ML20198F342
| ML20198F342 | |
| Person / Time | |
|---|---|
| Site: | Washington Public Power Supply System |
| Issue date: | 08/14/1975 |
| From: | Tedesco R Office of Nuclear Reactor Regulation |
| To: | Stello V Office of Nuclear Reactor Regulation |
| References | |
| CON-WNP-1085 NUDOCS 8605280481 | |
| Download: ML20198F342 (5) | |
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Docket Hos. 50-460 l
and 50-513 V. Ste11o, Assistant Director for Reactor Safety. TR SUPPLEMENT TO THE DRAFT SAFETY EVALUATION REPORT FOR WPPSS 1 & 4 Plant Name: WPPSS 1 & 4 Docket Nos. 50-460 and 50-513 Milestone No.: 27-04 Licensing Stage: CP NSSS Supplier: Babcock & Wilcox Architect Engineer: United Engineers & Constructors Responsible Branch & Project Manager:
RSB; G. Mazetts; LWR 2-3. T. Cox Requested Completion Date: Being Revised Review Status: Complete The Containment Systems Branch has reviewed the containment pressure calcu-lations used for the ECCS evaluation of WPPSS 1 & 4.
Attached is a draft Safety Evaluation for this matter.
The applicant references Topical Report BAW-10102. "ECCS Evaluation of B&W's 205-FA NSS" for its ECCS evaluation. The containment pressure calculations used in this ' evaluation were done using input parameters for the Bellefonte
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plants.
In a letter dated July 25, 1975 the applicant had provided a comparison of the containment pressure calculated in BAW-10102 with that calculated using the containment data for WPPSS 18. 4.
The intemal passive heat sinks for the calculation were consistent with our Branch Technical Position CSB 6-1.
The applicant concludes that the diffennce of containment pressure, (about 1 psi) between the two calculations has an insignificant effect on j
the peak cladding temperature.
Provided that RSS concurs with the applicant's conclusion regarding the peak i
cladding tageratum, we conclude that the containment pressure for WPPSS 1 & 4 is in accordar.ca with Appendix K.
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l Robert L. Tedesco, Assistant Director for Containment Safety Division of Technical Roview
Enclosure:
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SUPPLEMENT TO THE DRAFT SAFETY EVALUATION REPORT (CONTAIt! MENT SYSTEMS)
WPPSS NUCLEAR PROJECTS NOS.1 & 4 DOCKET NOS. 50-460 & 50-513 ECCS Containment Pressure Evaluation Appendix X to 10 CFR 50 of the Commission's regulations requires that the effect of operation of all the installed pressure reducing systems and processes be included in the ECCS evaluation.
For the evaluation it is conservative to minimize the containment pressure since this will increase the resistance to steam flow in the reactor coolant loops and reduce the relfood rate in the core. Following a loss-of-coolant accident, the pressure in the containment building will be increased by the addition of steam and water from the primary reactor system into the containment atmosphere. After initial blowdown, heat flow from the core, primary metal structures, and steam generators to the ECCS water, will produce additional' steam. This steam together with any ECCS water spilled from the primary system will flow through the postulated break into the containment. This energy will be released to the containment during both the blowdown and later ECCS operational phases; i.e., reflood and post-reflood phases.
Energy removal occurs within the containment by several means. Steam condensation on the containment walls and internal structures serves as a passive energy heat sink that becomes effective early in the blowdown transient. Subsequently.
the operation of the containment heat renoval systems such as containment sprays and fan coolers will remove energy from the containment atmosphere. When the energy removal rate exceeds the rate of energy addition from the primary system, the containment pressure will decrease from its maximum value.
-2 The ECCS containment pressure calculations for WPPSS 1 & 4 were done using Babcock & Wilcox ECCS evaluation model. The NRC staff reviewed B&W's model and published a Status Report on October 15, 1974, which was amended November 13,1974. We concluded that B&W's containment pressure model was acceptable for ECCS evaluation. We required, however, that justification of the plant-dependent input parameter used in the analysis be submitted for our review of each plant.
Justification for the containment input data were submitted for WPPSS 1 & 4 dated July 25, 1975. This justification consists of a comparison of the actual containment parameters for WPPSS 1 & 4 with those assumed by B&W in BAW-10102.
The assumptions made by Washington Public Suppfy System for the containment net free volume, and operation of the containment heat removal systems were con-servatively selected for the ECCS analysis.
Passive heat sinks were determined from guidelines contained in the Branch Technical Position CSB 6-1.
The WPPSS 1 & 4 containment data were shown to result in a containment pressure slightly lower (less than 1 psi) than that obtained using the B&W assumptions of BAW-10102 for the first 60 seconds after the accident and higher thereafter.
The applicant has concluded that little or no difference in peak cladding temperature would result between the two containment pressure calculations.
We have concluded that the plant-dependent infonnation provided by Washington Public Supply System for WPPSS 1 & 4 is conservative for ECCS analysis.
Provided that RSB concludes with the applicant that the WPPSS 1 & 4 containment parameters and those used in BAW-10102 produce an insignificant effect on the peak cladding taperature, we conclude that the containment pressure is in accordance with Appendix K to 10 CFR 50 of the Commission's regulations. At
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the operating license stage we will review the input data used in the analysis and make comparison to that for the as-built plant.
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