ML20236M264
| ML20236M264 | |
| Person / Time | |
|---|---|
| Site: | Brunswick  |
| Issue date: | 08/05/1987 |
| From: | Cutter A CAROLINA POWER & LIGHT CO. |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| Shared Package | |
| ML20236M268 | List: |
| References | |
| 87TSB15, NLS-87-132, NUDOCS 8708110001 | |
| Download: ML20236M264 (3) | |
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CP&L Carolina Power & Light Company SERIAL: NLS-87-132 l
AUG - 51987 10CFR50.12(a)(2)(ii) 10CFR50.90 87TSB15 l
United States Nuclear Regulatory Commission l
ATTENTION: Document Control Desk Washington, DC 20555 BRUNSWICK STEAM ELECTRIC PLANT, UNIT NOS.1 AND 2 i
l DOCKET NOS. 50-325 & 50-324/ LICENSE NOS. DPR-71 & DPR-62 l
CONTAINMENT INTEGRATED LEAK RATE TESTING l
REQUEST FOR EXEMPTION FROM 10CFR50, APPENDIX 3 l
AND TECHNICAL SPECIFICATION AMENDMENT REQUEST Gentlemen:
Carolina Power & Light Company (CP&L) hereby requests an exemption from 10CFR50, Appendix 3, paragraph Ill.A.3, for the Brunswick Steam Electric Plant (BSEP), Unit Nos. I and 2.10CFR50, Appendix 3 paragraph III.A.3 requires that all Type A (Containment Integrated Leak Rate), tests be performed in accordance with ANSI l
N45.4-1972, " Leakage Rate Testing of Containment Structures for Nuclear Reactors."
ANSI N45.4-1972 requires that leakage calculations be performed using the Total Time method. In 1976, the NRC recognized the merits of a newer method, the Mass-Point method. ANSI N45.4-1972 has been revised to a new standard, ANSI /ANS 56.8-1981,
" Containment System Leakage Testing," which incorporates the newer Mass-Point method. However, Appendix J has not yet been revised to reference the new standard.
The NRC issued a sim,ilar exemption for the H. B. Robinson Steam Electric Plant, Unit No. 2 on May 22,1987.
Analysis of data from a recently completed ILRT on BSEP, Unit No I has been performed using both the Total Time and Mass-Point methods. Due to initial data fluctuations and stabilization time associated with the Total Time method, it ap that the Mass-Point method is more appropriate as discussed below. Therefore, pears CP&L is requesting this exemption to allow use of the Mass-Poinc method, as provided for in ANSI /ANS 56.8-1981, paragraph 5.7, rather than the Total Time method described in ANSI N45.4-1972, paragraph 7.9.
In eddition, a change to the Technical Specifications is required in order to maintain consistency between Appendix 3 and the Technical Specifications. This is hereby submitted as well in accordance with 10CFR50.90 and 2.101.
DISCUSSION In 1973,10CFR50, Appendix 3, was issued to establish requirements for Primary Reactor Containment Leakage Testing. Appendix 3 incorporated,by reference, ANSI N45.4-1972,
" Leakage Rate Testing of Containment Structures for Nuclear Reactors." The standard requires that containment leakage calculations be performed using either the Potnt-to-Point or the Total Time method. The Total Time method was used most by the nuclear industry until 1976. As noted in N45.4-1972, the Point-to-Point method is suited to uninsulated containments where atmospheric stability is affected by outside diurnal changes, while the Total Time method is appropriate for insulated containments, such as those at BSEP, that are relatively unaffected b article published in " Containment Engineering"y diurnal changes. In February 1976, an compared the resu!ts of test analyses performed using Point-to-Point > Totai Ylme, and Mass-Point techniques. Subsequently, the Mass-Point method received NRC staff endorsement and became the staff-recommended method to use. A revision to the standard ANSI /ANS 56.8-1981,
" Containment System Leakage Testing," specifies the use of the Mass-Point method to the exclusion of the two older methods which were described in ANSI N45.4-1972. The draf t revision to Appendix 3 incorporates the new standard ANSI /ANS 56.8-1981.
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Document Control Desk W NLS-87-132 / Page 2 any believes that this exemption should be granted Carolina Power & Light Comp (ii); i.e., application of the regulation in the particular pursuant to 10CFR50.12(a)(2) circumstances is not necessary to achieve the underlying purpose of the rule. The need for this exemption is predicated on the determination that, although the technical adequacy of the Mass-Point method is not in question, the recommendation to use it is not conststent with the current requirements of Appendix 3.
l The Mass-Point method is a newer and more accurate method for calculatin containment leakage. The mass of air in the containment is calculated and lotted as a j
function of time. The slope of the least squares fit of the data represents t e rate of change of air mass with respect to time, which is the leakage rate. Because of the independent nature of each data point, an error will result in only one bad data point and not materially affect the test results.
The Total Time method is based upon the difference in air mass between an initial data point and each individual data point measured thereaf ter. The adequacy of the method is extremely sensitive to the accuracy of the initial data point. If the initial data point is l
not accurate, possibly due to instrument error, lack of temperature equilibrium, ingassing, or outgasstng, the results of the test will be affected. In addition, even if the initial data point is accurate, the calculated leak rate can be inaccurate because, during the early stages of the test, the leakage varies with time. As a result, each point must be weighted with respect to the time elapsed since the start of the test. This creates a situation where the increasing amount of' data available causes the results to become more erratic and the 95 percent confidence interval to become wider. The 95 percent confidence interval associated with the Total Time method may range from one-half to twice the measured leak rate. For the Mass-Point method, the 95 percent confidence interval is between 5 and 20 percent of the measured leak rate.
SIGNIFICANT IIAZARDS ANALYSIS The Commission has provided standards in 10CFR50.92(c) for determining whether a significant hazards consideration exists. A proposed amendment to an operating license for a facility involves no significant hazards consideration if operation of the facility in i
accordance with the proposed amendment would not: (1) involve a si the probability or consequences of an accident previously evaluated,gnificant increase in l
(2) create the or (3) involve a significant reduction in a margin of safety. Carolina Power &y evaluated, possibility of a new or different kind of accident from any accident previousl Light Company has reviewed this request and determined that:
1.
The proposed amendment will not involve a significant increase in the probability or consequences of an accident previously evaluated. The Mass-Point technique for calculation of the containment leakage rate is a newer, more accurate and NRC staff-endorsed method. It, or any other calculational method used to determine containment leakage rates during testing, is not considered to be an initiator of any accident previously evaluated.
The Mass-Point technique is judged to be a superior method for calculating containment leakage rates, and thereby a better method of verifying that leakage from the containment is maintained within allowable limits. By employing a more reliable calculational technique, the assessment of containment integrity, through integrated leak rate testing, is enhanced. As such, the consequences of previously evaluated accidents are not negatively impacted.
2.
The proposed amendment does not create the possibility of a new or different kind of accident from any accident previously evaluated. The proposed amendment provides for the use of a newer, more accurate technique for calculation of the leakage rate during a containment integrated leak rate test. No possibility of a new or different kind of accident is created since the technique used to calculate leak rates in itself is not considered to be an initiator of any accident, transient, incident, or event.
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Document Control Desk
- v. NLS-37-132 / Page 3 3.
The proposed amendment does not involve a significant reduction in a margin of safety. The proposed change allows the use of the Mass-Point technique to calculate the leakage rate from the containment when performing a containment integrated leak rate test. The Mass-Point technique is a newer, more accurate method which has been endorsed by the NRC staff. By adopting this technique, CP&L will be able to make a more reliable determination of containment leakage during an integrated leak rate test. As such, the degree of confidence in containment integrity would be enhanced. Therefore, this i
proposed revision does not impact the margin of safety.
Based on the above reasoning, CP&L has determined that the proposed changes involve i
no significant hazards consideration.
ADMINISTRATIVE INFORMATION j
The revised BSEP Technical Specification pages are provided in Enclosures I and 2. The Company has evaluated this request in accordance with 10CFR170.12 and determined that a license amendment application fee is required. A check for $150 is enclosed in payment of this fee. Carolina Power & Light Company requests issuance of this exemption and amendment by February 15,1988 in order to allow use of the Mass-Point method in the upcoming refueling outage on Unit No. 2.
Please refer any questions regarding this submittal to Mr. Sherwood R. Zimmerman at (919) 836-6242.
Your -very tr h l
At Y
. B. Cutter - Vice Plesident Nuclear Engineering ABC/ BAT /lah (5224 BAT)
Enclosures l
A. B. Cutter, having been first duly sworn, did depose and say that the information contained herein is true and correct to the best of his information, knowledge and belief; and the sources of his information are officers, employees, contractors, and agents of Carolina Power & Light Company.
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