ML20246E324
| ML20246E324 | |
| Person / Time | |
|---|---|
| Site: | Wolf Creek  |
| Issue date: | 07/05/1989 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20246E285 | List: |
| References | |
| NUDOCS 8907120192 | |
| Download: ML20246E324 (2) | |
Text
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. #yO' *%g'c UNITED STATES j j",4[,j NUCLEAR REGULATORY COMMISSION p p v'"'f f
W ASHINGTON, D. C,20555 e
SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION PELATED TO AMENDt'ENT tl0. 32 TO FACILITY OPERATING LICENSE NO. NPF-42 WOLF CREEK NUCLEAR OPERATING CORPORATION WOLF CREEK GENERATING STATION DOCKET NO. 50-482 INTRODUCTION Py letter deted April 13, 1989 the licensee proposed to revise Technical Specifications 3.1.3.4 and Figure 3.1-1 to change the fully withdrawn position of the Rod Cluster Control Assemblies (RCCAs) for Wolf Creek Generating Station to a range of 222 to 231 steps, inclusive.
. Wolf Creek Generating Station (WCGS) Technical Specifications require all shutdown rods to be fully withdrawn and all control rod banks to be withdrawn in accordance with Figurc 3.1-1.
Past operational history at WCGS has shown that 1cng periocs cf operation with the control rods withdrawn to 228 steps has led to control red wear by fretting against the upper internals guide surface due to flow induced vibration.
In order to rinimize the effect of this control rod weur, axial repositioning cf the control rods can be used to eliminate further degradatier at locations where control rod wear has been observed. This Technical Specification change would allow axial repositioning between 222 steps ard 231 steps withdrawn.
EVALUATION T'.e licensee proposed the change to minimize localized RCCA wear at the top cf the control rods.
The proposed technical specification change will allow operation with the RCCAs positioned between 222 steps and 231 steps withdrawn as compared te the current fixed pcsition of 228 steps. With the RCCAs positioned at 222 ster. withdrawn, the tips of the RCCAs will be approximately 3 steps (1.875 inches)intotheactivefuelregion.
Since the top region of the core has such low worth, the resultant power distribution perturbations are expected to be negligible and should be accommodated with available margin. As expected, calculations by the licensee show that operation with the rods positioned at 222 steps withdrawn will have minimal impact on axial peak power and axial cffset over the life of the fuel cycle.
The licensee has examined the impact of the RCCA repositioning for both transient and loss of coolant accident (LOCA) conditions. Mechanically, the RCCA repositioning will not effect the operation of the enntrol rod drive me c h ani st..s.
Since the technical specification proposal dces not change the control _ rod drop time limit of 2.2 seconds, the transient analysis found in the I!pdated Safcty Analysis Report (USAR) remains valid.
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. The small and large break LOCA analyses were also evaluated to determine the impact of this technical specificaticr. change.
For the small break analysis, l
crecit is taken for control rod insertion.
Since the naaximum rod drop time l
has not changed due to the RCCA repositioning, there will be no effect on the USAR small break LOCA analysis. The large break analysis does not take credit for control rod insertion.
During a large break LOCA, the reactor is assumed to be brought to subtritical by the presence of voids in the core caused by the rapid depressurization of the reactor coolant system. Since credit is not taken for the control rods, there will be no effect on the USAR large break analysis for RCCA repositioning.
Other licensed facilities have requested similar technical specification changes which the staff has found acceptable.
Eased on the staff's evaluation of the licensee's submittal, the staff agrees that the proposed change has negligible effect and is, therefore, acceptable.
EUVIR0tMENTAL CONSIDERATION The amendrent involves a change in the installation or use of a facility cccponent locatec within the restricted area as defined in 10 CFR Part 20.
The staff has deterr.inec that the amendment involves no significant increase in the amounts, anc re significant change in the types, of any effluents that may be released offsite, and that there is no significant increase in ir.dividual or cucciative occupational radiation exposures. The Commission has previously issued a proposed fincing that the amendment involves no significant hazards censidereticn and there has been no pcblic comment on such finding. Accordingly, the ar.encrent r;eets the eligibility criteria for categorical exclusion set forth in 10 CFR Section 51.22(c)(9).
Pursuant to 10 CFR 51.22(b), no environmental impact statenent er environmental assessrent need be prepared in connection with the issuance of the amendment.
CONCLUSION The staff has concludec, based on the cor.sideratiord discussed above, that:
(1) there is reascr.able assurarce that the health and safety of the will not be endangered by operation in the proposed manner, and (2) public such activities will be ccr. ducted in templiance with the Commission's regulations, ar.d the issuerte of the amenoment will not be inimical to the corron defense and security or to the health and safety of the public.
Date: July 5,1989 Principal Contributor: Douglas V. Pickett
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