ML20058G334
| ML20058G334 | |
| Person / Time | |
|---|---|
| Site: | Grand Gulf  |
| Issue date: | 11/07/1990 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20058G333 | List: |
| References | |
| NUDOCS 9011130080 | |
| Download: ML20058G334 (5) | |
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%....p SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. 72 TO FACILITY OPERATING LICENSE NO. NPF-29 ENTERGY OPERATIONS, INC.
GRAND GULF NUCLEAR STATION, UNIT 1 DOCKET NO. 50-416
- 1. 0 INTRODUCTION By letter dated February 16, 1990, as revised May 31 and June 22, 1990, the licensee (System Energy Resources, Inc., before June 6, 1990, and Entergy Operations, Inc., on or after June 6, 1990), requested an amendment to Facility Operating License No. NPF-29 for the Grand Gulf Nuclear Station, Unit 1.
License Condition 2.C.(36), of Operating Licensee No. NPF-29, requires that prior to startup from the fourth refueling outage, the licensee shall implement the requirements of Regulatory Guide (R.G.) 1.97 for neutron flux monitoring by installation of an additional flux monitor or by upgrading the existing flux monitoring system.
The proposed amendment would modify License Condition 2.C.(36) to delay the implementation of neutron flux monitoring system installation or modifications from prior to startup following the fourth refueling outage to prior to startup following the fifth refueling outage.
On January 12, 1987, the staff issued a safety evaluation regarding the licensee's conformance to R.G. 1.97.
This safety evaluation concluded that the Grand Gulf Nuclear Station design was acceptable with respect to the provisions of R.G. 1.97, Revision 2, except for instrumentation associated with the neutron flux variable.
The staff found that the existing neutron flux instrumentation was acceptable for interim operation; however, the safety evaluation concluded that prior to startup from the second refueling outage, the licensee must install or upgrade the neutron flux instrumentation to conform to R.G.1.97, Revision 2.
By "AECM-87-0018, Application for Amend to License NPF-29,changing OL Condition 2.C(36) & Reg Guide 1.97 to Delete [[system" contains a listed "[" character as part of the property label and has therefore been classified as invalid. Sys Flow Monitoring Requirement & Extend Implementation Date for Neutron Flux Monitoring.Fee Paid|letter dated July 1, 1987]], the licensee requested that the implementation date for the installation or upgrade of the neutron flux instrumentation be changed from prior to the startup following the second refueling outage to prior to startup following the third refueling outage.
The licensee stated that they followed the industry development of neutron flux instrumentation that meets R.G. 1.97 criteria and that the scheduling, procurement, and installation of a system meeting R.G.
1.97 would not be possible during the second refueling outage.
On December 2, 1987, the staff approved the requested schedule change in Amendment No. 37 to the license.
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By letter dated July 1, 1988, the licensee requested that the implementation date for the installation or upgrade of the neutron flux instrumentation be deferred until startup following the fourth refueling outage.
The basis for this request was that the Boiling Water Reactor Owners Group (BWROG) had submitted licensing topical report (LTR)
NED0-31558, which concluded that the present BWR neutron flux monitors for normal operation are also adequate for post-accident monitoring, although they deviate from the criteria of R.G.1.97.
The NRC staff approved the requested change in the implementation schedule by Amendment No. 37 to the license, dated December 6, 1988, based on the licensee's commitment to install the instrumentation in the fourth refueling outage if the NRC staff did not accept the BWROG LTR, and to provide quarterly progress reports on the design and procurement specifications of the instrumentation.
By letter dated January 29, 1990, the NRC staff provided to the BWD.0G ii.s l
Safety Evaluatior, of the BWROG LTR NE00-31558 in which the staff concluded that the proposed deviatic'1 from the Category 1 Criteria of R.G. 1.97 for post-accident neutron flux monitoring instrumentation is unacceptable and that BWR licensees should install instrumentation that fully complies with the Category 1 Criteria of R.G. 1.97.
At that time, the licensee had designed excore neutron flux instrumentation but expected it would not fully meet R.G. 1.97 Criteria, particularly in environmental qualification and the low end of the instrumentation range (10E-6% power).
The BWROG met with the staff to further discuss design criteria and to discuss the basis for the staff's conclusion.
The present request for deferral to the fifth refueling outage is based on achieving an excore design that would meet the low end of the range.
By letter dated August 16, 1990, the BWROG appealed the NRC staff's position to the Director, Office of Nuclear Reactor Regulation (NRR),
requesting reversal-of the staff's conclusion that BWR licensees must install instrumentation that meets the Category 1 Criteria of R.G.1.97.
By letter dated September 13, 1990, the Director, NRR, advised BWROG that he would consider the appeal and that, as requested, licensees may defer plant specific actions to install instrumentation pending resolution of the appeal.
The Director's decision on the appeal is expected to be made in November 1990.
The proposed change requested by the licensee's June 22, 1902 submittal would change the license condition to state that the licer,'.e shall implement the installation or upgrade recommendations of R.G. 1.97 for neutron flux monitoring prior to startup following the fifth refueling outage.
Since the fif th outage will begin in April 1992, there is adequate time to procure the instrumentation, should the Director, NRR, deny the appeal.
3-2.0 EVALUATION The excore neutron monitoring instrumentation designed for installation in the fourth refueling outage would have detectors outside the biological shield.
The licensee indicated that the low end of the instrumentation range for sensors, mounted external to the biological shield, was expected to be in the range of 10E-4 to 10E-5% power.
Deferral of the installation until the fifth refueling outage will allow the design of detector locations to increase the low end of the range to 10E-6% power.
The licensee is currently working with a vendor of excore detectors on a design which is expected to result in this sensitivity.
This design will use a detector placed in a hole in the biological shield so that the end is near the inner steel liner.
This design will use a smaller detector than the one previously designed for location outside the biological shield.
l The post-accident neutron monitoring system proposed for installation in the fourth refueling outage is expected to be within two decades of meeting the R.G. 1.97 low end range of 10E-6% power.
The intent of the post-accident neutron monitoring system is to provide warning of returning the reactor to a critical state.
Under anticipated design basis events, once all rods have been inserted, return to a critical state would not be expected.
However, under hypothetical events where certain rods would drif t out or where fuel would undergo some physical changes, the proposed system would provide 6 decades (10E-4% to 100% power) of power status information to the operator.
However, deferring installation of the proposed system one fuel cycle to allow for additional design at a better detector location will provide a post-accident monitoring system that will have a greater operating range (8 decades) for detecting approach to criticality.
This earlier warning of approach to criticality would allow more time for operators to initiate mitigative actions.
The current margin of safety is established by the existing operational neutron monitoring system and the shutdown margin of the control rod i
system.
The post-accident neutron monitoring system required by R.G.
I 1.97 provides additional information to the operator for responding to undefined post-accident reactivity anomalies.
The excore neutron monitoring system originally proposed for installation during the fourth l
refueling outage would provide neutron monitoring diversity and qualified instrumentation to approximately 10E-4% power.
Deferral of this system I
for one additional fuel cycle to allow for further review of system 1
design criteria and alternate detector locations for improving low end-range sensitivity to 10E-6% power will reduce the post-accident neutron monitoring margin of safety during fuel Cycle 5 operations.
Howevor, the margin of safety for a post-accident monitoring system having potentially 8 decades of operating range for the remainder of the GGNS plant operating life (about 30 years), would provide an overall long-term net improvement in post-accident neutron monitoring capability.
Therefore, the deferral of the installation for one fuel cycle (1 years) when viewed over tae i
complete operating life of the plant, would result in a net increase in the margin of safety.
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The licensee has committed to install an incore neutron monitoring system that meets the recommendatirens of R.G. 1.97.
The licensee has also agreed to provide the staff with quarterly updates of the progress of procurement, design, and installation of a qualified system.
Until the post-accident qualified neutron flux monitoring system is installed and operational, the licensee would use the presently installed neutron flux monitoring system and other post-accident qualified instrumentatiori.
The presently installed system is expected to function during the initial phase of an accident (including a LOCA) to indicate suberitical reactor power.
Long term monitoring is available through the APRM channels where operator action is required at the APRM down scale alarm.
However, since i
the presently installed system is not fully qualified to R.G. 1.97, Category 1 requirements, long-term monitoring in a harsh environment may not be directly available over the entire R.G. 1.97 range.
In this event, other measures and indications are available to the operator, as discussed below:
(a) The present control rod position indication system provides the reactor operator with the information that all rods are inserted.
(b) Qualified instrumentation, such as reactor pressure, suppression pool temperature and safety relief valve (SRV) actuation, provides the reactor operator with post-accident information of assessment of reactor power if direct neutron monitoring capability is not available.
(c) The Emergency Procedures (EP) are symptom based and provide appropriately conservative actions if reactor power can not be directly measured in a post-accident situation.
The EP contain action steps that mitigate the symptomatic effects of design basis events (such as LOCA), and beyond design basis events (such as ATWS).
The compensatory measures listed above ensure that the consequences of an accident previously evaluated will not be significantly increased by the absence of a post-accident neutron flux monitoring system during the fifth fuel cycle.
Based on the licensee's commitment to install an improved neutron flux-monitoring instrumentation that fully conforms to R.G. 1.97, Revision 2, by startup following the fifth refueling outage and to provide quarterly.
i reports on the status and schedule for procurement, design, and installation of the instrumentation, the staff concludes that the proposed delay is acceptable.
3.0 ENVIRONMENTAL CONSIDERATION
This amendment involves a change in 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.
The staff has determined that the amendment involves no significant increase in the amounts, and no significant change in the types, of any effluents that may be released off site, and that there is no significant increase in individual or cumulative l
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occupational radiation exposure.
The Commission has previously issued a proposed finding that this amendment involves no significant hazards consideration, and there has been no public comment on such finding.
AccoMingly, this amendment meets the eligibility criteria for categorical axclusinn set forth in 10 CFR 51.22(c)(9),
Pursuant to 10 CFR 51.22(b),
ro enviror, mental impact statement or environmental assessment need be rjrepared in connection with the issuance of this amendment.
4.0 CONCLUSION
The Commission.nade a proposed determination that this amendment involves no significa',t nazards consideration, which was published in the Federal Register on July 25,1990 (55 FR 30295), and consul',ed with the State of Mississioji.
No public comments or requests for hearing were received, and the State of Mississppi did not have any comments.
e The staff has concluded, based on the considerations discussed above, that:
(1} there is seasonable assurance that the health and safety of the public will not be erdangered by operation in the proposed manner, and (2) such actid ties will be conducted in compliance with the Commission's regulations, ano i.ne issuance of this amendment will not be inimical to the common defense and the security, or to the health and safety of the public.
Dated:
November 7, 1990 Principal Contributors:
L. Kintner B. Marcus