ML20217B447

Safety Evaluation Supporting Amends 159 & 150 to Licenses NPF-10 & NPF-15,respectively

ML20217B447
Person / Time
Site:	San Onofre
Issue date:	10/07/1999
From:	NRC (Affiliation Not Assigned)
To:
Shared Package
ML20217B444	List: ML20217B440 ML20217B447
References
NUDOCS 9910120263
Download: ML20217B447 (2)

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. NUCLEAR REGULATORY COMMISSION A -.

WASHINGTON, D.C. soseH001 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION l'

RELATER)TO AMENDMENT NO.159 TO FACILITY OPERATING LICENSE NO NPF-10 l

AND AMENDMENT NO.

150.TO FACILITY OPERATING LICENSE NO. NPF 15 SOUTHERN CALIFORNIA EDISON COMPANY SAN DIEGO GAS AND ELECTRIC COMPANY THE CITY OF RIVERSIDE. CALIFORNIA THE CITY OF ANAHEIM. CALIFORNIA SAN ONOFRE NUCLEAR GENERATING STATION. UNITS 2 AND 3 l.

DOCKET NOS. 50-361 AND 50-362

1.0 INTRODUCTION

By letter dated September 10,1998 (PCN-496), as supplemented July 19,1999, Southem Califomia Edison (SCE or the licensee) proposed changes to the San Onofre Nuclear Generating Station (SONGS) Units 2 and 3 technical specifications (TSs) to delete the requirements for equipment used to control hydrogen in the containment structure. The licensee proposed to delete TS 3.6.7 in its entirety to remove requirements for the hydrogen control system.

2.0 BACKGROU_N_Q Regulatory requirements for the hydrogen control system are specified in 10 CFR 50.44 and 10 CFR Part 50, Appendix A, (General Design Criteria 41,42, and 43). Different requirements apply to facilities according to the date of publication of the Notice of Hearing for the Construction Permit. With regard to hydrogen recombiner and purge-repressurization system requirements, SONGS Units 2 and 3 are subject to the requirements of 10 CFR 50.44(e) for controlling combustible gases following a loss-of-coolant accident (LOCA) by a combustible gas control system, such as recombiners, that does not result in a significant release from containment. By letter dated September 10,1998, as supplemented July 19,1999, the licensee applied for an exemption from the 10 CFR 50.44(d) and (e) requirements relating to hydrogen control from the SONGS Units 2 and 3 design basis. The NRC granted this exemption on September 3,1999. The licensee proposes to reflect the approved exemption by deleting TS 3.6.7.

3.0 EVALUATION The underlying purpose af 10 CFR 50.44 is to ensure that following a LOCA, an uncontrolled hydrogen-oxygen recomaination would not take place, or that the plant could withstand the consequences of uncontrolled hydrogen-oxygen recombination without loss of safety function.

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The licensos demonstrated that the plant could withstand the consequences of uncontrolled hydrogen-oxygen recombination without less of safety function without credit for.he hydrogen recombiners or the hydrogen purge system for both the design-basis and the more limiting severe accident with up to 75 percent metal-water reaction that remains in-vessel scenario.

Several risk studies, such as NUREG 1150," Severe Accident Risk: An Assessment for Five U.S. Nuclear Plants," and those performed by the licensee, have shown that the relative importance of hydrogen combustion for large, dry containments with respect to containment failure to be quite low. The licensee also demonstrated that hydrogen recombiners are insignificant from a large, dry containment integrity perspective and the radiological consequences remain unchanged with or without recombiners. Therefore, the requirements for hydrogen recombiners and the backup hydrogen purge capability for large, dry containments, such as SONGS Units 2 and 3, are not necessary. On September 3,1999, the NRC granted an exemption from the 10 CFR 50.44(d) and (e) requirements relating to hydrogen control from the SONGS Unite 2 and 3 design basis. The proposed TS change is consistent with the approved exemption and is therefore, acceptable.

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4.0 STATE CONSULTATION

i in accordance with the Commission's regulations the California State official was notified of the proposed issuance of the amendments. The State official had no comments.

5.0 ENVIRONMENTAL CONSIDERATION

The amendments change a requirement with respect to the installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20 and changes surveillance requirements. The NRC staff has determined that the amendments involve 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 radiat.'on exposure. The Commission has previously issued a propesed finding that the amendments involve no significant hazards consideration, and there has been no public comment on such finding (64 FR 43778). Accordingly, the amendments meet the eligibi!ity 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 i

connection with the issuance of the amendments.

6.0 CONCLUSION

1 The Commission has concluded, based on the considerations discussed above, that (1) there is l

reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, (2) such activities wip be conducted in compliance with the L

Commission's regulations, and (3) the issuance of the amendments will not be inimical to the common defense and security or to the health and safety of the public.

Principal Contributor:

L.Raghavan Date:

October 7,1999 I

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