ML17335A462
| ML17335A462 | |
| Person / Time | |
|---|---|
| Site: | Cook  |
| Issue date: | 12/31/1998 |
| From: | Roe J NRC (Affiliation Not Assigned) |
| To: | Congel F NRC OFFICE FOR ANALYSIS & EVALUATION OF OPERATIONAL DATA (AEOD) |
| References | |
| NUDOCS 9901080082 | |
| Download: ML17335A462 (9) | |
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UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 Ihceniber 31, 1998 MEMORANDUMTO:
Frank J. Congel, Director Incident Response Division, AEOD FROM:
Jack W. Roe, Acting Director Division of Reactor Program Management, NR
SUBJECT:
ABNORMALOCCURRENCE INPUT In a memorandum from Jack Roe to Frank Congel, dated June 5, 1998, the Events Assessment and Generic Communications Branch of NRR committed to evaluating the containment issues at D.C. Cook Nuclear Power Plant (Cook) to determine ifthey meet the abnormal occurrence (AO) or Appendix C criteria.
In a separate request, you asked us to evaluate an additional event at St. Lucie Unit 1 and to reevaluate our earlier recommendation regarding the containment sump issues in light of changes to the Appendix C criteria provided by the Commission.
The results of our evaluations are provided below.
Our considerations used the final abnormal occurrence criteria approved by the Commission for
, "At Occurrence Reporting Procedure."
We also used the guidance provided in the September 4, 1998, Staff Requirements Memorandum (SRM) provided in response to SECY-98-175, "Proposed Guidelines for Appendix C, 'Other Events of Interest,'o the Abnormal Occurrence Report to Congress."
SYNOPSIS Cook As a result of NRC inspections conducted at Cook from August 4, 1997, through April 15, 1998, a number of issues were identified related to the ability of the containment ice condenser and the emergency core cooling systems (ECCS) to perform their safety functions. Of particular concern were issues related to the ability of the containment sump to receive adequate water to support ECCS pump operation during a loss-of-coolant accident (LOCA) and the ability of the ice condenser to minimize containment pressure increase following a LOCA.
The issues related to the containment sump were discussed in the June 5, 1998, memorandum.
In that memorandum we stated our belief that the sump issues might warrant classification as an "Other Event of Interest." Since that time, the SRM was issued which provided Appendix C guidance.
Per your request, we reevaluated the containment sump issues using the new Appendix C guidance.
070025
Contact:
W. F. Burton, NRR 301-415-2853 990i080082 98i23i PDR ADQCK 050003i5 P
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Frank J. Congel We still believe that the sump issues warrant consideration as an Other Event of Interest.
The basis for our conclusion is the increased staff attention devoted to the issues and the perception by stakeholders that the issues were of a high safety significance.
As stated in our June 5, 1998, memorandum, the deficiencies identified during the inspections were initially considered highly safety significant, but were subsequently found not to be an actual major reduction in the degree of protection of the public health and safety.
In response to the sump problems, the licensee submitted an amendment requesting that the ice melt be credited to the overall sump inventory during a LOCA. This amendment request presumed that the ice condenser met its licensing'basis.
However, subsequent investigations of the ice condenser called its operability into question.
The function of the ice condenser at D.C. Cook is to reduce the containment pressure following a design basis LOCA. As a result of ice condenser inspections performed by both the licensee and the staff, a number of deficiencies were identified. These included missing ice segments, blocked flow passages between some of the ice baskets, damaged ice baskets, questionable integrity of ice baskets, and questionable operability of the ice condenser due to poor ice sampling and weighing procedures.
The cause of these deficiencies was inadequate licensee inspection and maintenance of the ice condenser, poor oversight of contractors who were responsible for weighing the ice baskets, inadequate surveillance procedures, and failure to update the final safety analysis report to reflect ice condenser analysis information.
In addition, debris was discovered in the ice which could lead to sump blockage during an accident.
As a result of these deficiencies, the NRC issued a Confirmatory Action Letter (CAL) to the licensee.
These deficiencies, when taken collectively, initiallyappeared to warrant consideration as an AO. However, in response to the CAL, the licensee provided analyses demonstrating that despite the numerous deficiencies, the ice condenser was capable of performing its safety function. Staff evaluation also concluded that the deficiencies would not prevent sufficient ice from melting during a LOCA, which ensures the operability of the ECCS pumps.
Because of this additional information, there did not appear to be an actual major reduction in the ability of the ice condenser or the ECCS systems to perform their safety functions. Therefore, we concluded that the Cook containment issues do not warrant consideration as an AO. However, due to the increased attention and focus by the staff on the issues and due to the heightened public interest generated by the issues, we believe that the issues, in total, warrant consideration as an "Other Event of Interest" as defined in the September 4, 1998, SRM.
It should be noted that, as a result of the deficiencies identified at Cook, the staff began evaluations of the ice condensers at other plants (Catawba, McGuire, Sequoyah, and Watts Bar) to determine ifsimilar problems may exist. To date, the deficiencies found at these plants have been less severe than those found at Cook.
St. Lucie Unit 1 The St Lucie Unit 1 event involved a non-conservative setting of the set point for switches used to change the operating mode of the ECCS pumps from injecting water from the refueling water tank into the reactor coolant system to recirculating water collected in the sump back into the reactor coolant system.
This incorrect setting was done in error and could potentially impact
Frank J. Congel operation of ECCS pumps by having the pumps operate with less than the intended and required net positive suction head.
This could lead to possible damage following a large break LOCA ifthe operators did not take action.
Because Emergency Operating Procedures, which would be utilized following a large break LOCA, direct operators to monitor this automatic mode change, there is a high probability that operators would detect any anomalous pump behavior when it first occurs and take corrective action prior to having pump damage.
Because it is unlikely that all ECCS pumps would become inoperable at this time and that there is another way that could be used to cool the core, we do not believe that it is likelythat core cooling would be lost. The staff evaluated the risk significance of this issue and concluded that the improper setpoint resulted in an increase in the core damage probability of 1.7 E-5 for a one year period.
No special staff action was required nor was there significant media coverage.
Therefore, we do not believe that this event meets the criteria for "other events of interest."
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k Frank J. Congel operation of ECCS pumps by having the pumps operate with less than the intended and.
required net positive suction head.
This could lead to possible damage following a large break LOCA ifthe operators did not take action.
Because Emergency Operating Procedures, which would be utilized following a large break LOCA, direct operators to monitor this automatic mode change, there is a high probability that operators would detect any anomalous pump behavior when it first occurs and take corrective action prior to having pump damage.
Because it is unlikely that all ECCS pumps would become inoperable at this time and that there is another way that could be used to cool the core, we do not believe that it is likelythat core cooling would be lost. The staff evaluated the risk significance of this issue and concluded that the improper setpoint resulted in an increase in the core damage probability of 1.7 E-5 for a one year period.
No special staff action was required nor was there significant media coverage.
Therefore, we do not believe that this event meets the criteria for "other events of interest."
DISTRIBUTION gC'ential.Fifer PUBLIC PECB R/F H. Karagiannis W. Burton J. Carter J.
Roe J. Zwolinski H. Berkow D. LaBarge S. Weiss P. Harris
- See previous concurrence DOCUMENT NAME: G:)WFBNO3.WPD To receive a copy of this document, indicate in the box C=Copy w/o attachment/enclosure E=Copy with attachment/enciosure N = No copy OFFICE NAME PECB WBurton*
PECB:DRPM RDennig*
C:PECB:DRPM JStolz A
JRo DATE 12/23/98 12/24/98
/~ 98 OFFICIAL RECORD COPY
/ /98
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Frank J. Congel operation of ECCS pumps by having the pumps operate with less than the intended and required net positive suction head.
This could lead to possible damage following a large break LOCA ifthe operators did not take action.
Because Emergency Operating Procedures, which would be utilized following a large break LOCA, direct operators to monitor this automatic mode change, there is a high probability that operators would detect any anomalous pump behavior when it first occurs and take corrective action prior to having pump damage.
Because it is unlikely that all ECCS pumps would become inoperable at this time and that there is another way that could be used to cool the core;:-we do not believe that it is likelythat core cooling would be lost. The staff evaluated the risk significance of this issue and concluded that the improper setpoint resulted in an increase in the core damage probability of 1.7 E-5 for a one year period.
No special staff action was required nor was there significant media coverage.
Therefore, we do not believe that this event meets the criteria for,."other events of interest."
DISTRIBUTION CC'entral."~F,ile PUBLIC PECB R/F H. Karagiannis W. Burton J. Carter J.
Roe J. Zwolinski H. Berkow D. LaBarge S. Weiss P. Harris
- See previous concurrence DOCUMENT NAME: G:>WFBNO3.WPD To receive a copy of this document, indicate in the box C=Copy w/o attachment/enciosure E=Copy with attachment/enciosure N = No copy OFFICE PECB PECB:DRPM C:PECB:DRPM NAME WBurton*
RDennig*
JStolz JRo DATE 12/23/98 12/24/98 OFFICIAL RECORD COPY
/ /98
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