ML19095A256
| ML19095A256 | |
| Person / Time | |
|---|---|
| Site: | Surry  |
| Issue date: | 05/05/1978 |
| From: | Stallings C Virginia Electric & Power Co (VEPCO) |
| To: | Case E, Schwencer A Office of Nuclear Reactor Regulation |
| References | |
| Download: ML19095A256 (3) | |
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VIRGINIA ELECTRIC AND POWER COMPANY RJ:CHMOND,VIRGJ:NIA. 23261 May* 5, l978;
- Mr. Edson_G. Case, Acting Director Nuclear Reactor Regulation United States Nuclear Regulatory Commission Washington D. C.
20555 Attention: Mr. Albert Schwencer, Chief Operating.Reactors Branch 1
Dear Mr. Case:
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The purpose of this letter is to provide information r_egarding the out-side recirculation spray (ORS) and low head safety injection (LHSI) pumps at the Surry Power Station.
As you know, unexpected bearing wear was experi-enced on the North Anna ORS and LHSI pumps.
Also, model.testing revealed un-acceptable suction flow conditions in the North Anna LHSI sump.
We have deter-mined that the potential for unacceptable-bearing wear and unacceptable suction flow conditions at Surry should be evaluated since the ORS and LHSI configura-tions are similar to North Anna.
The suction flow and bearing wear conditions are being evaluated separately since unacceptable suction flow may not be the only cause for unexpected bearing wear.
Each evaluation is divided into several phases.
The suction flow evalua-tion will consist of.design review and model.testing, and if necessary, modifi-cation development. and actual plant testing.
The bearing.wear evaluation will.
consist of des_ign review and actual plant. testing and,. if necessary, modification development and post modification inplant testing.
The suction flow evaluation is proceeding as planned.
We have carefully re-viewed the model test data from the North Anna tests and from the tests conducted by another utility.
As a result, we have taken steps to conduct Surry specific model flow tests for the ORS and LHSI pumps.
To assure that the Surry tests are compatible with previous tests for North Anna, we intend to use identical techni-ques.
We have contacted two firms regarding the desired tests.
The LaSalle Hydraulic Laboratory has been asked to propose a test program for the ORS pumps, and the Byron Jackson Pump Division of Bo_rg Warner has been asked to propose a test program for the LHSI pumps.
The manufacturer of the ORS pump has also been contacted and has agreed to provide the required support for the tests.
Since the LHSI pump man~facturer has been asked to perform the model tests, we don't expect any difficulties with regard to manufacturer support.
All required plant data has been submitted to these firms and. we are hoping to have a test schedule established in early May 1978.
We have had several detailed discussions on the subject of suction flow with Byron Jackson, Bingham-Willamette, LaSalle and our Architect-Engineer, Stone and Webster.
The purpose of these discussions has been to examine possible modifica-tions in the event that unsatisfactory flow conditions exist.
We have established that the most desirable modifications are those made_ to the.pump suction bell 7812';-()()33
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VIRGINIA ELECTRIC AND POWER COMPANY TO Mr.* Edson G. Case
~age 2 mouth.
This. would simplify the installation and eliminate the.personnel hazard and l~ngthy schedule involved with modifications to the sump can.. Therefore, the principle objective of the flow test is to identify pump modifications that can correct. any observed unsatisfactory suction. flow conditions.
Although we are thinking ahead to the potential for pump modifications, we.* also believe that there is a possibility that both ORS and LHSI pumps at Surry will not demonstrate a suctionflow problem.
The North Anna.test results show that. the Bingham-Willamette ORS pump suction ball mouth flow "splitter" acted to.reduce suction vortexing to an acceptable. level. The Surry ORS pumps are identical. to the North Anna Pumps.
The Byron-Jackson.LHSI. pumps at Surry are designed. with an impeller hub bearing in the suction bell mouth supported by.several vanes.
These vanes will serve to dampen any fluid rotation in the pump suction.
Therefore, there is a strong possibility that the model tests will. show no problem. We intend to rely heavily on the experience of the pump vendor and the testing laboratory to make
-this determination.
We will inform you of the results of our tests as soon as they are available.
The.bearing. wear evaluation is also proceeding as planned *.. A complete re-view of the* bearing materials,. journal. materia1s 9 journal hardness and journal surface. finish for the Surry ORS and LHST has been completed.
This information has been compared with similar, data from NG>rth Anna. and another utility.
We have also examined. bearing.design criteria with the pump and bearing manufacturers.
The findings of this review are inconclusive.
There. is not a consensus on specif-ic requirements for. bearings and.journals as: used on. the Surry ORS and. LHST pumps.
In addition, our experience with.similar pumps in different applications and the manufacturers' experience indicate.ff that.pump fhlid performance is not directly dependent on. bear1;ng wear..
- As a result of these findings, a. clear cut course of action.to.resolve the bearing wear issue is difficult to construct.
Regardless of.these difficulties,.we have been examining modifications that could.be made to reduce the bearing wear on the Surry ORS and LHSI. pumps.
The principle objective for these modi£ ications is to be ab.le to do the _work on the existing shafts at the station.
The work should also be such.as to minimize the generation of.radioactive waste.and minimize. the impact on.plant availability.
We are presently examining several. bearing/journal.modifications that meet these criteria.
We have looked. into a cold flame spray application of a new journal material, but it is believed that this has limited applicability on a rotating shaft.
We have ruled out any weld overlay or hot flame spray process due to the likelihood of shaft warpage.
We are considering the use.of. sleeves which can be slipped onto and key~d to.the shafts *. We have also considered chrome plating existing and/or new shafts, but due to the possibility of brackish water contam-ination of the containment sump at Surry, and the tremendous cost of a new shaft, we have all but ruled out this alternative.
We are also evaluating different bearing materials, but we have found a lack of industry data.to use in choosing the "best" material.
At this point, we have concluded that.actions could be taken to improve the
.bearing wear characteristics of the Surry ORS and LHSI pumps.
However, it has not been established that the existing level of bearing wear is unacceptable.
The. best course of action cannot.be *determined without elaborate in-plant testing.
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VIRGINIA ELECTRIC AND POWER COMPANY TO Mr.
- Edson G. Case We are still in the "studying 11 stage regarding plant testing.
How-ever, we have decided that the most clear cut test data can be obtained by testing Surry* pumps at Surry in their actual system configuration.
We have asked our Architect-Engineer to commence cievelopinent of *the.required test con-figuration.
We would like to duplicate* the North Anna Unit No. 2 test facility as much as. possible, but we must also take into account the possibility of radioactive contamination.
Therefore, we are evaluating the. various possibili-ties regarding temporary piping, instrumentation, source water and so forth.
The test. schedule is also a consideration, and tentatively, we plan to conduct these tests during the forthcoming steam generator replacement outage for the first Surry Unit.
This should provide ample. time to conduct lo_ng term tests to evaluate bearing wear. and. the suction flow modifications, if required.
Even though it cannot be concluded that a problem exists, we have examined the consequences of continued operation of the Surry units while our evaluation proceeds.
The Wash-1400 Reactor Safety Study ass_igns the following. median proba-bilities to various size LOCA's:
6" or greater lxlo-4 per reactor year 211 to 6" 3xlo-4 per reactor year k" to 2".
lxlo-3 per reactor year 2
Total
.l.3xlo-3 per. reactor year Assuming: that any necessary corrective action_ could.. be accomplished within about 9 reactor months of operation~ the risk exposure would.be approximately a bdQ-3 probability of a LOCA.
In consideration of these factors, and recognizing that this concern will be.resolved in a timely manner, it. is concluded that con-tinued operation. poses no undue risk. to the health and. safety of* the general public.
The information herein represents*the status of the Surry 0RS and LHSI pump evaluation to date.
We will continue to provide you with* periodic status reports as information becomes available.
cc:
Mr. James P. O'Reilly Very truly yours,
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Vice President-Power Supply and Production.Operations