ML20125C411
| ML20125C411 | |
| Person / Time | |
|---|---|
| Site: | LaSalle  |
| Issue date: | 12/04/1992 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20125C405 | List: |
| References | |
| NUDOCS 9212110175 | |
| Download: ML20125C411 (5) | |
Text
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UNITED STATES n
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NUCLEAR REGULATORY COMMISSION
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SAFETY EVALUATION BY THE OFFICE OF NVCLEAR REACTOR REGULATION BELATED TO AMENDMENT NO. 88 TO FACILITY OPERATING LICENSE NO. NPF-11 AND AMENDMENT N0. 73 TO FAClllTY OPERATING LICENSE NO. NPF-18 COMMONWEALTH CDISON COMPANY LASALLE COUNTY STATION. UNITS 1 AND 2 DOCKET NOS. 50-373 AND 50-374
1.0 INTRODUCTION
By letter dated April 2,1991, as supplemented June 2,1992, Commoawealth Edison Company (Ceco) requested an amendment to facility Operating License Nos. NPF-11 and NFP-18 for the LaSalle County Station, Units 1 and 2.
The proposed amendment requested the following changes:
- 1) the elimination of the required use of the Rod Sequence Control System (RSCS), and 2) the reduction of the Low Power Setpoint (LPSP) initiation for the turnoff of the Rod Worth Minimizer (RWM) from twenty (20) percent of rated power to ten (10) percent of rated power. The June 2,1992, submittal provided additional clarifying information that did not change the initial proposed no significant hazards consideration determination.
2.0 DISCVSSION The Rod Sequence Control System restricts rod movement to minimize the individual worth of control rods to lessen the consequences of a Rod Drop Accident (RDA). Control rod movement is restricted through the use of rod select, insert, and withdraw blocks. The RSCS is a hardwired, redundant backup to the RWM.
The rod sequence control system is independent of the rod worth minimizer in terms of inputs and outputs, but the two systems are compatible.
The RSCS is designed to monitor and block, when necessary, operator control rod selection, withdrawal, and insertion actions. The RSCS thereby assists in preventing significant control rod pattern errors that could lead to dropping a control rod having a high reactivity worth.
A significant rod pattern error is one of several abnormal events, all of which must occur coincidentally to have an RDA that might exceed fuel energy density limits.
The RSCS was designed only for mitigation of a RDA and is active only during low power operations (currently less than 20 percent power), when an RDA could be significant. A similar pattern control function is also performed by the RWM, which is a computer controlled system.
On August 15, 1986 (Reference 1), the BWR Owners' Group, in cooperation with the General Electric Company, proposed Amendment 17 to GESTAR II (Reference 2) which would:
- 1) eliminate the requirement for the RSCS while retaining the I
9212110175 921204 PDR ADOCK 05000373 P
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. RWM to provide backup to the operator for control rod pattern control, and 2) reduce the RWM low power setpoint from 20 percent of rated power to 10 percent
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of rated power.
The NRC staff review concluded that the proposed changes were acceptable, and approved Amendment 17, but imposed several additional requirements which would be necessary to implement the changes.
The additional requirements were:
1.
The Technical Specifications should include provisions for minimizing reactor operations with the RWM system inoperable.
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2.
The occassional necessary use of a second operator replacement should be strengthened by a utility review of relevant procedures, related forms, and quality control to assure that the second operator provides an effective and truly independent monitoring process.
A discussion of this review should accompany the request for RSCS removal.
3.
Rod pattern used should at least be equivalent to banked position withdrawal sequence (BPWS) patterns.
3.0 EVAtVATION Commonwealth Edison Company has proposed several changes to Technical Specifications 3/4.1, 3/4.10 and the associated Bases.
There are four categories to accomplish these changes and to meet the requirements discussed above. These changes are:
1.
Elimination of the RSCS requirements.
2.
Reduction of the RWM setpoint to 10 percent.
3.
Increased administrative control of RWM operability (intended to result in decreased use of the second operator as a substitute for the RWM),
and implementation of BPWS.
The licensee has also discussed the procedures for second operator actions when required, to ensure independent monitoring of the control rod patterns.
4.
Administrative changes improving clarity and overall organization, and relocation of text.
With respect to items 1) and 2) above, the NRC staff review and basis for approval of the removal of the RSCS and lowering of RWM setpoint, as proposed by the licensee, is provided in References 1 and 2.
The proposed changes fall within the scope of that staff review and approval.
The present staff review of the proposed TS changes that implement these operational changes concludes that they are appropriate, clearly stated and are acceptable.
In an effort to improve the RWM system, LaSalle installed a new system:
an Enhanced Rod Worth Minimizer (EHRWM).The new system has many improvements over the old RWM system, such as increased reliability, easier maintenance,
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l 9 faster scanning speed, and a color graphic CRT which operates by a touch screen.
With regard to item 3) above, to assure that the second operator provides an effective and independent verification during the infrequent occassions when the EHRWM is inoperable, a review of applicable station procedures was performed and revised guidelines developed.
The revised guidelines will provide a directive for second verification forcing the operator to request permission before moving the rod, followed by the second verifier granting permission.
Likewise, completion of the move will be announced by the operator and acknowledged by the second verifier. This will ensure a complete independent check of rod movements. Also, as required, the revised TS presciibes the use of rod patterns equivalent to the BPWS patterns to maintain low control rod reactivity worths.
The new EHRWH system enforces BPWS constraints at all times.
The staff has reviewed the proposed changes to the TS and find them to be consistent with the intent of the staff's safety evaluation approving Amendment 17 to GESTAR 11 and find the changes acceptable.
The administrative changes relating to item 4) above, which are applicable to TS 3/4.1, 3/4.10 and the Bases, are primarily corrections of wording and improvements in clarity or format.
The changes include the removal of section 3/4.1.4 (Rod Sequence Control System) and replacement of RSCS with RWM within the text.
The changes and reviews are in accordance with the staff requirements of Reference 3 and are acceptable, and the proposed changes to the TS and Bases appropriately implement the changes.
4.0 STATE CONSULTATION
In accordance with the Commission's regulations, the Illinois State official was notified of the proposed issuance of the amendments.
The State official had no comments.
5.0 ENVIRONMENTAL CONSIDERATION
The amendments change a requirement with respect to the installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20 and change surveillance requirements.
The NRC staff has 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 (56 FR 27038).
Accordingly, the amendments meet the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9).
Pursuant to 10 CFR 51.22(b), no environmental impact statement or environmental assessment need be prepared in connection with the issuance of the amendments.
e 9 6.0 f^?AqSl0B The Commission has concluded, based on the considerations discussed above, that:
(1) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, (2) such activities will be conducted in compliance with the Commission's regulations, and (3) the issuance of the amendments will not be inimical to the common defense and security or to the health and safety of the public.
Principal Contributor:
Brenda J. Whitacre Date:
December 4, 1992 l
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7.0 REFERENCES
1.
Letter with enclosures from T. A. Pickens, BWR Owners' Group to G. Lainas, NRC, " Amendment 17 to GE Licensing Topical Report flEDE-24011-P-A," dated August 15, 1986.
2.
" General Electric Standard Application for Reactor Fuel" (GESTAR II),
IIEDE-24011-P-A-9, September 1988.
3.
Letter from A. Thadani, liRC, to J. Charnley, General Electric,
" Acceptance for Referencing of Licensing Topical Report f4EDE-240ll-P-A, Revision 8, Amendment 17," dated December 27, 1987.
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