ML20077G526
| ML20077G526 | |
| Person / Time | |
|---|---|
| Site: | Summer  |
| Issue date: | 06/19/1991 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20077G523 | List: |
| References | |
| NUDOCS 9107010130 | |
| Download: ML20077G526 (2) | |
Text
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UNITED STATES y
In NUCLE AR REGULATORY COMMISSION co a
WASHINGTON, D C. 2056b 4,.....,6 SAFETY EVALUATION BY THE Off!CE Of NUCLEAP REACTOR REGUL ATION RELATED TO AMENDMENT NO.10010 FACILITY OPEPATING LICENSE NO. NPF-12 SOUTH CAROLINA ELECTRIC A GAS COMPANY SOUTH CAROLINA PUBlIC SERVICE AUTHORITY VIRGll C. SUMMER NUCLEAR STATION, UNIT NO. I
_ DOC KET No. 50-395 l
1.0 INTRODUCTION
By letter cated February 4,1991, South Cerolina Electric and Gas Company (SCE8G or the licensee) submitted a request for changes to the Virgil C.
Summer Nuclear Station, Unit No. 1 (Summer Station), Technical Specifications (TS).
The requested change would revise figure 3.1 3, " Required Shutdown Margin (Modes 3, 4 and 5)," to incorporate the more negative boron worths associated with the Cycle 6 core and subsequent cores.
in addition, an l
administrative change was included in the TS change request to revise Basis j
3/4.21, " Axial Flux Difference," to refer to the Core Operating Limits Report 1
(COLR) rather than the Peaking f actor Limits Report (PFLR).
2.0 EVALUATION Figure 3.1-3 specifies the shutdown margin that must be maintained for varying reactor coolant system (RCS) concentrations of boron in order to (1) control, within acceptable limits,(2) maintain the reactor suf ficiently sutaritical to the reactivity transients associated with postulated accident conditions; and prevent inadvtrtent criticality.
The current shutdown margin requirements for tne shutdown Mod'rs 3, 4 and 5 are based on the boron dilution accident evaluations submitted in support of Amendment 75 to the Virgil C. Sununer Nuclear Station Operating License.
These evaluations were performed using an accepted Westinghouse methodology that takes credit for the high flux at shutdown alarm set at twice background to alert the operator that a dilution event is in progress.
The results show that the operator has sufficient time to recognize and terminate an uncontrolled reactivity insertion before shutdown margin is lost and the l
reactor becomes critical.
For Cycle 6, however, the boron worths for Modes 3 and 4 were calculated to be more negative than the values assumed in the current boron dilution accident analyses.
The more negative boron worth reduces the required change in boron concentration necessary to achieve criticality during a dilution event and results in a reduction in operator action time of approximately two minutes.
To resolve this problem, SCE&G has proposed to revise the TS shutdown margin curve for Modes 3 and 4 to reflect the larger required shutdown margin to ensure that the operator action time to detect and terminate an inadvertent 9107010130 910619 PDR ADOCK 0D000395 p
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boron dilution event is not reduced.
These higher shutdown margin requirements will require higher boron concentrations to be maintained while in Modes 3 and 4 of the fuel cycle. Since the boron worth for Mode 5 was determined to be bounded by previously analyzed values, the Mode 5 curve was not changed from the one currently in the TS.
The proposed revision to change pFLR to COLR in TS Basis 3/4.2.1 is administrative in nature since it simply deletes a reference to an obsolete report (PFLR) and references the report which replaced it. This change is acceptable.
3.0
SUMMARY
The requested change is acceptable because the proposed shutdown margin curves were developed using the same approved methodology used to develop the current
- curves, in addition, the current margin to criticality, as reflected in the final Safety Analysis Report of the boron dilution accident, will be maintained.
Based on the above considerations, the staff finds the proposed changes acceptable.
4.0 STATE CONSULTATION
In accordance with the Commission's regulations, the South Carolina State official was notified of the proposed issuance of the amendment. The State official had no comments.
5.0 ENVIRONMENTAL CONSIDERATION
The amendment changes a requirement with respect to installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20. The NRC staff has determined that the amendnent 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 previously issued a proposed finding that the amendment involves no significant hazards consideration, and there has been no public comment on such finding (56 FR 9386). 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 i
l the amendment.
6.0 CONCLUSION
The Commission has concluded, based on the considerations discussed above, that:
(1) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, (2) such activities will be conducted in compliance with the Consnission's regulations, l
and(3)theissuanceoftheamendmentwillnotbeinimicaltothecommon defense and security or to the health and safety of the public.
I Principal Contributor:
L. Kopp Date: June 19, 1991
AMENDMENT NO. 100 TO FACILITY OPERATING LICENSE NO. NPF SUMMER, UNIT No. 1 Docket File NRC PDR Local PDR PDil-1 Reading)
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