Archive for the ‘Protective Gear’ Category

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.

Advertisements

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…)

I have recommended for us as citizens to monitor radioactivity also in our relatively spared areas, especially near incinerators and mountain spots where wild garbage dumps spoil forests (Cf. Mid-October Status & Editorial in SurvivalJapan). It turns out that the government seems to be candid about its intention to pollute forests with radioactive waste as reported by Yomiuri Shimbun, a mainstream news media which article is reproduced hereafter. The same newspaper also mentions, in a different article, the risk of internal contamination by radioactive pollen from cedars (cryptomeria or in Japanese “sugi”). Many people are allergic to these during pollination – the risk here is much more serious. When yellow dust was found in the rain in the no man’s land, I surmised it was sulfur (Cf. Typhoon Roke Aftermath In Fukushima in SurvivalJapan) created by nuclear reaction on-going at Fukushima while some other people proposed uranium, plutonium compounds or simply pollen from China. If pollen it was, one can imagine how far cedar pollen could fly within Japan. Fortunately, dominant winds usually spare our areas from the no man’s land fallout – but facial masks remain highly recommended during pollination even outside the no man’s land (Cf. Of Gloves And Masks in SurvivalJapan). Although now symbolic in Japan, sugi was introduced after WWII to replace forests burnt by American bombings and as an effort to promote wood industry. The article about sugi pollen is also reproduced below, however there is no “harmless” level, contrary to what Satoshi Yoshida, an expert on radiation ecology and a senior researcher at the Research Center for Radiation Protection of the National Institute of Radiological Sciences (again some Orwellian Newspeak), states in the article. Radioactive particles which gets into the human body are harmful in minute quantities which do not compare to external exposure effects of the same dose. In some regions within the no man’s land, local people have decided to fall whole forests with the aim to protect forest workers from cesium supposedly concentrated in tree leaves and burn the wood. However it may be true that these forests are dangerous places, the solution offered by human beings is as usual worse than the original problem. Radioactive forests will remain a hot topic.

(more…)

Paper masks are popular with Japanese and were recommended as a basic protective gear in the wake of 3-11. Foreign visitors usually mistake their purpose thanks to sensational TV programs about a supposedly higher pollution in Tokyo. Paper masks fill in fact multiple purposes, from allergy in-filter, flu virus out-filter, mouth humidifier, sexual harassment dissuasion, etc. Wearing a paper mask is among one of the last Japanese customs that foreigners adopt and I confess that I’m one of those who find it quite ridiculous to wear, especially for an expat. In fact, back in March, my family bought a pack and we did not use it. Another Japanese cultural idiosyncrasy that TV programs love to put on stage is the almost pathological fear of bacterial contamination, with some people wearing protective gloves and disinfectant spray bottles everywhere. Actually, I doubt most Japanese like shaking hands as westerners do. So it is highly surprising that a majority of Japanese seem unconcerned with radioactivity when they loath germs. This blog is not about cultural differences so I’ll make it short: wearing paper masks and latex gloves is not so ridiculous in my opinion anymore, especially if you live in the no man’s land and cannot leave (i.e. including Greater Tokyo, cf. Japan Livability Map September 2011 in SurvivalJapan), but also in the monitored land when radiation fall-out warnings are issued. Inhaling radioactive particles is a health hazard. Washing hands and even gargling / spitting when returning home is often seen at Japanese homes and I recommend it too, in order to avoid ingestion of contaminated dust. Hydrogen gas emission in Fukushima, radioiodine detection and yellow powdered-rain reports all point out to a new criticality in Fukushima without any reactor confinement and a lost corium this time so these basic protective measures are relevant (Cf. Fukushima in Recriticality and Typhoon Roke Aftermath In Fukushima in SurvivalJapan).