ML20012C504
| ML20012C504 | |
| Person / Time | |
|---|---|
| Site: | Vermont Yankee File:NorthStar Vermont Yankee icon.png |
| Issue date: | 03/07/1990 |
| From: | Fairtile M Office of Nuclear Reactor Regulation |
| To: | Tremblay L VERMONT YANKEE NUCLEAR POWER CORP. |
| References | |
| RTR-REGGD-01.097, RTR-REGGD-1.097 TAC-51365, NUDOCS 9003220087 | |
| Download: ML20012C504 (3) | |
Text
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Ma rch. 7,1990
.9-4 Docket No. 50-271 P[
Mr.. L. A. Tremblay Licensing Engineer Vermont Yankee Nuclear Power Corporation 580 Main Street.
.Bolton, Massachusetts 01740 1398
Dear Mr. Tremblay:
SUBJECT:
POST-ACCIDENT NEUTRON FLUX MONITORING FOR BWRS - VERMONT YANKEE NUCLEAR POWER STAT 10ll (VYNPS) (TAC N0. 51365)
BWROwr,23'Groupletter(R.F.Janecek)toNRC(T.E.Murley),
REF.:
"BWR Owners' Group Licensing Topical Report " Position on NRC Regulatory Guide 1.97, Revision 3 Requirements for Post-Accident Neutron Monitoring System" (General Electric Report NEDO-31558),
April 1, 1988 Regulatory Guide (R.G.) 1.97 and 10 CFR 50.49 require that neutron flux be monitored by Category l' instrumentation. The staff has allowed BWRs to
-operate with existing instrumentation until instrumentation was developed that l
conforms to the requirements of R.G. 1.97 and 10 CFR 50.49.
Instrumentation that meets these requirements is now available.
The Boiling Water Reactor Owners' Group (BWROG) submitted the above referenced letter for steff review. The attached letter (Enclosure 1) and Safety Evaluation (Enclosure 2)findstheBWROGpositionunacceptable. Therefore, we request
. Vermont Yankee Nuclear Power Corporation to install neutron flux monitoring in-l strunentation that conforms to the reouirements of R.G.1.97 and 10 CFR 50.49 1
at VYNPS, Please provide a schedule, within 60 days., for installation of neutron flux monitoring instrumentation that meets these requirements.
Sincerely, 1
L Qg Original signed by coa.
Morton B. Fairtile, Project Manager
$8 Project Directorate I-3
.gg Division of Reactor Projects I/II M
, As stated
Enclosures:
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c cc w/ enclosures:See next page
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DISTRIBUTION: Docket File, PDI.3 r/f, MFairtile, RWessman, ARCS (10), EJordan, Svarga, BBoger, AChu, MRushbrook, JJohnson,Rgn.I PMilano.BMarcus, NRC& Local PDRS
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. Document Name: VY HEUTRON FLUX MON. BWRS
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4o Mr. L. A. Tremblay,
CC:
Mr. J. Gary Weigand
' President & Chief Executive Officer Chairman, Board of Selectman Vermont Yankee Nuclear Power Corp.
Post Office Box 116 R.D. 5, Box 169 Vernon, Vermont 05354-Ferry Road Brattlebor" rmt 05u Mr. Raymond N. McCandless Vermont Division of Occupational Mr. John v t s >n
, Vice President and Radiological Health Yankee Atomic tiectric Company Administration Building 500 Main Street Montpelier, Vermont 05602 Bolton, Massachusetts 01740-1398 Honorable John J. Easton New England Coalition on Nuclear Attorney General Pollution State of Vermont Hill and Dale Farm 109 State Street R.D. 2, Box 223 Pontpelier, Vermont 05602 Putney, Vermont 05346 Vernont Public Interest Research Grcup, Inc.
43 State Street Montpelier, Vermont 05602 Diane Curran, Esq.
Regicnal Administrator, Region I Harmon, Curran & Tousley U.S. Nuclear Regulatory Comission 2001 S Street, N.W., Suite 430 475 Allendale Road Fashington, D.C.
20009 King of Prussia, Pennsylvania 19406 James Volz, Esq.
R..K. Gad, III Special Assistant Attorney General Ropes & Gray Vermont Department of Public Service One International Piece 120 State Street Poston, Massachusetts 02110 Montpelier, Vermont 05602 Fr. H. P. Murphy, Vice President G. Dana Bisbee, Esq.
and Manager of Operations Office cf the Attorney General Vermont Yankee Nuclear Power Corporation Environmental Protection Bureau R.D. 5, Box 169 State House Annex Ferry Road P5 Capitol Street Drattleboro, Vermont 05301 Concord, New Hampshire 03301-6397 Mr. George Sterzinger, Comissioner Atomic Safety and Licensing Board Vermont Department of Public Service U.S. Nuclear Regulatory Commission 120 State Street, 3rd Floor Washington, D.C. 20555 Montpelier, Vermont 05602 Public Service Board State-of Vermont 120 State Street Montpelier, Vermont 05602 l
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Mr.'t. A. Tremblay cC' Mr. Gustave A. Linenberger,Jr.
Robert M. Lazo, Chairman Administrative Judge Atomic Safety and Licensing Boerd Atomic Safety and Licensing Board U. S. Nuclear Regulatory Comission U.S. Nuclear Regulatory Comission Washington, D.C. 20555 Washington, D.C.
20555 Frederick J.~ Shon i
Resident inspector Administrative Judge Vermont Yankee Nuclear Power Station Atomic Safety and Licensing Board U.S. Nuclear Regulatory Comission U. S. Nuclear Regulatory Comission P.O. Box 176 Washington, D.C. 20555
.Vernon, Vermont 05354 Jerry Harbour John Traficonte, Esq.
Administrative Judge Chief Safety Unit Atomic Safety and Licensing Board e
I Office of the Attorney General V. S. Puclear Regulatory Comission l
One Ashburton Place, 19th Floor Washington, D.C. 20555 I
Boston, Massachusetts 02108 1
l Geoffrey M. Huntington, Esquire Office of the Attorney General Environmental Protection Bureau State House Annex 25 Capitol Street Concord, New Hampshire 03301-6397 Charles Bechhoefer, Esq.
l Administrative Judge Atomic Safety and Licensing Board U.S. Nuclear Regulatory Comission Washington, D.C.
20555 Dr. James H. Carpenter
~ Administrative Judge Atomic Safety and Licensing Board U.S. Puclear Regulatory Comission Washington, D.C.
20555 l
Adjudicatory File (2)
Atomic Safety and Licensing Board Panel Docket U.S. Nuclear Regulatory Comission Washington, D.C. 20555 1
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UNITED STATES
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January 29, 1990 Mr. Stephen D. Floyd, Chairman L
BWR Owners' Group i
Carolina Power and Light 411 Fayetteville Street Raleigh, NC 27602
Dear Mr. Floyd:
SUBJECT:
BWR OWNERS' GROUP LICENSING TOPICAL REPORT " POSITION ON NRC REGULATORY GUIDE 1.97, REVISION 3 REQUIREMENTS FOR POST-ACCIDENT NEUTRON MONITORING SYSTEM" (GENERAL ELECTRIC REPORT l
References:
1)
BWR Owners' Group letter (R. F. Janecek) to NRC (T. E.
Murley), "BWR Owners' Group Licensing Topical Report l
" Position on NRC Regulatory Guide 1.97, Revision 3 Requirements for Post-Accident Neutron Monitoring System" (General Electric Report NEDO 31558), April 1, 1988.
2)
BWR Owners' Group letter (D. N. Grace) to NRC (T. T.
Martin), "BWR Owners' Group Licensing Topical Report
" Position on NRC Regulatory Guide 1.97, Revision 3 o
Requirements for Post-Accident Heutron Monitoring System" (General Electric Report NEDO 31558), June 13, 1988.
Reference 2 requested that the staff expedite its review of Reference 1.
Reference 1 submitted the BWR Owners' Group (BWROG) Licensing Topical Report (LTR) for staff review and approval.
The LTR proposed functional criteria for l
post-accident neutron flux monitoring as an alternative to the Category 1 recommendations specified in Regulatory Guide (R.G.) 1.97.
Based on our review,.the staff concludes that a Category 1 designation, and associated lower range for neutron flux monitoring equipment is acpropriate.
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 iny staff on 49-20776.
Sincerely, Frank J.
iraglia, Associate Director for Inspection and Technical Assessment Office of Nuclear Reactor Regulation
Enclosure:
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Q,c.u. T 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, theBoilingWaterReactorOwners' Group (BWROG) 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 post-accident neutron flux monitoring instrumentation might be required, the effect of neutron flux monitoring instrumentation failure, and proposed functional criteria based on the event analysis.
2.0 BACKGROUND
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 recommending 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 monitoring instrumentation that was available to the industry did not conform to the criteria of R.G. 1.97. However, the staff was informed that instrumentation to conform to the criteria of R.G. 1.97 was under development.
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't 2-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 monitoring systems were not available and instructed applicants and licensees to follow industry development and install qualified neutron flux monitoring systems when they became available.
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 informed 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 neutron 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.
1 R.G.1.97 recomends Category 1 neutron flux monitoring instrumentation to monitor reactivity control during post-accident situations.
R.G. 1.97 specifies neutron flux as a key variable for determining 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.
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L 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 monite i4 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 r
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 establich 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 Se: tion 5.2.1), reducing the R.G.
1.97 recomendations of 10-6% to 100% power to an " alternate" of 1% to 100%
power.
This in effect would eliminate any requirement (for this purpose) for the source range monitor (SRM) and intermediate 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 nonnally 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 ar.ticipated by following the usually clearly defined paths of standard event
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' analyses.
In particular, the proposed elimination of the 10-6% to 1% power portion of the range would delete a primary purpose of the post-accident neutron flux monitoring instrumentation. This purpose was intende~d to provide, with maximum forewarning time, operator information (via indications of 3
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 recommendations 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, 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 l
melting. Environmental conditions external to the pressure vessel to be i
L considered should include high temperature, high humidity, radiation, and possible flooding, associated with external LOCA conditions. Fire conditions which might affect control rod actuation and/or position readout and thus require the use of the low range neutron flux monitoring instrumentation
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should also be considered.
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 infonned that industry has developed and made available, to L
the nuclear power industry, at least two different wide range neutron flux 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 systems 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 proposed LTR NE00-31558 functional criteria for post-accident neutron flux monitoring instrumentation is unacceptable.
It is also concluded that the proposed alternate range requirement of LTR Section 5.2.1.1% to 1005 power does not meet the intent of R.G.1.97, and is therefore unacceptable. The range of neutron flux monitoring instrumentation should remain 10'05 to 100% power.
It is the staff's position that BWR licensees should install neutron flux monitoring instrumentation that fully complies with the Category 1 criteria of R.G. 1.97 and 10 CFR 50.49.
.