ML20012C590
| ML20012C590 | |
| Person / Time | |
|---|---|
| Site: | Clinton  |
| Issue date: | 03/13/1990 |
| From: | John Hickman Office of Nuclear Reactor Regulation |
| To: | Spangenberg F ILLINOIS POWER CO. |
| References | |
| RTR-REGGD-01.097, RTR-REGGD-1.097 NUDOCS 9003220246 | |
| Download: ML20012C590 (4) | |
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WASHINGTON, D, C. 20655 Q
., 5 March 13, 1990 Docket No.'50-461
.Mr. Frank A. Spangenberg Manager - Licensing and Safety
~ Clinton Power Station-P..O. Box 678 Mail-Code V920 Clinton, Illinois.
61727
Dear Mr. Spangenberg:
SUBJECT:
POST ACCIDENT NEUTRON FLUX MONITORING INSTRUMENTATION TO MEET THE REQUIREMENTS OF REGULATORY GUIDE 1.97 FOR THE CLINTON POWER STATION ~
Ref: -1)_ BWR Owners Group letter (R. F. Janecek) to NRC (T. E. Murley), BWR Owners' Group Licensing Topical Report, " Position on NRC Regulatory Guide 1.97,: Revision 3, Requirements for Post-Accident Neutron Moni-toring System," (General Electric Report NED0-31558), April 1, 1988.
' Regulatory Guide (R.G.) l'.971and 10 CFR 50.49 require that neutron-flux be nonitored by Category 1 instrumentation. The staff has allowed BWRs to' operate'with existing instrumentation until instrumentation was developed that conforms to the requirements of R.G. 1.97 and 10 CFR 50.49.
TheBoilingWaterReactorOwnersGroup(BWROG)submitteda_ report (Reference
- 1) which proposed functional criteria for post-accident neutron flux monitoring
-as an alternative to the Category 1 instrumentation recommendations specified i
'in R.G. 1.97. The BWROG proposed alternative position,-which was determined to be_ wacceptable by the staff, is contained in the enclosed letter and Safety Evaluation Report.
4 Since instrumentation that meets the requirements of R.G. 1.97 and 10 CFR 50.49 is now available, and the staff has determined that the BWROG alternative position is unacceptable, it is requested that Illinois Power Company provide a-schedule for installation of neutron flux monitoring instrumentation that meets the requirements of these documents for the Clinton Power Station.
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P,r. Frank'A. Spangenberg 2
March 13, 1990 1
Please provide this schedule within 45 days of receipt of this letter.
If you have any problems related to this issue on.the reouested information, please contact me.-
Sincerely,
/s/
John B. Hickman, Project Manager Project Directorate III-2 Division of Reactor Projects - III, IV, Y and Special Projects Office of Nuclear Reactor Regulation L
Enclosures:
1:
As stated cc w/ enclosures:
See next page.
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l DISTRIBUTION Docket File PDIII-2 r/f NRC & Local PDRs JZwolinski LLuther JHickman 0GC EJoidan ACRS(10)
Plant File OFFICAL RECORD COPY Doc ment Name:
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-.Mr. Frank A. Spanginberg Clinton Power Station Illinois Power Company.
Unit 1 1
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Mr. J. S. Perry -
Illinois Department Vice President-of Nuclear Safety Clinton Power Station Office of Nuclear Facility Safety
.J P. O. Box 678-1035 Outer Park Drive Clinton,-Illinois, 61727 Springfield, Illinois 62704 Mr. R. D. Freeman Mr. Donald Schopfer Manager-Nuclear Station Engineering Dept.
Project Manager Clinton Power Station Sargent & Lundy Engineers P. O. Box 678 55 East Monroe Street-
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Clinton, Illinois 61727 Chicago, Illinois 60603 1
Sheldon Zabel, Esquire Schiff, Hardin & Waite 7200 Sears Tower 233 Wacker Drive Chicago, Illinois 60606 Resident Inspector U. S. Nuclear Regulatory Commission RR#3, Box 229-A Clinton 1111n,.is 61727 Mr. L. Larson Project Manager General Electric Company 175 Curtner Avenue, N/C 395 San Jose, California 95125-Regional Administrator, Region III 799 Roosevelt Road, Bldg. #4 Glen Ellyn, Illinois 60137 Chairman of DeWitt County c/o County Clerk's Office DeWitt County Courthouse Clinton, Illinois 61727
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. 'Mr.: Frank A. Spangenberq' March 13, 1990 w
m Please' provide this schedule;within 45 days of receipt _of this letter.
If you
- have any-problems related to this issue on the reouested information, please contact me, p
Sincerely, H/
John B.-Hickman, Project Manager Project Directorate III-2 a
Division:of Reactor Projects - III, t-IV, V' and Special Projects Office of Nuclear Reactor Regulation
Enclosures:
As stated ccw/ enclosures:
.See next page i
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Mr. Stephen D. Floyd, Chairman BWR Owners' Group 1
Carolina Power and Light 411 Fayetteville Street Raleigh, NC 27602
Dear Mr. Floyd:
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$UBJECT:
BWR OWNERS' GROUP LICENSIllG TOPICAL REPORT " POSITION ON NRC REGULATORY GUIDE 1.97, REVISION 3 REQUIREMENTS FOR POST-ACCIDENT NEUTRON MONITORING SYSTEM" (GENERAL ELECTRIC REPORT NED0-31558) s
References:
1)
BWR Owners' Group letter (R. F. Janecek) to NRC (T. E.
Murley), "BWR Owners' Group Licensing Topical Report
" Position on NRC Regulatory Guide 1.97, Revision 3 Requirements for Post-Accident Neutron Monitoring System" (GeneralElectricReportNEDO31558), April 1,1988.
2)
BWR Owners' Group letter (D. N. Grace) to NRC (T. T.
Hartin), 'BWR Owners' Group Licensing Topical Report
" Position on NRC Regulatory Guide 1.97, Revision 3 Requirements for Post-Accident Heutron Monitoring System" (GeneralElectricReportNEDO31558), June 13,1988.
Reference 2 requested that the staff expedite its review of Reference 1.
Reference I submitted the BWR Owners' Group (BWROG) Licensing Topical Report L
(LTR) for staff review and approval.
The LTR proposed furctional criteria for l
post-accioent neutron flux monitoring as an alternative to the Category 1 recomendations specified in Regulatory Guide (R.G.) 1.97.
F Based on our review, _the staff concludes that a Category 1 designation, and associated lower range for neutron flux monitoring equipment is appropriate.
Therefore, the proposed LTR NEDO-31558 is unacceptable and the neutron flux monitoring equipment must be' environmentally qualified to comply with 10CFR50.49.
If you have any questions regarding the above information, please contact Barry Marcus, of my staff on 49-20776.
Sincerely.
Al Frank J.
iraglia, Associate Director for Inspection and Technical Assessment 1
Office of Nuclear Reactor Regulation l
Enclosure:
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ENCLOSURE i
l SAFETY EVALUATION REPORT BWROG LICENSING TOPICAL REPORT NE00-31558 POSITION ON REGULATORY GUIDE 1.97 REQUIREMENTS FOR POST-ACCIDENT NEUTRON FLUX MONITORING SYSTEM
1.0 INTRODUCTION
By letter dated June 13, 1988, the Boiling Water Reactor Owners' Group (BWROG)
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requested that the staff expedite its review of BWROG Licensing Topical Report (LTR) NED0-31558 " Position on NRC Regulatory Guide (R.G.) 1.97 Revision 3 Requirements for Post-Accident Neutron Monitoring System", submitted by letter dated April 1, 1988. The LTR provides an event analysis'of selected postulated events where pcst-accident neutron flux monitoring instrumentation might b'e required, the effect of neutron flux monitoring instrumentation failure, and proposed functional criteria based on the event. analysis.
2.0 BACKGROUND
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The following is a chronology of events for neutron flux monitoring as related to R.G. 1.97:
In December 1980, R.G.1.97, Revision 2, was issued recomending that Category 1 neutron flux monitoring instrumentation be used to monitor reactivity control in boiling water reactors (BWRs).
In March 1983, based on a number of surveys within the nuclear power industry it was concluded, by the staff, that existing neutron flux L
monitoring instrumentation that was available to the industry did not confonn to the criteria of R.G.1.97.
However, the staff was infonned L
that instrumentation to conform to the criteria of R.G.1.97 was under development.
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Beginning February 1985, with the issuance of the first R.G. 1.97 Safety Evaluation Reports (SERs), the staff acknowledged that fully qualified neutron flux monitor'ing systems were not available and instructed applicants.and licensees to follow industry development and install qualified neutron flux monitoring systems when they became available.
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The SERs also included acceptance of existing neutron monitoring systems for interim use until fully. qualified neutron flux monitoring systems became available..
Early in 1987, the staff was infomed that fully qualified neutron flux monitoring systems were now available to the nuclear power industry.
Beginning in December 1987, R.G. 1.97 SERs acknowledged that industry had developed neutron flux monitoring systems that meet the R.G. 1.97 criteria and instructed applicants and licensees to evaluate these newly developed systems and install heutron flux monitoring instrumentation which complies with the Category 1 criteria of R.G. 1.97.- The SERs also included acceptance of existing neutron flux monitoring systems for interim use until fully qualified neutron flux monitoring systems were installed.
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R.G.1.97 recocnends Category 1 neutron flux monitoring instrumentaticn to monitor reactivity control during post-accident situations.
R.G. 1.97 specifies neutron flux as a key variable for detemining the accomplishment of reactivity control because it is a direct measurement and not an indirect lagging indication. The regulatory guide specifies that Category 1 systems should be environmentally qualified.
10 CFR 50.49 explicitly references this regulatory guide and therefore requires that all Category 1 equipment shall be environmentally qualified. Existing installed neutron flux monitoring
- instrumentation typically do not meet these environmental qualification requirements for detectors, cables, and detector drive mechanisms. Some existing systems are not powered by Class 1E power supplies.
-4 R.G.1.97 recomends that the neutron flux monitoring instrumentation be capable of monitoring a range of 10-6% to 100% full power.
Initiating and post reactor shutdown events could involve environmental conditions more extreme than the conditions the typical existing neutron flux monitertng-instrumentation was designed to operate in. Neutron flux monitoring instrumentation capable of monitoring readings down to the 10-6% power level must be able to operate satisfactorily in these extreme environmental conditions. The instrumentation must be reliably in place imediately after initial shutdown, and be fully operable for an extended period of time, i.e.,
in the order of six hours.
3.0 EVALUATION, The LTR provides a discussion of BWR safety analyses relevant to post-accident neutron flux monitoring instrumentation requirements and uses the results of the analyses to establish functional design criteria. These criteria include several deviations from the recomendations of R.G.1.97.
Among these deviations is a proposed " alternate" requirement for the range recomendation of the neutron flux monitoring system (LTR Section 5.2.1), reducing the R.G.
1.97 recomendations of 10-6% to 100% power to an " alternate" of 1% to 1001 power. This in effect would eliminate any requirement (for this purpose) for L
the source range monitor (SRM) and intemediate range monitor (IRM) instruments.
The LTR justifies this alternate requirement by examining representative extreme events selected from the range of FSAR and ATWS events. The analyses and related considerations such as the availability of alternate monitoring equipment (e.g., control rod position indication or boron concentration measurements) are based on anticipated conditions resulting from standard event analyses.
These might normally be considered as reasonably comprehensive for, e.g., FSAR design bases analyses. However, at least some of the instrumentation recomendations of R.G.1.97 were intended to cover a wider range of possibilities, including conditions not necessarily to be i
anticipated by following the usually clearly defined paths of standard event L
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In particular, the proposed elimination of the 10-61 to 11 power portion of the. range would delete a primary purpose of the post-accident 1
neutron flux monitoring instrumentation. This purpose was intended to provide, with maximum forewarning time, operator information (via indications of deviations from normal post shutdown flux levels) warning of possible post-event approaches or return to a critical state. This might be under circumstances which would involve reactor states and evolving events and conditions not anticipated from analyses following normally considered event scenarios.
It would thus be virtually impossible to either predict or demonstrate the implausibility of such event paths and resulting conditions with assurance.
Therefore, while not disputing the analyses or results presented in the LTR, it must be concluded that they do not address the above conceptual basis that set the low power range recomendations of R.G.1.97.
The required power level is set by expected flux levels existing for some extended period of time (in the order of several hours) after shutdown and for reactivity status and neutron (installed and operational) source levels resulting from normal rapid shutdown from power operation.
The normal flux levels serve as a base for observable deviations of anomalous reactivity states in the (unknown)' anomalous events indicated above.
10CFR50.49 requires that certain post-accident monitoring equipment (Category 1 and 2) be environmentally qualified. Therefore, based on the above evaluation, i
the staff continues to conclude that the Category 1 designation is appropriate and neutron flux monitoring equipment must be environmentally qualified to comply with 10CFR50.49.
-To provide suitable interpretation, neutron flux monitoring detectors internal to the pressure vessel (e.g., in standard SRM locations) appear to be preferable, but neutron flux monitoring detectors external to the pressure vessel (e.g., in the drywell) could be considered. The chosen neutron flux monitoring system, should be operational during degraded core cooling conditions leading to some fuel clad failure, but not significant clad or fuel melting. Environmental conditions external to the pressure vessel to be
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- possible flooding, associated with external LOCA conditions. Fire conditions l
which might affect control rod actuation and/or position readout and thus require the use of the low range neutron flux monitoring instrumentation should also be considered.
L Because the functional criteria proposed in the LTR does not meet the requirements of 10 CFR 50.49, the LTR functional criteria is unacceptable.
l-The staff has been infomed that industry has developed and made available, to L
the nuclear power industry, at least two different wide range neutron flux L
monitoring systems that satisfy all the Category 1 criteria of R.G. 1.97.
Therefore, it is the staff's position that BWR licensees should evaluate these newly developed systens and install neutron flux monitoring instrumentation which fully complies with the Category 1 criteria of R.G. 1.97.
4.0 CONCLUSION
Based on our review the staff concludes that, as an alternative to the Category 1 criteria of R.G. 1.97, the propcsed LTR NED0-31558 functional criteria for post-accident neutron flux monitoring instrumentation is unacceptable.
It is also concluded that the proposed alternate range requirement of LTR Section 5.2.1. It to 100% power does not meet the intent of R.G. 1.97, and is therefore unacceptable.
The range of neutron flux monitoring instrumentation should remain 10 % to 100% power.
It is the staff's position that BWR licensees should install neutron flux monitoring instrumentation that fully complies with the Category I criteria of R.G.1.97 and 10 CFR 50.49.
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