ML20044G004
| ML20044G004 | |
| Person / Time | |
|---|---|
| Site: | Perry  |
| Issue date: | 05/24/1993 |
| From: | Stratman R CENTERIOR ENERGY |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| CAL-RIII-93-07, CAL-RIII-93-7, PY-CEI-OIE-0405, PY-CEI-OIE-405, NUDOCS 9306010309 | |
| Download: ML20044G004 (5) | |
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CENTEENOR l
ENERGY i
PERRY NUCLEAR POWER PLANT Mail Address:
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10 CENTER ROAD PERRY, OHIO 44081 VICE PRESIDENT. NUCLEAR j
PERRY, OHIO 44081 (216) 259 3737 May 24,.1993 PY-CEI/01E-0405 L
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l U. S. Nuclear Regulatory Commission 3
Document Control Desk Washington, D. C.
20555 Perry Nuclear Power Plant Docket No. 50-440 I
Response to Confirmatory Action Letter Gentlemen:
I This letter is submitted as the third partial response to Confirmatory Action Letter (CAL) RIII-93-07, dated April 16, 1993, which detailed actions requested by the NRC regarding the performance of ECCS Suction Strainers at the Perry Plant.
Your Confirmatory Action Letter specifically identified the following five actions which the Perry Plant had committed to perform in response to the strainer issue:
1.
Conduct an investigation to determine the cause'of.the reduced. capability
't of the RHR pump strainers located in the suppression pool. Include in the
'i evaluation consideration of design adequacy, reasons for fouling, and l
reasons for any deformation.
.i 2.
Maintain documentary evidence of the investigation effort and make this available to the NRC.
3.
Prior to startup, provide Region III vith the basis for considering the ECCS suppression pool strainers to be capable of performing their required design function.
1 4.
Prior to starRup, provide Region III with plans and a commitment to ensure that the suppression pool is maintained at an acceptable level.of-cleanliness, including any surveillances planned to be performed.
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5.
Provide within 30 days to Region III a documented evaluation of the above issues including any additional corrective actions taken or planned.
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the report, describe the basis for considering the RHR system to be j
capable of-performing its safety function during past operation, i
particularly in light of the problems identified in RF03.
During the May 18, 1993, conference call between Region III, NRR, and Perry personnel, one of the discussions focused on the Letter PY-CEI/01E-0404L response to CAL RIII-93-007, Action 5 and the use of operator intervention to l
mitigate the consequences of a loss of long term cooling following an accident.
j Generic Letter 91-18 Section 6.7 addresses use of manual action in place of automatic action in its detailed discussion of specific operability issues.
Although the Section 6.7 discussion does not directly apply to the situation vith the RHR suppression pool suction strainer foulings and the operability determination, some of the concepts included in the discussion are pertinent in considering operator mitigation of the degraded 20H1 systems.
Control room operators are expected to use their training and the assistance of the fully staffed Emergency Response Organization in the event of a postulated accident. RHR pun:p flov, discharge pressure, and motor amperage are monitored i
from the control room. Operators are fully trained on monitoring and j
interpreting the changes in pump parameters. Although RHR suction strainer l
fouling would not have been anticipated and there were no procedures in place to backflush the strainers or otherwise alleviate pump NPSH degradation as a result of such fouling, it is realistically expected that the operators vould detect and react to degraded pump performance. Operators are trained and i
experienced at assessing and prioritizing cooling requirements, taking full
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advantage of available redundant equipment, and fully utilizing the technical j
expertise available through the Emergency Response Organization. Therefore, it is reasonable to assume that operator action vould have been effective in mitigating the effects of strainer fouling on long term residual hea*. removal
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capabilities in the event of an accident.
Additionally, in the May 17, 1993, letter PY-CEI/01E-0404 L, it was stated that further development of methods for monitoring suppression pool
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cleanliness / strainer condition vill be communicated to the NRC prior to j
startup. Attachment I to this letter provides the required information about the methods developed for monitoring suppression pool cleanliness / strainer condition. Vithin the next several days, all necessary modifications to the ECCS strainers, all improvements to Containment, Dryvell, and the Suppression Pool conditions, and all program and procedure modifications for the. sustained =
enhancement of those conditions vill have been completed, in preparation.for l
restart from the current maintenance outage.
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i USNRC PY-CEI/01E-0405 L May 24, 1993 Your attention to this matter is greatly appreciated.
Sincerely, j
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- Robert A. Stratman i
RAS:CRE:ss l
1 Attachment cc: NRC Project Manager NRC Resident Inspector Office NRC Region III i
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PY-CEI/0IE-0405 L Page 1 of 2 OPERATIONAL SUPPRESSION POOL CLEANLINESS / STRAINER CONDITION MONITORING Letter PY-CEI/01E-0402L Response to CAL Item 4 detailed the use of strainer differential pressure to establish " action," " alert," and " differential" levels to initiate corrective actions. Analysis of test data obtained during testing of the new strainer design on RHR "B" has necessitated a reassessment of the use of strainer differential pressure information in this manner.
Due to the increased flow area of the new strainer design, differential pressure increases vould not be a meaningful indication of strainer fouling.
Using installed instrumentation to monitor suction pressure, a strainer differential pressure increase attributable to strainer fouling would not be detected until the strainer is approximately 80% fouled. Although an 80%
fouled strainer would provide adequate NPSH for the pump under accident conditions, dependence upon this parameter as an assurance of suppression pool cleanliness / strainer condition on a continuing basis is not appropriate. A program of visual inspections as part of ECCS Pump Technical Specification Quarterly Surveillance Instructions and as part of daily Plant Equipment i
Rounds (except as noted below) vill give reasonable assurance that suppression r
pool cleanliness /straiaer condition is being maintained at an acceptable level.
The specified techniques to be added to the above mentioned surveillance instructions and rounds include:
i Visual inspection of ECCS/RCIC suppression pool suction strainers vill be l
performed using a high-powered light or other suitable equipment. The l
strainers vill be inspected for the presence of visible accumulation of fibrous material or debris, and strainer deformation. If any of these conditions are observed, the Unit Supervisor vill be notified and appropriate evaluations vill be initiated.
l This inspection vill not be required to be performed during the daily Plant i
Equipment Rounds if evolutions utilizing the suppression pool-as a suction 8
source have not occurred within the past 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.
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An increase in strainer differential pressure is an important indication of
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decreasing NPSH availability for the affected pump and as such, is important i
information that should be utilized to determine further actions.
In addition to the visual inspection requirements that are being added to the ECCS Pump Ouarterly Technical Specification Surveillance Instructions, requirements to read and record pump suction pressure at appropriate times during the test are also being included. The data obtained vill be compared to the following j
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limits which will be specified in the surveillance instructions.
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If suction pressure decreases to 1.5 psi less than the static j
suction pressure, the surveillance test vill be suspended and the responsible system engineer (RSE) notified. The RSE vill evaluate advisability of continuing pump operation, and the extent of suction monitoring required, to determine the cause of the suction pressure
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decrease.
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.o PY-CEI/0IE-0405 L Page 2 of 2 If pump suction pressure degrades to 4 psi less than the static suction pressure, the pump vill be secured and considered inoperable
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until an evaluation is completed.
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Implementation of these monitoring and action requirements in conjunction with visual inspections vill ensure that suppression pool cleanliness / strainer condition is maintained at an acceptable level.
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