ML20244C877
| ML20244C877 | |
| Person / Time | |
|---|---|
| Site: | Diablo Canyon  |
| Issue date: | 06/07/1989 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20244C875 | List: |
| References | |
| IEIN-87-019, IEIN-87-19, NUDOCS 8906150186 | |
| Download: ML20244C877 (2) | |
Text
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- o UNITED STATES
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g NUCLEAR REGULATORY COMMISSION
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WASHINGTON, D. C. 20555 L
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PACIFIC GAS AND ELECTRIC COMPANY DIABLO CANYON NUCLEAR POWER PLANT, UNIT NOS. 1 AND 2 DOCKET NO. 50-275 AND 50-323 l
1.0 INTRODUCTION
By letter dated December 19,1988(ReferenceLAR88-09),PacificGasand Electric Company (PG&E or the licensee) requested amendments to the combined Technical Specifications (TS) appended to Facility Operating License Nos. DPR-80 and DPR-82 for the Diablo Canyon Power Plant (DCPP),
Unit Nos. -1 ane 2, respectively.
The amendments change the TS to allow the fully withdrawn position for the shutdown and control rod banks to be redefined as 225 steps or greater, rather than 228 steps, with ins'ertion limits remaining the same. The amendments provide the flexibility to reposition the rod banks as part of a control rodlet wear management program and involve changes to TS 3.1.3.5 and 4.1.3.5 and Figures 3.1-la and 3.1-1b.
Also, the amendments add x and y axis intercepts to Figure 3.1-la.
This administrative change facilitates the interpretation of this figure by operations personnel who wish to determine the value of rod bank positions for specific power conditions. The values for the x and y intercepts were taken from the Diablo Canyon " Precautions, Limitations and Setpoints" document.
2.0 EVALUATION InNRC(IE)InformationNotice87-19,"PerforationandCrackingofRod Cluster Control A!semblies," the NRC notified Westinghouse PWR licensees of a potentially significant safety problem in which w trol rod wear may result in perforation and cracking of rod cluster antrol assemblies.
Based on the information notice, and recs t experience at other Westinghouse PWRs, the licensee requested these amendments to address 6his concern at Diablo Canyon. Control rod wear appears to be due to fretting of the control rodlets against the upper internals guide plate as a result of flow-induced vibration. These amendments will allow periodic axial repositioning of the rod banks, which will move the worn control rodlet cladding away from the guide plate, thus reducing the possibility of wear-through of the rodlet cladding. Therefore, the
. likelihood of a malfunction of the rods will be decreased.
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o Tne licensee also stated that, based on Westinghouse recommendations, the Diablo Canyon reactor coolant system is monitored for the presence of rod absorber material (Ag-110 in a metastable state) to provide early detection of significant control rodlet wear prior to experiencing operational problems.
In its letter of December 19, 1988, PG&E provided the results of a safety analysis performed by Westinghouse to evaluate the proposed l
changes. The analysis'showed that sufficient margin exists that redefining the fully withdrawn position for the rod banks to 225 steps or greater will not have a significant effect on any of the key safety parameters. ' Specific safety parameters evaluated include the power distribution, peaking factors, axial offset, shutdown margin, control rod worths, and departure from nucleate boiling ratio (DNBR).
The NRC staff has reviewed the analysis results, and finds them acceptable.
Specifically, changinn the rod position by such a small amount, near the top of the actiu
)re, is expected to result in very small changes in the key safety parameters. Based on this, the staff finds the proposed amendments to be acceptable.
3.0 ENVIRONMENTAL CONSIDERATION
These amendments involve changes in the installation or use of facility components located within the restricted area as defined in 10 CFR Part 20. We have determined that the amendments 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 cumulative 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.
Accordingly, set forth in 10 CFR 51.22(c)(gibility criteria for categorical exclusion these amendments meet the eli9). Pursuantto10CFR51.22(b),no environmental impact statement or environmental assessment need be prepared in connection with the issuance of these amendments.
4.0 CONCLUSION
We have concluded, based on the considerations discussed above, that:
(1) there is reasonable assurance that the health and safety of the ublic will not be endangered by operation in the proposed manner, and p(2) such activities will be conducted in compliance with the Commission's regulations and (3) the issuance of these amendments will not be inimical to the common defense and security or the health and safety of the public.
Principal Contributor:
Harry Rood Dated: June 7, 1989 h
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