Water crisis; “Now and in the Future” evaluated by the SVCF Watcher Group
The basic role of water is to cool down the damaged reactor core.
An approximate amount of 350 tons of cooling water is needed daily to cool down the damaged reactor core in the reactors 1 to 3. Water is sprayed from the reactor walls to cool the damaged reactor core and is concurrently contaminated with radioactive materials from the reactors.
In order not to spread contamination outside, TEPCO keeps the level of water in the reactor building below that of the groundwater, with the result that groundwater enters the building through cracks and crevices. By this countermeasure, 400 tons of groundwater flows daily in the 350 tons of original contaminated water. Consequently, the influent underground water mixes together with the contaminated water, amounting to 750 tons in total per day.
Curtailing the cooling loop is crucial.
The 350 tons of cooling water goes through pumps, pipes, and tanks after the elimination process of the most terrible contaminative material, cesium, and salt. The cooling loop extends some 4 kilometers and still remains to some extent in a makeshift structure.
As for curtailing the cooling loop, the use of nearby tanks is under consideration, which reduces the length of loop down to 3 kilometers. Installation of an individual cooling loop completely within each reactor and turbine building is also under consideration. Although the two measures would be effective, the environmental radiation is too high to make them realistic.
Problem of storage tanks
After the elimination of cesium, the wastewater of 400 tons per day is stored in storage tanks without desalination. These tanks; 0.3 million tons in 900 tanks occupy the premises. Most of them are of a prefabricated structure and at risk for leaking water at various bolt-and- nut connecting parts by aging. In this regards, connection by welding is much preferable. However, on-site welding exposes workers to heavy radiation. It is estimated that the required capacity of the tanks will be 0.8 million tons in 2016. Seven underground water storage pits have been built to cope with the enormous volume. However, one of them revealed leaks in April (cause unknown) and then TEPCO stopped the use and transferred salty water to ground tanks.
If the groundwater level is too high in reference to that of wastewater in the reactor buildings, the influx of groundwater into the reactor buildings will be excessive. To control the groundwater level in relation to that of wastewater in the reactor buildings, TEPCO has dug 12 wells to pump out groundwater with an intention to dump the pumped out water into the sea. However, the public outcry over the discharging the water into the sea was so loud that TEPCO gives up the idea.
A committee created by the government to oversee the cleanup and decommission has, after three rounds of deliberations, adopted a proposal for an implementation of a frozen underground wall and proceeds to review the plausibility of the frozen underground wall.
Additionally, circumspect measurements of radioactivity in underground water would be necessary to monitor whether or not underground water gets mixed with wastewater during the construction of the frozen wall. The water-tight shielding wall in between the reactor and turbine buildings and the bay is now under construction to prevent wastewater from going into the sea. It would be a formidable task properly to control the level of underground water at the frozen wall (up-stream), that of wastewater in the reactor and turbine buildings (middle) and that of underground water at the water-tight shielding wall along the bay (downstream).
Elimination of radioactive nuclei
Advanced Liquid Processing System (ALPS) has been in operation since April to eliminate nuclei, mainly remaining strontium, from the increasing contaminated water. In regard to discharge the processed water into the sea, the last hurdle is tritium which cannot be removed by the ALPS. At present there is no solution but to reduce the concentration of tritium by dilution below the permissible concentration.
Adsorbent containing radioactive cesium and strontium eliminated from contaminated water is packed in a container and saved in an exclusively shielded area in the south part of the premises. However, it must be stored for a time span of hundreds to thousands of years, until its radioactivity ceases. A long range challenge would be how to replace the containers which become degraded by aging or where the storage place is determined.
In the first stage toward the decommissioning, water plays crucial roles, to cool the spent fuel pools which stay on the top floor of the damaged reactor buildings, to cool the damaged reactor cores, and to shield hazardous radiation from the damaged reactor cores. If the containment vessels were water-tightly shielded, installation of an individual cooling loop with a small sized ALPS-like system completely within each reactor and turbine building becomes possible and then, volume of wastewater would drastically be reduced, and decontamination of wastewater would be easier, which leads to discharge the processed water into the sea. If we, Senior Veterans Corps for Fukushima, were allowed to help in the present water crisis, such work that needs no specialty and physical strength as supervision of cooling loop, tanks, and storage of radioactive waste would be suitable for us.
Monitoring in Kawauchimura
On June 16th, we measured the dosage rage in a home in the Gomaizawa district, which is inside the former 20 km zone. Decontamination efforts in this area by the Ministry of Environment (MOE) have been completed, but there are mountains behind this home, and the radioactive material that remain on the steep slopes and atop the Japanese cedar trees have had a large effect on the home. We came to understand just why Mayor Endo asked the MOE at the last Diet meeting to consider decontaminating the mountains and forests.
|Questionnaires sent to technicians and scientists in the nuclear power industry
By request from Director Yamada, Professor Emeritus Kunio Ito of theUniversityofTokyohas been put in charge of SVCF, and he sent out questionnaires to SVCF volunteers who are technicians and scientists in the nuclear power industry. The results of this survey are below.
The Intent of the Questionnaire
It has been over 2 years since the Fukushima Daichi Power Plant accident, which occurred in March, 2011. However, the SVCF, which has offered to take over cleanup efforts at the power plant, still hasn’t been able to complete its goal. Therefore, in order to determine how we can get more involved in the future, we sent a questionnaire via e-mail to SVCF members who are technicians and scientists in the nuclear power industry.
The questions on the questionnaire were as below. The below questions are as they relate to the beginning stages and the removal of fuel and debris within and outside the nuclear reactor building.
1) What kind of work needs to be done?
The possibility of being accepted into Fukushima Daichi
Also, Respondent E (an employee at an equipment manufacturer), Respondent J (a researcher), Respondent M (a researcher), and Respondent O (a researcher) said that TEPCO probably will not allow SVCF onto the premises at Fukushima Daichi for expertise and safety reasons, and that the SVCF should probably change its objectives. Finally, Respondents K and L said that individual Task Force members may be able to get involved at Fukushima Daichi if they work for relevant companies, but the Task Force as an organization probably would be unable to do so.
Working in the nuclear reactor building
Therefore, the 5 individuals think that the Task Force would only be able to be involved in an ancillary role within the reactor building. Specific jobs that were mentioned were:
Summing up the questionnaire