The investigation and repair of primary containment vessel (PCV) leak locations are indispensable for water filling according to the fuel debris retrieval plan in the “Mid- and-Long-Term Roadmap” and for preventing contaminated water levels from increasing.
The progress status of the R&D project for the “inspection/repair of leaking locations using PCV lower-section repair technology” in the subsidy project of the Japanese Ministry of Economy, Trade and Industry (METI) is as follows:
The repair technology, currently under development, comprises a method to stop leakage by sealing vent piping which connects drywell and the suppression chamber (S/C). Specifically, swelled sealing supporting material (high-tenacity polyester fabric) temporarily stops water flow. To seal the vent piping, the water cutoff material (plastic grout) is poured and solidified at the upper stream of the sealing supporting material.
The “water and air filling test” and “unfolding confirmation test” of the sealing supporting material were conducted using a half-scale model. The results revealed that sealing supporting material can swell and adhere to the vent piping without an interference structure. However, a gap between the vent piping and the sealing supporting material is larger than intended with an interference structure and presents future challenges.
For the water cutoff material, a “water stoppage test” was conducted using a one-tenth scale model to fill the gap between the vent piping and the sealing supporting material. In this test, the sealing capability in water flow, the suitable material composition for stoppage, and the appropriate injection speed were confirmed. Additional feasibility tests are planned based on the findings from these tests.
※TOSHIBA Corporation Nuclear Energy Systems& Services Division Webpage http://www.toshiba.co.jp/nuclearenergy/english/index.htm (English)
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