ML17164A452
| ML17164A452 | |
| Person / Time | |
|---|---|
| Site: | Susquehanna  |
| Issue date: | 11/28/1994 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML17164A451 | List: |
| References | |
| RTR-REGGD-01.197, RTR-REGGD-1.197 GL-82-33, NUDOCS 9412070184 | |
| Download: ML17164A452 (5) | |
Text
WASHINGTON> D.C. 2055!I-0001 RELATING TO REGULATORY GUIDE 1.97
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATIO POST-ACCIDENT NEUTRON FLUX MONITORING INSTRUMENTATIO FOR BOILING WATER REACTORS
- 1. 0 INTRODUCTION Section 6.2 of Generic Letter 82-33 (Reference
- 1) requests applicants and licensees to provide a report on their implementation of Regulatory Guide (R.G.) 1.97, Revision 2 (Reference 2),
and methods for complying with the Commission's regulations, including supporting technical justification of any proposed deviations or alternatives.
A review of the applicants'nd licensees'ubmittals was performed and a safety evaluation (SE) was issued for each plant.
These SEs conclude that the applicants and licensees either conformed to, or adequately justified deviations from, the guidance of R.G..
1.97 for each post-accident monitoring variable except for the variables identified in the SEs.
A large number of Boiling Water Reactor (BWR) applicants and licensees requested deviations from the regulatory guide position for Category 1 neutron flux monitoring instrumentation.
The R.G.
1.97 Category 1 criteria includes environmental qualification, seismic qualification, Class 1E power sources, and redundant channels.
Current operating BWRs, with the exception of Susquehanna Steam Electric Station Units 1
and 2 and Washington Public Power Supply Nuclear Project (WNP-2),
do not have environmentally qualified neutron flux monitoring instrumentation.
- However, none of the submittals requesting neutron flux monitoring instrumentation deviations provide sufficient justification for granting the deviations.
These requests were denied to the applicants and licensees, except for Limerick Generating Station Units 1
and 2.
Additionally, Big Rock Point is not bound by the provisions of R.G. 1.97.
In support of these requests the BWR Owners Group submitted NEDO-31558 "Position on NRC Regulatory Guide 1.97, Revision 3, Requirements for Post-Accident Neutron Monitoring System" (Reference 3).
The NEDO report proposes criteria for neutron flux monitoring instrumentation, in lieu of the Category 1 criteria included in R.G. 1.97, Revision 3 (Reference 4).
The staff rejected the BWR Owners Group proposal (Reference
- 5) because of the judgement that neutron flux is fundamentally a key safety parameter and existing neutron flux monitoring instrumentation is not likely to survive a
post-accident harsh environment.
The BWR Owners Group appealed the staff's position to the Director of the Office of Nuclear Reactor Regulation (NRR)
(Reference 6).
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P ENCLOSURE
The Director of NRR upheld the appeal (Reference 7) and concluded that Category 1 neutron flux monitoring instrumentation is not needed for existing BWRs to cope with Loss-of-Coolant Accident (LOCA), Anticipated Transient Without Scram (ATWS), or other accidents that do not result in severe core damage conditions.
Instrumentation to monitor the progression of core melt accidents would be best addressed by the current severe accident management program'.
Therefore, for existing BWRs, the staff will accept the criteria of NEDO-31558.
However, for new license applications for both conventional and advanced BWR designs there will be no change in the R.G.
1.97 criteria.
2.0 EVALUATION The Code of Federal Regulations 10 CFR 50.49 requires licensees to establish a
program for qualifying certain post-accident monitoring equipment for which specific guidance concerning the types of variables monitored is provided in R.G. 1.97, Revision 2.
This regulatory guide identifies neutron flux as a
Type B variable that provides information to indicate whether plant safety functions are being accomplished.
The guide identifies Category 1 criteria for this instrumentation.
The Category 1 criteria includes environmental qualification, seismic qualification, Class 1E power sources, and redundant channels.
gualification criteria for instrumentation is established based on the safety function of the system whose variables are being monitored.
The selection criteria for R.G.
1.97 variable qualification category is based upon whether monitoring of system parameters is needed during and following an accident and whether subsequent operator actions are dependent on the information provided by this instrumentation.
The NEDO-31558 report analyzes event scenarios to determine the consequences of neutron flux monitoring unavailability and concludes that the failure of this instrumentation will not prevent the operator from determining reactor power levels.
Alternate par'ameter status will be available from which reactor power may be inferred.
Some alternate indications may require more than one input to determine reactor power.
- However, based on the multiple inputs available to the operator, sufficient information will be available upon which to base operational decisions and to conclude that reactivity control has been accomplished.
- Further, NEDO-31558 contains criteria regarding the range, power supplies, and qualifications for neutron flux monitoring instrumentation that provide.sufficient confidence that the neutron flux monitoring instrumentation will be available to confirm reactor shutdown for a wide range of events including ATWS.
The BWR Owners Group also stated that for BWR design basis events, recriticality is not a significant contributor to core melt risk for BWR accident scenarios that go beyond the design basis.
Based on the BWR Owners Group submittals, the Director of NRR has determined that Category 1 neutron flux monitoring instrumentation is not needed for existing BWRs to cope with LOCA, ATWS, or other accidents that do not result
in severe core damage conditions.
Instrumentation to monitor the progression of core melt accidents is best addressed by the current severe accident management program.
Therefore, for existing BWRs, neutron flux monitoring instrumentation does not need to meet the Category 1 criteria of R.G. 1.97.
Neutron flux monitoring instrumentation, at existing
- BWRs, needs to meet the new criteria proposed by the BWR Owners Group in NEDO-31558.
- However, new applications for conventional and advanced BWR designs will be required to meet the R.G.
1.97 criteria.
Licensees should review their neutron flux monitoring instrumentation against the criteria of NEDO-31558 and confirm that they meet this criteria.
If the instrumentation does not meet the criteria, licensees should make a commitment to meet the criteria and state when this commitment will be fulfilled. If a commitment to the criteria cannot be made, licensees should explicitly state any deviations from the criteria and provide supporting justification or alternatives.
The criteria in NEDO-31558 includes the use of uninterruptible and reliable power sources.
The BWR Owners Group and the staff agree that each redundant neutron flux monitoring channel should be powered from a different uninter-ruptible power supply (UPS).
Therefore, a loss of a single UPS would not cause the loss of both channels of neutron flux monitoring instrumentation.
As stated in Section 5.2.8 of NED0-31558, each licensee should perform a
plant-specific evaluation to review power distribution to the neutron flux monitoring instrumentation, including recorders.
The intent of this review is to verify that neutron flux monitoring instrumentation power would not be lost during events by load shedding logics or similar schemes or that a single power supply failure would not cause the loss of redundant channels of neutron flux monitoring instrumentation.
The licenses for Grand Gulf Nuclear Station Unit 1 and River Bend Station contain license conditions that require the installation of Category 1 neutron flux monitoring instrumentation.
Since neutron flux is no longer considered to be a Category 1 variable, the staff will entertain licensee requests for removal of these license conditions.
The licensees for Nine Nile Point Unit 1, Perry Nuclear Power Plant Unit 1, and WNP-2 have designated neutron flux as a Type A variable because this information is required to permit the operator to take specific-manually controlled actions.
These licensees will not be required to upgrade the qualification of the neutron flux monitoring instrumentation to meet the Category 1 criteria.
These licensees should review their Emergency Operating Procedures (EOPs) to assure that there is no plant-specific role for neutron flux monitoring that differs from the evaluation in NEDO-31558.
If the role of neutron flux monitoring does not differ from the evaluation in the NEDO report, the staff will entertain licensee requests for removal of neutron flux from their Type A instrument lists..
V Since neutron flux monitoring is no longer Category 1 instrumentation, licensees may request the removal of this instrumentation from their post-accident monitoring technical specifications if they so desire.
Licensees wishing to maintain a post-accident monitoring technical specification on neutron flux monitoring instrumentation will be allowed to do so.
I'ig Rock Point is not bound by the provisions of R.G. 1.97, and Limerick Generating Station Units 1 and 2 were granted deviations from the Category 1
criteria for neutron flux monitoring instrumentation.
Therefore, these plants do not need to meet the criteria of NEDO-31558.
The neutron flux monitoring instrumentation installed at Susquehanna Steam Electric Station Units 1 and 2
and WNP-2 exceed the criteria of NEDO-31558 and, therefore, these plants may take advantage of any relaxation that the new criteria might provide.
~NL Based on its review, the staff concludes that the post-accident neutron flux.
monitoring instrumentation at existing BWRs should meet the criteria in NEDO-31558.
Licensees should provide a commitment to these criteria and perform a plant-specific power distribution review for neutron flux monitoring instrumentation.
- However, new applications for conventional and advanced BWR designs will be required to meet, the R.G.
1.97 criteria.
Principal Contributor:
B. Narcus Date.
November 28, 1994
REFERENCES Letter from D.
G. Eisenhut (NRC) to All Licensees of Operating Reactors, Applicants for Operating
- Licenses, and Holders of Construction Permits, "Supplement No.
1 to NUREG-0737Requirements for Emergency
Response
Capability, (Generic Letter No. 82-33)," dated December 17, 1982.
2.
3.
5.
6.
7.
Regulatory Guide 1.97, Revision 2, "Instrumentation for Light-Water-Cooled Nuclear Power Plants to Assess Plant and Environs Conditions During and Following an Accident,"
NRC Office of Standards Development, dated December 1980.
Letter from R.
F. Janecek (BWROG) to T.
E. Hurley (NRC)
"BWR Owners'roup Licensing Topical Report Position on NRC Regulatory Guide 1.97, Revision 3 Requirements for Post-Accident Neutron Monitoring System" (General Electric Report NED0-31558),
dated April 1, 1988.
Regulatory Guide 1.97, Revision 3, "Instrumentation for Light-Water-Cooled Nuclear Power Plants to Assess Plant and Environs Conditions During and Following an Accident,"
NRC Office of Nuclear Regulatory
- Research, dated May 1983.
)
Letter from F. J. Hiragl i a (NRC) to S.
D. Fl oyd (BWROG),
"BWR Owners'roup Licensing Topical Report Position on NRC Regulatory Guide 1.97, Revision 3 Requirements for Post-Accident Neutron Monitoring System" (General Electric Report NED0-31558),
dated January 29, 1990.
Letter from G. J.
Beck (BWROG) to T.
E. Hurley (NRC), "Appeal of NRC Staff Decision Regarding Upgraded Neutron Flux Monitoring Systems for BWRs," dated August 16, 1990.
Letter from T.
E. Hurley (NRC) to C. L. Tully (BWROG), "Appeal of NRC Staff Decision Regarding Upgraded Neutron Flux Monitoring Systems for BWRs," dated October 14, 1992.