ML20248C527
| ML20248C527 | |
| Person / Time | |
|---|---|
| Site: | South Texas  |
| Issue date: | 07/31/1989 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20248C525 | List: |
| References | |
| NUDOCS 8908100070 | |
| Download: ML20248C527 (3) | |
Text
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'o UNITED STATES 8"
NUCLEAR REGULATORY COMMISSION h
WASdlNGTON, D. C. 20555
%g.....h SAFETY-EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NOS.10 AND 2 TO FACILITY OPERATING LICENSE NOS. NPF-76 AND NPF-80 HOUSTON L,1GHTING & POWER COMPANY CITY PUBLIC SERVICE BOARD OF St.N ANTONIO CENTRAL POWER AND LIGHT COMPANY CITY OF AUSTIN, TEXAS DOCKET NOS. 50-498 AND 50-499 SOUTH TEXAS PROJECT, UNITS 1 AND 2
1.0 INTRODUCTION
By application dated June 1., H89, Houston Lighting & Power Company, et.
al., (the licensee) requested changes to the Technical Specifications (TS)
SouthTexasProject(STP)peratingLicenseNos.NPF-76andNPF-80)forthe (Appendix A to Facility O
, Units 1 :and 2.
The proposed changes would allowthecombineduseofhafnium(Hf)andsilver-indium-cadmium (Ag-In-Cd)
Rod Cluster Control Assemblies (RCCAs) within the core of STP Units 1 and 2.
A safety evaluation was provided to justify the change from Hf to Ag-In-Cd in selected control rod banks.
2.0 DISCUSSION AND EVALUATION The present STP reactors use Hf-design RCCAs core-wide in each reactor.
The intent of the licensee's proposal was to allow the replacement of a portion of the Hf control assemblies with Ag-In-Cd assemblies in the upcoming reload cycles for each reactor. STP will replace all Hf assemblies in future cycles. The proposed TS and Final Safety Analysis Report (FSAR) pages are revised to make the Design Feature Section correct for the upcoming reload cycles.
Both the Hf and Ag-In-Cd RCCA designs nave received app ~roval for use in commercial reactor cores and bave been used core-wide in facilities in the past several years. Prior staff approvals, based on good agreement of calculations of nuclear characteristics by Westinghouse with critical experimental data, and independent c51culations by NRC staff consultants indicated that Hf and Ag-In-Cd provide essentially the same control characteristics (NUREG-0797, Supplement No. 1, Safety Evaluation related to the operation of Comanche Peak Steam Electric Station Units 1 and 2, October 1981), The licensee, in its safety evaluation, has stated that neutronic calculations comparing Hf to Ag-In-Cd and combinations of types of RCCA have indicated that the largest change in total rod worth resulting 8908200070 890731 NT gDR ADOCK 05000498 j
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from the substitution of absorber material is 0.1 percent or less and the
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1argest increase in ' peaking factors will be 1 percent of less. Since these numbers are derived on a control rod bank basis, the proposed change in TS design description is written to specify that mixtures of RCCA types are not permitted within a bank.
The overall RCCA design and physical geometry will remain the same for each RCCA type. The licensee identified a 31 pound difference in weight between the RCCA types. 'This would result in a difference in scram drop time. However, all assemblies are subject to the same tescing program prior to startup to ensure the TS requirements on scram time are met.
The staff finds this acceptable.
1 The licensee has addressed other potential effects of the RCCA change in accordance with guidance provided in the NRC-approved Westinghouse Reload Safety Evaluation Methodo' logy topical report. The non-LOCA safety analysis l
includes consideration of trip reactivity, shutdown margin, ejected rod worth and rod drop time. These parameters affecting the safety analysis, as identified in the prior discussion, are within those assumed in the plant licensing basis. Since sufficient shutdown margin and rod worth is maintained, the reactivity considerations are satisfied.
The propc4ed technical specification changes would identify the use of mixed RCCA types in each reactor core and would correctly describe the design features relevant to the control rod assemblies.
Based on its review, the staff concludes that the use of a mixture of Hf and Ag-In-Cd RCCAs has no adverse impact on safety and is therefore acceptable.
The staff has reviewed the licensee's proposal to use a mixture of RCCA types (Hf and Ag-In-Cd) in the cores of South Texas Project, Units 1 and 2.
Based on prior approval of the use of each type core-wide, the similarity of mechanical characteristics of the two types, the minimal effect on shutdown margin and on total rod worth in the core, and the application of TS requirements on rod drop times for each type, the staff finds the proposal acceptable.
3.0 ENVIRONMENTAL CONSIDERATION
The amendments relate to changes in installation or use of a facility cocponent located within the restricts aren. The staff has determined that the emendments involve 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 cumula-tive occupational radiation exposure. The Commission has previously issued a proposed finding that the amendments involve no significant hazards consideration and there has been no public comment on such finding.
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4 Accordingly, the amendments neet' the eligibility-criteria for categorical exclusionsetforthin.10CFR51.22(c)(9). Pursuantto10CFR61.22(b),.
no environmental impact statement or environmental assessment-need be p
prepared in connection with the issuance of these amendments.
4.0 CONCLUSION
Based upon'its evaluation of the proposed changes to the' South Texas -
Project Units l'and 2, Technical Specifications, the. staff has concluded that:
(1) there is' reasonable assurance that the health and safety _of the.
public will not be endangered by operation in the prctosed manner, and (2) such activities will be conducted in compliance with the' Commission's' regulations and the issuance of the amendments will not be inimical to the' common defense'and security or to the health and ' safety of the public.
The staff, therefore, concludes that the proposed changes are acceptable, and are hereby incorporated into the South Texas Project, Units.1 and 2 Technical Specifications.-
Date:' July ' 31,1989 Priticipal, Contributor:
M. McCof Y
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