ML20084P569

Informs NRC of New Test Method Which Approx as Closely as Possible Primary Containment Conditions During LOCA Because of Excessive Leakage Results During Local Leak Rate Tests

ML20084P569
Person / Time
Site:	Dresden
Issue date:	12/14/1976
From:	Stephenson B COMMONWEALTH EDISON CO.
To:	James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML20084P553	List: ML20084P569
References
76-871, NUDOCS 8306100316
Download: ML20084P569 (2)

Text

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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.Ill -

U. S. Nuclear Regulatory Commission 799 Roosevelt Road Glen Ellyn, Illinois 60137

SUBJECT:

Dresden Station Feedwater Check Valve Local Leak-Rate Testing

REFERENCE:

Letter to J. G. Keppler from B. B. Stephenson dated November 4, 1976 (Reportable Occurrence report no. 50-249/1976-25)

Because feedwater check valve local leak-rate tests (LLRT's) have repeatedly yielded excessive "as found" leakage results, a new test method has been developed which approximates as closely as possible the primary con-tainment conditions during a loss-of-coolant accident (LOCA).

The new test method involves pressurizing the voluma upstream of the feedwater check valve with water.to approximately 50 psig, then draining the system and performing a LLRT utilizing isolation valve test procedures.

Current isolation valve test procedures specify a pneumatic pressure decay test as required by the Technical Specifications. The station procedures will be revised to reflect the new method of testing the feedwater check valves in the "as found" condition.

Development of this new test method was based on typical postulated conditions following a LOCA. The conditions 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 feedwater check valves. For these conditions, reactor and containment pressure would be approximately 50 psig when 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 differential pressure available to seat the check valves following the subsequent loss of off-site power. Since there would still be water on the valves due to their position in the low point of the line, the new method of seating the valves with water is representative of accident conditions.

10 C.F.R. part 50, appendix J, section Ill.C.1 specifies that each valve

, to be tested shall be closed by normal operation and without any preliminary exercising or adjustments. Feedwater check valve seating with water is con-sidered a normal operation since the valve is normally seated with water and a differential pressure. ,

Based on the res.ults of testing performed during the Dresden Unit-3 t

i976 refueling outage, it is anticipated that the utilization of the new 8306100316 770201 PDR P ADOCK 05000249 pyg _l

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a o 2 O test method will significantly reduce the incidence of excessive "as found" l 1eakage test results on the feedwater check valves. (The method used to test the Unit-3 feedwater check valves is described in the referenced re-

. portable occurrence report.) As stated previously, the Dresden Station LLRT procedure for the feedwater check valves will be revised to include this new testing method. ,

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.- " tep Station Su,he'nson perintendent Dresden Nuclear Power Station BBS:CES:Jo cc: Director of Inspection & Enforcement Director of Management information & Program Control File /NRC S

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R.R. #1 0 Morris, lilinois 60450 Telephone 81s/942-2920 BBS Ltr. #76-871 December 14, 1976 Mr. James G. Keppler, Regional Director Directorate of Regulatory Operations - Region lli -

U. S. Nuclear Regulatory Commission ,

799 Roosevelt Road Glen Ellyn, Illinois 60137

SUBJECT:

Dresden Station Feedwater Check Valve Local Leak-Rate Testing

REFERENCE:

Letter to J. G. Keppler from B. B. Stephenson dated November 4, 1976 (Reportable Occurrence report no. 50-249/1976-25)

Because feedwater check valve local leak-rate tests (LLRT's) have repeatedly yielded excessive "as found" leakage results, a new test method has been developed which approximates as closely as possible the primary con-tainment conditions during a loss-of-coolant accident (LOCA).

The new test method involves pressurizing the volume upstream of the feedwater check valve with water to approximately 50 psig, then draining the system and performing a LLRT utilizing isolation valve test procedures.

Current isolation valve test procedures specify a pneumatic pressure decay test as required by the Technical Specifications. The station procedures will be revised to reflect the new method of testing the feedwater check valves in the "as found" condition.

Development of this new test method was based on typical postulated conditions following a LOCA. The conditions 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 feedwater check valves. For these conditions, reactor and containment pressure would be approximately 50 psig when 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 differential pressure available to seat the check valves following the subsequent loss of off-site power. Since there would still be water on the valves due to their position in the low point of the line, the new method of seating the valves with water is representative of accident conditions.

f 10 C.F.R. part 50, appendix J, section Ill.C.1 specifies that each salve to be tested shall be closed by normal operation and without any preliminary exercising or adjustments. Feedwater check valve seating with water is con-sidered a normal operation since the valve is normally seated with water and i a differential pressure.

Based on the results of testing performed during the Dresden Unit-3 1976 refueling outage, it is anticipated that the utilization of the new t

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test method will significantly reduce the incidence of excessive "as found" leakage test results on the feedwater , heck valves. (The method used to test the Unit-3 feedwater check valves is described in the referenced re-portable occurrence report.) As stated previously, the Dresden Station LLRT procedure for the feedwater check valves will be revised to include this new testing method. _ ,

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,, uf i. .'Stephenson Station Superintendent Dresden Nuclear Power Station BBS:CES:Jo cc: Director of Inspection & Enforcement Director of Management Information & Program Control File /NRC i

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