AECM-83-0674, Part 21 Rept Re Potentially Defective Presray Airlock Seal in Drywell Personnel Airlock Supplied by Wj Woolley. Initially Reported by Vendor on 830919.New Seal Being Designed by Presray Corp Will Be Installed When Available

Part 21 Rept Re Potentially Defective Presray Airlock Seal in Drywell Personnel Airlock Supplied by Wj Woolley. Initially Reported by Vendor on 830919.New Seal Being Designed by Presray Corp Will Be Installed When Available

ML20081A220
Person / Time
Site:	Grand Gulf
Issue date:	10/24/1983
From:	Dale L MISSISSIPPI POWER & LIGHT CO.
To:	Harold Denton Office of Nuclear Reactor Regulation
References
REF-PT21-83-051-000 AECM-83-0674, AECM-83-674, PT21-83-051-000, PT21-83-51, NUDOCS 8310260186
Download: ML20081A220 (3)

Text

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P MISSISSIPPI POWER & LIGHT COMPANY Helping Build Mississippi P. O . B O X 1640, J AC K S O N. MIS SIS SIP PI 3 9 2 05 October 24, 1983 NUCLE AR PRODUCTION DEPARTMENT U. S. Nuclear Regulatory Commission Office of Nuclear Reactor Regulation Washington, D. C. 20555 Attention: Mr. Harold R. Denton, Director

SUBJECT:

Grand Gulf Nuclear Station Units 1 and 2 Docket Nos. 50-416 and 50-417 License No. NPF-13 File 0260/L-860.0/5018 Drywell Personnel Air Lock 10CFR Part 21 Report AECM-83/0674 In a September 19, 1983 letter, W. J. Woolley Co. informed the Nuclear Regulatory Commission (NRC) that a Presray airlock seal had failed the 465*F LOCA environment qualification test for the Midland Nuclear Station and that this failure constituted a possible 10CFR 21 defect. Since the Grand Gulf Nuclear Station (GGNS) drywell personnel airlock is a Woolley supplied component using Presray Seals, the GGNS 330*F drywell LOCA environment was believed to constitute a threat to the drywell airlock seals. As a result, the GGNS drywell airlock was identified in the Woolley letter as one of the potentially inadequate components. Mississippi Power & Light Company (MP&L) was notified of this potential deficiency by a September 22, 1983 letter from Woolley to Bechtel Power Corporation.

As discussed in an October 10, 1983 telephone conversation between representatives of Woolley and Bechtel, two seals were subjected to the following conditions during the qualification test:

o artificial aging for an equivalent of five years by exposure to 201*F for 200 hours0.00231 days <br />0.0556 hours <br />3.306878e-4 weeks <br />7.61e-5 months <br /> exposure o exposure to an integrated radiation dose of 1 X 10 rads o exposure to a test chamber post LOCA environment of 465'F.

E, Failure occurred on one seal after the high temperature had weakened the elastomer allowing it to stretch and rupture under a 90 psig internal n pressure. Radiation exposure is not thought to be a factor in the failure i because the seal material, an EPDM elastomer, has high resistance to radiation

{ damage. The other seal was intact and functioning at the completion o,f the test.

The GGNS drywell personnel air lock consists of a cylindrical steel shell DO

-cr with steel bulkheads at each end, and two steel doors in the bulkheads which

$ open towards the reactor. Sealing of each door is accomplished by two I;

Member Middle South Utilities System

AECM-83/0674

1. E" MISSISSIPPI POWER O LIGHT COMPANY continuous, inflatable seals which surround the door edge. When the door is closed, the seals inflate outwardly from the door and impinge against a smooth stainless steel sealing surface. The pressure within the seals can be monitored during normal operation to further ensure the integrity of the lock.

Even though the Woolley test indicates that the seals may not be qualified for GGNS, the test parameters which were used were in excess of GGNS specific values. To compare the Woolley test results with the conditions at Grand Gulf, a calculation was performed to determine the temperature in the area between the two doors while arbitrarily assuming that both of the door seals on the drywell side of the airlock had failed. This calculation shows that the maximum temperature under these conditions is 258'F. During operation, the Grand Gulf seals are pressurized to 60 psig at 135*F; therefore, a tempera-ture increase to 258*F during a LOCA would increase the internal pressure to a maximum of 72 psig. A comparison of these conditions to the existing qualiff-cation conditions of 200*F cnd 90 psig shows that although the calculated temperature of 258*F is 58*F above the qualification temperature, the 72 psig internal pressure is 18 psig below the qualification pressure. The failure of the Midland test sample was a combination of much higher temperatures and higher pressures on an artificially aged material. Although the Presray seals have not been specifically qualified by test for the Grand Gulf post-LOCA environment, it is our engineering judgement that the unaged seals at Grand Gulf would withstand the temperatures and pressures associated with a postulated design basis accident.

In addition to the above evaluation a worst case failure which assumes the loss of all four seals in the drywell personnel airlock was examined. The results of the calculations showed that the flow through the air lock assembly would be approximately 3,100 scfm. A second case which assumes the loss of both of the inner door seals with the outer door open was also evaluated. The flow through the air lock assembly was determined to be 5000 scfm for this case. These two flows represent 8.9 percent and 14.3 percent, respectively, of the 35,000 scfm allowable bypass leakage as defined in the FSAR. Therefore, neither of these cases would cause drywell bypass leakage in excess of the containment design levels.

MP&L believes that no significant hazards to the public due to continued operation exists and that interim operation until the first scheduled outage is justified. As indicated above, the failure of the seals will be highly unlikely, but even if it does occur, the leakage levels will remain in the acceptable region.

W. J. Woolley is working with Presray Corporation in the design of a new seal and is continuing the qualification test program. Once the new seals are qualified and become available, they will be procured for installation during the first refueling outage.

1 e

AECM-83/0674

• E' MISSISSIPPI POWER O L12HT COMPANY Should you have any questions, please advise.

Yours truly, BlMk L. F. Dale

[, y Manager of Nuclear Services GWS/SHH: sap cc: Mr. J. B. Richard Mr. R. B. McGehee Mr. T. B. Conner Mr. G. B. Taylor Mr. Richard C. DeYoung, Director Office of Inspection & Enforcement 7

U. S. Nuclear Regulatory Commission Washington, D. C. 20555 Mr. J. P. O'Reilly, Regional Administrator U.S. Nuclear Regulatory Commission

~ Region II 101 Marietta St., N.W., Suite 2900 Atlanta, Georgia 30303 f

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