ML19207B740

Submits Info Memo 17 on Temp Effects on Level Measurements Re Westinghouuse Reporting Potential Safety Hazard Per 10CFR21.Recommends That Ref Leg Temperature Change Be Reviewed as Part of Specific SERs

ML19207B740
Person / Time
Issue date:	08/15/1979
From:	Eisenhut D Office of Nuclear Reactor Regulation
To:	Schroeder F Office of Nuclear Reactor Regulation
Shared Package
ML19207B741	List: ML19207B740 ML19207B746
References
REF-SSINS-6820, TASK-A-21, TASK-OR NUDOCS 7909050173
Download: ML19207B740 (2)

Text

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UNITED STATES f

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AUG 151979 MEMORANDUM FOR:

Frank Schroeder, Jr., Deputy Director, Division of Systems Safety FROM:

D. Eisenhut, Acting Director, Division of Operating Reactors

SUBJECT:

INFORMATION MEMORANDUM NO. 17 - TEMPERATURE EFFECTS ON LEVEL MEASUREMENTS INTRODUCTION On June 22, 1979, Westinghouse Electric Corporation reported to NRC, a potential safety hazard under 10 CFR 21 (Encicsure 1). This report addresses errors generated in the steam generator level indication sensors following high energy pipe break accidents inside containment.

Further, the report implies that previous analyses of peak containment temperature and pressure may have been nonconservative.

Breaks of this type can result in heatup of the steam generator level measurement reference leg resulting in a decrease of the water column density with a conseque.nt apparent increase in the indicated steam generator water level (i.e., apparent level exceeding actual level' Westinghouse has supplied their customers with tables ret'ecting correc ions to indicated steam generator water level for refe.ence leg heatup effects (Table 1 and 2 of Enclosure 1).

In addition, Westinghouse has advised that boiling could conceivably occur in the reference legs following depressurization, and could cause erroneous indications.

SAFETY SIGNIFICANCE The effect of increased reference leg witer column temperature on the indicated steam generator water level.ould delay or prevent actuation of protection signals and provide erroneous infomation during post-accident monitoring.

Soecifically, this potential level bias could result in delayed initiation of a s.eam generator low-low level indica-tion and, therefore, delay initiat :n of auxiliary feedwater and/or reactor trip.

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. D0R ACTION 00R has discussed this matter with I&E to ensure that all the affected licensees take appropriate action.

Since this may be a common problem in other reactor designs, I&E has issued a Bulletin containing actions to be taken by all power reactor facilities with an operating license (Enclosure 2).

DOR and DSS comments have been incorporated in this Bulletin.

RECOMMENDATIONS 00R recommends that the Containment Systems Branch consider this information with regard to their efforts on Tcsk Action Plan A-21 and its impact on Main Steam Line Break "best estimate" temperature inside containment.

In addition, D0R recommends that the Instrumentation and Control Systems Branch consider this information in their reviews and determine whether greater error bands should be assumed in the accident and transient anal; sis or whether some means of temperature compensation should be provided.

Further, we recommend that this problem, i.e.,

reference leg temperature change, be reviewed on a plant specific basis as part of the staffs CP and OL safety evaluations.

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J D. Eisenhut, Acting Director Division of Operating Reactors s

Enclosures:

As stated

Contact:

R. Kendall X-27110 cc w/ enclosures:

S. Hanauer L. Nichols E. Jordan J. Sniezek W. Butler D. Tondi R. Satterfield E. Butcher F. Rosa M. Chiramal G. Lain-R. Kendall D. Eise:

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