ML13310A826

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Submits Info Obtained to Date & Expected Completion Dates of Work Re Adequacy of PORV Block Valves Per TMI Item II.D.1. Verification of Anchor/Darling Assumptions Will Be Submitted by 831001
ML13310A826
Person / Time
Site: San Onofre 
Issue date: 07/13/1983
From: Baskin K
Southern California Edison Co
To: Crutchfield D
Office of Nuclear Reactor Regulation
References
RTR-NUREG-0737, RTR-NUREG-737, TAC-44128, TASK-2.D.1, TASK-TM NUDOCS 8307250450
Download: ML13310A826 (4)


Text

Southern California Edison. Company P. 0. BOX 800 2244 WALNUT GROVE AVENUE ROSEMEAD. CALIFORNIA 91770 K. P. BASKIN TELEPHONE MANAGER OF NUCLEAR ENGINEERING, July 1 (213) 572-1401 SAFETY, AND LICENSING Director, Office of Nuclear Reactor Regulation Attention: D. M. Crutchfield, Chief Operating Reactors Branch No. 5 Division of Licensing U. S. Nuclear Regulatory Commission Washington, D.C.

20555 Gentlemen:

Subject:

Docket No. 50-206 PORV Block Valve Adequacy Report San Onofre Nuclear Generating Station Unit 1

References:

1. Letter, K. P. Baskin, SCE, to D. M. Crutchfield, NRC, NUREG-0737, Item II.D.1 - Performance Testing of PWR Relief and Safety Valves, December 2, 1982
2.

Letter, K. P. Baskin, SCE, to D. M. Crutchfield, NRC, Implementation of TMI Action Plan Requirements, May 12, 1981 Reference 1 provided you with the PWR Safety and Relief Valve Adequacy Report for San Onofre Unit 1. The letter indicated that the report provided justification of the existing valve and piping configuration at San Onofre Unit I when the required modifications are completed. Reference 1 also indicated that due to a design difference between the San Onofre Unit 1 PORV block valves and the block valve tested at Marshall Steam Station, we would develop a plant specific justification for the block valves.

We indicated that the plant specific justification would include valve specific analyses, to be performed by the valve manufacturer Anchor/Darling. The PORV Block Valve Report was scheduled in Reference 1 to be submitted by June 1, 1983.

This commitment was confirmed by your Order Confirming Commitments dated March 14, 1983. As discussed in Reference 2, we interpret the completion dates contained in the Order Confirming Commitments to require the item to be completed by the specified date or the station shutdown until completion of the item, unless otherwise authorized by the NRC.

As you know, San Onofre Unit 1 was shutdown prior to June 1, 1983 and will remain shutdown until completion of the work related to the adequacy of the PORV block valves.

The information obtained to date, and the expected compl6tion dates of our work related to the adequacy of the PORV block valves are provided below.

8307250450 830713 PDR ADOCK 05000206 P

PDR1

Mr. D.

July 13, 1983 The Anchor/Darling contribution to the subject report is complete as of May 6, 1983. The Anchor/Darling portion of the effort yielded conclusive evidence that the block valves will perform the intended blocking function in the event of a post-accident stuck-open PORV scenario. The review and subsequent draft of a Westinghouse "PORV Block Valve Adequacy Report for San Onofre Unit 1" is currently scheduled to be completed by October 1, 1983, assuming successful verification of the items to follow.

The San Onofre Unit 1 block valve design, with the exception of the actuator, is comparable to the valve design used during the Marshall testing as shown in Table 1 (enclosed). The required opening and closing thrusts of the San Onofre Unit 1 block valve were derived from the test values adjusted for the differences in valve size and differential pressure. The calculated opening thrust is the maximum thrust required to unseat the valve based on the design differential pressure. The calculated closing thrust is the thrust necessary to seat the valve which is also based on the design differential pressure.

The actuator used to operate the San Onofre Unit 1 block valve is a pneumatic diaphragm actuator utilizing an internal, coil spring to provide the open force and pneumatic pressure the closing force. The available actuator opening force is based upon the spring rate and initial compression of the coil spring. The actuator closing force is based upon the air pressure supplied to the actuator. The actuator supplied with the San Onofre Unit 1 block valve is adequate to open and close the valve. The spring used in the actuator should have a spring rate of 1020 lbs. per inch and an initial compression of 2 inches. Since the actuator manufacturer supplies four (4) different spring sizes with this actuator, the spring size used in the San Onofre Unit 1 valve will be verified. The minimum supply air pressure to provide the required actuator closing force is 85 psig and this will be verified at San Onofre Unit 1.

The seating surfaces of the EPRI test valve were badly galled after the cycle testing and exhibited high seat leakage but, the leakage was not quantified.

We are attempting to define the precise impact this seat leakage will have on the function of this valve and will provide a more detailed description in the adequacy report. Additionally, the bonnet bolting needs to be verified to be torqued to 640 ft.-lbs. in order to prevent possible joint separation and external leakage during the anticipated valve loading.

A structural analysis of the valve shows stresses at critical sections which are below the allowable stresses (90% of yield strength),

except for the body-bonnet flange. Certain stresses in the flanges are approximately 5 percent greater than the yield strength of the flange material at the design temperature (6800F).

Although the stresses are above the yield strength, they are below the allowable stress limit permitted by ASME Section III, Division 1, paragraph NC-3647 which is the method that was used to determine the stresses.

Mr. D.

July 13, 1983 Based upon the above discussion, we will have to verify some Anchor/Darling assumptions and incorporate all of the information into a Westinghouse prepared San Onofre Unit 1 Block Valve Adequacy Report. As previously mentioned, this effort is scheduled to be complete, and will be submitted to you on or before October 1, 1983. We will advise you if there are any changes to this schedule.

If you have any questions regarding this issue for San Onofre Unit 1, please let me know.

Very truly yours, Enclosure

TABLE I Comparison of EPRI Test Valve and SCE Block Valve EPRI SCE BLOCK PARAMETER TEST VALVE VALVE Valve Description 3"-1540# Gate 2"-1500# Gate Drawing No.

93-15268 10529 Operating/Design Conditions Pressure (psig) 2405 2485 Temperature (oF) 650 680 Differential Press. (psi) 2405 2485 Flow Rate (lb/hr) 176,000 Material Body SA351-CF8M A351-CF8M Seat Surface Stellite No. 6 Stellite No. 6 Packing Crane 187-I Crane 187-I Valve Design Mean Seat Dia/Area (in/in 2) 2-7/8/6.49 1-7/8/2.76 Stem Dia/Area (in/in 2) 1-1/4/1.23 3/4 /.442 Stroke (in) 3-1/2 2-1/2 Packing Rings 4 Rings-Double 12 Rings Required Open Force (lb.)

Seat Load 6458 2838 Stem Unbalance (2958)

(1098)

Packing Drag 3000 1800 Total Open Force (lb.)

.6500 3540 Required Close Force (lb.)

Seat Load 8442 3714 Stem Unbalance 2958 1098 Packing Drag 3000 1800 Total Close Force (lb.)

14400 6612