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January 2013

Janauary 2013

 

January, 30, 2013,  Disappointment at unit 2

Remember what has happened in unit 2 on March 15, 2011? At 6:10, it was still dark, a loud explosion boom was heard coming from the condensation chamber of unit 2 and the instruments in the control room indicated a sudden loss of pressure in the unit 2 containment. The instruments also showed a major radioactive release. At day break it was discovered that the blowdown panel of unit 2 reactor building had been blown out. Since that time due to high level of radioactivity no in-depth investigtion of the unit 2 reactor building basement has been carried out. Some experts claimed a substantial amount of the molten core had been relocated to the condensation chamber.

 

Last week TEPCO contract workers drilled a hole from the top into the room with the condensation chamber. Basically, it was expected that the radioactivity inside the room would be much higher than in the upper parts of the reactor building. The first examination did not confirm these expectations. No "radioactivity high", no hydrogen, no visible damage.(Hydrogen would indicate high radiation levels in the water leading to hydrolysis). So what? Until now it remains a mystery what has happened in unit 2.

January, 24, 2013,  Dishonest excitement over peanuts in Japanese Press

Public press has an important role in a free society: Report and Inform. Ashai Shimbun hass done a great job on Fukushima so far. But lately  they have done some exaggerated reports on peanuts:

1) The maximum radioactivity fish
Most fish caught in the sea off Fukushima show low radioactiviy levels below the 100 Bq/kg limit. TEPCO has landed one single fish with 254 000 Bq/kg. This is not surprising radioactivity is not evenly distributed amoung the individual animals but a random distribution with some extremely and aso some extremeely high values.

The limits are set in such a way that a man eating food with the limit value every day will not experience health problems. Eating this special fish once in a life does not constitute any risk.

In addition the expectations of the Asahi Shimbun readers are grossly exaggerated: This fish does not glow at night and it is not going to experience any health damage from the incorporation of this dose. Two aspects are relevant: The radioactive dose is too small and fish like all other animal can sustain higher doses than human beings without health impact. Human beings are the most sensitive of all beings to the effects of ionizing radiation.

 

2) Sloppy decontamination works

Huge sums of money are spent on decontamination clean-up in the towns close to Fukushima. As the admin has pointed out, this kind of activity does not really help to reduce the radiation dose but helps to appease the public and make the people living in these areas feel better. Unfortunately, it also leads to higher radiation exposure of the workers engaged in this "clean-up" process. It is important to remember that radioactivity cannot be eliminated or converted into non-radioactive material other than by radioactive decay. So decontamination means moving the contaminated material from one place to some other place, e.g. from your real estate to some kind of storage, hopefully not to your next door neighbor. The reduction rates of 50% or so are not really relevant as radiation effects change only with orders of magnitude. A change of 50% is basically the same value.

This being understood, it is obvious it does not matter if a worker kicks some leaves and branches into a small river instead of putting them into a plastic bag. This "violaiton of decontamination rules" is nothing to be become excited about: peanuts. The same holds for the report on a worker who cleans a roof and does not collect the cleaning water but is happy that it flows away down the drain pipe into the sewage system. You can bet that the systemis full of radiocativity from the Fukushima fall-out and this additional radioactivity cannot even been measured. No reason for excitied reports! 

 

January, 21, 2013,  New requirements by Japanese Nuclear Regulatory Authority (JNRA)

The JNRA is going to add five new safety standards to the existing requirements:

1) Emergency control room
Funny but it is true, Fukushima Daichi did not have an emergency control room, which is a standard feature of most nuclear power plants. The  emergency control room is a highly protected installation with an independent I&C and power supply. It is designed to enable safe shut-down in case the control room is lost. In Fukushima, an emergency control room would not have helped since the control room was not lost.

2) Additional  cooling features and additional power supply.
The information on this issue is not very specific. Anyway, addition cooling systems and power supply cannot replace the availability of long term cooling systems (typically by mobile injection with fire trucks). The systems can help to extent the grace period but in Fukushima they would not have helped.

Basically, the problem is a matter of believe. There are so many well designed and well built safety systems in a nuclear power plant and all these systems have to fail in order to arrive in a situation as in Fukushima. So if one new additional safety systems is added, does the reader really believe that this system will be available and perform its mission? Or does the reader believe that when all things go wrong, this additional system will fail as well.

3) Central anti-seismic building

The Fukushima plant was equipped with an anti-seismic building which proved very useful as the headquater for on-site accident management operations. It did not help to prevent the accident.

4) Filtered Containment Venting

Fukushima was equipped with a Containment Venting System of a robust design. The key elements of reliability were the air operated valves and rupture disks. In the accident, the decision to vent the containment came too late and for some reasons or other, much of the air to operate the valves was lost and not available for the final venting. So the valves had to be operated by hand in a high radiation level environment.
This shows the main safety issue connected with Controlled Containment Venting: The system has to be actuated by the operator and an inadvertant actuation is a real big problem. The rupture disks were a good idea to make sure that the venting system only work with high pressure in the containment. But there is no good method to ensure it is operated only to prevent uncontrolled release due to containment failure.

Filtered Containment Venting is a MUST in an up-to-date nuclear power plant. From Fukushima it cannot be concluded that filters in the containent venting line would have helped to reduce the radioactive emission.

5) Equipment for mobile Injection on site

Equipment for mobile injection (power trucks and fire engines) must be positioned at strategic locations on site to ensure the availabilty in any circumstances.
This is a simple rule but it is hard to implement in view of the fact, that in Fukushima two of the three fire trucks on site were lost in the tsunami. If the equipment is on-site it has to be kept in protected buildings and if the equipment is close by, one has to make sure that the trucks can reach the accident area. which may not be easy in case of earthquake, land slide or floods.

This is exactly the point the admin has identified as a safety deficit in German Nuclear Power Plants (see Die Sicherheitslücke) and has annoyed many of his ex-collegues and co-experts. This was not a smart move of the admin - nuclear experts do not have many friends and acquaintancies - who in the world wants to be friends with someone who has something to do with nuclear energy? Even banker is better! So no one in the nuclear business can afford loosing anyone of his few friends.

January, 8, 2013,  Finally, TEPCO gets down to business at unit 4

At the time of the accident the complete core of unit 4 was in the SPF (spent fuel pool). After the explosion of unit 4 fifth floor the SPF swimming pool was in the open without any kind of cover or protection. In view of the high amount of radioactivity in the used fuel elements in the pool this constituted by far the highest risk on the acccident site. Any damage to these elements would immediately lead to a deastrous release of radioactivity to the envriroment. So the most urgent task is to remove the fuel elements from the pool and put them in storage casks and store them in a water pool in a safe intermediate storage for the next months and years until dry storage is feasible. Removing the fuel element is risky and cannot be done without some hermetic closure to control the radioactivity in case some damage occurs during the removal operation. Month ago TEPCO had published the plan of installing a partial cover over the unit 4 allowing to filter the atmosphere belo the cover. The figure shows the cover.

In the last month TEPCO workers have cleaned up the debris from the fifth floor to prepare for the installation of the hermetic cover. Now the first step in direction of putting up the cover was made, Concrete has been poured and the first columns have been installed. This is really good news after the long time no serious business was done on the accident site.

Only if the cover has been completed and the unit 4 SPF has been isolated from the environment, the danger of a desastrous radioactive release has been elimininated. For the non-experts: Used fuel elements are particularly dangerous since they contain a substantial amount of plutonium generated by neutron capture from the unranium and what is worse, a large amount of fission products.

 

January, 3, 2013,  Payments to neighbors of the Japanese nuclear power plants

In his presentations the admin has always pointed out that the low public acceptance of nuclear power is mainly caused by the fact that people are only willing to accept risks if they have some benefit: Just the inversion of the well-known slogan: "No risk - no fun". The heighbors of the German power plants carry the risk of a nuclear accident but do not obtain any direct benefit, the money made by nuclear power goes to the power company, the shareholders and the politicians fed by the power companies.

So it is quite interesting to see that the high local acceptance of nuclear power in Japan is based on direct payments to the neighbors. Quoting from ASAHI SHIMBUN:
In fiscal 2011, 14 prefectures paid 7.6 billion yen ($87 million) in benefits to 1.03 million households, according to figures obtained by The Asahi Shimbun through interviews and freedom-of-information requests.
In 2011, 171 households declined the benefits, an increase of 80 percent from 94 the previous year. The number ranged between 80 and 100 in preceding years. The number of households declining benefits for living near nuclear plants has nearly doubled since the Fukushima disaster, reflecting growing opposition to a system long criticized as paying off citizens to promote nuclear power.

If the numbers are correct, ASAHI SHIMBUN says that 171 of 1.03 millions (1 030 000) households have refused the payment. 171 households constitute a very small minority comparable to the risks of design basis accidents (10^-4 - 10^-6).