Riken Open Campus, April 20 2013

Logo of the event

Also this year, the RIKEN open campus will be held Saturday, April 20, 2013 - from 9:00 to 16:00 ( here the link in Japanese). This event, which involves all the laboratories of the institute,wants to show the researches carried out in the fields of physics, biology, medicine, chemistry .... There are both  lectures and experiments be carried out with the participants.

As last year, our laboratory will be involved with a number of lectures on space (in Japanese and English), with 3D video, the use of Fresnel lenses and the model of JEM-EUSO, for the study of cosmic rays from the International Space Station.

Mock-up model of the space telescope JEM-EUSO

Posters on environemntal radiation 

We qill also measure the radiation environment and compare with that of objects of common use.

The RIKEN is located in Wako, Saitama Prefecture, about fifteen minutes from Ikebukuro.

Those who can not participate in the 20, are of course welcome anytime!

Fukushima two years later: a scientific report (2) - Gamma spectroscopy

This post appeared in Italian on wired.it. This is the secon part of a (poor) English translation. First part is here

Not only  the food is continuously monitored: also construction wood from the forests of the region is controlled. In this case too the safety limits are much more severe than that of  the volcanic pozzolans often used in the construction of houses and Italian schools.

Monitoring of radiation in a supermarket 10 km
from the coast of Fukushima

Comparison between radiation Italy (Rome) and Japan (Tokyo and Saitama). It is possible to see how radioactive background is higher in Rome than Tokyo. In  Rome the radiation environment is dominated by the peaks of Radon 222. The arrow indicates  where   the Cesium 137 (660 keV) peak should be located.

An estimation of  the amount of Cesium in food, wood or forage requires a spectrometer capable of determining the energy of each gamma ray. Since each isotope emits gamma rays of specific energies, it is possible to determine the quantities of the various isotopes present.

Among the recent devices there is a portable detector consisting of a crystal to stop the gamma  (CsI) and a Silicon Photomultiplier (MMPC or as they call them) to detect the energy measuring the light emitted in the crystal. The simplicity of this type of tools is that they do not require high voltages, are   small as a pack of cigarettes and is used as a USB device. The cost, however, is about 20 times that of a Geiger counter.

A spectrometer can  count, for each decay, the energy of the rays that strike it. In about an hour and then it is possible to obtain a spectrum which describes the type and amount of environmental radiation. To improve the statistics and better highlight the peaks is, however, advisable to wait a while longer. The picture above shows the value measured at Rome in an apartment on the fourth floor: it is 0.25microSv/hour  (with peaks of 0.35).

In the figure above it is possible to see how the spectrum in Rome (and in much of Italy) is dominated by radon 222, a noble gas source to the high amount of environmental radiation. Usually the radon comes from the soil and tuff, but in this case, since it is an apartment on the fourth floor, is more likely to come from pozzolana used in the construction materials . In figure are compared the spectra taken in Rome with those  acquired in Japan. The value of Rome is  higher (0.25microSv / h), followed by the basement workshops of Tor Vergata (0.10 microSv / h, where, however, there is much radon), Kokubunji (0.05), and the fourth floor in Wako (0035 microSv / h). Note the almost total absence of radon in Japan. It is worth mentioning that the environmental radiation at the onsen baths is higher due to the volcanic nature of the sulphurous waters.

Monitoring radiation in wood to be used for construction

In the samples collected in the hot spots, Cesium-137 is present in large quantities: this isotope decays into an excited state of barium (emitting an electron and an antineutrino). The de-excitation of barium emits a signal characteristic of this element: a gamma ray energy of 660 keV. The process is similar to that of fluorescence, only that in this case atomic electrons are excited. The return to the ground state emits light (between 2 and 3 eV), e.g. electromagnetic radiation. The energy levels in the nucleus are thousands of times more intense and therefore the electromagnetic radiation emitted has an frequency and associated energy thousands of times greater.

To the left of the peak  there is the so-called 'Compton edge', produced by gamma rays hitting an atomic electron of the Cesium crystal in the detector and accelerating it with a slightly lower energy (depending on the angle with which it is emitted). The spectroscopic analysis of a particularly contaminated sample, taken on  the side of a mountain road between the city of Fukushima and the coast. This sample shows the presence of the isotope cesium-134, which decays into barium with several peaks at 600, 790, 1400 and 1600 keV (the latter is out of range of the detector).

The cesium-134 has a decay time of two years, therefore the presence of this isotope represents the "signature" of the origin of the  Fukushima power plant. In other cases, the absence of cesium-134 was used to show how well mushrooms that had radioactivity above the threshold of 100 Bq / kg were not contaminated by the panel, but presumably from nuclear tests in the ‘60s.

Gamma spectrum from a pure Cs 137 source

Spectrum of a sample of soil containing cesium 134 and 137 of Fukushima region

The measures in the region of Fukushima were extremely interesting, but equally important on a personal level was the contact with the local population. Far from being disheartened, the people in Tohokoku did not give up and have rebuilt many of the structures destroyed by the tsunami. Although the plant has not resulted in deaths due to radiation (morbidly sought by national and international journalists), many deaths are due to poor management of the emergency in the first frantic days after the earthquake. Others are due to suicides after resettlement. The inhabitants of the regions closer to the center have been forcefully moved away and are now rebuilding the social fabric elsewhere, so sometimes it is difficult to return to their town of origin, even if it were decontaminated. The most relevant problem is economic: the damage to the primary sector and tourism are visible to all and will require years to get back to normal.

2. end  First part is here

Radon from Rome, Cesium from Fukushima: environmental radiation and gamma spectroscopy

The detector C12137, at the bottom right in the photo. 
(iaIt connects via USB to the computer for the acquisition

(Italian version here)

The Fukushima accident released large quantities of radioactive materials in the environment, especially iodine and cesium. Iodine decayed in  a few weeks, leaving  cesium-134 and 137 as potential contaminants of the environment and food. A Geiger counter is sufficient to measure the amount of environmental radiation. This detector, however, counts indistinctly each gamma ray that hits it, regardless of the energy of the particles.To estimate the amount of cesium in the environment (and especially in food) is necessary a spectrometer, capable of determining the energy of gamma rays. Since each isotope emits gamma rays of specific energies, from the analysis of the peaks, it is possible to determine the amount  of the various isotopes present.

Recently, Hamamatsu photonics, a company specializing in the development of detectors for space physics, particle and medical devices, has released a portable detector ( C12137) with a crystal to stop the gammas (CsI) and a Silicon Photmultiplier (or a MMPC as they call them) to reveal the energy by measuring the emitted light . The simplicity of this relatively new detector, invented by a Russian scientist, is that it does not requires high voltages, is as small as a pack of cigarettes and you can connect to any USB port. As all  spectrometers,  however, the cost is about 20 times that of a Geiger counter.

The  picture above   shown the radiation in Rome, in a fourth (fifth by Japanese counting) floor apartment: it is 0.25microSv/hour (with peaks of 0.35).
As mentioned, the advantage of the gamma spectrometer, however, is to count, for each decay, the energy of the rays that hit him. In about an hour and then it is possible to obtain a spectrum which describes the type and amount of ambient radiation. To improve the statistics and better highlight the peaks is, however, advisable to wait a while longer. In the figure below you can see how the spectrum in Rome (and in much of Italy) is dominated by radon 222, a noble gas source to the high amount of environmental radiation. Usually the radon comes from the subsoil and from tuff, but in this case, being a flat on the fourth floor, is more likely to come from pozzolanas of construction materials. 

Spectrum of the radiation environment in a home 
of Rome. The peaks of radon 222 are clearly visible. 
Spectrum of an hour equivalent averaged over 7 hours

The figure below compares two spectra  taken in Rome with two acquired in Japan. The value of Rome is the higher (0.25microSv /h), followed by the basement laboratories of Tor Vergata University in Rome(0.10 microSv / h, where, however, there is not much radon), Kokubunji (0.05), and the fourth floor in Wako (0035 microSv / h).Note the almost total absence of radon in Japan (in the onsen, however, may be  higher). The peak at 1460 keV is probably due to Potassium 40 (aka Calium - the same present  in bananas).

Radiation comparison between Italy and Japan. 
The radioactive background is higher in Rome than in Tokyo

The arrow marks the 660 keV regiorn where   the peak of cesium 137 should be located: as is evident there are no measurable quantities of this species above the bottom of the radiation environment. 

Cesium can be detected detected in various hotspots in the region of Fukushima and in soil samples: this topic will be discussed in a next post.

(1) continues

Previous post on this topic in english:

Let's measure Radiation: the radioactivity of everyday objects　放射線を測って見よう (also in Japanese)

Survivalism and the real radiation contamination in Japan

Nuclear Plants, Radiation and Food in Japan - updates

Nuclear Plants, Radiation and Food in Japan - updates

Currently in English, Italian translation will follow. 

Power Production

No electricity is generated from nuclear plants in Japan. All but one reactors are down, officially for maintenance. Whether they will be reactivated is still debated. Oki reactors are now less likely to be put back on line, pending the complaints by local government and some still unclear safety issues.

As of now, both Kanto and Kansai (that are on different grids) are consuming about 80% of the full power production. If this figures are correct, there is the clear possibility to have scheduled black-outs this summer, especially if it will be warmer than last year. The situation might be more critical for Kansai  which had a larger nuclear-produced energy fraction and that last summer had still the nuclear power plants online. 

Environmental radiation in case of no decontamination
in 10 and 20 years from now

Environmental radiation

Outside the exclusion zone, Japan has  an average  lower environmental radiation than Italy.  

Recent simulations show that - in absence of any decontamination - the Fukushima expelled Cesium will leave the exclusion zone unsafe for more than 10 years. This is hardly surprising given the 30 years half-life of Cesium 137. Decontamination strategies are under study, either by removing the ground, by letting radiation penetrate deepen in the soil in case of hot spots, or by physically separating the radioactive material from the rest. A truck from Toshiba has been set up to demonstrate the principle. The first method seems more expensive but is much more reasonable,  provided that all the material is stored around the site of the now destroyed power plant. The truck option would be the cleanest one, but cost of the procedure and the possibility of large scale production are not clear. 

Is there radiation in food in Japan?

A vegetable wholesaler has been found relabeling the origin of Fukushima cucumbers in other prefectures. He was just scolded, no fine or charges. The cucumbers were not dangerous in themselves, since it still is below the new limit of 100Bq/kg for Cesium, but the lack of legislation is worrying. This new lower limit (previously was 500Bq/kg) is causing a lot of trouble to fruit and vegetable companies, since the value is extremely low too meet. .  All food (and our body) contains radioactive material: as a reference it is worth remembering that bananas  have 125 Bq/kg of  Potassium 40 (even though it is expelled faster from the huma. body).

Left and right: radiation data of Coop food products

All are below the new limit of 100Bq/Kg (mentioned in the top page). The food with highest radiation content are Shiitake mushrooms. Note that Germanium detectors have an higher resolution than those of NaI  and can distinguish between the isotopes of Cs134 and Cs137. 

The total amount of radiation in Ge-measured products is the sum of the two isotopes. Cs134 has a shorter half-life, two years, compared to the 30years of Cesium 137, so it is expected that Cs134 content will be negligible by next year.

Rate of disappearance of Cesium from human body
from here

 

Survivalism and the real radiation contamination in Japan

Japan is catching up with the tradition of bad newspaper articles, depicting an apocalyptic,  post-nuclear vision of the life in the  island. If the term "post-nuclear" might apply to a country that has all but one nuclear reactors off the power production grid, many of the personal views expressed in one recent article were especially puzzling. This is an excerpt of the letter I sent to the editors of the daily newspaper. I hope it might be a useful recap of the situation in Japan. The letter did not contain the links (that unfortunately are in italian, but google translate does a decent job).

Dear Sirs,

in reading your article [...] I cannot help but be puzzled by the content and implications.  

[...] in the article there is no mention of real measurements of environmental or food contamination,  only hearsay and very general and unhelpful comments that would probably better find its place in a personal blog rather than on a daily newspaper that is widely read by the foreign community in Japan and by foreigners that are interested on Japan.

The risk in reading the personal comments and life-style expressed in the article is that all foreigners are mindlessly scared about radiation and/or  that the situation of the radiation in Japan after the Fukushima accident is out of control.

As you might be aware, the foreign press in general, and in particular the Italian one, has been extremely inaccurate and unprofessional in dealing with the accident, its effects and the risks of radiation in Japan and abroad.   This kind of old-maid’s tale articles can be misinterpreted or voluntarily misused by foreign press to depict an incorrect situation in Japan and on the people -  foreigners or not -  living in this country.

Some points that are worth remembering,  at least  to ease the worries of the author:

1.       Radiation in Tokyo area is roughly one third than in Rome (0.1 microSv/h vs 0.3microSv/h and 0.4 at the University of Rome Tor Vergata, near volcanic rocks – personally measured)

2.       Radiation on airplanes is 20 times higher than on the ground. Even though we spend less time on an airplane this is relevant for airline crews.

3.       Radiation in space is 1000 times higher than on ground. No ill effect have been found on astronauts who lived  for months on the International Space Station.

4.       Bananas have 125 Bq/kg of radioactive potassium 40 (higher than the Cesium safety levels of 100 Bq/kg).  It is possible that the process of eliminating cesium and potassium is different, though. (edit May 2012, here  the time of permanence of Cesium in human body).

5.       The amount of food consumed comes into play in calculating the radiation exposure.  Five grams of “radioactive” tea, even assuming  the old limit of 500Bq/kg amount to 0.5 Bq.

6.       A number of independent measurements point to no risk in the food, my colleagues in Italy have tested personally the amount of cesium in rice of Miyagi-ken and found 0.1 Bq/kg, less than 1per mil of what found in bananas.

7.        Chernobyl and Fukushima are two completely different accidents: in the former case the reactor core was exposed and radioactivity was dispersed in the air. This did not happen in Fukushima plant, where most of the radiation went in the water.

8.       Cigarettes contain polonium 210 (the same isotope used to kill the Russian dissident Litvinienko), present in the tobacco due to fertilizers. A two pack per day smoker is exposed to 250 mSv/year in the bronchial region, compared to about 1-3mSv/year of non-exposed persons.  In Europe, every year 5000 people die because of radiation induced cancers in the lungs (this is about 15% of all cancers in lungs).

9.       The highest risk of radiation in Europe is due to radon gas seeping through the underground cracks. This radioactive , but chemically inert gas, can accumulate in places where air is not changed often. 

At this point it should be mentioned that I have been living with two small children and a Japanese wife since before the fateful earthquake and accident at the power plant, and that, even though we took precautions and monitor closely the situation, we do not live in the state of fear that might be mistaken to be typical of foreigners in Japan. The same can be said of my colleagues, Japanese and foreigners  at RIKEN  and the many foreigners living in Japan, equally puzzled by the tone of the article and the discrepancy with their daily lives and behavior.  

This is not to attempt to deny the tragic events of the accident and its devastating implications, but to put them in the correct context and to analyze the situation individually and independently with real measurements.  This is the effort that has to be painstakingly pursued by everyone.  

My main research field is space physics with satellites and radiation environment studies on astronauts, but I am also struggling – for what is possible – to inform on the real situation and correct the excesses and apocalyptic visions that have been evoked in my country since the Fukushima accident.  [...]  

I sincerely hope that – in line with your excellent editorial policy and quality of the articles  that have kept us informed of the situation in Fukushima - of you might publish in the future a “review” article with more circumstantiated numbers, values and  reading, but also on the life in daily Japan,  so that the general public can be made aware of the current situation. If possible, please print the main points of this letter on your newspaper.

yours sincerelly....

-------------
It might be worth adding that very cheap and relatively precise geiger counters are available from many shops. Radiation is one of the most easily measurable quantities, also by non-specialists. If you have doubts, it is very easy to make your own measurements. 

TEPCO Electricity production in Japan before and after the Tohoku Earthquake 1) general analysis

Note: this blog is usually in italian: I've been asked to write this post in english to make it more widely available. The italian version is below. 

In the frenetic months after the  Tōhoku earthquake, the struggle to keep Fukushima power plant under control was mirrored by a quieter, but equally dramatic effort to contain Japan electricity consumption within limits.

Drop in power production immediately
after the  Tōhoku  Earthquake.
Calo di produzione di energia elettrica immediatamente 
dopo il terremoto.

All nuclear power plants  went in safe mode at the beginning of the seismic activity, around 14:46. The drop in electricity  production is about 30%, from 38GW to 27GW. It took a few days for power production to grow back to 35GW. Even though rolling blackouts started officially only on March 14th, the lower power consumption during both day and night is clearly visible immediately after the earthquake.

Comparison of power  production in 2010 and 2011
note the sharp drop after March 11 and the effect of rolling
blackouts and power saving.
Confronto di produzione di energia elettrica nel 2010 e 2011 
notare il forte calo dopo il 11 marzo e l'effetto del  risparmio energetico e dei
black-out programmati.

As fossil fuel production was increased to compensate for the shut down of many nuclear power plants all over Japan, both public and private sector had to reduce energy consumption by at least 15%. Every day TEPCO produced real-time graphs which showed the maximum available power vs the power consumption (here, in italian). In autumn TEPCO officials admitted that there had been a "mistake" in these estimates and that actual power production capability might have been higher. With historical data now available from the TEPCO website we can estimate the effect of the Tōhoku earthquake from the power production standpoint. 

Power saving procedures and a cooler Summer (2010: 24-37oC, average 27-33 oC, 2011: 19-35oC, average 25-31 oC) kept the power usage within acceptable limits until the end of the 2011, where the difference  with the previous year was not so big. In 2012 the lower power consumption is still evident but not so significant. However a hot summer might require more  energy than what can be produced with conventional fuels. Almost all nuclear reactors have been taken off the production line, although 2.3GW Oi power plant  (discussed here, in italian) will probably be reopened next week to prepare for  next Summer.  

Comparison of the power production from 2008 to 2012:
nota how the pre-earthquake electricity  consumption is roughly the
same in all years and that the power production levels
 in the first  months of 2012 are very close to the pre-earthquake time.
Confronto tra la produzione di energia elettrica 2008-2012: 
Notare  come i consumi 2008-2010 siano più o meno 
gli stessi e come  i consumi dei primi mesi del 2012 
siano quasi pari ai livelli pre-terremoto

Versione in italiano

Nei mesi frenetici dopo il terremoto del  Tōhoku , la lotta per mantenere la centrale elettrica di Fukushima sotto controllo è stata rispecchiata da uno sforzo più nascosto, ma ugualmente drammatico per contenere il consumo di elettricità del Giappone entro i limiti.
Tutte le centrali nucleari sono andate in sicurezza  all'inizio dell'attività sismica, intorno alle  14:46. Il calo della produzione di energia elettrica è circa il 30%, da 38GW ai 27GW. Ci sono voluti alcuni giorni perchè la produzione tornasse a 35GW. Anche se i blackout programmati sono iniziati ufficialmente solo il 14 marzo, il minor consumo energetico durante il giorno e di notte è chiaramente visibile subito dopo il terremoto.

Anche se la produzione di combustibili fossili è stata aumentata per compensare la chiusura di molte centrali nucleari in tutto il Giappone, sia il settore pubblico che quello e privato hanno dovuto ridurre il consumo energetico di almeno il 15%. Ogni giorno la TEPCO produceva in tempo reale grafici che mostravano la massima potenza disponibile rispetto al consumo di energia. In autunno i funzionari della compagnia hanno ammesso che c'era stato un "errore" in queste stime e quella attuale capacità di produzione di energia elettrica sarebbe stata più alta. Con i dati storici sono ora disponibili dal sito web di TEPCO possiamo stimare l'effetto del terremoto del Tōhoku dal punto di vista della produzione di energia elettrica.

Grazie alle procedure di risparmio energetico ed un'estate non troppo calda (2010: 24-37 ° C, media 27-33 o C, 2 011: 19-35 ° C, media 25-31 o C) è stato possibile mantenere il consumo energetico entro limiti accettabili sino alla fine del 2011, dove la differenza con l'anno precedente non era così grande. Nel 2012 il minor consumo energetico è ancora evidente, ma non molto significativo. Tuttavia, una calda estate 2012 potrebbe richiedere più energia di quello che può essere prodotta con combustibili convenzionali. Come già accennato qui, quasi tutti i reattori nucleari non producono più energia  anche se la centrale elettrica da 2.3GW di Oi  sarà probabilmente riaperta la prossima settimana per preparare la prossima estate.