ML17252A262
| ML17252A262 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 12/14/1976 |
| From: | Stephenson B Commonwealth Edison Co |
| To: | James Keppler NRC/RGN-III |
| References | |
| BBS Ltr. #76-871 | |
| Download: ML17252A262 (3) | |
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.. jW-\\IUISTRATIVE PROCEDURES
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(APPENDIX B)
. Heguf atory Docket 8f e:
. SUPPLEMENT TO DVR.
DVR NO.
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SeptE!n1ber 1974 PART 1 I TITLE OF EVENT
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CommonweaAEdison
- Dresden Nuclear ~;
Station R.R. #1 Morris, Illinois 60450 Telephone 815/942-2920 BBS Ltr. #76-871 December 14, 1976 Mr. James G~ Keppler, Regional Director Directorate of Regulatory Operations - Region I I I U. S. Nuclear Regulatory Commission 799 Roosevelt Road G 1 en E 11 yn, I 11 i no is 6013 7
SUBJECT:
Dresden Station Feedwater Check Valve Local Leak-Rate T~sting
REFERENCE:
Letter to J. G. Keppler from B. B. Stephenson dated N.ovember 4, 1976 (Reportable Occurrence report no. 50-249/1976-25)
Because feedwater check valve local leak-rate tests (LLRT's) have repeatedly yielded excessive 11as found" leakage results, a new test method has been develop~d which approximates as closely as possible the primary con-tainment conditions during a Joss-of-coolant accident. (LOCA).
The new test method involves pressurizing the vol~me ~pstream of the feedwater check valve with water to approximately 50 psig, the~ draining the system and performing a LLRT utilizing isolatton valve test procedures.
Current isolation valve test procedures specify a pneumatic pre,ssure decay test as required by the Technical Specifications.
The station ~~ocedur~~*will be revised to reflect the new method of testing the feedwatet check valves *in the 11as found" condition.
Development of this new test method was based on typical pqstulated conditions following a LOCA.
The condition.s selected were the design basis LOCA followed by a loss of**off*site power, two* failures which would result
- in the lowest differential pressure available to seat the feedw.at.er check
.valves.
For these conditions, reactor and containment press.ure would. be a~p~oximately 50 psig wh~n the feedwater system pressure dropped to zero as the result of the loss of off-site power.
Postulated LOCA's with less than design basis-size breaks would result in longer blowdown rates and potentially higher ~ifferential pressure ~vailable to seat the check valves following the subsequent Joss of off-site power.
Since there would still be water on the valves due to their position in the low point of the 1 ine, the new met~odof seating the valves with water is ~epresentative 6f acciden~ conditions.
JO C.F.R. part 50, appendix J, section I I l.C. 1 specifies that each valve to be tested shall be closed by.normal operation and without any preliminary exercising or adj~stments. Feedwater check valve seating with water is con-side*red a normal operation since the valve is normally seated with water and a differential pressure.
Based.on the r~sults of testing performed during the Dresden Unit-3 1976 refuel in~ outage, it is anticipated that the utilization of the new
- test method will significantly reduce the incidence of excessive "as found" leakage test results on the feedwater check valves.
(The method used to test the Unit-3 feedwa~er check valves is described in the ref¢r~nced re-portable occur~enc~ iepo~t.)
As stated previously, the Dresden Station LLRT procedure for the feedwater check valves will be revised to include thii new testing method.
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Dirett6r of inspection & Enforc~m~nt Dfrector'of Management Information & Program Contiol Fi le/NRC