ML20205T026
| ML20205T026 | |
| Person / Time | |
|---|---|
| Site: | Palisades  |
| Issue date: | 11/03/1988 |
| From: | Holahan G Office of Nuclear Reactor Regulation |
| To: | CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| Shared Package | |
| ML20205T031 | List: |
| References | |
| NUDOCS 8811140082 | |
| Download: ML20205T026 (6) | |
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7590-01 i
UNITED STATES OF ANERICA NUCLEAR REGUL ATORY COMMISSION l
In the Matter of CONSUMERS POWER Docket No. 50-255 i
COMPANY (PalisadesPlant) l h
EXEMPTION i
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The Consumers Power Corpany (the licensee) is the holder of Provisional Operating License No. OPR-20, which authorfres operation of the Palisades Plant l
(Palisades)atasteady-statepowerlevelnotinexcessof2530 megawatts i
thermal. The plant is a pressurized water reactor located at the licensee's site ire Van Buren County, Michigan. The license provides, among other things, i
that Palisades is subject to all rules, regulations, and orders of the Nuclear
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Regulatory Corsission (the Comissicn) now or hereafter in effect.
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I The Code of Federal Regulations,10 CFR 50.54(o), specifies that primary j
reactor contaiteents for water-cooled power reactors shall corply with f
t Appendix J, "Primary Reactor Containse'.t Leakage Test;ng for Water-Cooled Power Reactors." Paragraph III.A 3 of Appendix J incorporates by reference
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t the American National Standard ANSI N45.4-1972, "Leakage Rate Testing of Centainment Structures. for Nuclear Reactors." This standard requires that l
contaire+nt leakage rate calculations for containment integrated leakage rate f
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j GS111400s2 881103 i
DR ADOCK 05000255 PDC ii
2 tests (CILRTS) be performed usir.g either the Poirt-to-Foint method or Total i
Tire method.
Further advances in leakage rate testing technology have previded l
l in. proved test methods, including a newer method of evaluating test data called the Mass Point method. This Mass Point method was incorporated in a newer standard, ANSI /ANS-56.8-1981, "Contairant System Leakage Testing Requirements" l
(revised 1987) and in fact has been accepted by the Ccrmission's staff as an l
improved alternative rethod of calculating containment leakage rates. However, a strict interpretation of the specific wording of Appendi). J, III. A.3, by
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referencing only the older ANSI standard, precludes use of the newer improved rxthod, unless the licensees who wish to use this tethod receive an exerption from the Appendix J recuirement of conforming to tisis provision of ANSI N45.4-1972.
i By letter dated Septe ter i,1968, as supplemented Fy letter dated 4
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i Septetter 16, 1908, the liter.see equested an exerption from 10 CFR Part 50, J
j Appendix J. Paragraph III.A 3, which recuires that all CILRTs be performec it.
accordance with ANSI N45.4-1972. ANSI N45.4-1972 requires that leakage rate calculations be perforred using either the Total Tire rethod or the Point-to-l Point method.
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t The licensee indicated that since the issuance of ANSI N45.a-1972, a j
more accurate method of determining containment leakagr rates, the Mass Point
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method, has been developed as described in ANSI /ANS-56.8. Therefore, the i
licensee has requested an exerption to allow the use of the Mass Point metFod j
for calculating containment leakage rates.
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it has been recognized by tre professional cocr. unity that the Mass Point method is superior to the Point-to-Point and Total Time nethods which are referenced in ANSI N45.4-1972 and endorsed by the present regulations. The Mass Point method calculates the air re s at a series of points in time, and plots it against time.
A linear regression line is plotted through the mass-time points using a least square fit.
The slope of this line is divided by the intercept of this line, Ond the result is multiplied by an appropriate 4
constant to obtain the calculated leakage rate.
Tbc superiority of the Mass Foint method becomes apparent wher it is cortpared with the two other rethods.
In the Total Time rethod, a series of lealage rates are calculated on the basis of contaiteent air mass differences between an initial data point and each individual data point thereafter, and an average of these leakage rates is then determined.
If for any reason (e.g., instrurent error, lack of terperature equilibriut', ingassirs, or outgassing) the initial data point is not accurate, the results of the test will be affected.
In the Point-to-Point method, the leak rates are based on the rass differetice between each pair of consecutive data points, and these leakage rates are then averaged to yield a single leakage rate estirate.
Pathematically, this can be shown to be the difference between the air rass at the beginning of the test and the air rass at the end of the test expressed as a percentage of the containment air mass.
It follows from the above that the Point-to-Point method ignores any mass readings taken during the test and thus the leakage rate is calculated on the basis of the dif ference in rass between two reasurerents taken at the beginning a.d at the end of the test, which are 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> apart.
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On February 29,1988 (53 FW 5985), the Commission published a proposed amendment to Appendix 0 to explicitly permit the use of the Mass Point rethoc, subject to certain conditions that have been accepted by the Cormission's staff since approximately 1976, as well as to permit the use of the prior rethods referenced in ANSI N45.4-1972.
In addition to the method of calculation, considerstion of the length of the test should also be included in the overall program.
In accordance with Section 7.6 of ANSI N45.4-1972, a test duration of less than 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> is only allowed if approved by the Commission, and the only currtotly approved methodology fur such a test is contained in Bechtel Topical Fefort BN-TOF-1, Revision 1, "Testing Criteria for Integrated Leakage Rate Testing of Frinary Cortainment Structures for Nuclear Power Plants," dated November 1,1971.
This approach only allows use of the Tetal Time tetrod.
Therefore, the Commission conditier.5 the exemption to require a minieur test duration of 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> when the Mass Point method is used.
By letter dated Septerber 16,19ES, the licensee confirmed that a minictm test duration of 24 hcurs will te utilized when the Fass Foint uttted is used.
In the Septerber 9, 1986 letter, the licensee also submitted information to identify the special circumstances for granting this exttption for Falisades pursuant to 10 CFR 50.12. The purpose of Appendix 0 to 10 CFR Part 50 is to assure that containment leak-tight integrity can be verified periodically throughout the service lifetire in order to r.aintain containment leakage rate within the limit specified in the facility Technical Specifications. The underlying purpose of the rule, in specifying particular setheds for calculatirg leakage rates, is to assure that accurate and conservative rethods are uted to assess the results of containment leakage rate tests.
The
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Coasnission's staff has determined that the Mass Point method is an acceptable method for calculating containment leakage rates and satisfies the purpose of the rule.
Based on the above discussion, the licensee's proposed exerption from paragraph !!!.A.3 of Appendix J to allow use of the Mass Point raethod as requested in the submittal dated September 9, 1966, as revised by letter dated Septeater 16, 1988, is acceptable, until such provisicn of Appendix J is l
modified. Thereafter, the licensee shall comply with the provisions of such 1
rule. The exemptien applies only to the method of calculating leakage rates 1
(by use of the Mass Point method) and not to any other aspects of the tests.
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/,ccordingly, the Comission has determined pursuant to 10 CFR 50.12(a)(1),
that this exerption is authorized by law, will not present an ur.due risk to the public health and safety, and is consistent with the comon defense and security. The Corriission has further determined that special circunstances, as stt forth in 10 CFR 50.1?(t.)(2)(ii), are present justifying the exerpticri, namely that applicatier. of the regulation in the particular circumstances is not necessary to achieve the underlytrig purpose of the rule. Accordingly, the Consnission hereby grants an exerption as described in Section 111 above from Paragraph !!!.A 3 of Appendix J to the extent that the Mass Point method may be used for containment lenkege rate calculations, providing it is used with a rinimum test duration of 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />. The exemption is granted until such provision of Appendix J is crdified. Thereafter, the licensee shall comply
6-with the provisions of such rule. The exemption applies only to the method of calculating leakage rate (using the Mass Point uthod) and iet to any other aspects of the tests.
Pursuant to 10 CFR 51.32, the Coornission has determined that granting of this exemption will not have a significant effect on the quality of the human environment (t:oveuber 3 1988, 53 FA44246),
This exempticn is effective upon issuance.
F0F, THE NUCLEAR REGULATORY COMMIS$10N NQ M Gary M. Holahan, Acting Director Divistor of Reactor Projects - Ill IV, Y and Special Projects Office cf Nuclear Reactor Regulation Cated at Rockville, Maryland this3rd day ofNovember 1988.
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