Vol.1 No.4 GA 11 - 12 - AA SP1 ( 11 - 12 - 13 - 14 ) - NT 19 - 20 - 21 - 22 Vol.2 No.2 |
Vol.2, No.1, NT19
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INLAY Method Using the Cylindrical Container for Reactor Vessel of PWR |
THE KANSAI ELECTRIC POWER CO., INC. (KEPCO) MITSUBISHI HEAVY INDUSTRIES, LTD. (MHI) |
KEYWORDS: |
1. Technical summary |
Classification (I: Inspection, II: Repair, III: Replacement, IV: Preventive Maintenance, V: Others) |
(1) This is a repair method against PWSCC (Primary Water Stress Corrosion Cracking) of outlet / inlet nozzle to safe-end weld of Reactor vessel (RV) of PWR. (2) INLAY method using the cylindrical container was applied for Ohi Nuclear Power Station Unit 3 of KEPCO in 2009 for the first time in Japan. (Fig.1,2,3) Fig.1 INLAY method using the cylindrical container for RV
(at Ohi Nuclear Power Station Unit 3 of KEPCO) Fig.2 The procedure of INLAY method applied for
Ohi Nuclear Power Station Unit 3 of KEPCO Fig.3 Installation of the cylindrical container for RV
at Ohi Nuclear Power Station Unit 3 of KEPCO (3)The cavity must be filled with water to avoid much exposure from Core Internals (CI) while out of RV. The cylindrical container is installed on RV to secure atmospheric working space inside outlet nozzle. (Fig.4 ,Fig.5)
(a) Test in water (b) Inner view Fig.4 Photos of cylindrical container at the shop of MHI
Fig.5 Installing test of the cylindrical container into water at the shop of MHI
(4) INLAY method using the cylindrical container was performed as follows (Fig.2);
1. Machining for the part where SCC had been found and removed during the last outage 2. Partial repair welding with Alloy 600 3. Circumferential grooving to remove Alloy 600 of the inner surface 4. Circumferential welding with PWSCC resistant Alloy 690 (5) The partial repair welding is performed close to the nozzle as shown in Fig.1. This means the heat treatments for the nozzle, made of low allow steel, shall be applied to relief the welding heat effect, however it is difficult to apply them because of the structural situation. Then the ambient temperature temper bead welding technique was developed to make the heat treatments unnecessary. (Fig.6) Fig.6 Monitoring view of the ambient temperature temper bead welding
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2. Scope |
(1) Components: Reactor Vessel (RV) of PWR
(2) Location: Dissimilar welds of outlet / inlet nozzle of RV concerned PWSCC (3) Material: Alloy600 (Nickel based alloy) (4) Condition: This method can be applied underwater. |
3. Features |
(1) The cylindrical container: Repair or preventive maintenance can be applied, even when the cavity is filled with water.(Reduction of drainage process)
(2) The ambient temperature temper bead welding is applied. (3) Reduction of radiation exposure by the following measures; 1. Blast decontamination 2. Thick wall of the platform and equipped shielding tube into the nozzle |
4. Examples of Application |
(1) Ohi Nuclear Power Station Unit 3 of KEPCO in 2009 |
5. Reference |
None |
6. Contact |
Japan Society of Maintenology (ejam@jsm.or.jp) |