Posts Tagged ‘Geiger counter’

This post is an update of Geiger Counter Case Study: Inspector Alert published on SurvivalJapan in which some questions remained open, mainly about the relatively high values (although still in the safe range) which I measured with the system kindly lent to me by Safecast and from whom I received some further advice.

The Safecast bGeigie system is designed to measure mainly gamma rays (high energy protons, akin to X-rays) and hence is used at least one meter above ground in their radiation maps. Since I live in the monitored land, several hundred miles away from Fukushima, gamma radiation is low and not really a concern. Therefore I had measured instead beta radiation (high energy electrons or positrons which are emitted back from the ground after radioactive fall-out) at about one foot above ground. For convenience, I monitored the level of radiation with the Safecast display which communicates by radio with the Inspector Alert safely cast in its lunchbox style (in Japanese “bento”) box, along with the GPS and SD memory card to geo-locate and store results. The Safecast team advised against this methodology for beta radiation pick-up and advised me to use the Inspector Alert alone for that matter – which I did.

I read the user manual to set the Inspector Alert display in uSv/h as opposed to CPM (count per minute) as I am more familiar with this unit and it is more relevant for body effects. The user manual explains that the factor used by the device to convert CPM into uSv/h is based on Cesium-137, the radionuclide used for its calibration, so the uSv/hr display is less accurate for other nuclides (such as Cesium-134, Strontium-90, Iodine-131 and of course Uranium and Plutonium…). This is why Safecast uses the CPM raw data instead.

The first measure that I made was inside my home and the display changed widely even in a single place. A Geiger counter is not like a weighing scale: it does not give a result at once nor does it give a stable result. Therefore when a value is broadcast either by citizens or a governmental organization, it should be taken with a grain of salt. For instance, I could measure 0.120 uSv/h and any value between 0.090 and 0.150 uSv/h, that is about 25% more or less than the central value. Sometimes, some wilder values would come up: how do we interpret these?

Radiation is a random phenomenon which occurs naturally, so when a particle hits the Geiger counter sensor plate, it is registered and changes the overall measure value. The Inspector Alert averages measures over 30 seconds in order to get a more statistically relevant measure. Even then, the result is only displayed every 3 seconds so if one is moving, there is a delay between the measure and the display. Then there is the 15% accuracy which is probably an average: it means that some wild values (standard deviation) can occur from time to time. Other factors which can affect the results are solar flares (there was just a sunstorm by the way) and, probably, thermal drift if the device electronics is not properly compensated when temperature changes (any kind of electronics sensor is subject to this phenomenon). The bottom line is that measures could be twice as high depending on temperature, solar activity, randomness of natural radioactivity, types of radionuclides (including artificial ones from nuclear plants) and radiation (here it is a synthetic result of alpha, beta, gamma and X-rays), accuracy, resolution, etc.

Indeed, I could still measure inside and outside values from 0.055 to 0.225 uSv/h and even up to 0.355 uSv/h when spot on granite blocks which are naturally radioactive. These new measures were consistent with the range I had already measured with the full Safecast system. I could also check that the outer casing of Safecast suitcase and bento box did not emit stronger radiation than the room so the Geiger counter is likely not contaminated (and there should not be any calibration issue either according to the user manual).

I still could not double-check with another type of Geiger counter yet but these new results convinced me that they are normal. The maximum international value (except in post-Fukushima Japan) accepted is 1 mSv/year, which equates to 0.114 uSv/h. Given a 15% accuracy, it means that the Inspector Alert should read between 0.097 and 0.131 uSv/h which is indeed what it does most of the time (so we can dismiss occasional lower and higher results as products of standard deviation).

A final word of advice which I received from Safecast and which is also documented in the user manual is to use the timed count function of the Inspector Alert over at least 10 minutes to further smooth out results. There should be about 15% difference maximum between two such timed counts.

I hope that this update helps you to get a better idea about the capabilities and limitations of Geiger counters in general and specifically of the Inspector Alert – and of the analytical mindset and of the basic radiation knowledge necessary to properly use them. In any case, purchasing a Geiger counter to try and measure radioactivity in food does not make any sense (unless the food is irradiated to such a level that just staring at it is dangerous) and that monitoring the food trace is a safer and more reliable procedure. Thankfully, this is getting easier.


Choosing an appropriate Geiger counter to monitor environmental radiation levels in Japan can be confusing due to the large choice of devices, including handheld electronic dosimeters that offers similar capabilities. Counters differ by the type of radiation that they can detect (alpha, beta, gamma, X-rays and sometimes even neutrons), their accuracy, price, availability, etc. Rather than presenting an extensive comparison between all devices, this post introduces a specific Geiger counter used by Safecast to map radiation mainly in the no man’s land: the Inspector Alert distributed by International Medcom (SurvivalJapan has no interest in promoting this company, this review is purely on a volunteer basis and I decline all responsibilities as to opinions shared here). It is also the device used by Pr. Frank Daulton, Ph.D., Applied Linguistics, Ryukoku Univ., Kyoto, Japan when he detected 0.377 uSv/h close to ground around his home in Otsu-City, Shiga Prefecture, not far from Kyoto and 311 miles (500 km) from Fukushima (his picture reproduced here) as reported on Earthfiles website. (more…)

My risk analysis for Japan remains unchanged for October, please refer to Japan Livability Map September 2011 in SurvivalJapan for my definitions of  “no man’s land”, “monitored land” and “nuclear-free land”. I only report on events which affect the latter two – and there has been no news lately. After a summary of the current status to the best of our knowledge, I take the opportunity of the news black hole to offer a more editorial piece with further recommendations for those who choose to stay in Japan, out of the no man’s land.


The reason for the dysfunctional steam condenser which prompted the emergency shutdown of a reactor at the Genkai nuclear plant in Kyushu island ten days ago has still not been disclosed. Genkai encountered issues in the past as most Japanese nuclear plants and is the object of much political controversy and scandal so the reason may never be known by the general public. Officially no radiation was leaked and citizen seem to not make any measurements anymore in Kyushu. The monitored land on the whole is not properly monitored.

The government announced that they will handle the spread and disposal of nuclear waste themselves without disclosing any detail, which is open to any interpretation.

The free circulation of contaminated food is now in full gear, with for instance Fukushima rice declared safe and available in supermarkets all over the country.

Mainstream media now occasionally publish information that used to be available only on blogs and alternative media, the latter focus on the no man’s land.

Editorial and Further Recommendations

1. Improved environment radiation monitoring

The general lack of information and action is a temporary psychological relief but it is also dangerous. Besides previous recommendations about food made in SurvivalJapan (cf. tag “food”), we should monitor radiation on following sites in every prefecture of the monitored land and nuclear-free land:

  • near each incineration plants
  • on sites in the mountains where citizens and businesses alike illegally dump their garbage (old TV sets, stolen bikes, etc. – where all the great Japanese electronics companies products usually end up their life)
  • near sites where construction-related companies and so-called “gumi” (associations) park their trucks in the mountains, usually hidden behind corrugated sheet metal walls like entrenched forts, with or without dogs (careful with these people)
  • at each garbage disposal sites
  • near cement companies (careful again with construction-related workers…)
  • near companies that specialize in construction material recycling (same remark as construction sector)

Lakes and ponds were also always favored to dispose of hazardous material (Lake Geneva in Switzerland is filled with all kinds of weapons, nerve agents, etc., the Baltic Sea is littered with Russian nuclear waste and Biwako lake in Japan is heavily polluted too as a few examples). Streams should also be monitored. As it is difficult to measure radiation in liquids, fresh water fish, shells and algae like aonori should be monitored as to give an indication.

2. Example of unsuspected and widespread food contamination : irradiated seaweed extracts

Besides this constant environmental monitoring which is completely lacking in these regions, radioactivity ingestion risks exists in forms that are not well-known to the general public and which are difficult to avoid (in order to grasp the extent of the issue, read for instance Exa-Becquerel Now In Pacific Ocean ? on SurvivalJapan and related posts). For example, seaweed yields :

  • alginic acid (slimming aids, appetite suppressants, etc.),
  • agar (many Western and Asian desserts alike including delicious Japanese yokan – but also used in dentistry, modelling clay for kids, etc.),
  • carrageenan (desserts, ice cream, cream, milkshakes, sweetened condensed milks, sauces, beer, pâtés and processed meats like ham, etc. fatty foods without fat, toothpaste, fruit gushers, as a excipient in pills / tablets, in soy milk, diet sodas, but also fire fighting foam, shampoo and cosmetic creams, air freshener gels, fabric marbling, shoe polish, pet food, personal lubricants and sexual lubricants, etc.).

Ocean radiation spill has further increased the risk of eating processed food, but also of using cosmetics, etc.

Here is a link to hydrocolloids producers worldwide, among which a few Japanese companies of course, for example :

A positive side of the Japanese nuclear crisis in Japan is that it may have raised the awareness of the multiple dangers of the nuclear industry of course, but also of industrial food, etc.


Although it is of course impossible to avoid every risk, we should remain on our guard and probably purchase and use a Geiger counter anywhere in the world now, as some industrial countries soils are as irradiated as in Japan “monitored land” from wild dumps of uranium extraction waste, nuclear bomb testings, nuclear plant spills and wild waste dumps – including from medical and research facilities, etc. Leaving Japan is not necessarily the solution as it might be worse in your home country without you never having realized it for lack of any large-scale disaster happening yet. Education, positive action and life choices, citizen monitoring are part of the solution to a multi-dimensional problem which is bigger than just a nuclear issue.