ML20245A371
| ML20245A371 | |
| Person / Time | |
|---|---|
| Issue date: | 11/26/1986 |
| From: | Harold Denton Office of Nuclear Reactor Regulation |
| To: | Sniezek J NRC OFFICE OF THE EXECUTIVE DIRECTOR FOR OPERATIONS (EDO) |
| Shared Package | |
| ML20244D710 | List:
|
| References | |
| NUDOCS 8703200235 | |
| Download: ML20245A371 (3) | |
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MEMORANnUM F00: James H. Snierek, Deputy Executive Director for Regional Operations and Generic Requirements FRDM: Harold R. Denton, Director ,
Office of Nuclear Reactor Regulation
SUBJECT:
CONTAINMENT INTEGRATED LEAKAGE RATE TESTS A recent OGC review of containment integrated leakage rate test (CILPTT methodology found that use of the " mass point" method, a widely used method for calculating the leakage rate from measured data, is not in compliance with the requirements of Appendix J to 10 CFR 50. As a result, we propose issuance "
of the attached generic letter to all light water reactor applicants and licensees.
As discussed in the attached generic letter, the staff believes that the mass point method has technical merit. However, Appendix J requires that a specific national standard, ANSI N45.4 147?, be followed when per'orming CILRTs; the standard further requires that one of two methods, " total time" and " point-to-point", be used to calculate leakage rate. Absent a rule change or a specific exemption from the rule, the mass point method cannot be used.
The purpose of this generic letter, then, is to infonn the recipients of, .and clarify, the regulatory requirements. This is advisable because staff practice had been, before the OGC review, to accept the mass point method. Although this represents a change in staff position, it is a change which returns us to the regulatory requirements of Appendix J to 10 CFR 50, which have been in effect since Appendix J was issued in 1973. Therefore, we do not believe that CRGR review is necessary. We plan to issue the ceneric letter within 10 working days of the date of this memorandum, unless we hear to the contrary.
Harold R. Denton, Director Office of Nuclear Reactor Degulation
Attachment:
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[ \^r UNITED STATES NUCLEAR REGULATORY COMMISSION WA$mGTON, D C. 20555 j ,1 TO: All Light Water Reactor Applicants and Licensees SUR.1ECT : CONTAINMENT INTEGRATED LEAKAGE RATE TESTS Gentlemen:
A recent NRC review of the different types of test computations used to detemine leakage rate for containment integrated leakage rate tests (CILRTs) performed throughout the industry has indicated that applicants and licensees are frequently using a test computation method that is not in compliance with the explicit regulatory requirements of 10 CFR 50, Appendix J. This method of computation is the mass point calculation described in ANSI /ANS-56.8-1981,
" Containment System Leakage Testing Requirements."
In order to meet the regulatory requirements of Appendix J, applicants and licensees must measure the integrated leakage rate using one of the CILRT methods described in ANSI N45.4-1972, " Leakage-Rate Testing of Containment Structures for Nuclear Reactors."Section III.A.3.(a) of Appendix 0 requires that all CILRTs shall be conducted in accordance with the provisions of ANSI N45.4 Section III.A.3.fc) of Appendix J also requires that test leakage rates be calculated using absolute values corrected for instrument error. In Section 5.1 of ANSI N45.4, the following two methods of perfoming CILRTs are provided:
the absolute method and the reference-vessel method. In addition. Section 7.9 of the standard describes the types of leakage rate computations pemitted for the 24-hour period absolute method CILRTs. The only types of leakage rate computations specified in this standard are the point-to-point and the total time calculations. Hence, compliance with the regulatory requirements of Appendix J for absolute method CILRTs can only be achieved through the use of ,
the point-to-point or total time leakage rate computational methods, corrected for instrument error.
Additionally, the total time test methodology presented in the Bechtel Topical Report BN-TOP-1, Revision 1. " Testing Criteria for Integrated Leakage Rate Testing of Primary Containment Structures for Nuclear Power plants" has been approved for use in accordance with ANSI N45.4, with a test duration as defined in BN-TOP-1.
ANSI N45.4 also requires that a " statistically averaged" leakage rate be detemined (Paragraph 7.9). However, ANSI N45.4 does not provide a specific l method for accounting for random and instrument error during a CILRT, as required by Appendix J. The NRC staff believes that the calculated leakage rate as detemined by using the mass point method described by ANSI /ANS-56.8-1981 has technical merit. However, compliance with the
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regulatory requirements requires a CILRT leakage rate calculated by,totti time or point-to-point, with a test duration of at least 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> except as provided for in BN-TOP-1. Random and instrument error should be accounted for by an acceptable calculation of a statistically-determined 95% confidence level. The 95% confidence level calculation will be acceptable if it is derived from either: (11 the total time or point-to-point method; or (2) the mass point method, as provided in ANST/ANS-56.R-1981. The calculated leakage rate, with the 95% confidence level added to it, must then meet the acceptance criterion of Appendix ' (f.e., not exceed 0.75 La or 0.75 Lt as appropriate).
The supplemental, or verification, test required by Section III.A.3.(b) of Appendix J must also have its leakage rate calculated by the total time or point-to-point method.
It is suggested that applicants and licensees review their CILRT programs with
. respect to the above to assure future consistency with regulatory requirements.
Sincerely, Harold R. Denton, Director Office of Nuclear Reactor Regulation o
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