ML20247H162

Informs of Util Proposal to Delete post-accident Sampling Commitment to Provide in-line Monitoring & Grab Sample Capability for Dissolved Gases (Hydrogen) in Liquids, Specifically Reactor Coolant.Basis & Justification,Encl

ML20247H162
Person / Time
Site:	Wolf Creek
Issue date:	05/11/1998
From:	Warren C WOLF CREEK NUCLEAR OPERATING CORP.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
WO-98-0047, WO-98-47, NUDOCS 9805210084
Download: ML20247H162 (3)

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b Clay C. Warren WF) LF NUCLEAR CREEKOPERATING Chief Operating Officer May 11, 1998 WO 98-0047 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Mail Station: Pl-137 Washington, D. C. 20555

Subject:

Docket No. 50-482: Wolf Creek Generating Station Change to Post-Accident Sampling System Commitments Gentlemen:

Wolf Creek Nuclear Operating Corporation (WCNOC) proposes to modify ats commitments, as described in the Wolf Creek Generating Station (WCGS) Updated Safety Analysis Report (USAR), Section 18.2.3, regarding NUREG 0737,

" Clarification of TMI Action Plan Requirements,"' sampling requirements for the Post Accident Sampling System (PASS). Specifically, WCNOC proposes to delete the commitment to provide in-line monitoring and grab sample capabi)ity for dissolved gasses (e.g., hydrogen) in liquids (specifically, reactor coolant).

The attachment provides the bases and justification for making this change.

Based on the results of this evaluation, WCNOC concludes that implementation of this change does not represent an unreviewed safety question. However, since these commitments were made in response to NUREG-0737 and are discussed in the WCGS Safety Evaluation Report (NUREG-0881), WCNOC is requesting NRC approval prior to implementing this change.

If you should have any questions regarding this submittal, please contact me at (316) 364-8831 Extension 4485, or Mr. Michael J. Angus at extension 4077.

Very truly yours,  ;

9805210084 980511 Cl y C. Warren PDR ADOCK 05000482 p PM CCW/rir Attachment i cc: W. D. Johnson (NRC), w/a E. W. Merschoff (NRC), w/a J. F. Ringwald (NRC), w/a K. M. Thomas (NRC), w/a I r .e , PO. Box 411/ Burhngton, KS 66839 i Phone: (316) 364-8831 l .4 - UA An Equal Opportunity Empk>yer M r'HCVET l

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, Attachment to WO 98-0047

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BASES AND JUSTIFICATION FOR CHANGES

!'1-l l INTRODUCTION The Wolf Creek Generating Station (WCGS) Updated Safety Analysis Report (USAR)

Section 18.2.3 states that the WCGS design provides an in-line monitoring l system (for post accident monitoring). This system (the Post-Accident Sampling System, or PASS) includes provisions for monitoring reactor coolant system (RCS) hydrogen in accordance with NUREG-0737 Section II.B.3.

WCNOC proposes to delete the commitment to provide in-line monitoring and grab l

sample capability for dissolved gasses (e.g., hydrogen) in liquids (specifically, reactor coolant),

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BACKGROUND NUREG-0737 Section II.B.3 specifies eleven criteria which a post accident sampling system must meet in order to perform its design function. The second of these criteria states:

"The licensee shall establish an onsite radiological and chemical analysis capability to provide, within the 3-hour time frame established above, quantification of the following:

(a) certain radionuclides in the reactor coolant and containment atmosphere that may be indicators of the degree of core damage I (e.g., noble gases; iodines and cesiums, and nonvolatile isotopes);

l (b) hydrogen levels in the containment atmosphere; (c) dissolved gases (e.g., H), 2 chloride (time allotted for analysis subject to discussion below), and boron concentration of liquids.

(d) Alternatively, have inline monitoring capabilities to perform all or part of the above analyses."

l The WCGS design incorporated an in-line hydrogen analyzer for measuring dissolved hydrogen in the reactor coolant, as described in USAR Section 18.2.3.2. The in-line monitoring system is normally isolated; however, it could be manually initiated and operated after an accident.

The purpose of using an in-line monitor is to minimize personnel exposure.

Provisions were also included for providing both diluted and undiluted grab samples of the reactor coolant consistent with NUREG-0737 The grab samples are shielded, and the system is designed to minimize personnel exposure while obtaining grab samples.

The sample lines in the PASS panel are flushed or purged after each analysis, and the sampled fluids are returned to the containment. Since the PASS panel is located in the auxiliary building, any leakage from the system would be filtered through the charcoal adsorber and HEPA filters of the auxiliary building emergency exhaust system.

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Additional details on the PASS design, and post-accident reactor core damage {

assessment, were submitted to the NRC by the Standardized Nuclear Unit Power

! Plant System (SNUPPS) letters dated February 4, 1983, April 24, 1984, and June 21, 1984.

EVALUATION OF PROPOSED CHANGE TO PASS SAMPLING COMMITMENTS As stated above, NUREG-0737 requires the licensee to establish the capability .

to provide, within 3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> of making the decision to take a reactor coolant l l sample, an analysis of dissolved gasses (e.g., hydrogen) in the reactor i coolant or, alternatively, have inline monitoring capability to perform this ,

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, Attachment to Wo 98-0047

• Page 2 of 2 function. WCNOC is proposing to delete the requirement to take and analyze a reactor soolan' sample for dissolved gasses (e.g., hydrogen). This proposal includes the < eletion of WCNOC's commitment to provide inline monitoring and grab sample c' ability of reactor coolant system (RCS) dissolved gasses (e.g.,

hydrogen), as tescribed in USAR Section 18.2.3.2.

In order to satisfy the requirement for a dissolved gas sample and analysis, WCNOC utilizes the PASS RCS hydrogen analyzer to obtain and analyze reactor coolant samples for hydrogen content during accident conditions. The intent of this analysis is to determine if a hydrogen bubble is building under the Reactor Vessel head. In the event of a gas bubble buildup under the reactor vessel head, Operational procedures require the reactor head vent valves to be opened to vent the hydrogen, as well as any other gases contained in the bubble, to the containment atmosphere. The hydrogen contained within the released gas bubble would then be sampled and analyzed by the two containment hydrogen analyzers, which are safety-related components. Hot WCGS design utilizes safety-related instrumentation (i.e., the Reactor Vessel Level Instrumentation System, or RVLIS), to provide this indication of a gas bubble buildup under the reactor vessel head. As a result, the analysis performed for the dissolved hydrogen is not used as part of any Core Damage Assessment Methodology at WCGS, the RCS hydrogen analysis provides no information which is used to mitigate or reduce the severity of an accident response, and no WCGS procedure currently utilizes the PASS RCS hydrogen analyzer for any purpose. Therefore, there will be no impact on the ability to determine the hydrogen gas concentration in the containment atmosphere or safely mitigate l any core damage as a result of eliminating the RCS dissolved gas and inline l RCS dissolved hydrogen sampling capability.

The PASS RCS hydrogen analyzer used for the PASS panel (SJ-145) is a non-safety related component. The PASS hydrogen analyzer has had significant past 1 maintenance and operational problems. A modification to replace the currently l installed hydrogen sensor with a different model would cost a minimum of i $121,000. In addition, replacing the current computer system, which is not Year 2000 compliant, would cost approximately $500,000 due to the extensive j computer programming required. i SU144ARY WCNOC is pursuing this change in commitment due to the high cost of replacing the hydrogen analyzer (and computer system) and the cost of maintaining the hydrogen analyzer over the life of the plant. Since the dissolved hydrogen analysis is not used as part of any Core Damage Assessment Methodology at WCGS, and because no WCGS procedure utilizes the Post Accident Sampling System hydrogen analyzer for any purpose, there is no safety impact from this commitment change.

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