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October 2012 Incidents

October 2012 Incidents

2012.10.17     TEPCO holds mobile injection training at Fukushima II (Daini)

Tepco has published information on the successful training of the mobile injection at the Fukushima Daini plant. When adequate equipment and trained man power is available the mobile injection is incredibly easy and simple to implement and it is obious that something went terribly wrong in the Fukushima accident. The picture shows a worker connecting the mobile injection piping.

The admin strongly believes that adequate equipment and trained man power is the key element in mastering severe accidents. One has to keep in mind that the mobile injection is implemented and started before a substantial amout of radioactivity has been released: workers can go anywhere the plant and perform all kind of tasks necessary without radiation restriction.

2012.10.14     TEPCO report reveals interesting facts about the Fukushima NPPs

Tepco has published a handout "Fundamental Policy for the Reform of TEPCO Nuclear Power Organization, October 12, 2012
Nuclear Reform Special Task Force" ( http://www.tepco.co.jp/en/press/corp-com/release/betu12_e/images/121012e0101.pdf) in which the following information can be found:

The figure reveals two interesting facts:

1) The Fukushima NPPs were not equipped with a separate "filtered containment venting system". In the past TEPCO has always tried to keep this fact obscured. The venting system of the Fukushima NPPs which had been retrofitted in the 90th was just an additional venting line with valves which may or may not have used the operational filter system. It was not equipped with accident filters. That means that TEPCO had no real option to filter out the radioactivity in case of controlled containment venting.

2) One of the open points in the TEPCO accident report was the question why the Reactor Core Isolation Cooling System (RCIC) was not operating in unit 3. Was it switched off by the automatic control system or the operater mistake or did it experience some kind of failure? Now TEPCO proposes to install a second RCIC which is a strong indication that failure of the RCIC in unit 3 was not caused by the operator but by some kind of misfunction.

2012.10.12     Unit 1 containment inspection shows molten core is still inside the pressure vessel

TEPCO has introduced a video camera into the unit 1 dry well and has measured the radiation levels shown in the picture

The results show the highest radiation levels are close to the original position of the core and not at the bottom, where the radiation level is only half of the maximum. In the pool water the radiation level has been expected to be low due to shielding but it is too low for a substantial amount of molten core material to have prenetrated the pressure vessel (PV) wall and to have slumped down into the containment.

The findings are in evident contrast to the statements in the TEPCO accident report where based on simualtions by the MAAP code it was stated that the core has relocated to the bottom of the PV and a substantial part of the molten material has located further to the bottom of the dry well via holes in the PV.

The figure shows the MAAP simaultions from the TEPCO accident report.

Basically, this simulation is nonsense and the statements are wrong. From the very beginning, the admin has claimed that only part of the core has been relocated to the lower  head of the PV and has found a coolable geometrical configuration in the forest of pipes in the lower head. Only a small amount of the molten material has left the PV by leackage through cracks etc. Clearly it has be expected that after the heat attack the lower head penetrations are no longer leak tight.

The admin has always pointed out that the standard severe accidents codes MAAP and MELCOR are nonsense codes since they do not simulate the physical processes oberseved in the severe accidents at TMI and Chernobyl and the findings from a large number of severe accident experiments. Nevertheless the US NRS and other licensing authorities have approved the use of these codes in licensing and the permit of operation of many nuclear power stations is based on simulations with these codes.

In Germany also, the Cologne based TSO GRS is using the code MELCOR for licensing applications. It cannot be ruled out that based on inappropriate MELCOR results inadequate measures will be taken by the Germn authorities in case of a severe accident.

The admin would like to emphasize that severe accidents can be succesfully mitigated supposed the accidents measures are planned and organized by real experts which can make use of adequate equipment and trained man power. Fukushima demonstrates that experts taking their knowledge from MAAP and MELCOR simulation and unable to make adequate use of available equipment and man power will worsen the situation.

The pictures taken by the video camera show the typical impact of hot steam ( > 1000°C) on steel. The steel is still of silver color but the surface looks highly corroded.