Development of Repair Technology for Water Leakage Sections in PCV Testing Concrete Injection Technology for Water Leak Stoppage Treatment inside Suppression Chamber Using Full-Scale Mock-up Facility [Led by TOSHIBA]. (October 15, 2016)

Oct.15,2016

IRID is advancing the development of repair technology for water leakage sections in the Primary Containment Vessel (PCV) under a project led by Ministry of Economy, Trade and Industry (METI) in FY 2016-FY 2017 towards the decommissioning of the Fukushima Daiichi Nuclear Power Station (NPS). As a part of this project, a method of injecting concrete to repair water leakage points inside suppression chamber (S/C), a structure that lies at the lower part of the PCV, is currently being examined.

To test this method, concrete was injected into a full-scale mock-up of the S/C.

・ Testing Overview
Based on the actual structure found in Fukushima Daiichi NPS Unit 2, internal components such as a full-scale quencher and strainer were placed in a water tank that models the lower half of a circler shape placed at 45 degrees. In addition, holes were created to simulate actual damage conditions. Underwater inseparable concrete was injected into this facility to confirm long-distance concrete fluidity, concrete behavior that exceeds stiffening rings, water leak blockage conditions inside components, and if holes in the structure had been repaired.

・ Test Location
Hazama Ando Corporation, Technical Research Institute, (Tsukuba city, Ibaraki Prefecture)

・ Test Date of Concrete Placing
Saturday, October 15, 2016

・ Test Information
– Placing concrete in mock-up test facility (Approx. 9:30 – 16:30)
＜Water stoppage test on 50mm damaged holes＞
– Performance verification of S/C damaged holes for water leak blockage and coarse aggregate size that can stop water leakage.
(50mm damaged holes used in testing; it is assumed 20mm holes exist in actual conditions)
＜Water stoppage test for quencher and strainer＞
– Verification of material behavior exceeding stiffening rings (T-flange); performance verification of water leak blockage for strainer and S/C damaged parts due to material flow.
– Further testing of water pressure resistance required to verify water leak blockage capability performed 28 days after concrete injection.

[Future Developments]
Based on the test results, IRID will perform similar water leak blockage tests through injecting filling inside S/C, using the full scale mock-up facility at Naraha Remote Technology Development Center.
*We expect to post an update accordingly when the test details are confirmed.

＜Attachment 1: Full scale S/C testing conditions, overview ＞
https://irid.or.jp/wp-content/uploads/2016/10/20161018_001.pdf PDF
＜Attachment 2: Time series events in the progression of concrete placing, diagram＞
https://irid.or.jp/wp-content/uploads/2016/10/20161018_002.pdf PDF

[On site photographs]


Inside S/C (before testing)	Concrete pumping vehicle that can inject concrete at 30㎥ / hour

Injecting concrete	Injecting water in S/C (75 L / min.)

Strainers before starting test	Submerged strainers

Quencher	Down-comer

Measuring concrete precipitation every 10 min.	Transporting from concrete agitator vehicle to pumping vehicle

Confirming water leakage volume (Conditions before water leak blockage)	Confirming water leakage volume for damaged area (Conditions after water leak blockage)

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