ML20127N837
| ML20127N837 | |
| Person / Time | |
|---|---|
| Site: | Catawba  |
| Issue date: | 05/06/1985 |
| From: | NRC |
| To: | |
| Shared Package | |
| ML20127N678 | List: |
| References | |
| NUDOCS 8505230618 | |
| Download: ML20127N837 (4) | |
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UNITED STATES 3
a NUCLEAR REGULATORY COMMISSION
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,I WASHINGTON. D. C. 20555 SAFETY EVALUATION REPORT CATAWBA NUCLEAR STATION, UNIT 2 RELATED TO AMENDMENT NO. 3 TO CONSTRUCTION PERMIT CPPR-117 INTRODUCTION By letter dated April 17, 1985, Duke Power Company (DPCo or.the applicant), the lead construction agent of the Catawba Nuclear Station, Unit 2, requested an amendment to Construction Pennit CPPR-117, to incorporate the partial Exemption previously requested by the applicant by letter dated May 11, 1984, pertaining to General Design Criterion (GDC) 4 of 10 CFR 30, Appendix A.
The limited schedular exemption granted by the Commission permits the applicant not to install protective devices and not to consider dynamic effects and loading con-ditions associated with postulated pipe breaks of the eight locations per loop in the Catawba Unit 2 primary coolant system for a period ending at the comple-tion of the second refueling outage, pending the o.utcome of rulemaking on this subject.
By letter dated September 14, 1984, the applicant submitted.an analysis of the occupational radiation dose reduction which, together with the submittals dated December 20, 1983, and May 11, 1984, provided a value-impact analysis associated with'the exemption request. The value'-impact analysis together with the technical information contained in Westinghouse Reports MT-SME-3166 and WCAP-10546, provided a comprehensive justification in support of requesting a partial exemption from the requirements of GDC 4.
EVALUATION The staff's detailed evaluation and basis for granting the partial exemption to the requirements of GDC 4 are delineated in the Exemption enclosed with the staff's April 23, 1985, letter. A summary of the staff's evaluation findings and conclusions immediately follow.
SUMMARY
OF EVALUATION FINDINGS From its evaluation of the analysis contained in Westinghouse Reports MT-SME-3166 and WCAP-10546 for Catawba, Unit 2, the staff found that the applicant presented an acceptable technical justification, which adequately addressed the staff's evaluation criteria, to: (1) eliminate the need to postulate circumferential and longitudinal pipe breaks in the Reactor Coolant System (RCS) primary loop (hot leg,. cold leg and cross-over leg piping); (2) eliminate the need for associated pipe whip restraints in the RCS primary loop and eliminate the requirement to design for the structural effects associated with RCS primary loop pipe breaks including jet impingement; ind (3) eliminate the need to consider dynamic effects and loading conditions associate'd with previously postulated primary loop pipe breaks.
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This finding does not in_any way affect the design bases for the containment.
the emergency core cooling system, the environmental qualification of equip-ment for Catawba Unit 2, or the supports for heavy equipment, and does not
- alter the' design basis of reactor cavity and subcompartment pressurization.
This finding is predicated on the fact that each of the parameters evaluated i
for Catawba is enveloped by the generic analysis performed by Westinghouse.
l contained in Westinghouse Report WCAP-9558,-Revision 2, and accepted by the
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I staff in Enclosure (1) to NRC Generic Letter 84-04 (February 1,1984). Specifi-cally, the'NRC determined that:
-(1) Although the moment associated with the highest stressed location in-the main loop primary system piping (which for Catawba Unit 2 occurs I
in the cross over leg piping) is lower than the bounding moment used L
by Westinghouse in Reference (5) for the hot leg pipin higher than that established by the staff as a limit (g, it is slightly -
i.e., a moment of 42,000 in-kips in Enclosure 1 to Reference 4). However, this is compensated for in that the pipe diameter and thickness are larger:
than those analyzed by Westinghouse and the staff for the reference case. Thus, the resultant net stresses are within the bounds-established by the staff in Enclosure 1 to Reference (4). The Catawba loads are 1,864 kips (axial) and 43,407 in-kips (bending momeht).
(2) For Westinghouse plants, there is no history of cracking failure in
' reactor primary coolant system loop piping.
The Westinghouse reactor coolant system primary loop has an operating history which demon-strates its inherent stability. This iicludes a. low susceptibility.
to cracking failure from the effects of corrosion (e.g. intergranular stress corrosion cracking), water hammer, or fatigue (low and high cycle). This operating history totals over 400 reactor-years, including five (5) plants each having 15 years of operation and 15 other plants with over 10 years of operation.
(3) The results of the leak rate calculations performed for Catawba, using an initial through-wall crack of 7.5 inches, are identical to those of Enclosure 1 to Generic Letter 84-04. The Catawba plant has an RCS pressure boundary leak detection system which is consistent with the guidelines of Regulatory Guide 1.45, and it can detect leakage of one (1) gpm within one hour. The calculated leak rate through the postu-lated flaw is at least 10 gpm. Therefore, the Catawba plant leak detection system is capable of detecting leaks one-tenth that of the calculated leak rate.
(4) The margin in terms of load based on fracture mechanics analyses for the leakage-size crack under normal plus SSE loads is within the-bounds calculated by the staff in Section 4.2.3 of Enclosure 1 to Generic Letter 84-04. Based on a limit-load analysis, the load margin is about 2.4 and based on the J limit discussed in (6) below, the margin is at least 1.3.
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, (5) The margin between the leakage-size crack and the critical-size crack was calculated by a limit load analysis. Again, the results demon-strated that a margin of at.least 3 on crack size exists and is within
~ the. bounds.of Section 4.2.3* of Enclosure 1 to Generic Letter 84-04.
(6) As an integral part of its review, the staff's evaluation of the material properties data in Westinghouse Report WCAP-10456 is enclosed as Appendix I to the Exemption granted by the Commission.
In WCAP-10456, data for ten (10) plants, including the Catawba units, are presented, and lower bound or " worst case" materials properties were identified and used in the analysis perfonned in WCAP-10546 by Westinghouse. The applied J for Catawba in WCAP-10546 was less than 3000 in-lb/in. Hence, the staff's upper bound of 3000 in-lb/ina on z
the applied J (refer to Appendix I of the Exemption, page 6) was not exceeded.
ENVIRONMENTAL ASSESSMENT In advance of issuing the Exemption, the Commissio,n published in the _ Federal Register on April 22, 1985 (50 FR 15802) an " environmental assessment.and finding of no significant impact." It was stated in that assessment that the planned Exemption action would not have a significant effect on the quality of the human environment. The Exemption granted involves des'ign features located entirely within the plant restricted area as defined in 10 CFR Part 20; does
.not affect plant radioactive and non-radioactive-effluents; has no other environmental impact; and does not involve the use of resources not previously considered in the Final Environmental Statement (construction permit) for Catawba, Units 1 and 2.
The staff has determined that the amendment involves no significant increase in the amounts, and no significant change in the types, of any effluents that may be released offsite, and that there is no significant increase in individual or cumulative occupational radiation exposure. The Commission has determined that the amendment involves no significant hazards considerations. Accordingly, the amendment meets the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9). Pursuant to 10 CFR 51.22(b) no environmental impact statement or environmental assessment need be prepared in connection with the issuance of this amendment.
CONCLUSION In granting the limited schedular Exemption, the staff found that the advanced fracture mechanics techniques used by the applicant provided an assurance that flaws in primary system piping will be detected before they reach a size that could lead to unstable crack growth.
For this reason, further protection pro-vided by protective devices against the dynamic effects resulting from the discharge from postulated breaks in the primary piping is unnecessary. Addition-ally, consideration of such dynamic effects associated with previously postulated pipe breaks is unnecessary. With full protection against dynamic effects pro-vided by advanced analysis techniques, and based on the considerations discussed
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above, we conclude that: (1) the proposed amendment to Construction Permit.
CPPR-117 permitting the use of the' Exemption in construction of Unit 2 does not involve a significant increase in the probability or consequences of accidents previously corsidered, does not create the possibility of an accident of a type different from any evaluated previously, does not involve a significant decrease in a safety margin, and thus does not involve a.significant hazards considera-tion; (2) there is reasonable assurance that the health and safet of the public will not be endangered by operation in the proposed manner; and (y) such 3
activities will be in compliance with the Commission's regulations, and the issuance of the amendment will not be inimical to the common defense and-security, or to the health and safety of the public.
Principal contributor:
K. Jabbour, Licensing Branch No. 4, DL Date of Issuance:
May 6, 1985 E
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