, which RN's map icons and legend attempts to take note of, by distinguishing between "high" and "normal" sensitivity instruments (thus: those two graphed lines/bands).
* For presentation on their public (Web page) map, the determination of individual station trends and "Alert" status is being averaged over intervals longer than a minute.
* Radiation Network's current "Alert Level" of 100 CPM was a good compromise choice, but later it was individually adjusted to accommodate the disparities among their monitoring stations.
* None of the stations are characterized as to what's
being counted or how and where those instruments are positioned --but (again),
high and normal (low) sensitivity stations are identified and their responses
are being roughly equalized as to trend status.
Not to be confused with "Radiation Network", RadNet is the EPA's no-bid private contractor for keeping tabs on radiation blowing across the United States. It's performance and readiness over the years has been and remains disappointing. RadNet's data is now posted to the public as one-line (all gamma counts totaled) graphs, much as we've seen them at Greg's site. To get at the original 9 energy channel format, scroll down at EnviroReporter's web site. Unfortunately, to see historical RadNet data (and current data in context), it takes an NETC membership.
* RadWatch (fka: The BRAWM Team)
University of California's Berkeley Campus Air Monitoring:
I've not checked this site recently, but they didn't seem to be up to speed in the past. I've been unable to reach them with questions. They were at one point doing great and professional work, monitoring milk, water and air filters, plus explaining the complexities of radiation science.
It's not clear to me how their "RadCon" levels are determined on the public map, so I tend not to pay them much mind. However, if you've got $20 per year for a paid subscription, network owner Harlan has done an exemplary job of graphing years worth of RadNet's and NETC's own private stations --your choice of averaging and time spans. NETC reaches into Japan as well. [Update: I last read that the owner of this system was moving its connectivity to the "short-wave" bands --presumably meaning amateur radio.] Here's an example of the NETC's graphs:
* Black Cat Systems:
The main advantages of this private network are equalized monitoring stations which use Black Cat's excellent software and Geiger-Mueller tube sensing units. Black Cat posts no characterizations for its stations --no matter how high they might read, other than the fixed message: "--things are currently normal". Nor do I see any station graphs.
RadViews has been a promising new, potentially global, radiation monitoring network. It's manually posted, so members don't need to maintain a 24/7 Internet connection. (In the United States, Internet access is via several corporations which amount to regional cable monopolies. Phone company and satellite alternatives are more collusively priced than competitive.)
Radioactive@Home is an interesting kit and (crowd sourced) BOINC software based, global monitoring network that's based in Poland. I suggest this operation is more about amateur experimentation and radiation as a hobby.
--which is run by one Radu Motison. He apparently supplies DIY automatic reporting device kits which detect a variety of polluting factors (to judge from a recent promotional video). He's setting up a serious monitoring network. (I'm doubtful about DIY kit based networks, however. Standardization and quality control in equipment and methods are vital for reliable data.)
Radmon.org is another global, kit based network with appeal to hobbyists and amateur radiation experimenters.
* Germany's Network:
* The following link is based on BFS data, but it hasn't
been working lately. I'm hoping it gets restored.
My Choice of Geiger Counters and Radiation Units
(partially revised: 1/5/2017)
** Were I now just starting out to monitor local background radiation, I'd very likely purchase the GMC-320 version-4, produced by GQ Electronics. This affordable (currently: $118 via Amazon.com for the version-3), self-logging Geiger counter has a timed total count function (like the expensive counters: Gamma-Scout, Inspector, Mazur, etc). Both versions 3 and 4 permit outside monitoring (sealed up with desiccant in a "Ziploc" freezer bag and placed in a steep roofed "bird house" shelter) without having to bury cable to it, since you can periodically take it back into the house or office for a minute-by-minute debriefing to your computer --or simply to read its display for the day's timed count (say: 12 to 24 hours).
~ If you go this route, be sure to let the Ziploc bagged/packaged 320 (or any other such instrument) warm up to within 5 degrees of room temperature before opening it in the house. (The 320 displays its own internal temperature --nice!)
~ The 320 is a bit power hungry, so if you plan to leave it in the shelter for (say) a week at a time, replace its lithium battery with a good brand name lithium having a 2500mah capacity. (My current outside unit is a cabled GMC-200 --which uses the same G-M tube as the 320.) See here for more about my setup.)
* The earliest graphs on this page report Geiger counter ("GC") radiation measurements in terms of indicated "uR/hr" (micro-REMs per hour, which equals uSv/hr times 100) --"dose rate" units. The use of Geiger counter "REM" units (Roentgen equivalent man") is nearly always invalid since it's supposed to be about a hypothetical person's received bodily dose from a single, defined, external, isotope source. My Quarta-Radex and Medcom "Inspector" Geiger counters' REM calibrations can only be roughly correct for a cesium-137 source. For other types of radiation --like external alpha radiation (which doesn't even penetrate the skin), it becomes meaningless. In short: a (windowed) Geiger counter counts alpha, beta, weak and strong gamma as equal *clicks* --but they are not physiologically equal.
(The other radiation unit you'll encounter is the "gray"/"Gy", which is usually the same as the "sievert" for gamma radiation.)
* The alternative of simply using "CPM" (counts/clicks per minute) is far more rational and honest --but unfortunately, people are using many different GCs which report varying CPMs for the same kind and intensity of radiation. However, since most GCs have been factory calibrated to yield similar uR/hr or uSv/hr values for cesium-137 under similar circumstances --we can at least hope to get similar readings with respect to "background" radiation by using those "dose" units --especially if our radiation sources are largely gamma/photonic in nature.
* After buying a Medcom "Inspector" Geiger counter with CPM readouts (and alpha sensitivity), I began logging my readings as "counts", averaged to counts per minute, over long periods of time (usually: 10 to 100 minutes).
** However: for 2014 through to the present, I've been logging very long term averages (now about a 24 hour count each day) --as a percentage of my outside station's average for the first two weeks of 2014. I think that beats any other radiation unit --for integrity, station-to-station comparisons and for avoiding confusion.
** During the first hours of the Fukushima disaster, our government's and the Navy's estimates of radiation exposure were being logged and quoted with errors of up to 1000x, simply because they were not prepared to convert between the several units which are still in use: milli, micro and pico versions of REMs, Rads, Sieverts, Grays and a variety of CPM rates from various instruments --not always correctly deployed and read.
* That (the above) all having been said, and for better and worse: Europe's and Asia's government and private network's use of Sieverts (micro and pico), their accessibility and transparency (compared to the USA's horseshit, sweetheart contracted RadNet system), has pretty much set the Sievert as the standard radiation unit for us all. Some affordable Geiger counters only read and log in micro-Sieverts per hour.
* My average outside and inside office ambient (or "background") readings here are very similar and usually vary from about 8 to 12 "uR/hr", which averaged about 36cpm with the Medcom GC, but comes in close to 16cpm with the M4011 and SBM-20 Geiger-Mueller tubed units I'm now using. But I simply log it all as a percentage of my station's long term average.
The best policy is to -always- use Geiger counters in the same way and at the same monitoring stations.
* The G-M tube (an LND-7317) in my Medcom "Inspector" Geiger counter failed. The unit still had high voltage which measured at an indicated 480 volts, using a 40 meg-ohm loading probe. (The unloaded voltage might well be the 500v that the 7317 is rated for.) I can only assume that the brief starting voltage (too brief to see w/o an O-scope?) is in the range of the specified 400v to 425v.
* The Inspector's electronics counted up when I brushed the isolated test probe across the G-M tube anode connection^.
^**^ Caution: Don't have the G-M tube in the circuit when you do this test! As little as 20pF (20 uuF) of external capacitance to circuit ground (like what's between the test leads from your meter), if placed directly across a G-M tube, can destroy it, so if the G-M tube is in the circuit, stand off your test probe with at least a 4.7 meg-ohm resistor at the tip. (I like to use the input resistance of the volt meter for the stand-off resistor --so I can simply double what's displayed. By knowing the combined DC probe impedance of your meter, and knowing the effective source impedance of the circuit you're probing, you can multiply the display voltage by whatever factor is required --should you need to know the unloaded voltage in a high impedance circuit.)
* Unimpressed by the life span of my pancake G-M tube (AND its original 90 day warranty via Medcom --recently (2014) extended to a full year), I replaced it with a Russian SBM-20, which can be had for about $35 ($20 if ordered direct from the old Soviet countries). These are tough, durable puppies with about 43% the gamma sensitivity of an LND-7317, no low energy beta sensitivity, and (of course) no alpha sensitivity at all.
* The operating voltage and the initial voltage had to be reduced to about 400 and 300 respectively. Consequently, I added a high resistance voltage divider consisting of five 10 megohm ("10M") resistors between the original G-M tube anode connection and circuit ground, then tapped off about 380 volts after the first 10M. That first 10M (R1) is bridged with a 15pf (15 uuf) disk capacitor (C1), so that the Inspector's electronics can feel the brief pulses. (This photo will enlarge.)
* This modification resulted in a steady 2ma drain on the 9v battery (18 milliwatts) --for about 23 days of battery life, where I use to get about 3 months per battery. However, I no longer use this GC continuously. Even though the divider string only accounts for only 4.2 milliwatts, one might consider doubling all of the resistors.
It's my guess that this will degrade the high rate performance of the tube, but by using a pulse data cable connection to my PC, the high end already starts rolling off above 5000cpm anyway, and badly above 15,000cpm (compared to Inspector's internal rating as being good to 350,000cpm --with the original G-M tube, of course).
* With an SBM-20, the uR/hr display would of course be way off, but I've only ever used timed CPM totals (since the Inspector's sampling period is only 30 seconds or less for anything else).
* I operated my Medcom Inspector pretty much continuously for the 14 months I got to use it. In an average 36cpm background field of radiation, that works out to 22 million total counts (2.2 x 10^7), whereas the expected G-M tube life is quoted at from 10^9 to 5 x 10^10 total counts --so it failed about 100 years short of the mark.
My comments, questions --and drivel
* While all radiation carries an estimable hazard (per:
--so do things like getting out of bed in the morning, breathing city air, driving a car, etc. --all of which a rational, caring person (especially a parent) attempts to minimize. Possibly it's the case that a healthy person's body is usually able to repair the damage (at a cellular level) --for the prevailing rates of "background" radiation --at least in one's ancestral home. Whether or not that's the case, the hazards of external radiation can at least be rationally compared to every-day exposures --natural (like the radiation from potassium 40 in your own body) and artificial (like disturbing the ground for your home's foundation), which seem largely unavoidable in modern life.
That having been said: you especially want to minimize eating/drinking, breathing in or somehow wearing a radioactive substance. You also want to avoid counsel from anyone who proposes to compare ingesting radioactive substances to chest X-rays, sunshine, air travel, or eating bananas.
See the preamble to this page for my latest take on what the heck it is I think I'm counting.
* Our society needs supportive feedbacks at all levels, but does not have a method certain for earnest amateurs (once upon a time encouraged with the title: "citizen scientist") --to get competent counseling.
~ This is a much broader issue in that many amateur interest groups (concerned with [say] UFOs, contrails, fluoridation, vaccines, 911 and other issues/conspiracies) --find themselves isolated and left to their own --perhaps self-defeating-- devices, methods and assumptions. These factions then drift further apart from the "main stream" and from each other.
Be my guess: this is due to that familiar "high school popularity contest effect". The competent professional (usually educated at great public expense) can not personally afford to engage such people (the public), lest s/he suffer the "de classe" effects of being tainted by association with the "great unwashed" or "the wrong sort", get stupidly quoted out of context, perhaps flat out misquoted --thus ending up with less credibility among and traction with his/her colleagues --on that slippery upward slope to a successful career. The integrity, coherency, mutual respect and trust of our society suffers as a consequence.
* As to the integrity of traditional handheld Geiger counters, I can answer that one. Despite recent versions being explicitly designed and sold for background radiation monitoring, their original purpose was for use as survey instruments --to help clean up a messy lab, to be deployed during an accident or an attack involving radioactive materials. Typically, they're calibrated at a level of 1000 uR of cesium-137 radiation --100 times above my average background levels.
That be as it may, we use them in our monitoring work because they're affordable ($100 to $1000).
* At first I thought that my Geiger counter background/baseline readings were mostly about "NORM" --naturally occurring radioactive material/isotopes in the ground, beach sands and in the air --plus any fall-out from the events in Fukushima Japan or elsewhere. (I use to supplement my fixed station readings with remote beach station readings and occasional one-shot air filter readings, plus outsourced gamma spectrometry for suspicious filters.)
* Then I became persuaded that I'd been largely counting "muons"
--those secondaries which reach the Earth, generated by the steady rain
of cosmic primary rays, but Robert Hart (see:
--and others suggested that the muon component (at sea level) amounts to 10% or less of even a low background count.
* As of July, 2016, it appears that about half of a count at low "background" levels (say: 10 uR/hr) is cosmogenic plus a minority of internal G-M tube noise. (It's tough to discern the difference. A coincidence detection setup should help.)
* On 5/25/2016 I submerged my mobile Geiger counter to a depth of 2 meters --off the end of a dock on our salt water bay (using an old army ammo box for a pressure vessel).
My earlier submersion tests had cut the counts roughly in half.
* Previous shielded tests indicated an irreducible minimum in the range of 75%. Another test run on 5/30/2016 (lead shielding only) indicated a 72% remainder (of noise/whatever).
~ *Click here* to see my data and supportive particulars. Perhaps you can draw more informed conclusions.
* Adding to the confusion is that Tom "Anti-Proton" (nom-de-Net) has repeatedly passed through medium altitude null zones of close to zero Geiger counts --when taking his Geiger counters and a compact scintillator/gamma spectrometry setup along on his many business related airline flights. (I believe that Tom is too well informed/experienced and equipped --to have been fooled by sensor overload.)
* A Geiger counter's own internal noise might be sourced from the G-M tube or other materials in the Geiger counter. --Those counts, of course, would not have been reduced by submersion --or truly effective shielding.
You might find it dismaying to check the noise specifications for your Geiger counter and/or its G-M tube, which is variously listed as "self", "own", "inherent" or "maximum shielded background". (They don't seem to like the term "noise".)
The noise in some G-M tubes is rated in "CPS": counts per second. For instance: the big Russian "SBM-19" G-M tube's specifications indicate an "inherent counter background" of 1.83 pulses per second --which would be a whopping 110cpm (--SHEESH!). My outside station's G-M tube (an M4011) lists noise at 76% of my long term average --and a drop to 75% is what I got by packing an SBM-20 tubed counter of mine in 40 pounds of lead shot. (Lead shot is a poor substitute for the good stuff used in a gamma spectrometry lab, but it's cheap, widely available and it packs well.)
* Straight away, I hope you can see the consequence. Let's say your averages go up from 35cpm to 40cpm. That might not be a 14% increase in what we're worrying about (Fukushima or domestically sourced radioactive contamination). It might actually be a 250% increase --right?-- but after an atmospheric or oceanic plume of radioactivity arrives, perhaps it won't look like much of a change in a Geiger counter's total counts (noise + muons/whatever + an actual on/in the ground increase). (As of July, 2016, I'm assuming that most "noise" is due to cosmogenic radiation, and that all noise makes up about half of a count at an indicated "10 uR/hr".)
6/16/2015: * That 6/9 peak extended into the 2nd day with what looks something like a decay curve. I've seen no such readings elsewhere, so I'm still guessing it was a neighbor's bout with "nuclear medicine", but using something other than technetium-99m.
6/8/2015: Have begun watching for (and noting) 10 minute averaged periods which reach or exceed 4.4 standard deviations (21cpm), per my copy of a GeigerGraph beta program. It may be (and has already been) that highs occur without an accompanying 1 minute count peak (of any special note) --and vice-versa.
5/25/2015b: I've discontinued my 30 minute remote (beach and bay) station counts in favor of beach "wanders".
* The difficulty of getting qualified comments about radiation issues is disappointing. I'm old enough to remember a readiness among the academically/professionally qualified to encourage earnest amateur pursuits and the "citizen scientist". Of course there use to be more willingness to uncritically accept authoritative answers, and now there's the Internet. I imagine that professionals are apprehensive about being blaringly misquoted out of context, held up to ignorant ridicule, becoming suspect of indiscretions with "privileged information", and simply being widely seen to be consorting with the academically unwashed.
5/24/2015: * I reached back and added a percentage range to all the program generated graphs --which made for an interesting review. At some point --shortly after my Medcom Inspector Geiger counter failed, and maybe about the time I broke my leg, I seem to have gotten about 1cpm out of calibration, as I transitioned through my 2nd and then to a 3rd Geiger counter. The graphs themselves, however, evidence what the equivalency should be, so that's what I've gone by. (Tentatively: I'm claiming that my new SBM-20 G-M tube "matured" into a bit more sensitivity.)