ML20085M825
| ML20085M825 | |
| Person / Time | |
|---|---|
| Site: | Comanche Peak  |
| Issue date: | 10/18/1991 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20085M824 | List: |
| References | |
| NUDOCS 9111120254 | |
| Download: ML20085M825 (3) | |
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! " 3 mf[',i NUCLE AR REGULATORY COMMISSION
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. 5 TO FACILITY OPERATING LICENSE NO. NPF-87 TEXAS UTILITIES ELECTRIC COMPANY, ET AL.
COMANCHE PEAK STEAM ELECTRIC STATION, UNIT 1 DOCKET NO. 50 445
1.0 INTRODUCTION
By application dated August 9,1991, Texas Utilities Electric Company (the licensee) requested changes to the Technical Specifications (Appendix A to Facility Operating License No. NPF-87) for the Comanche Peak Steam Electric Station,. Unit No. 1 (CPSES) (Ref. 1).
The proposed changes to TS 3.1.1.2, 3.1.2.2, 3.1.2.4, and 3.1.2.6 and the associated Bases would increase the required minimum shutdown marg *n (FDM) for operational Mode 5 (Cold Shutdown) from 1 percent delta-k/k to 1.3 percent delta-k/k, aad increase the minimum boration iequirement from a SDM-equivalent of 1 percent delta-k/k at 200 F to a SDM-equivalent of 1.3 percent delta-k/k at 200 F for the action of the limiting conditions for operation (LCO) for the boration systems.
The proposed changes resuic from revisions to an analysis of the boron dilution event to account for cycling time delays associated with the flux doubling circuitry of the boron dilution mitigation system (BDMS).
Westinghouse has revised the baron dilution event analysis as part of the CPSES Unit 1, Cycle 2 reload safety evaluation to support the implementation of the proposed change.
The BDMS is desi ved to detect and tritigate a boron dilution e"ent occurring in operational Mooes 3, 4, or 5 prior to the loss of shutdown margin as described in Section 15.4.6 of the CPSES Final Safety Analysis Report (Ref. 2) 2 and Section 15.2.3.1 of the CPSES Safety Evaluation Report (Ref. 3).
The BDMS 3
microprocessor detects a boron dilution event by monitoring the output of the source range neutron flux ctectors to determine if the neutron flux has increased by a factor of two or more over a time period of approximately ten minutes.
Upon detection of a flux-doubling, the BDM5 triggers an appropriate alarm and initiates the opening of isolation valves to the Refueling Water.
Storage Tank (RWST) and the closure of isolation valves to the Volume Control Tank (VCT).
This change in valve alignment blocks the source of the diluted water and lines up the borated water source from the RWST for injection into the Reactor Coolant System (RCS).
9111120254 91101G PDR r.1)OCK O yD P
. l 2.0 EVALUATION The NRC Standard Review Plan (SRP), Section 15.4.6, covers the moderator dilution events.
It states that during cold shutdown through power conditions, at least 15 minutes must be available between'the positive indication of a boron dilution in progress to loss of shutdown margin if operator action is required to terminate the transient.
During cold shutdown through hot standby conditions the BDMS micronrocessor detects a doubling of the neutron flux by comparison of the current source rea90 flux to that of approximately ten minutes earlier.
TU Electric noted that the circuitry delay asscciated with averaging of the source range flux signal over a specified time period for the generation of the flux-doubling-4 signal may not have been properly moualled.
As a result, the actual BDMS response time might be longer than assumed in the licensing-basis boron dilution
~
event analysis presented in the FSAR.
TO Electric, in conjunction with Westinghouse, performed a technical evaluation and concluded that tnel current TS SDM was sufficient for Cycle.1 operation.
As part of the Cycle 2 reload safety evaluation, Westinghouse performed an analysis of the licensing-basis boron dilution event initiatad from Modes 3, 4, and 5.
This analysis determined that, for the Cvele 2 reload conditions, an increase in the TS minimum SDM when T,yg is less. Nan or equal to 200 F (Mode 5) from 1.0 percent delta-k/k to 1.3 percent delta-k/k is. required.
This higher SDM requirement will result in an increase in the minimum boration requirement to a SDM equivalent of 1.3 percent delta-k/k at 200 F.
i The licensee has proposed changes to the affected TS to' increase the minimum SDM for Mode 5 from 1 percent delta-k/k to 1.3 percent delta-k/k.
The specific TS and the arsociated Bases to be revised are:
3/4.1.1.2 Shutdown Margin
-T,yg-Less Than or Equal to-200 F 3/4.1.2.2 Flaw Paths - Operating 3/4.1.2.4 Charging Pumps - Operating 3/4.1.2.6 Borated Water Sources - Operating--
The requested changes are acceptable because-the boron dilution analyses used approved analytical methods to determine the new minimum SDM requirement to preclude a return to critical.during a boron dilution' event.
In Modes 3 and 4,-the existing minimum SDM (1.6 percent delta-k/k)1contiaues to preclude a return to criticality.
Based on the above considerations, the staff finds the proposed changes acceptable.
3.0 STATE CONSULTATION
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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.
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4.0 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 and changes 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 (56 FR 47244). Accordingly, the amendment meets the eligibility criteria for categorical exclusion set forth in 10 CFR 51.72(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, besed on the considerations discussed above, that:
(1) there is reasonable assurance that the health and safety of the oublic 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.
REFERENCES 1.
Letter f rom W. J. Cahill, Jr. (TUEC), to USNRC, " Comanche Peak Steam Electric Station (CPSES) - Unit 1, Docket No. 50-445, License Amendment Request 91-014. Increase in Mode 5 Shutdown Margin," dated August 9,1991.
2.
" Comanche Peak Steam Electric Station Unit 1 Fir.:! Safety Analysis Report Update," Docket No. 50-445, as amended through January 15, 1990.
3.
Comanche Peak Steam Electric Station Safety Evaluation Report, NUREG-0797, through Supplement 23, February 8, 1990.
Principal Contrioutor:
E. Kendrick, 3RXB/ DST Date:
October 18, 1991
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