ML20066E577

Forwards Addl Info Re Containment Leakage Testing Program, in Response to Open Items Identified in NRC . Penetration M-44 Will Be Tested Per 10CFR50 App J.Util Amend Application Will Be Revised

ML20066E577
Person / Time
Site:	Fort Calhoun
Issue date:	11/05/1982
From:	William Jones OMAHA PUBLIC POWER DISTRICT
To:	Clark R Office of Nuclear Reactor Regulation
References
LIC-82-370, TAC-8910, NUDOCS 8211150307
Download: ML20066E577 (4)

Text

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Omaha Public Power District 1623 HARNEY ' OMAHA, NEBRASKA 68102 ' TELEPHON E 536-4000 AREA CODE 402 November 5, 1982 LIC-82-370 Mr. Robert A. Clark, Chief U. S. Nuclear Regulatory Commission Office of Nuclear Reactor Regulation Division of Licensing Operating Reactors Branch No. 3 Washington, D.C. 20555

Reference:

Docket No. 50-285

Dear Mr. Clark:

10 CFR 50, Appendix J Containment Leakage Testing Program Omaha Public Power District's letter to the Commission dated September 3,1982 provided the District's initial response to the three open items identified in the Commission's letter dated July 23, 1982 regarding the subject issue. The District stated in our letter that further analysis regarding the first and third open items would be conducted and the Commission would be provided a final response after the evaluation was completed. The District has completed this evalu-ation and, accordingly, please find attached the District's response to the subject open items.

Sin rely, 4 W. C. Jones Division Manager Production Operations WCJ/TLP:jmm Attachment cc: LeBoeuf, Lamb, Leiby & flacRae 1333 New Hampshire Avenue, N.W.

Washington, D.C. 20036 8211150307 821105 PDR ADOCK 05000285 P ppg

Attachment Open Item #1 OPPD's correlation to extrapolate leakage rates at 5 psig to 60 psig for containment airlocks is not sufficiently conservative.

Response

The District has reviewed the extrapolation methodology presented in Appendix A to the Comission's letter dated July 23, 1982. This method-ology was prepared by the Franklin Research Center. The District also reviewed the four references provided in Appendix A, specifically i Reference 4 (i.e. , "U.S. Reactor Containment Technology", edited by Cottrell and Savolainen). The results of our review are provided below:

1. Appendix A begins the discussion by stating, "that if (a) the test medium is air, (b) Pa is appreciable compared to one atmosphere, and (c) the leakage path.is such as to produce laminar viscous flow (i.e., capillary-like rather than orifice-like), the calculation appropriate to this test medium yields a substantially higher calculated value of Pa than would be obtained by assuming leakage to be directly proportional to the pressure differential to the one-half power." It should be noted that the rationale for at least two of the above assumptions is ambiguous as background derivation and discussion is not provided. In contrast, the Cottrell and Savolainer, reference states that investigations which emphasize the effects of pressure on the flow rate of leakage are not always simply apparent because a given leak can exhibit several different types of flow. Also, for a particular characteristic geometry of a leak in a vessel, it is desirable to recognize the type of flow that may occur, since it defines the expected leakage rate.

Cottrell and Savolainen continue by stating that although for many reported containment leakage tests it has been assumed that com-pressible flow through orifices is representativ~e of the leakage behavior, no available test data or evidence justify the assumption

. or support this conclusion. Each containment structure should preferably be considered as uniquely influenced by several or all of the following factors that ultimately determine its leakage rate: temperature and pressure in containment, composition and physical properties of the containment atmosphere, number of

- potential leakage paths, dissimilarity of flow characteristics among existing leaks, variations of leak geometry with variations of internal containment pressures, and the extent of containment boundary limits beyond the containment shell.

2. Appendix A provides the calculations and results that apparently demonstrate that the District's correlation enderestimates the leakage mass flow rate by approximately 20%. However, Cottrell and Savolainen state that for extrapolation of leakage rates from a low l test pressure to a higher pressure, laminar flow will yield a I

higher leakage rate than other modes of flow.

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3. Appendix A also justifies, based on purely viscous flow, that the District's methodology is unconservative by a factor of 8.9. In contrast, Cottrell and Savolainen state, "that because of the various leak geometries (cross section dimensions and length of leak path) encountered ir. containment vessel structures, two leaks exhibiting the same flow rate at one pressure condition will probably not have the same flow rate for a different set of con-ditions. Although the majority of significant leaks in a con-tainment vessel may well be in the laminar flow regime at one pressure, it is conceivable that with higher velocities, turbulent flow conditions will be attained in irregular leak passages."

Therefore, assuming that all flow is laminar may be overly con-servative. The degree of conservatism is reflected by the fol-lowing statement taken from Appendix A: " . . . the conversion should not be more conservative than necessary in light of avail-able data, because excess conservatism could frequer.tly result in the interpretation that a given leak exceeds its maximum allowable limit when in fact it would not exceed that limit if Pa were actually applied."

Based on the above arguments and the discussions provided in Reference 4 to Appendix A, the District concludes that the proposed changes to the District's method for calculating the leak rate of the personnel access lock (PAL) do9r are not appropriately justified because Appendix A proposes the adoption of overly conservative and unpractical estimates. It should also be emphasized that the present reduced pressure test on the PAL door system is conducted by pressurizing the space between the two resilient seals on each door and that testing at a very high pressure (e.g. , Pa) would tend to unseat the resilient seals because this pressure is applied opposite to the accident pressurc which tends to seat the resilient seals for a tighter closure. Therefore, the District will continue to use the ASME Code endorsed pressure extrapolation methodology and, in order to increase the degree of conservatism in utilizing this methodology, we propose to increase the reduced pressure test from 5 psig to 15 psig. The District will submit a revised amend-ment application under separate cover which incorporates this change, along with other administrative changes.

Open Item #2 The valve or valves associated with penetration M-3 should be tested in accordance with Appendix J.

Response

A complete response to this item was provided in the District's letter dated September 3, 1982.

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i l Open Item #3 The valve or valves associated with penetration M-44 should be tested in i

accordance with Appendix J.

Response

Penetration M-44 will be tested in accordance with Appendix J, and the

! District's amendment application will be revised accordingly.

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