ML19254E430

Forwards Request for Addl Info Re Level Measurement Sys,Per IE Bulletin 79-21

ML19254E430
Person / Time
Site:	Sequoyah
Issue date:	10/05/1979
From:	Rubenstein L Office of Nuclear Reactor Regulation
To:	Parris H TENNESSEE VALLEY AUTHORITY
References
NUDOCS 7911010095
Download: ML19254E430 (3)

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UNITED STATES

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e OCT 5 1979 Docket Nos. 50-327 and 50-328 Mr. H. G. Parris Manager of Power Tennessee Valley Authority 500A Chestnut Street Tower II Chattanooga, Tennessee 37401

SUBJECT:

REQUESTS FOR ADDITIONAL INFORMATION ON SEQUOYAH Enclosed is a request for additional information on level measurement systems for. Sequoyah that was raised in I/E Bulletin 79-21.

This information is needed by October 24, 1979.

Sincerely,

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Lester ubenstein, Acting Chief Light Water Reactors Branch No. 4 Division of Project Management

Enclosure:

As Stated cc:

See next page 1283 965 09 7911 010 4i

'lennessee Valley Authority ccs:

Herbert S. Sanger, Jr. Esq.

General Counsel Tennessee Valley Authority 400 Commerce Avenue E11B33 Knoxville, Tennessee 37902 Mr. E. G. Beasley Tennessee Valley Authority 400 Commerce Avenue W10Cl31 C Knoxville, Tennessee 37902 Mr. Michael Hc-ding Westinghouse Electric Corporation l'.

O. Box 355 Pittsburgh, Pennsylvanic 15230 Mr. David Lambe: c Tennessee Valley Authority 400 Chestnut Street Tower 11 Chattanooga, Tennessee 37401 128?

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LEVEL MESSUREMENT ERRORS DDE TO ENVIRONMENTAL TEMPERATURE EFFECTS ON

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LEVEL INSTRUMENT REniRENCE LEGS 2s

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Dn June 7.2,1979, Westinghouse Elect ric Corporation reported to NRC, a potential safet;y hazard under 10 CD 21. This report addresses errors generated in the stea;n generator level indication sensors following high energy pipe break accidents inside containment. Jurther; the report inplies that previous analyses of peak cortainment temperatorme and pressure may'.have been nonconservative.

Breaks of this type can msult in heatup of the steam generator level measurement reference leg resulting in a decrease of the water column density with a consequent increase in the indicated steam generator water level (i.e., indicated level exceeding actual level);

IE Bulletin 79-21 includes further information on this problem and addresses appropriate actions which are to be taken by licensees of operating plants.

Applicants 'for an operating license are requested to submit a response to the following questions and to revise their safety ar.alysis report consistent with this response.

1.

Describe the liquid level mea'suring systems within containment that are used to initiate safety actions or are used to provide post-accident monitoring infonnation.

Pmvide a description of the type' of reference leg used i.e., open column or sealed reference leg.

Pmvfde an evaluation of the effect of post, accident _ ambient temperatures 2.

on the indicated water level to determine the change in indicated level relative to actual water levt.l.

This evaluation must include other sources of error including the effects of varying fluid pressure and flashing of reference leg to steam on the water level measurements.

Provide an analysis of the~ impact th'at the MvWmeasurement errors in 3.

control and protection systems (2 above) have on the assumptions used in the plant transient and accident analysis, This should include a review of all safety and control setpoint: derived from level signals to verify that the setpoints will initiate the action required by the plant safety analyses throughout the ranp of ambient temperatures encountered by the instrumentation, inclu*ng accident temperatures.

If this analysis demonstrates that level measurement errars at a greater than assumed in the safety analysis, aMress the corrective action to be taken.

The corrective actions consido ed should_ include design changes that could be made to ensure that containment temperature effects are automatically accounted 'or.

These measures may include setpoint changes as an acceptable corcective action for the short term.

However, some form of temperature compensation or codification to eliminate or reduce temperature errors should be investigated as a 1 n enn 01 tion.

4.

Review and indicate the required revisions, as necessary, of emergency procedures to include specific information obtained from the review and evaluation of Items 1, 2, and 3 to ensure that the operators are instructed on the potential for and magnitude of erroneous level signals. Provide 9 copy of tables, curves, or correction factors that wouTd be applied to post, accident monitoring systems that will be used by plant operators.