ML20244E529
| ML20244E529 | |
| Person / Time | |
|---|---|
| Issue date: | 12/23/1986 |
| From: | Marsh L Office of Nuclear Reactor Regulation |
| To: | Ballard R Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML20244D710 | List:
|
| References | |
| NUDOCS 8612310020 | |
| Download: ML20244E529 (4) | |
Text
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UNITED STATES NUCLEAR REGULATORY COMMISSION 8
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DECEMBER 23, 1986 1
MEMORANDUli FOR:'
Ronald L..Ballard, Chief Engineering Branch Division of PWR Licensing-A FROM:
L. B. Marsh, Chief Engineering Branch' Division of PWR Licensing-B
SUBJECT:
GENERIC LETTER, CONTAINMENT INTEGRATED LEAK RATE TESTS
Reference:
Memorandum from Ronald L. Ballard to multiple addressees
~
dated December 18, 1986.
indicated We have reviewed the referenced memorandum and our comments 4
on the enclosed marked-up copy of the generic letter.
7 L. B. Marsh, Chief Engineering Branch Division of PWR Licensing-B
Enclosure:
As stated cc:
R. Vollmer R. Bernero W. Shields
.W. Minners C. E. Rossi ; -
3 R. L. BallarT~
J. Pulsipher
Contact:
R. Lipinski, DPLB/EB X29433 hh)
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DRAFT-TO: All Light Water Reactor Applicants and Licensees
SUBJECT:
CONTAINMENT INTEGRATED LEAKAGE RATE TESTS f
Gentlemen:
A recent NRC review of the different types of test computations used to determine' leakage rate for containment integrated leakage rate tests (CILRTs) performed throughout the industry has indicated that applicants and ifcensees are frequently Usinn a test computation method that is not in compliance with the explicit regulatory requirements of 10 CFR 50, Appendix J.
The method being used for computetton is-the mass point calculation described in ANSI /ANS-56.8-1981, " Containment System Leakaoe Testing Requirements."
In order to meet the regulatory requirements of Appendix J, applicants and licensees must measure the integrated Teakage 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 J requires that all CILRTs shall be conducted in accordance with the provisions of ANSI N45.4.Section III.A.3.(c) of Appendix J also requires that test leakage rates be calculated using absolute values corrected for instrument error. Section 5.1 of ANSI N45.4 pemits two methods of perfoming CILRTs, the absolute method and the reference-vessel method.
In addition, Section 7.9 of the standard describes the types of leakage rate computations permitted 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.
It should be noted that 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 determined to be in accordance with ANSI N45.4, with a test duration as defined in D'-TOP-1.
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Consiacuta n.Y, MY Ni1*+*o MHIcH Is REccour'ndo ay mg pe,vess, a CrM MUH!ly is dec.6PTA BL.C, N OV[bGb THetT IT is ReviaWG * * *> o i
A U'10VH BY THE STAFF -
DRAFT N N
s ANSI N45.4 also' requires that a " statistically averaged" leakage rath~be s
i determined (Paragraph 7.9).
However, ANSI N45.4 does not provide a specific 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 determined by using the mass point method described by AN51/ANS-56.8-1981 has technical merit. Although the NRC staff has in some
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instances accepted test results calculated by this method, recent review has determined that compliance with the regulatory requirements requires a CILRT leakage rate calculated by total 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 /> or as provided for in BN-TOP-1. Random and instrument error is typically accounted for by calculation of a statistically-determined 951confidencelevel.]Foratestwithadurationofatleast24 hours,the955 confidence level calculation will be acceptable if it is derived from eithe @
- p9t tS;d, as
%the total time or point-to-point method 6 c' (2) th:
p=Wd " "?/f 5 55.:-;Z;. For a test with a duration of less than 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />..the leakage rate and the 951 confidence level must be calculated in accordance with BN-TOP-1. The calculated leakage rate, with the 951 confidence level amount added to it, must then meet the acceptance criterion of Appendix 0 (i.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 same method (i.e.,
total time or point-to-point) as is the CILRT.
The regulatory requirements concerning acceptable calculational methods, described above, are applicable only to future CILRTs, and will not be applied to the calculational method of any test previously determined by the staff to be acceptable. It is suggested that applicants and licensees review their CILRT programs with respect to the above to assure future consistency with regulatory requirements.
In a related action, the NRC has released for public coment a general revision to Appendix J to 10 CFR 50 (51 FR 39538, dated October 29,1986). This l
revision would, among other changes, relax existing constraints on C1LRT
o 4
DRAFT calculational methodologies and would permit the use of the mass phint method for future CILpT determinations. A proposed Regulatory Guide (MS 021-5, October, 1986) has also been published for comment as a companion document to, and referenced by, the Appendix J revision. The draft Regulatory Guide identifies the mass point method, with certain constraints, as an acceptable nethod for future CILRT determinations, in accordance with the revised Appendix J.
However, until a revision is complete and in effect, the current Appendix J requirements apply.
No written response or specific action is required by this letter.
Therefore, no clearance from the Office of Management and Budget is required.
If you have any questions on this matter, please contact your project maracer.
Sincerely, Harold R. Denton, Director Office of Nuclear Reactor Regulatier