ML13317A628
| ML13317A628 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 06/09/1981 |
| From: | Moody W Southern California Edison Co |
| To: | Crutchfield D Office of Nuclear Reactor Regulation |
| References | |
| TASK-03-07.D, TASK-3-7.D, TASK-RR NUDOCS 8106150257 | |
| Download: ML13317A628 (4) | |
Text
Southern California Edison Company P. 0. BOX 800 2244 WALNUT GROVE AVENUE ROSEMEAD, CALIFORNIA 91770 W. C. MOODY TELEPHONES MANAGER, NUCLEAR LICENSING (213) 572-1817 June 9, 1981 (213) 572-1806 Director, Office of Nuclear Reactor Regulation Attention: D. M. Crutchfield, Chief Operating Reactors Branch No. 5 Division of Licensing U. S. Nuclear Regulatory Commission Washington, D.C.
20555 4
Gentlemen:
61
Subject:
Docket No. 50-206 Systematic Evaluation Program, Topic III-7.D San Onofre Nuclear Generating Station Unit 1 As a consequence of the February 19, 1981 meeting of the NRC Staff and the SEP Owners Group, SCE agreed to generate several draft topic assessments. The enclosure to this letter is the draft topic assessment of SEP Topic III-7.0, Containment Structural Integrity Tests, as set forth in our letter of April 7, 1981, and modified in our letter of April 28, 1981.
If you have any questions regarding the enclosed, please contact me.
Very truly yours, Enclosure Ao3~
8106150)57.
SAN ONOFRE UNIT 1 DRAFT TOPIC ASSESSMENT SEP TOPIC III-7.D Containment Structural Integrity Test Introduction The original structural integrity test procedure employed to test the containment structure for San Onofre Unit 1 has been reviewed against present day criteria. This report demonstrates that the original structural integrity test is equal to or more conservative when compared to today's criteria.
Current Review Criteria The current criteria to review the structural integrity test are the following:
o 10 CFR 50, Appendix A, GDC 2 o
NRC Standard Review Plan, Section 3.8.2 o
ASME Boiler and Pressure Vessel Code,Section III, Division 1, Article NE-6000, 1980 Edition including Winter 1980 Addenda Related Safety Topics and Interfaces The containment structural integrity test of San Onofre Unit 1 was performed based on the original calculated design pressure of 46.4 psig. The adequacy of this original design pressure is reviewed within the scope of SEP Safety Topic VI-3, "Containment Pressure and Heat Removal Capability." Thus, the validity of this safety evaluation is contingent upon the conclusions drawn in the review of Topic VI-3.
Containment Original Code of Construction The materials, design, fabrication, and erection of the containment vessel of San Onofre Unit 1 conform to the requirements of the ASME Boiler and Pressure Vessel Code,Section III, Nuclear Vessels, 1963 Edition, and other sections of the ASME Code (including Sections II, Material Specifications, VIII, Unfired Pressure Vessels, and IX, Welding Qualifications) to the extent that they are applicable.
The containment vessel is a steel sphere, inside diameter 140 feet, slightly more than one inch plate thickness.
The containment is constructed of ASTM A212, Grade B Firebox quality steel produced to ASTM A300 specification.
The design of the containment, as extracted from the Containment Sphere Design Report, February 1965, was based on the following:
Maximum Combined Stress = 33,458 psi Allowable Stress
= 57,750 psi Allowable per ASME Code,Section III, paragraph N414
-2 Original Structural In'tegrity Test A pneumatic test was conducted at a maximum pressure of 53.4 psig which is 1.15 times the design pressure of 46.4 psi.
The maximum pressure was held for one hour. Based on a review of available documents, it has been determined that the structural integrity test was conducted in accordance with the requirements of:
o Proposed Safety Standard for Design Fabrication and Maintenance of Steel Containment Structures for Stationary Nuclear Power Reactors, prepared by Subcommittee No. 6, American Standards Association Sectional Committee N 6, Reactor Safety Standard, latest published edition as of May, 1965.
o Bechtel Corporation Specification BSO-280 o
Chicago Bridge & Iron Initial Test Procedure, Contract 9-0381 The test was witnessed by the AEC Reactor Inspector and the State of California Pressure Vessel Inspector.
Revised Pressure and Temperature Analysis The "Containment Post-Accident Reanalysis" for San Onofre Unit 1 was transmitted to the NRC by letter dated January 19, 1977. That analysis indicated the post-accident temperature and pressure to be 2910 F and 49.4 psig. The initial conditions for that analysis included an initial contain ment pressure of 14.7 psia or 0 psig. The Technical Specifications for San Onofre Unit 1 contain a limiting condition for operation for the containment sphere. Specification 3.6.C requires that the reactor shall not be made critical nor be allowed to remain critical if the sphere internal pressure is greater than 0.4 psig or is less than -2.0 psig. This allows operation of Unit 1 with an internal sphere pressure between 0.4 and -2.0 psig. Therefore, in an April 13, 1981 letter, we committed to evaluating the containment post-accident pressure utilizing an initial condition of 0.4 psig.
The evaluation of the containment post-accident pressure has been performed to determine the effect of utilizing 0.4 psig as an initial condition. This evaluation included an analysis performed in accordance with the Bechtel Topical Report BN-TOP-3, Revision 4, Performance and Sizing of Dry Pressure Containments. The previous analysis utilized Revision 3A of the report.
Revision 4 incorporates changes made in response to NRC.comments. The results of the analysis provide a peak post-accident temperature and pressure of 288 0F and 48.2 psig.
Current Structural Integrity Test Requirements In accordance with ASME Section III, Division 1, Article NE-6000, 1980 Edition including Winter 1980 Addenda, the minimum required pneumatic test pressure is 1.1U times the design pressure of the vessel.
If applied to the most recent evaluation of the San Onofre Unit 1 containment, the test pressure would be 53.0 psig which is less than the original test pressure.
-3 Conclusion Based on the review of the conduct of the original structural integrity test and a review of current structural integrity test requirements, it is concluded that the original test is more conservative than the present day codes and regulations would require. The test procedure employed originally is consistent with the test procedures used today. Therefore, the containment structure will satisfactorily. perform its intended safety function as it relates to SEP Topic III-7.D.