ML19208B720
| ML19208B720 | |
| Person / Time | |
|---|---|
| Site: | Haddam Neck File:Connecticut Yankee Atomic Power Co icon.png |
| Issue date: | 08/14/1979 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML19208B715 | List: |
| References | |
| TASK-05-03, TASK-5-3, TASK-RR NUDOCS 7909210270 | |
| Download: ML19208B720 (4) | |
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SAFETY EVALUATICT REPORT ELECTRICA. INSTRUMENTATION AND CONTROL ASPECTS OF THE HADDAM NECK OVERPRESSURE IR0TECTION SYSTEM PREPARED BY:
Plant Systems Branch Division of Operating Reactors ff /3 Ole'.I 190921 ogyo
1.0 INTRODUCTION
By letter to the Connecticut Yankee Atomic Power Company (CYAPCO) dated August 11, 1976, we requested an evalut ion of system designs to determine susceptibility to overpressurization events and an analvsis of these possible events, and pr posed interim and perman-ent cdifications to che systens and pr-cedures to reduce the likelihood and conseq. ences of such e'gnts.
By letter datrd September 3,1976 an' subsequent letters (refer to the Appendix), the Ccnnecticut Yankee Atomic Power Company submitted the additionalinforma-tion requested by us, including the administrative operating pro-cedures and the proposed low temperature overpressure protection miti-gating system.
The system hardware includes sen ors, actuating mech-anisms, alarms,aand valves to prevent a reactor coolant system trans-ient from exceeding the pressure and temperature limits of the Technical Specifications for Heddam Neck as required by the Code of Federal Regulations, Title 10, Part 50 (10 CFR 50), Appendix G.
2.0 EVALUATION' The enclosed Technical Evauation Report was prepared for us by the Lawrence Livermore Laboratory as part of our technical assistance program.
3.0 OVERPRESSURE PROTECTION SYSTEM DESIGN The_CYAP_C0 desion for the Haddam Neck OPS is based gn the use of two new spring loaded relief valves (SLRV's) which are isolated from the pressurizer / reactor coolant system during normal operating con-ditions by two new motor-operated isolation valves.
In conjunction with specific procedural controls, the following requirements are defined:
1.
Each SLRV will provide sufficient and redundant relief capacity to ensure that the reactor coolant system (RCS) pressure remains within the operating l'mits.
The SLRV low pressure setpoint will be 380 psig.
2.
Each isolation motor-operated valve (MOV) will be controlled by an independent control switch located on the reactor control board in the main control room.
3.
A 340*F temperatum interlock and alarm will be pro-vided to ensure SLRV system lineup at RCS temperatures below 340'F.
The pressore and temperature limits used for the operation of the mitigating system are based on the projected 14-year operating limit curve, relief valve accumulation, and the objective to retain opera-tional flexibility to the maximum extent practical.
4.
Additional assurance of preventing inadvertent blow-down at RCS temperatures above 340 F is provided by the inclusien of a 360 psig pressure permissive signal which prevents opening of the isolation M0V's during normal reactor cperating conditions and in the high pressure ranges of RCS heatup and cooldown.
We%0AO
. The control circuits for the two isolation MOV's in each relief train utilize independent instrument loops and control logic. The two pressure-sensing instrument loops are P-403 and P-404, one for each relieftrain.
The two temperature-sensing loops are T-423 and T-433.
The control circuits are separated from one another as much as physical limitations permit. To ensure that the SLRV's are in direct contact with the RCS at the require pressure and temperature, a basic sequence which combines operator action and warning alarms has been incorporated into the isolation MOV circuitry logic.
We find these design features acceptable.
4.0 CONCLUSION
S Based on our review of the enclosed consultant's Technical Evaluation Report, we agree with their findings that the administrative controls and harc, are changes proposed by the licensee provide protection for the Haddam Neck Plant from pressure transients at low RCS temperatures by reducing the probability of initiation of a transient and by limiting the pressure of such a transient to below the limits set by Appendix G in the Technical Specification.
We, therefore, conclude that the EI&C aspects of th.e overoressure protection system meet our criteria, and are acceptable as a long term solution to the problem of overpressure transients.
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F. 0 REFERENCES
- 1. NRC (Schwencer) letter to CYAPC0 (Switzer) dated August 11, 1976.
- 2. CYAPC0 (Switze*r) letter to NRC (Schwencer) dated September 3,1976.
- 3. CYAPC0 (Switzer) letter to NRC (Schwencer) dated October 15, 1976.
- 4. CYAPC0 (Switzer) letter to NRC (Schwencer) dated December 3,1976.
- 5. NRC (Schwencer) letter to CYAPC0 (Switzer) dated January 10, 1977.
- 6. NRC (Schwencer) letter to CYAPC0 (Switzer) dated February 14, 1977.
- 7. CYAPC0 (Switze?) letter to NRC (Schwencer) dated March 1,1977.
- 8. CYAPC0 (Switzer) letter to NRC (Schwencer) dated March 21, 1977.
- 9. NRC (Schwencer) letter to CYAPC0 (Switzer) dated April 1,1977.
- 10. CYAPC0 (Switzer) letter to NRC (Schwencer) dated April 26, 1977.
- 11. CYAPC0 (Switzer) letter to NRC (Schwencer) dated June 1,1977.
- 12. CYAPC0 (Switzer) letter to NRC (Schwencer) dated September 7,1977.
- 13. NRC (Schweacer) letter to CYAPC0 (Switzer) dated November 1,1977.
- 14. CYAPC0 (Switzer) letter to NRC (Schwencer) dated November 30, 1977.
- 15. CYAPC0 (Switzer) letter to NRC (Schwencer) dated January 3,1978.
- 16. CYAPC0 (Switzer) letter to NRC (Schwencer) dated March 6,1978.
- 17. " Staff Discussion of Fifteen Technical Issues Listed in Attachnent G, November 3, 1976 Memorandum from Director NRR to NRR Staff,"
NUREG-0138, November 1976.
- 18. " Pressure Mitigating System Transient Analysis Results," prepared by Westinghouse for the Westinghouse User's Group on Reactor Coolant System Overpressurization, July 1977 (submitted as Attachnent 1 to reference 12 above).
- 19. " Specific Pl ant Re po rt, Low Temperature RCS Overpressure Prottction for Connecticut Yankee," August 1977 (sutmitted as Attachnent 2 to Refe ence 2 above).
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