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It could be that, even after an atmospheric or oceanic plume arrives, it would barely budge my Geiger counter readings --but since my years of requests for qualified counsel on that question have gone unanswered, best I continue with this effort. Note that I'm mainly reading what's on the ground, supplemented by air filter readings (and gamma spectrometry, as available), which I do periodically or when I suspect that "something's in the air". I'm fairly certain that I'd be able to detect a "hot particle" were one to lodge in my air filters.
4/20/2014: * Updated the April graph.
4/19: * There was an M7 solar flare on the 18th at 13:07 hours UT/GMT --which should only graze the Earth.
4/17/2014: * No more than M-1 solar flares the past week.
4/14/2014: * Read and graphed background at the two beach stations.
4/12/2014: * We've been enjoying a rather quiet Sun for tha past week.
4/4/2014: * Started the April graph.
3/31/2014: * completed the March
* Noted: As my graph indicates, the average CPM took a significant leap of 4.7% today (about 4.7 "sigma") above the recent averages.
3/30/2014: *Noted: there was a brief and unusual X-1 solar flare at 17:52 UT/GMT from spot AR1890 on the 29th (UT). That would have been 10:52 hours (AM) local time (PDT). Its CME will only deliver a "glancing"blow to the Earth: (a geomagnetic disturbance on April 1st. What made the flare unusual was that it immediately ruffled the Earth's magnetic field. Unfortunately, I stupidly lost my own data from other Radiation Network stations for the 29th (but I'll blame it on our dog Sammy), so I've put out a request to Radiation Network's station keepers to check their data. My own minute-by-minute CPMs log show nothing special, nor did anything stand out when I checked the graphs for 6 west coast NETC stations.
3/29/2014: * Updated the March graph
3/27/2014: * Correction (below).
3/25/2014: * Made yet another change in the graphing
standard by averaging only those morning to late PM hours when my computer
is normally running.
* An hours-long, but otherwise modest "C" class solar flare on the 23rd will result in a modest geomagnetic storm today.
3/22/2014: * There was an M1 flare on the 20th and the Sun has once again become mildly active.
3/19/2014: * The Sun has been quiet --despite having a number of spots. However, it's recently been determined that we narrowly missed being hit by a Carrington level event on 7/23/2012 --per the 3/20/2014 edition of Space Weather. The consequences would have been as described here.
3/15/2014: * The Sun spots, one of which (AR2002) was very large, have mostly faded. AR1996 produced an M9 flare on the 12th (nearly an X1), but it was facing well away from Earth at the time. The current worry are two very long magnetic filaments, which appear like rifts across portions of the Sun. These have been known to produce extremely large flares when they collapse. Let's hope our luck holds.
3/9/2014: * The Sun has undergone
several M-1 and C class flares --minor stuff.
*(3/27/2014 correction) Goodness: this entry's taking on a life of its own.
Sorry --and special apologies to anyone who's already quoted me. / If there's anything I hate more than being wrong, it's having to retrace my Internet steps and make amends. / Of course I can't give 100% assurance that I was indeed wrong, but it does seem likely --that the EPA limit for cesium-137 has been set at 200 pCi/Liter for some while now --not 3 pCi/L, and per this (referenced in 2011) list, which was commented on at: http://www.nuc.berkeley.edu/node/5874
It's my guess that Jeff McMahon will stand by his reportage/blogage at the lower figure, and I can sympathize with that. This stuff is devilishly hard to find and to understand. However I quite agree with Jeff that the new "PAGs" are a caution.
Craig (who knows little for sure here --other than the
*click* - *click* - *click*.)
3/6/2014: * Update to the
* I'll periodically fill in the days between 24-hour averages with isolated dots for 12-hour daytime averages on the new graphs.
3/1/2014: * Started the March graph.
3/1/2014: * Starting this month, the aim point will be to conduct 24 hour averaging on the 1st, 3rd, 7th, 14th, 21st, 28th and final day of the month. The first post should occur on the 3rd or 4th day. If we start getting significant spikes or elevated background levels, more frequent averages or a return to 24/7 averaging will result.
2/28/2014: * Completed the February graph,
2/25/2014: * We dodged the bullet --once again. At 00:49 UTC (16:49 PST on 2/24), sunspot AR1990 (which, I gather, is the 2nd time around now for old AR1967) --belched out a powerful X4.9 flare, but almost 90 degrees away from the Earth.
2/22/2014: * Did an air filter draw.
* Checked the two beach stations.
2/20/2014: * The Earth is being buffeted by a series of minor to medium CMEs from a series of mostly C-class solar flares.
2/16/2014: * The Sun is relatively quiet --and that solar storm didn't materialize.
2/14/2014: * In recent days there's been a series of medium solar flares a C and low M class (M-2 earlier today). Two of 3 closely spaced CMEs will arrive almost simultaneously on the 15th with a good chance of polar solar storms.
2/5/2014: * AR1967 appears to have coughed up no more than an M5 flare since January and is now turning away from us.
2/1/2014: * Corrected the new January graph's percentages line to the new (last week in January) average of 15.77. Recently, it was set at 15.99, based on 20 days of spaced hours, through January 28th. Before that it was tentatively set at 16.10cpm, buy direct comparison with an SBM-20 G-M tube instrument and earlier LND-7317 G-M tube based logs. That last week swings a bit, but not unlike the range of earlier weeks. The important thing is to pick a number and stay with it, or else trouble to reach back and correct all earlier logged percentage or "sigma" values to any newly determined base line/average --which I've just done.
1/31/2014: * Sunspot AR1967 continues to be active, with an M1 flare and CME earlier today.
1/30/2014: * The Sun released an M6 level flare
and CME today at 16:17 hours UTC/GMT --from the monster sunspot "AR1967".
This less than "X" class, but still strong flare occured with AR1967 facing
well away from Earth.
* I wasn't satisfied with the graphing modes I've tried, so I've gone to day averaging --which, by being more inclusive, should be less suseptible to statistical artifacts. The graph will now account for nearly 24 hours out of the day --instead of 5 hours distributed throughout the day. I'll continue watching for and noting any unusual short term spikes at my station. Unless grouped, isolated spikes of less than 4 standard deviations/"sigmas" will be ignored, since 3 sigma counts occur several times per day --by statistical probability alone. At a station average of 16cpm, a 4 sigma spike would come in at 32cpm (by my calculation).
1/17/2014: * Reduction of this page is fairly complete. The last (1/15/2014) edition of the original verbose page is available upon request --as an email attachment.
The USS Reagan Lawsuit
--has rhetorically taken the high ground:
People of the World versus the international corporate nuclear industry.
(This class action is actually been open to about 70,000 people.)
Charles Bonner, attorney representing US sailors exposed to Fukushima radioactive releases during Operation Tomodachi [Japanese for "Friend"): We intend to put the nuclear industry on trial here, because it is the misrepresentation from the nuclear industry that nuclear energy is safe that has allowed this particular incident to occur. There's this false sense of security that these for-profit energy companies such as Tepco, created in the public. The public believes that these power plants are totally safe; in fact Tepco guaranteed the Japanese public that this particular power plant was safe. . . These nuclear power plants threaten the world, the entire planet is threatened.
Bonner: [Radiation-contaminated water] undoubtedly is going to hit the northern coast of California, Oregon, Washington, Alaska - probably by the end of this year or the beginning of next year. This kind of contamination threatens the entire planet and it has left an entire generation of young people now crippled, genetically as well as mentally, as well physically. As you well know radiation doesn't just affect the person, it causes genetic mutations so it affects the offspring of an irradiated person. So the harm and damage here to the human beings is far reaching, let alone considering the damage to the environment which is ongoing. Tepco is still releasing 300 tons of radiation contaminated water every day and it's been going on every day, as it is stated in the lawsuit, since March 11, 2011 - since the earthquake happened. This is a very serious problem. So yes, this lawsuit indicts not only Tepco, but indicts the entire nuclear industry and it requires that citizens of the world demand that these power plants actually be shut down because it is impossible to make them completely safe.
from: http://www.nuclearhotseat.com - 2/11/2014
(Alert and Transcript thanks to Energy
My Background Radiation Graphs
March-April 2011 (Note: 10 uR/hr = 35cpm with the new Geiger counter)
22nd: That peak is probably no more significant than the next, since I was only taking 2.7 minute counts (+/- 7.2cpm or +/- 2uR),
going to 10.7 minutes on the 24th (+/-3.6cpm). (I'm using twice the "standard error", based on the square root of the total count.)
May-June 2011 (Note: 10 uR/hr = 35cpm with the new Geiger counter)
August 2011 (Note: 10 uR/hr = 35cpm with the new Geiger counter)
October 2011 (Note: 10 uR/hr = 35cpm with the new Geiger counter)
December 2011 (Note: 10 uR/hr = 35cpm with the new Geiger counter)
February 2012 (Note: 10 uR/hr = 35cpm with the new Geiger counter)
April 2012 (10 uR/hr = 35cpm with the new Medcom Geiger counter)
The graphs beyond this point change scale and are primarily calibrated in (Medcom "Inspector") CPM,
sometimes with supplemental uR/hr equivalents on the right margin. (10 uR/hr = 35cpm with the new Medcom Geiger counter)
June 2012 (Note: 10 uR/hr = 35cpm with the new Geiger counter)
* That increase in variation after the 11th is due to reducing the averaging period from hours to 100 minutes. We expect +/-0.6cpm of jiggle at this level of detection and averaging of "Poisson distributed" radiation data.
23rd: Confirmed high BG with 2 extra mid-day 100min counts; 26th: +24.5/14.4cpm mid-day AFs. (Mid-day 10min BGs of 38 & 41.2cpm.)
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 outside Radex Geiger counter (SBM-20
tube) outside check twice, once open, again with 1/8" aluminum shielding:
no difference --but 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). The 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 changeits
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 patient.)
September - 2013b
October - 2013
A map of my two field stations, my fixed outdoor Geiger counter and my portable Geiger counter
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.
*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.
November - 2013
December - 2013
I keep an eye on the daily, minute-by-minute (Radiation Network) "GeigerGraph", which looks like this:
January - 2014a
January - 2014b
February - 2014
March - 2014
April - 2014
Graphing modes compared
* I trust averages and moving averages to better represent data than relying on some sort of spline "best curve fit", "exponential" or "binomial regression" graphing program routine.
The several graphs I've generated all look different --and I don't like any of them ----so I might as well stay with what I've been doing (5 manual operations), despite its tendency to miss events and produce statistical artifacts (dips and peaks).
Again: I'll keep an eye on the daily minute-by-minute graphs, so as not to miss anything egregious.
* It's my guess that food seriously contaminated with a gamma emitting nuclide (say: Cs-137) would test reasonably well with a Geiger counter, but not sufficiently well to prevent the ingestion of just a few scattered particles). Per my own experience with liquids and moist foods, I expect that measuring beta emitting contamination requires either desiccating the food item, mixing reasonably transparent food with a scintillating substance in a blender, or doing something like spectrometry on the incidental gamma radiation involved (which takes honorable equipment).
* To be quite clear: beta radiation is nearly all blocked by the moisture content and bulk of foods. When desiccated and/or thinly sliced, the available beta count goes considerably, but even serious traces of polluting radio nuclides are likely to be swamped by the natural potassium-40 content of many foods.
* Even though Geiger counters are very inefficient at detecting gamma rays (maybe 3% of what passes through), gamma emitters seem (to me) to be the only practical isotopes for an amateur with a Geiger counter to check for. That requires timed counts (at least 10 minutes) of the sample and a background reading (to be subtracted), and an a 1/8 to 1/4 (3mm to 6mm) thick aluminum plate to knock down any beta. (Alpha readings require an unbagged, mica window Geiger counter, very close (1/4") proximity and a paper shield to see if the count goes down significantly.)
* Be very careful not to contaminate your Geiger counter. Bagging it in a ZipLoc is a good idea.
* William Milberry is obviously sincere and gets across the idea the difficulty of capturing sparse radiation in his video, but he should be talking gamma from cesium-137 (actually: from the barium-137 daughter), since we don't see much of the Cs-137 beta decay with a GC --unless the contaminated sample is desiccated and spread thin.
Also: I see that the Green Party (USA) has been opposed to nuclear power plants for years --never having bought into the greenwashing of nuclear energy.
The Solar Flare Threat
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 roulette.
* Nuclear power plants, despite that they might end up literally bursting with thermal energy, are 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.
* 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.
* To be very clear about this: there has been 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 --to the boiling point, if needs be (which might take as little as 24 hours), and to then replace boiled off water by means of manually deployed fire hoses.
* 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 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 has 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 t 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 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 started now, there are 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.
Realistically, this is unlikely to happen before the dangerous 2012-2013 period has passed --unless key government and military officials can be made to think about, and publicly discuss --how dangerous it is to continue operating our nuclear power plants. Let's hope and pray that our luck holds through 2013.
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),
* I started it by default of anyone else doing this work for my part of Oregon (which I found hard to believe) --and I still appear to be the only entity, public or private, doing and posting regular monitoring along the Oregon coast. This page use to have links to other radiation monitoring networks, domestic and foriegn, but only a couple of those have been retained (and to be maintained)..
* I no longer make much of an effort to popularize my own monitoring numbers --which (to date, and thankfully) have been pretty steady and mild here in Oregon. I worry about giving people false assurances. Should my numbers go up, I'd worry about spreading false alarms. However, it would be wrong to stop keeping and posting this record.
* Greg's Lab:
Greg's Lab is everything that the EPA's RadNetand other private monitoring networks should be --but often aren't: map based "at a glance" clarity, the basis of the displayed radiation levels clearly explained, simple, concise, 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.
* 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. 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 low sensitivity instruments.
* 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 seems a good compromise choice, but it will probably be individually adjusted later 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 low sensitivity stations are identified and their responses are being equalized as to trend status.
My Choice of Radiation Units
* The earliest versions of this page reported Geiger counter ("GC") radiation measurements in terms of indicated "uR/hr" (microREMs per hour, which equals uSv/hr times 100). The use of GC "REM" units (Roentgen equivalent man") is usually invalid, since it's supposed to be about a hypothetical person's received bodily dose from a single, defined, external, isotopic source. My Geiger counters' REM calibrations were only roughly correct for a cesium-137 source, and for other types of radiation --like external alpha radiation, which doesn't even penetrate the skin, it becomes meaningless. In short: a Geiger counter counts alpha, beta, weak and strong gamma as equal *clicks*.
* The alternative of using "CPM" (counts/clicks per minute) is much more honest. Unfortunately, people are using many different GCs which report varying CPMs for the same kind and intensity of radiation. However: they've mostly been factory calibrated to yield similar uR/hr or uSv/hr values for cesium-137 --such that we can at least hope to be in the same ballpark with respect to "background" and other readings --which, like cesium-137 radiation, are largely gamma in nature.
* After buying a Medcom GC with alpha sensitivity, I began logging all of my as "counts", averaged to CPM over longer periods of time (usually: 10 to 100 minutes).
* The average outside and inside office ambient (or "background") readings here usually vary from about 8 to12 "uR/hr", which was about 36cpm with the Medcom GC, is now logged in the SBM-20 Geiger-Mueller tube equivalent of 15.1cpm, and transmitted to Radiation Network in the M4011 G-M tube equivalent of 16.2cpm. While I changed from doing inside (the house) readings to outside readings, the CPMs have been nearly the same --perhaps with more variation now.
The best policy is to use Geiger counters in the same way at the same monitoring stations: consistency.
Geiger Counter Failure
* The G-M tube (LND-7317) in my Medcom "Inspector" Geiger counter failed. The unit still had high voltage: measured at an indicated 480 volts, using a 40 meg-ohm loading probe. (The actual 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, so I can simply double what's displayed.) (And know what the DC input impedance of your meter is, so you can multiply the display voltage by whatever factor is required --should you need to know the actual voltage in a high impedance circuit.)
* Unimpressed by the lifespan of my pancake G-M tube (AND its original 90 day warranty via Medcom --60 days via Mazur's instruments, but 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 expected G-M tube life is quoted at 10^9 to 5 x 10^10 total counts --so I'm about 100 years short, but well long of Medcom's original 90 day warranty on that pancake tube.