ML20126G165
| ML20126G165 | |
| Person / Time | |
|---|---|
| Site: | Cooper  |
| Issue date: | 12/22/1992 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20126G158 | List: |
| References | |
| NUDOCS 9301040095 | |
| Download: ML20126G165 (4) | |
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UNITED STATES gIni NUCI EAR REGULATORY COMMISSION
'o WASHINGTON, D.C. 20666 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. 156 TO FACILITY OPERATING LICENSE-NO. DPR-46 NEBRASKA'PUBLIC POWER DISTRICT COOPER NUCLEAR STATION
~ DOCKET NO. 50-298
1.0 INTRODUCTION
By letter dated November 15,1991 (Reference' 1), Nebraska Public Power District (the: District,.NPPD, or the licensee) submitted a request for changes-
-to the Technical Specifications -(TS) for Cooper Nuclear' Station (CNS).. The requested changes would remove the rod sequence control system (RSCS) from the
-TS and reduce the rod worth minimizer (RWM) low-power set point (LPSP) from-its current power level of 20 percent to a power level of 10 percent.
The changes will enable the licensee to disable the RSCS for the unit and thereby improve reactor startup and ' controlled shutdown operations.
2.0 DISCUSSION The RSCS restricts rod movement to minimize the. individual worth of control-rods to lessen the consequences of a Control Rod Drop Accident (CRDA).
Control rod movement is restricted through-the use of rod select, insert, and withdrawal blocks.
The RSCS is a hardwired > (as opposed to a computer controlled),_ redundant backup to the RWM.
It'is somewhat independent of the RWM in terms of direct inputs and outputs but~ the two. systems are similar and =
compatible and have the same intent., The.RSCS and RWM are designed to monitor and block when necessary operator control rod selection,-withdrawal and insertion actions, and_thus assist in preventing significant control rod pattern errort which could lead to a control rod with a high reactivity worth (if dropped). - A significant pattern error is ~one of several abnormal events, all of which must-occur to have a CRDA which might. exceed fuel energy density-limit criteria for the event. The RSCS was designed only for possible; mitigation of_ the CRDA and is active only during low. power' operation-(currently generally less_than 10 or 20 percent power) when a CRDA might be significant.
It provides--rod blocks on detection'of a significant pattern error. The RSCS does not prevent a'_CRDA. A similar pattern control function is also performed by the RWM, a computer-controlled system. All reactors.
having an RSCS also have. an RWM.
9301040095 921222-PDR ADOCK 05000298 P
PDR, _
2 In August 1986, the Boiling Water Reactor Owner's Group (BWROG), in cooperation with the General Electric Company, proposed Amendment 17 to GESTAR II (References 2 and 3), which would eliminate the requirement for the RSCS and retain the RWM with lowered setpoint for turn-off (during startup) or turn-on (during shutdown) from 20 to 10 percent. The NRC staff reviewed the proposed amendment and concluded that the proposed changes were acceptable.
However, the staff's generic approval of Amendment 17 to GESTAR II imposed several additional requirements which must be met by licensees desiring to implement the proposed changes for specific plants. The staff safety evaluation and the additional requirements were provided in an attachment to Reference 4.
The additional requirements that must be met by licensees are:
(1) The TS should require provisions for minimizing operations without use of the RWM.
(2) The occasional 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 patterns used should be at least equivalent to Banked Position Withdrawal Sequence (BPWS) patterns in order to reduce potential maximum rod worth.
3.0 EVALUATION The CNS licensee has proposed several changes to the TS to implement the removal of the RSCS, to lower the RWM LPSP from 20 to 10 percent, and to meet the three additional requirements imposed by Reference 4.
With regard to requirement (1), above, the licensee states that "In accordance with the NRC's safety evaluation accepting Amendment 17 to GLSTAR II, the District has reviewed its control rod movement procedures to ensure verification of control rod movement during RWM inoperability, and has incorporated provisions in the proposed Technical Specification changes to minimize reactor startup with the RWM inoperable." Specifically, TS 3.3.B.3.c has been revised to state that " Reactor startup shall not be initiated more frequently than once per calendar year with the RWM inoperable." This increased administrative control of the RWM follows the pattern of previously approved RWM TS for BWR 3 operation (discussed in Reference 4) and previous reviews of RSCS removal (e.g., Limerick - see Reference 5).
These measures have been found to provide the desired improvement in the reliability of the system. The NRC staff has reviewed the licensee's proposed TS changes that implement these operational changes and concludes that they are acceptable, and therefore finds that requirement (1) of Reference 4 has been adequately met.
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i With regard to requirement (2), above, the licensee states that "In accordance with the NRC's safety evaluation accepting Amendment 17 to GESTAR 11. the-District has reviewed the CNS operating procedures to verify that' adequate controls are in place to ensure an independent verification of correct control rod movement sequence takes place during rod movement _with the RWM _
unavailable.
This review has determined that all CNS procedurcs which govern control rod movements require that while the' reactor operating at oi below the RWM LPSP a second licensed operator or other qualified employee must verify conformance to the correct control rod movement sequence when the RWM is
-i noperabl e. " lhe NRC-staff has reviewed the licensee's discussion of its procedure r'eview and concludes that these procedures provide a suitable,.
independent check on the rod patterns, and are-acceptable.' On this basis the staff finds that requirement (2) of Reference 4 has been adequately met.
With regard to requirement (3), above,:the licensee states that "CNS employs the Banked Position Withdrawal. Sequence (BPWS) control rod movement pattern.
The BPWS is a method by which control rods are inserted and withdrawn such-that incremental control rod worth are maintained at low values, thereby mitigating the consequences of the CRDA in the startup and low power operating ranges.
The BPWS is enforced through the RWM which prevents withdrawing an out-of-sequence control rod more than one notch past the pre-programmed limit." The use of BPWS at CNS was previously approved by-the staff in Reference 6.
The NRC staff has reviewed the licensee's statements regarding use of the BPWS at CNS and finds them acceptable. _On this basis the staff concludes that requirement (3) of Reference 4 has been-adequately. met.
In summary, the NRC staff has reviewed the proposed TS changes to remove the Rod Sequence Control System from the CNS TS and reduce the Rod Worth Minimizer low-Power Set Point from its current power level of 20 percent to a power level of 10 percent. The NRC-staff has previously reviewed and found acceptable the generic technical justification prepared by the General Electric Company for implementing these changes (Reference 4).- The staff-l
-approval of these changes for specific plants is conditional on the' licensee-meeting the three additional requirements defined in Reference-4.
The staff review of the proposed changes to-the CNS TS~ concludes that the-licensee's application and the proposed changes meet the three additional' requirements i
detailed in Reference 4.
Accordingly, the TS changes proposed in Reference 1-are acceptable to the staff and.are hereby approved.
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4.0 STATE CONSULTATION
In accordance with the Commission's regulations, the Nebraska State official was notified of the proposed issuance of the amendment.
The State. official had no comment.
5.0 ENVIRONMENTAL CONSIDERATION
The amendment changes a requirement with respect to installation or use of a:
facility component located within the restricted area as defined in 10 CFR:
Part 20 and changes in surveillance requirements. The NRC staff has determined that the amendment _ involves no significant increase in the amounts, and no significant change in the types, of any effluents tha't may be released J
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- offsite, and that there is no significant increase in individual or cumulative occupational radiation exposure. The Commission has previously issued a pro-posed finding that the amendment involves no significant hazards consideration-and there has been no public comment on such finding (57 FR 30251).
Accordingly, the amendn.ent meets 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 statement or environmental assessment need be prepared in connection with the issuance of the amendment.
6.0 CONCLUSION
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 amendment ~ will not be inimical to the common defense and security or to the health and' safety of the public.
7.0 REFERENCES
(1)
Letter and enclosures from G.'R. Horn, Nebraska Public Power District, to USNRC, dated November 15, 1991, " Proposed Change No. 86 to. Technical-Specifications, Rod Sequence Control System Removal /RWM Setpoint Reduction, Cooper Nuclear Station, NRC Docket No. 50-298, DPR-46."
(2)
Letter and enclosures from T. A. Pickens, BWR Owner's Group, to G. Lainas NRC, dated August 15, 1986, " Amendment 17 to GE Licensing Topical Report NEDE-240ll-P-A."
(3) NtDE-240ll-P-A-9, September 1988, " General Electric Standard Application for Reactor Fuel," (GESTAR II).
(4)
Letter and enclosures from A. Thadani, NRC, to J. Charnley, General-Electric Company, dated December 27, 1987, " Acceptance for Referencing of Licensing Topical Report NEDE-240ll-P-A, Revision 8, Amendment 17."
,I (5) Amendment 17 to Facility Operating License No. NPF-39 Philadelphia j-Electric Company,' Limerick Generating Station, Unit 1, Docket No. 50-352, i
dated March 22, 1989.
j-(6) Amendment 117 to Facility Operating License No. DPR-46, Nebraska Public Power District,-Cooper Nuclear Station, Docket No. 50-298, dated February 23,-1988.
n-Principal Contributor:
H. Rood Date: December 22, 1992 I
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