ML20044C359
| ML20044C359 | |
| Person / Time | |
|---|---|
| Site: | South Texas  |
| Issue date: | 03/09/1993 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20044C358 | List: |
| References | |
| NUDOCS 9303220330 | |
| Download: ML20044C359 (3) | |
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i SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION
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RELATED TO AMENDMENT NOS. 48 AND 37 TO j
FACILITY OPERATING LICENSE NOS. NPF-76 AND NPF-80 HOUSTON LIGHTING &' POWER COMPANY 7
CITY PUBLIC SERVICE BOARD OF SAN ANTONIO l
CENTRAL POWER AND LIGHT COMPANY CITY OF AUSTIN. TEXAS DOCKET NOS. 50-498 AND 50-499 SOUTH TEXAS PROJECT. UNITS 1 AND 2
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1.0 INTRODUCTION
-i By application dated September 28,1992 (ST-HL-AE-4222) as supplemented by i
[[letter::ST-HL-AE-4260, Forwards Response to NRC 921026 Telcon Request for Addl Info Re 920928 Application for Amends to Licenses NPF-76 & NPF-80,consisting of Rev 1 to SE for Proposed Rev to Shutdown Margin in TS 3.1.1.1|letter dated November 12, 1992]] (ST-HL-AE-4260), Houston Lighting & Power.
Company, et.al., (the licensee) requested changes to the. Technical I
Specifications (Appendix A to Facility Operating License Nos. NPF-76 and NPF-
- 80) for the South Texas Project,-Units 1 and 2.
Thelproposedchangeswould' replace the variable shutdown margin requirements for Modes 1'and'2 with a j
constant value. The constant value for MODES l'and 2 is and will continue to be 1.75% delta rho. The variable shutdown margin is intended to be a prevention against the-loss of shutdown margin during a' boron dilution I
accident in MODES 3 and 4, and consequently, is not required for MODES l'and I
2.
1 The licensee has also proposed a change 'to surveillance requirement, TS i
4.1.1.1.2, clarifying reactivity balance' calculations to. confirm core design predictions, leading to the validation of shutdown' margin. The proposed
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. changes will modify figure 3.1-1 of TS 3.1.1.1 and change the text of TS 4.1.1.1.2.
These changes will only impact MODES I and 2, and will have no 1
impact on MODES 3 and 4.
2.0 EVALUATION i
2.1 Variable Shutdown Marain In MODES 1 and 2, the most restrictive condition. occurs at end-of-life (EOL),
i with T (AVG) at no load operating temperature, and is generally associated with a postulated steam line break accident, resulting in a reactor coolant system (RCS) cooldown.
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J. The presence of the variable shutdown margin requirements for MODES I and 2 places an undue restriction on the design of the reactor core at beginning-of-life (BOL) conditions. The present use of Figure 3.1-1 (TS 3.1.1.1), suggests that additional shutdown margin over and above the constant value of 1.75%
delta rho is required for critical boron concentrations over 900 ppm. The safety analyses were performed using a constant shutdown margin of 1.75% delta rho, consequently, the change to figure 3.1-1 will reflect the use of the constant shutdown margin of 1.75% delta rho in the safety analyses.
Similarly, the proposed change to Figure 3.1-1 will not reduce the margin of-safety for MODES 1 and 2.
In MODES 3 and 4, the most restrictive condition occurs at BOL when the boron concentration is greatest.
In MODES 3 and 4, the required shutdown margin is composed of a constant and a variable requirement. The variable portion is a function of the RCS boron concentration. The constant shutdown margin requirement of 1.75% delta rho is based on an uncontrolled RCS cooldown from a steamline break accident. The variable shutdown margin requirement is based on the results of a boron dilution accident analysis, whereby the shutdown margin is varied as a function of RCS boron concentration, to guarantee a minimum time for operator action after a boron dilution alarm.
Consequently,_
the above analysis suggests that the shutdown margin requirements for MODES I and 2 are separable from those for MODES 3 and 4.
It should be pointed out that the change to Figure 3.1-1 doe, not constitute a change to the design basis of South Texas Units 1 and 2, since the design limits for MODES I and 2 remain at 1.75% delta rho. The change to Figure 3.1-1 is acceptable.
2.2 Technical Specification 4.1.1.1.2 Specification 4.0.4 states that:
" entry into an Operational Mode or other specified condition shall not be made unless the Surveillance Requirement (s) associated with the '
Limiting Condition for Operation has been performed within the stated surveillance interval or as otherwise specified."
However, as Surveillance Requirement 4.1.1.1.2 is currently written, Specification 4.0.4 would require that a core reactivity balance be performed for all operational Mode evolutions for which Specification 3.1.1.1 is currently applicable, which are MODES 1, 2, 3, 4.
Since the reactor must be in critical condition for a core reactivity balance to be performed, it is not possible to perform the surveillance for all evolutions.
Therefore, Surveillance Requirement 4.1.1.1.2 should be modified to be exempted from the requirements of Specification 4.0.4.
The proposed change to the surveillance requirement will not affect the accuracy of the parameters used in the shutdown margin calculation performed for Specification 3.1.1.1.
Neither of the changes proposed by the licensee constitute a change to the design basis.
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_3-The NRC staff has reviewed the licensee's request to modify the Technical Specifications of the South Texas Nuclear Project, Units 1 and 2 regarding the removal of the variable shutdown margin requirements for MODES I and 2, and the change to Surveillance Requirement 4.1.1.1.2.
The staff find these changes acceptable.
3.0 STATE CONSULTATION
In accordance with the Commission's regulations, the Texas State official was notified of the proposed issuance of the amendment. The State official had no comments.
4.0 ENVIRONMENTAL CONSIDERATION
t The amendment changes a requirement with respect to installation or use of a i
facility component located within the restricted area as defined in 10 CFR Part 20 and surveillance requirements. The NRC 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 previously issued a proposed finding that the amendment involves no significant hazards consideration, and there has been no public comment on such finding (58 FR 595). Accordingly, the amendment meets the eligibility criteria for i
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 the amendment.
5.0 CONCLUSION
The Commission has concluded, based on the considerations discussed above, i
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 Commission's regulations, and (3) 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:
A. Attard Date:
March 9, 1993
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