ML19209B119
| ML19209B119 | |
| Person / Time | |
|---|---|
| Site: | 05000484 |
| Issue date: | 08/13/1979 |
| From: | James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| To: | Dienhart A NORTHERN STATES POWER CO. |
| References | |
| NUDOCS 7910090196 | |
| Download: ML19209B119 (1) | |
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UNITED STATES NUCLEAR REGULATORY COMMISSION 3
'3A I oE REGION lli o
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799 ROOSEVELT ROAD
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GLEN ELLYN, ILLINOls 60137 i
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Docket No. 50-484 i
AUG131979 Northern States Power Company ATTN:
Mr. A. V. Dienhart Vice President - Tyrone Energy Park 100 North Barstow Street Eau Claire, WI 54701 Gentlemen:
The enclosed IE Bulletin No. 79-21 is forwarded to you for information.
No written response is required.
If you desire additional information regarding this matter, please contact this office.
Sincerely,
[h.
ames G. Keppler Director
+
Enclosures:
1.
List of IE Bulletins Issued in the Last 6 Honths cc w/encls:
Central Files Director, NRR/DPM Director, NRR/ DOR PDR Local PDR NSIC TIC Regions I & IV 1116 079 7910090[fb e
Accession No:
7908090193 SSINS No:
6820 UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D.C.
_20555 August 13, 1979 IE Bulletin No. 79-21 TEMPERATURE EFFECTS ON LEVEL MEASUREMENTS Description of Circumstances:
On June 22, 1979, Westinghouse Electric Corporation reported, to NRC, a potential substantial safety hazard under 10 CFR 21.
The report, Enclosure No.1, addresses the effect of increased containment temperature on the reference leg water column and the resultant effect on the indicated steam generator water level.
This effect would cause the indicated steam generator level to be higher than the actual level and could delay or prevent protection signals and could, also, provide erroneous information during post-accident monitoring.
Enclosure No. I addresses only a Westinghouse steam generator reference leg water column; however, safety related liquid level measuring systems utilized on other steam generators and reactor coolant systems could be affected in a similar manner.
Actions To Be Taken By Licensees:
For all pressurized water power reactor facilities with an operating license:^
1.
Review the liquid level measuring systems within containment to determine if the signals are used to initiate safety actions or are used to provide post-accident monitoring information.
Provide a description of systems that are so employed; a description of the type of reference leg shall be included, i.e., open column or sealed reference leg.
2.
On those systems described in Item 1 above, evaluate the effect of post-accident ambient temperatures on the indicated water level to determine any change in indicated level relative to actual water level.
This evaluation must include other sources of error including the effects of varying fluid pressure and flashing of reference lag to steam on the water level measurements.
The results of this evaluation should be presented in a tabular form similar to Tables 1 and 2 of Enclosure 1.
3.
Review all safety and controi setpoints derived from level signals to veriiy E
that the setpoints will initiate the action required by the plant safety analyses throughout the range of ambi instrumentation, including accident these setpoints.
DUPLICATE DOCUMENT Entire document previously entered
" Boiling water reactors have been request into system under:
NRC to provide similar information.
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ANO No. of Pages:
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June 22,1979 KS-TMA-2104 Mr. Victor Stello Director, Office of Inspection and Enforcement U.S. Nuclear Regulatory Comission
. East West Towers Building 4350 East West Highway Bethesda, Maryland 20014
Dear Mr. Stello:
Subject:
Steam Generator Water Level This is to confirm my telephone conversation of June 21, 1979 with Mr.
Norman C. Moseley, Director, Division of Reactor Operation and Instec-tion and Mr. Samuel E. Bryan, Assistant Director for Field Coordination.
In that conversation, I reported that Westinghouse had inforined its utility customers of corrections that should be applied to indicated steam generator water level and recomended that they incorporate those ccrre:tiens in the steam generator low water level protection system setpoir.ts and emergency operating procedures for operating plants as appropriate.
High energy line breaks inside containment can result in heatup of the steam generator level measurement reference leg.
Increased reference leg water column temperature will result in a decrease of the water column density with a consequent apparent increase in the indicated steam generator water level (i.e., apparent level exceeding actual level). This potential level bias could result in delayed protection signals (reactor trip and auxiliary feedwater initiation) which are based on low-low steam generator water level.
In the case of a feedline rupture, this adverse environment could be present and could delay or prevent the primary signal arising from declining steam generator water level (low-low steam generator level).
The following is a list of backup signals available in those Westinghouse plants which take credit in their Final Safety Analysis Reports for steam generator water level trip with
_ an adverse containment environment:
overtemperature delta T; high pressurizer pressure; containment pressure and safety injection.
For other high energy line breaks which bias to the steam generator water 1 E DomEM level does not provide the primary would not interfere with needed pro Entire document previously entered into system under:
.e 1116 081 T
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