ML20235E676
| ML20235E676 | |
| Person / Time | |
|---|---|
| Issue date: | 02/03/1989 |
| From: | Murley T Office of Nuclear Reactor Regulation |
| To: | Marriott P GENERAL ELECTRIC CO. |
| References | |
| NUDOCS 8902210633 | |
| Download: ML20235E676 (3) | |
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W'd Patrick W. Marriott, Manager Customer Service Projects FEB 0 519s8 General Electric Nuclear Energy s
175 Curtner Avenue, MC 834 an San Jose, CA 95125 P
Dear Mr. Marriott:
j As we discussed in our meeting on February 3, we have become aware of weld cracks in the recirculation pump in-water bearing ring at two Japanese BWR nuclear power plants. Enclosure 1 is our latest understanding of the Japanese experience.
At your earliest convenience, we would like to meet with General Electric and possibly Byron Jackson (the pump manufacturer) to detennine your understanding of this issue and possible safety implications for U. S. plants.
is a list of questions we would like to discuss at that meeting.
Please contact Mr. J. E. Richardson of my staff to make detailed meeting arrangements (phone: 301-492-0821).
Sincerely, j
1 Orif;inal signed b1
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TEofnYs'b NEr1Yy, Director Office of Nuclear Reactor Regulation
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DESCRIPTION OF DAMAGE OF BWR RECIRCULATION PUMP IN-WATER BEARING RING IN JAPANESE REACTORS Cracking and failure of BWR recirculation pump in-water bearing ring was reported in two reactors (BWR-5) in Japan. The extent, severity, and safety implications were assessed.
It was concluded that there is no inmediate safety concern for the domestic plants. However, we are following closely the d
development of these events to ensure safe operation of domestic plants.
Description of Japanese Experience
]
The staff has learned that damage of a recirculation pump in-water ring was
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identified at Tokyo Electric Power's Fukushima-Daini Unit 1 during annual maintenance last year. The same incident was reported at the same unit in 1984. The damage was repaired but it occurred again in 1988 and was fixed at that time. The most recent problem was found at Fukushima-Daini Unit 3 in January 1989. They are both BWR-5 plants.
In January 1989, vibration of the primary loop recirculation (PLR) pump was observed during operation. The plant was shut down for inspection. 'It was found that the bearing ring was broken into three pieces (2 large pieces, and many small pieces). One piece was sticking on the upper impeller; another piece -
was found inside the reactor vessel; and the third piece became a loose part but was finally recovered, i
The PLR pump in Fukushima-Daini Unit I was manufactured by Byron-Jackson Co., but the Unit 3 pump was made by EBARA Co., a Japanese manufacturer. MITI officials feel that the cracks were due to high stresses of the component induced by water flow. They consider that this problem does not depend on BWR types and pump suppliers, but it might occur at any plants which used the same welding technique (a fillet weld joining a stainless steel bearing).
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o QUESTIONS TO BE DISCUSSED REGARDING DAMAGE OF BWR RECIRCULATION PUMP IN-WATER BEARING RING IN JAPANESE REACTORS a.
Is there any additional information regarding the cause of cracking (e.g.,
design, fabrication, service-induced, material problems) and effective-ness of corrective actions?
b.
What is the US experience on BWR recirculation pump in-water bearing ring cracking?
c.
What is the extent, severity, and generic implication of the problem?
Identify plants that may be affected.
d.
Is there a need for inspecting the pump bearing ring?
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