ML18057B389
| ML18057B389 | |
| Person / Time | |
|---|---|
| Site: | Palisades  |
| Issue date: | 11/26/1991 |
| From: | Slade G CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9112030185 | |
| Download: ML18057B389 (4) | |
Text
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consumers Power PDWERINli
- MICHl&AN'S PROliRESS Palisades Nuclear Plant:
27780 Blue Star Memorial Highway, Covert, Ml 49043 November 26, 1991 Nuclear Regulatory Commission Document Control Desk Washington, DC 20555 GB Slade General Manager DOCKET 50-255 - LICENSE DPR PALISADES PLANT - COMMENTS ON THE DRAFT AEOD REPORT, "EXPERIENCE WITH PUMPS SEALS INSTALLED IN REACTOR COOLANT PUMPS MANUFACTURED BY BYRON JACKSON" In response the NRC's letter dated September 27, 1991, comments on the draft report entitled "Experience with Pumps Seals Installed in Reactor Coolant Pumps Manufactured by Byron Jackson," developed by the Office for Analysis and Evaluation of Operational Data (AEOD) are provided in the Attachment.
- ~L*U.., *.f2Vl. GBS Gerald B Slade General Manager CC Administrator, Region III, USNRC NRC Resident Inspector - Palisades Attachment A CMS ENERGY COMPANY
ATTACHMENT Consumers Power Company Palisades Plant Docket 50-255 Palisades Plant Comments on draft AEOD report "EXPERIENCE WITH PUMPS SEALS INSTALLED IN REACTOR COOLANT PUMPS MANUFACTURED BY BYRON JACKSON" November 26, 1991 2 Pages
COMMENTS ON AEOD REPORT ON BYRON-JACKSON PUMP SEALS Page and/or Section Number Page VIII, 3 and Page 11, 2 Page 19, Section 2.3.1
, 1, 3rd sentence Comments Per the reference section of the report, the definition used for evaluating seal performance (ie.
seal failure) is "... loss or damage of one or more stages." It seems that this definition may be appropriate for Westinghouse seals, which have only two stages designed to seal against full system pressure.
However, since the seals utilized in C-E plants are a four stage seal with each stage designed to seal against full system pressure, the seals used in Byron Jackson pumps have basically 3 times the redundancy of the Westinghouse seal.
Therefore~ the loss of a single stage leaves the B-J pump seal with 2 redundant or back-up seals where as the Westinghouse seal would have zero redundancy.
It is this fact that forms the basis of B-J's and the industry guidelines for operating with orte failed stage. Therefore, it does not seem appropriate to utilize this definition of "seal failures" for an evaluation of B-J pump seals operating experience. It is suggested that a definition of 2 or more failed stages would be more appropriate for the Byron Jackson seal.
Palisades has found that the seals are reliable for longer than one cycle and has established a "rule of thumb" of 20 months run-time for scheduling preventative maintenance.
We are currently considering extending the length of the run-time.
Also, between 1984 and 1988, Palisades experienced 6 occurrences of seal staging failures. There have been zero failures from 1988 to present.
Five of the six failures involved a single stage failure and one involved the failure of the first 3 stages.
The multistage failure was the result of the separation of the impeller from the shaft.
It should be noted that during the event causing the 3 stage failure, the seal continued to function for roughly 23 hours2.662037e-4 days <br />0.00639 hours <br />3.80291e-5 weeks <br />8.7515e-6 months <br /> after the shaft/impeller separation before the staging failure.
Furthermore, the vapor seal remained functional throughout the event. This event exemplifies B-J's superb seal reliability.
- J Page 19, Section 2.3.1 Palisades' seals are a partially modified SU type seal. Of the 7 modifications available for the SU seal, Palisades has utilized the following:
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modified U-cup shape, 2) modified rotating face body to accommodate the U-cup, and 3) the super polished shaft sleeve.
Page 26, Item 5 This should read; "Palisades (9/16/84) all three stages in one seal failed (vapor seal remained functional) while the plant was operating at 60%
power.
The seal failure was caused by the pump impeller separating from the pump shaft and the resulting unbalance and vibration.
Page 27, 1 Palisades Operating Procedures will allow continued operation only with one failed stage, not with 2 failed stages.
Page 30, 3 Palisades experience on 9/16/84 showed the vapor seal to survive the sudden increase in pressure and perform through shutdown.
We therefore find the statement that "... sudden exposure of the vapor seal to RCS temperature and pressure may introduce enough stress on the seal to cause damage" to be speculative and unfounded.
Our records indicate that controlled bleedoff remained below 3.5 gpm throughout the event.
Page 31, 1 Palisades has indication of first stage (lower) seal temperature contrary to the statement that "... B-J RCPs installed in operating plants do not have direct first stage (lower) seal temperature measurement capability."