ML20135F225
| ML20135F225 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 12/06/1996 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML20135F220 | List: |
| References | |
| NUDOCS 9612120455 | |
| Download: ML20135F225 (3) | |
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UNITED STATES g
j NUCLEAR REGULATORY COMMISSION l
2 WASHINGTON, D.C. 2000H001
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO.135 TO FACILITY OPERATING LICENSE NO. NPF-10 AND AMENDMENT NO.124 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 i
SAN ONOFRE NUCLEAR GENERATING STATION. UNITS 2 AND 3 l
DOCKET NOS. 50-361 AND 50-362
1.0 INTRODUCTION
By application dated May 29, 1996, Southern California Edison Company (SCE or the licensee) requested changes to the Technical Specifications (Appendix A to Facility Operating License Nos. NPF-10 and NPF-15) for San Onofre Nuclear Generating Station (SONGS), Unit Nos. 2 and 3.
The proposed changes would revise Technical Specification (TS) Surveillance Requirement 3.5.1.4 for SONGS Units 2 and 3 to increase the minimum boron concentration in the safety injection tanks (SITS) from 1850 ppm boron to 2200 ppm boron.
The proposed change is required to support the operating cycle length extension to approximately 590 effective full power days.
2.0 DISCUSSION SCE is extending the operating cycle for SONGS, Unit Nos. 2 and 3, to approximately 590 effective full power days. To a%omplish this cycle length extension, SCE is increasing the initial Uranium-135 fuel enrichment above 4.1 w/o up to 4.8 w/o and changing the burnable poisore from B,C to Erbia.
Erbia is an Asia Brown Boveri Combustion Engineering teim used to describe an Erbium-Oxide Er 0 and fuel mixture.
23 Based on the completed analyses supporting Cycle 9 core reload analysis, TS Surveillance Requirement 3.5.1.4 needs to be changed to support the planned increased cycle length to increase the minimum boron concentration in the SITS I
from 1850 ppm to 2200 ppm.
9612120455 961206 PDR ADOCK 050003 i P
3.0 EVALUATION The SITS have a minimum boron concentration limit to ensure the reactor remains subcritical by at least 1 percent shutdown margin (Mode 3) during the post LOCA refill, reflood, and recirculation phases. "he SITS have a maximum limit on boron concentration to prevent boron precipitation from the coolant during the post-LOCA time frame.
The SIT minimum boron requirement is based on beginning-of-life reactivity values and is selected to ensure that the reactor will remain subcritical during the refill stage of a large-break LOCA. During a large-break LOCA, no control element assembly (CEA) is assumed to insert into the core. The initial reactor shutdown is accomplished by void formation due to depressurization.
Sufficient baron concentration must be maintained in the SITS to prevent a i
l return to criticality during the core refill. The minimum SIT boron j
concentration is based upon the requirement to maintain the reactor core subcritical without assistance from the CEAs or any other boron source.
l SCE is increasing the fuel enrichment up to 4.8 w/o and changing the burnable poison from B C to Erbia to achieve a longer cycle length. Erbia is an Asia BrownBoveribombustionEngineeringtermusedtodescribeanErbium-Oxide Er 0 and fuel mixture. This change in core configuration requires additional 3
negative reactivity at the start of the fuel cycle. Therefore, for the SIis to perform their design function post-LOCA with the increase in fuel enrichment, the minimum required boron concentration in the tanks needs to be increased.
In its May 29, 1996 amendment request, SCE provided a technical summary of the l
SIT boron concentration change calculations that were performed based on the increase in fuel enrichment to ensure the core remains subcritical (i.e.,
conservatively 1 percent shutdown) with the proposed minimum boron concentration of 2200 ppe. The required SIT boron concentration was conservatively calculated to be less than 2150 ppe.
In addition to the conservative assumptions used in the calculation, 50 ppa was added to the results. As a result, the licensee proposes to increase the minimum boron concentration in the SITS from 1850 ppe to 2200 ppe.
As indicated above, the upper limit on SIT boron concentration is set to ensure boron precipitation will not occur during post LOCA recirculation. No change in the upper boron concentration limit is required to maintain this acceptance criteria. No other accident conditions, design conditions, TSs, or TS Bases are affected by this proposed change in boron concentration.
The SITS are filled from the refueling water storage tank (RWST), which has a TS minimum boron concentration requirement of 2350 ppe.
In its May 29, 1996 amendment application, SCE stated that it maintains the RWST boron concentration higher than the minimum limit, and, as a result, for the past several years, the SIT boron concentration has been approximately 2500 ppm.
j Therefore, changing the SIT minimum boron concentration from 1850 ppm to
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2200 ppe does not involve a physical change in the plant or impact plant operation.
In addition, the licensee reviewed surveillance data from the past two years and found little change in boron concentration as a function of time.
Therefore, the 31 day surveillance test frequency remains acceptable.
Based on the above, the staff finds SCE's proposal to increase the minimum rtquired TS boron concentration in the SITS from 1850 ppa to 2200 ppe acceptable.
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4.0 STATE CONSULTATION
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 installation or use of a facility component located within the restructured area as defined in 10 CFR Part 20. The NRC staff has determined that the amandments 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 radiation exposure. The Commission has previously issued a proposed finding that the amendments involve no significant hazards consideration, and there has been no public comment on such finding (61 FR 40029). Accordingly, the amendments l
meet the eligibility criteria for categorical exclusion set forth in 10 CFR l
51.22(c)(9).
Pursuant to 10 CFR 51.22(b) no environmental' impact statement or l
environmental assessment need be prepared in connection with the issuance of l
the amendments.
6.0 CONCLUSION
The Commission has concluded, based on the considerations discussed above, l
that (1) there is reasonable assurance that the health and safety of the I
public will not be endangered by operation in the proposed manner, (2) such activities will be conducted in compliance with the 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: Kris Thomas Date:
December 6, 1996 4
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