ML20044H519
| ML20044H519 | |
| Person / Time | |
|---|---|
| Site: | 05200001 |
| Issue date: | 06/04/1993 |
| From: | Borchardt R Office of Nuclear Reactor Regulation |
| To: | Marriott P GENERAL ELECTRIC CO. |
| References | |
| IEB-93-003, IEB-93-3, NUDOCS 9306090142 | |
| Download: ML20044H519 (10) | |
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UNITED STATES Glj NUCLEAR REGULATORY COMMISSION
[{.'l* (j]g ' s WASHINGTON, D.C. 20 % 5 0001 June 4, 1993 Docket No.52-001 Mr. Patrick W. Harriott, Manager Licensing & Consulting Services GE Nuclear Energy 175 Curtner Avenue San Jose, California 95125
Dear Mr. Marriott:
SUBJECT:
ADVANCED B0ILING WATER REACTOR (ABWR) OPEN ITEMS 4.4-1 AND 20.3-8, ANTICIPATORY TRANSIENT WITHOUT SCRAM (ATWS) STABILITY AND REACTOR PRESSURE VESSEL (RPV) WATER LEVEL INSTRUMENTATION This letter addresses the resolution of two open items from the Reactor Systems Branch.
For the first, Open Item 4.4-1, ATWS Stability, the staff and Boiling Water Reactor Owner's Group (BWROG) are currently reviewing the emergency procedure guidelines (EPGs). The primary subject areas under consideration are the time of initiation of boron injection (via standby.
i liquid control system (SLCS)), RPV water level reduction (when and how far) and interlock bypass (to stop main steam isolation valve (MSIV) closure with lowered level in order to maintain the heat sink via main condenser rather than the suppression pool).
Despite the BWROG EPG development process, it is the staff's position that for approval of the ABWR design, GE Nuclear Energy (GE) must propose EPGs to address the 4TWS stability issue for the ABWR design at this time.
The second open item, 20.3-8, concerns RPV water level instrumentation.
Enclosed NRC Bulletin 93-03, " Resolution of Issues Related to Reactor Vessel Water Level Instrumentation in BWRs" dated May 28, 1993, provides the back-ground information.
During a teleconference with GE on May 17, 1993, the staff discussed this issue with GE.
The staff stated that since the BWROG has already identified design modifications for operating boiling water reactors, it is time for GE to decide on design modifications for the ABWR.
GE took the position that the BWROG activities are still in progress, and there is no complete agreement with the staff on proposed modifications; therefore, it would be premature to implement any modification on the ABWR.
The staff has concluded that design modifications are necessary for the RPV water level instrumentation.
GE is required to submit its modification for the RPV water level instrumentation in the standard safety analysis report for staff review and approval.
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fr. Patrick W. Marriott June 4, 1993 The ABWR RPV level instrumentation are all differential pressure (dp) based level instruments.
A common mode failure of the dp instruments could make all the RPV level instr iments inoperable.
Based on current-BWR operating experi -
ence, in addition to the design modifications described above, it is our position that the ABWR design should provide a diverse means of measuring RPV water level (two independent RPV level measurement methods),
e.g., differen-tial pressure and heated junction thermocouples or ultra-sonic means.
GE should provide a schedule for inputs for these two issues by June 9th, 1993.
Prompt response would allow the staff the opportunity to resolve Open Items 4.4-1 and 20.3-8 in an expeditious manner.
If you have any questions, please contact Stephen Koenick of my staff at (301) 504-1113.
Sincerely, Original 9%ss.!nh R. W. Borchardt, Acting Director Standardization Project Directorate Associate Directorate for Advanced Reactors and License Renewal Office of Nuclear Reactor Regulation
Enclosure:
I As stated cc w/ enclosure:
See next page DISTRIBUTION:
Docket File PDST R/F DCrutchfield RBorchardt PDR CPoslusny SNinh SKoenick TBoyce DTang JNWilson PShea RJones, 8E23 AThadani, 8E2 JWermiel, 8H7 WSwenson, 10D24 BBoger, 10H5 WRussell, 12G18 GSuh (2), 12E4 LShao, RES BHardin, RES J0'Brien, RES JMoore, 15B18 MGrant, 17G21 ACRS (11)
JCStewart, 8H3 MChiramal, 8H3 MRubin, 8E23 WSwenson, 10D24
- See previous concurrence
.y bI:' POST (A)DMDST 0FC LA:PDST PE:PDST PM:PDST*
SRXB*
HHFB*
NAME PSheaOl!j 'SKoenichkh CPoslusny RJones WSwenson JNN1 son RBMardt DATE 06/ Ifh3 06/1/93 06/02/93 06/02/93 06/04/93 06/k/93 06/k/93 0FFICIAL RECORD COPY: GE528.SSK
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Mr. Patrick W. Harriott Docket No.52-001 General Electric Company cc:
Mr. Robert Mitchell Mr. Joseph Quirk General Electric Company GE Nuclear Energy 175 Curtner Avenue General Electric Company San Jose, California 95125 175 Curtner Avenue, Mail Code _782 San Jose, California 95125 Mr. L. Gifford, Program Manager Regulatory Programs GE Nuclear Energy 12300 Twinbrook Parkway Suite 315 Rockville, Maryland 20852 Director, Criteria & Standards Division Office of Radiation Programs U. S. Environmental Protection Agency 401 M Street, S.W.
Washington, D.C.
20460 f
Mr. Sterling Franks U. S. Department of Energy NE-42 Washington, D.C.
20585 Varcus A. Rowden, Esq.
Fried, Frank, Harris, Shriver & Jacobson 1001 Pennsylvania Avenue, N.W.
Suite 800 Washington, D.C.
20004 Jay M. Gutierrez, Esq.
Newman & Holtzinger, P.C.
1615 L Street, N.W.
Suite 1000 Washington, D.C.
20036 i
s
.cr.
OMB No.: 3150-0012
/' _,w NRCB 93-03 UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF NUCLEAR REACTOR REGULATION WASHINGTON, D.C.
20555 May 28, 1993 NRC BULLETIN 93-03:
RESOLUTION OF ISSUES RELATED TO REACTOR VESSEL WATER LEVEL INSTRUMENTATION IN BWRs Addressees All holders of operating licenses or construction permits for boiling water reactors (BWRs) with the exception of Hillstone, Unit 1, and Big Rock Point.
Eurpose The U.S. Nuclear Regulatory Commission (NRC) is issuing this bulletin to (1) notify addressees about new information concerning level indication errors that may occur during plant depressurization, (2) request that all addressees take certain action (s), and (3) require that all addressees report to the NRC if and to what extent the requested actions will be taken and notify the NRC when actions associated with this bulletin are complete.
Backaround As discussed in NRC Information Notice 92-54, " Level Instrumentation Inaccuracies Caused by Rapid Depressurization," and Generic Letter 92-04,
" Resolution of the Issues Related to Reactor Vessel Water Level Instrumentation in BWRs Pursuant to 10 CFR 50.54(f)," the staff is concerned that noncondensible gases may become dist>lved in the reference leg of BWR i
water level instrumentation and lead to a false high level indication after a rapid depressurization event.
Generic letter 92-04 requested that addressees determine the impact of potential level indication errors after a rapid depressurization event on how the plants are operated.
Generic Letter 92-04 also requested that addressees take short term compensatory measures to mitigate the consequences of potentia'i level indication errors after a rapid depressurization event and provide the staff with plans for long term corrective actions, including any proposed hardware modifications. The generic letter requested that 4ddressees implement the long term corrective actions during the first refueling outage commencing after November 19, 1992.
The industry, through the BWR Owners Group (BWROG), requested a delay in the implementation of the long term corrective actions until a de-gas test program could be completed. The test program was intended to gather data to support i
the design of any necessary hardware modifications. On December 2, 1992, the staff agreed to extend the deadline for the submission of addressee plans for the long term actions to July 1993, with implementation at the earliest opportunity.
Enclosure
May 28, 1993 Page 2 of 6 Descriotion of Circumstances 21, 1993, operators at the During a normal plant cooldown on JanuaryWashington Public Power Syst indication error of 0.81 meters [32 inches] that gradually recovered over aThe li period of approximately 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />. type could result in failure to automatically is On heat removal (RhR) system during shutdown cooling operation.
April 8, 1993, the staff issued Information Notice 93-27, "LevelIn as to discuss level indication errors that may occur during normal plant depressurization.
E Discusjj_ga following the event reported by the licensee at WNP-2, the NRC staff requested the BWROG to evaluate the effect of level indication errors on events, such as reactor pressure vessel (RPV) drain-down, initiated from low-pressureOperator Several paths have the potential to drain the RPV.
misalignment of one or more valves can establish a flow path resulting conditions.
drain-down of the RPV. Automatic isolation signals based on low RPV level are normally BWRs.
However, automatic isolation of the credited for terniinating these events.
RHR system, and other systems, will not occur if there are large levsl errors in multiple instruments.
In response to the staff request, the BWROG submitted a report, " Supplementary information Regarding RPV Water Level Errors due to Honcondensible Gas in Cold 20, 1993. The BWROG determined Reference legs of BWRs," to the NRC on May that the most limiting drain-down event is an RPV drain-down to the suppression pool through the low-pressure coolant injection suction flow path.
The BWROG report indicated that, for this event, the core could reach 1100 *C
[2000 'f] in as little as 16 minutes if there is no makeup to the coolant system.
On the basis of the assessment of the NRC staff and the information provided by BWROG, the staff concluded that additional compensatory measures are ne Although the interim procedures currently in for normal cooldown evolutions.
place are appropriate for events initiated from full power, t when automatic safety systems may be defeated by level instrum Although the data are still preliminary, initial results of the test inaccuracies.
program show that large errors in the indications from the levelThis informati program.
instrumentation are possible.
that the noncondensible gas problem is real and not theoretical, and that the Therefore, for longer term problem applies even to slow depressurizations.
operation this problem needs to be addressed promptly with hardware modifications and immediately with compensatory measures for cooldown conditions.
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'May 28, 1993 Page 3 of 6 Millstone, Unit 1, is exempt from this bulletin because Northeast Utilities, the licensee, has already implemented a hardware modification to prevent the buildup of noncondensible gases in the RPV level instrumentation reference legs. Big Rock Point is exempt from this bulletin because the RPV level instrumentation system installed at that facility is not susceptible to the de-gas problem described in this bulletin.
Recuested Actions
- 1. }_hort Term Compensatory Actions (a) Within 15 days of the date of this bulletin, each licensee is requested to implement the following measures to ensure that potential level errors caused by reference leg de-gassing will not result in improper system response or improper operator actions during transients and accident scenarios initiated from reduced pressure conditions (Mode 3):
(1) Establish enhanced monitoring of all RPV level instruments to provide early detection of level anomalies associated with de-gassing from the reference legs.
(2) Develop enhanced procedures or additional restrictions and controls for valve alignments and maintenance that have a potential to drain the RPV during Mode 3.
(3) Alert operators to potentially confusing or misleading level indication that may occur during accidents or transients initiating from Mode 3.
For example, a drain-down event could lead to automatic initiation of high-pressure emergency core cooling systems (ECCS) without automatic system isolation or low-pressure ECCS actuation.
Facilities that are in cold shutdown during this 15 day period are requested to complete the above actions within 15 days of the date of this bulletin or prior to startup, whichever is later.
(b) By July 30, 1993, each licensee is requested to complete augmented operator training on loss of RPV inventory scenarios during Mode 3, including RPV drain-down events and cracks or breaks in piping.
Facilities that are in cold shutdown as of July 30, 1993, are requested to complete this action prior to startup from that shutdown.
All of the short term actions described above shall remain in effect until the hardware modifications described below have been implemented.
- 2. Hardware Modifications Each licensee is requested to implement hardware modifications necessary to ensure the level instrumentation system design is of high functional i
NRCB 93-03 May 28, 1993 Page 4 of 6 This includes level instrumentation reliability for long-term operation.
performance during and after transient and accident scenarios initiated The hardware from both high pressure and reduced pressure conditions.
modifications discussed here are the same as the modifications requested Since the level instrumentation plays an in Generic Letter 92-04.
important role in plant safety and is required for both norma 30, 1993.
If implemented at the next cold shutdown beginning after Julyeach licensee is 30, 1993, a fa:ility is in cold shutdown on July requested to implement these modifications prior to starting up from that outage.
N Reportina Reauirements Written reports are required as follows:
Addressees choosing not to take the requested short term actions must description of the proposed alternative course of action, (1) for completing it, and a justification for any deviations from the requested actions.
(2) By July 30,'1993, all addressees must submit a report providing:
the description of the short term compensatory actions taken, and (a) a description of the hardware modifications to be implemented at 30, 1993.
If an addressee (b) the next cold shutdown after July chooses not to take the requested actions specified in the Hardware Modifications section, the report shall contain a description of the proposed alternative course of action, the schedule for completing it, and a justification for any deviations from the requested actions.
Within 30 days of completion of the requested hardware modifications, a report confirming completion and describing the modification implemented.
(3)
Address the required written reports to the U.S. Nuclear Regulatory or affirmation under the provisions of Section 182a, Atomic Energy Act of Commission, ATTN:
In addition, submit a copy to the 1954, as amended, and 10 CFR 50.54(f).
appropriate regional administrator.
Backfit Discussion The level errors that could result from the effects of noncondensible gases in the level indication reference legs may prevent the level instrumentation systems in BWRs from satisfying the following regulations:
General Design Criterion (GDC) 13, " Instrumentation and control," of" Inst (1)
Appendix A to 10 CFR Part 50 which states:provided to monito
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May 28, 1993 Page 5 of 6 for normal operation, for anticipated operational occurrences, and for accident conditions as appropriate to assure adequate safety." Existing instrumentation may not accurately monitor reactor vessel water level under normal cooldown or accident conditions.
(2) GDC 21, " Protection system reliability and testability," which states:
"The protection system shall be designed for high functional reliability... commensurate with the safety function't'o be performed."
The instrumentation may not be reliable during and following normal depressurization and rapid depressurization.
(3) GDC 22, " Protection system independence," which states:
"The protection system shall be designed to assure that the effects of natural phenomena, and of normal operating, maintenance, testing, and postulated accident conditions...do not result in loss of the protection function."
Degassing inay cause a loss of the reactor vessel water level indication function during and following normal depressurization and rapid depressurization.
(4) Section 50.55a(h) of Title 10 of the Code of Federal Reaulations (10 CFR 50.55a(h)), which requires that protection systems, for those plants with construction permits issued after January 1, 1971, meet the requirements stated in. editions of the Institute of Electrical and Electronics Engineers Standard, " Criteria for Protection Systems for Nuclear Power Generating Stations" (IEEE-279).
Section 4.20 of IEEE-279 states:
"The protection system shall be designed to provide the operator with accurate, complete, and timely information pertinent to its own status and to generating station safety." The water level instrumentation for the reactor vessel may not be accurate during and following normal depressurization and rapid depressurization.
The hardware modifications discussed here are the same,as the modifications requested in Generic Letter 92-04 and, therefore, the modifications are not considered to be additional backfits beyond those requested in Generic Letter 92-04. The short term compensatory actions requested by this bulletin are considered necessary to ensure that the addressees are in compliance with existing NRC rules and regulations. Therefore, this bulletin is being issued as a compliance backfit und?r the terms of 10 CFR 50.109(a)(4).
A notice of opportunity for public comment on this bulletin was not published in the Federal Reaister because of the urgent nature of the short term compensatory actions requested by this bulletin and because the hardware modifications requested are the same as those previously requested in Generic letter 92-04.
Paperwork Reduction Act Statement This bulletin contains information collection requirements that are subject to the Paperwork Reduction Act of 1980 (44 U.S.C. 3501 et seq.). These requirements are covered by Office of Management and Budget clearance number 3150-0012, which expires June 30, 1994. The estimated average number of burden hours is 200 hours0.00231 days <br />0.0556 hours <br />3.306878e-4 weeks <br />7.61e-5 months <br /> per licensee response, including the time for
NRCB 93-03 May 28, 1993 Page 6 of 6 reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information.
Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for further reducing reporting burden, to the Information and Records Management Branch (MNBB-7714), U.f. Nuclear Regulatory Commission, Washington, D.C. 20555; and tc the Desk Officer, Office of Information and Regulatory Affairs, NE0B-3019, (3150-0012), Office of Management and Budget, Washington, D.C. 20503.
Compliance with the following request for information is purely voluntary.
The information would assist NRC in evaluating the cost of complying with this bulletin:
(1) the licensee staff time and costs to perform requested inspections, corrective actions, and associated testing (2) the licensee staff time and costs to prepare the requested reports and documentation (3) the additional short-term costs incurred as a result of the inspection findings such as the costs of the corrective actions or the costs of down t'ime (4) an estimate of the additional long-term costs which will he incurred in the future as a result of implementing commitments such as the estimated costs of conducting future inspections or increased maintenance If you have any questions about this matter, please contact the technical contact or the lead project manager listed below or the appropriate Office of Nuclear Reactor Regulation project manager.
\\d i ameh G. Part ow Associate Director for Projects Office of Nuclear Reactor Regulation j
Technical contact:
Amy E. Cubbage 1
(301) 504-2875 l
Lead project manager: James W. Clifford (301) 504-1323 Attachmen+-
List of Recently Issued NRC Bulletins j
l
Attachment NRCB 93-03 May 28, 1993 Page 1 of 1 LIST OF RECENTLY ISSUED NRC BULLETINS Bulletin Date of No.
Subject Issuance Issued to j
93-02 Debris Plugging of 05/11/93 All holders of OLs for
)
Emergency Core Cooling nuclear power reactors.
i Suction Strainers i
93-01 Release of Patients 04/20/93 Brachytherapy Licensees After Brachytherapy Authorized to Use After-Treatment with Remote loading Devices 90-01, Loss of Fill-Oil in 12/22/92 All holders of OLs or cps Supp. 1 Transmitters Manu-for nuclear power reactors.
l factured by Rosemount j
92-03 Release of Patients 12/08/92 For Action - Brachytherapy after Brachytherapy Licensees Authorized to use l
the Omnitron Model 2000 High Dose Rate (HDR) j Afterloading Brachythe apy Unit For Information - None 92-01, Failure of Thermo-Lag 330 08/28/92 For Action - All holders of i
Supp. 1 Fire Barrier System to operating licenses for Perform its Specified nuclear power reactors.
Fire Endurance Function For Information - All holders of construction permits for nuclear power
- reactors, j
92-02 Safety Concerns 08/24/92 For Action - All Teletherapy Relating to "End of Licensees Life" of Aging For Information - None Theratronics Tele-therapy Units 92-01 Failure of Thermo-Lag 06/24/92 All holders of OLs or cps 330 Fire Barrier System for nuclear power reactors.
to Maintain Cabling in Wide Cable Trays and Small Conduits Free from Fire Damage OL = Operating License CP - Construction Permit
.