ML20128G838
| ML20128G838 | |
| Person / Time | |
|---|---|
| Issue date: | 02/03/1993 |
| From: | Clifford J Office of Nuclear Reactor Regulation |
| To: | Quay T Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 9302160124 | |
| Download: ML20128G838 (58) | |
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UNITED STATES,
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NUCLEAR HEGULATORY COMMISSION '
- WASHWGioN, D.C,20n66, February 3.-1993-a MEHORANDUM FOR:
Theodore R. Quay, Director Project Directorate V-Division of_ Reactor Projects III/IV/V-FROM:-
-James W. Clifford, Senior.. Project Manager Project Directorate V Division of Reactor Projects III/IV/V
SUBJECT:
-MEETING
SUMMARY
FROM BWROG MEETING ON WATER LEVEL' INSTRUMENTATION ERRORS i
We held a meeting with the BWR Owners' Group-(BWROG);on October 29,L1992, toj discuss current Owners' Group activities to: assess andLaddrestipctential-reactor pressure vessel-level instrumentation-inaccuracies.: The 11st of-attendees is provided in Enclosure 1.
The slides used by the'BWR Owners. -
Group in its presentation:are provided in Enclosure 2, Land providelthe: details for the summary of issues provided:below.
The BWROG discussed the history of their activities regarding BWR -level.
instrumentation concerns. The Chairman of the BWROG Regulatory Response Groupi (RRG) stated that the BWROG was considering establishing a standing committee' specifically to-address BWR level instrumentation concerns.
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The BWROG next discussed their conclusion that two different-phenomena had 31 l
been observed. 0ne phenomenon was the " notching" observed:at-.Pilgrimiduring; normal plant shutdown and cooldown. Ultrasonic N
revealed a slow migration.of gas through-the lev; measurements taken"atTRilgrim' el instrument piping.--
resulting -in a ' transient' level indication; error whenithe; gas; translated -
z through a vertical run of pipe.
Level was observed"to return tol normal' when m
ga:. was detected in-horizontal-runs of-pipe. The. BWROG~ determined that?
~ i leakage from instrument-rack connections causes-gas-laden water lto migrate; down the reference legs, with subsequent controlled dept'essurization causing "x
the gases to evolve. The BWROG concluded that " notching" is not a significant safety concern.
The BWROG then discussed concerns related to_ rapid'depressurization' and'itsi effect on RPVllevel instrumentation, including followup to open; issues fromi i
1 the July 29,_1992, meeting'between the NRC staff and BWROG..iThe BWROG' based:
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Beodore R. Quay its conclusion that there is no imediate safety concern on (1) conservative analyses performed by the BWROG that demonstrated that no signficant level errors will occur above 450 psig, and (2) operator sensitization that will assure identification of indeterminate water level when implementing the BWROG emergency procedure guidelines.
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The BWROG provided details of additional guidance presented in an October 16, 1992, letter to BWR plant operations superintendents for additional sensitization of operators. The guidance provided the basis for determining if RPV level instrumentation was reliable,.and methods for determining an approximate level in the case that rapid depressurization may cause gas evolution in the reference legs..
The BWROG then outlined its proposed long-term action plan, including a test program and more detailed analytic work. The BWROG explained that while the initial portions of the 3rogram are behind the schedule proposed at-the.
July 29,1992 meeting, tie overall schedule to identify safety issues and proposed modifications remained unchanged. The BWROG made it clear that-any data collection, plant specific calculations, and implementation of any operator guidance or training were plant specific issues, and would have to be addressed on a plant-specific basis.
The BWROG also stated that they had not yet determined acceptance criteria for their test ad analysis programs. The BWROG then discussed potential modifications-that were possible if the test' and analysis programs identdfied any need for modifications.
The NRC staff provided the opportunity for public _ comments. One member of the public provided his personal vie,,s on the issue, and how it-has been handled to date.
These comments are being considered in the, staff review.
The NRC staff questioned the BWROG on their basis for no significant safety concern, on operator guidance, and implementation of the operator guidance ~at all BWRs. The BWROG stated that no changes to procedures were recommended, but the information that was sent to BWR plant superintendents on October 16, 1992, would enhance operator guidance with respect to potential RPV level indication errors. As discussed <reviously, the BWROG stated that.
operator guidance im;)1ementation would have to be addressed on a plant specific basis. One utility representative stated.that'the guidance was being incorporated into plant training programs, and would be provided to operators during the normal training cycle. Another utility representative stated that the guidance had.been put into the night orders for reading by-all shift personnel. The NRC staff stressed the need to assure that operators were
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1sufficiently. _" sensitized" to;be ablet to apply)the information-developed by-the~
- BWROG..The.BWROG again stated that the level of understanding ~by' operators would have to be addressed by each BWR utility.
l The meeting was' closed to the public for a presentition of proprietaryy j
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information from Barsebeck in Sweden.
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Ja es W. Clifford,-; Senior Project Manager Project Directorate V'
- Division of-Reactor Projects III/.IV/V..
Enclosures:
As stated cc w/ enclosures:
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-T. Martin RI-S.-Ebneter RII-4 B.-Davis RIII-J. Milboan RIV J. Martin -RV-
- t D. Ward-ACRS
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S. Newberry
- T. Collins-4-
E. Jordan'AE00
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- C. i 'si NRRL
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>s Theodore R. Quay February 3,1993 sufficiently " sensitized"- to be able to apply the information developed by the BWROG. The BWROG again stated that the level of understanding by operators would have to be addressed by each 3WR utility.
The meeting was closed to the public for a presentation of proprietary information from Barsebeck in Sweden.
Original signed by James W. Clifford, Senior Project Manager Project Directorate V Division of Reactor Projects III/lV/V
Enclosures:
As stated cc w/ enclosures:
T. Martin RI S. Ebneter Rll B. Davis Rlli J. Milhoan RIV J. Martin RV D. Ward ACRS S. Newberry T. Collins E. Jordan AE0D H. Denton OIP C. Rossi NRR B. Grimes NRR J. Richardson NRR F. Congel NRR DISTRIBUTION:
Docket File NRC & Local PDRs D. Foster PDV Reading File T. Murley,12G18 C. Hehl, RI F. Miraglia, 12G18 W. Russell, 12G18 E. Merschoff, RII J. Partlow, 12G18 A. Thadani, 8E2 E. Greenman, RIII S. Varga, 14E4 J. Roe A. Beach, RIV.
M. Virgilio T. Quay V. McCree, 17G21 M. Boyle, 14E4
_R. Jones, 8E23 L. Plisco, 17G21 A. Cubbage OGC (15B18)
G. Grant, 17G21 ACRS (10)(P315)
J. Mitchell, 17G21 E. Leeds K. Perkins, RV C. Carpenter 0FC PDV/LA PDV/PM /
PDV/D NAME DFoster d b JCliNord TQuay [
DATE
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( /1/gi t/\\\\/9h 0FFICIAL RECORD COPY DOCUMENT NAME:
BWROG.MEM-
s-w DISTRIBUTION:
8-Docket File:
NRC & Local PDRs PDV Reading-File T. Murley,12G18 a
F. Miraglia, 12GlB
-J. Partlow, 12G18 S.-Varga, 14E4 A. Beach,- RIV W. Russell, 12G18 A. Thadani, 8E2 T. Martin RI J. Roe C. Hehl, RI-E. Herschoff, Rll S. Ebneter Ril E. Greenman, Rlll B. Davis Rill J. Milhoan RIV J. Martin: RV D. Ward, P315 S. Newberry, 1103 T. Collins, 8E23 E. Jordan, MNBB3701 H. Denton, 17F2 C. Rossi, 9A2 B. Grimes, llEl J. Richardson, 7D26 F. Congel, 10E2 H
O. Foster M. Virgilio M. Boyle, 14E4 A. Cubbage, 8E23 ACRS (10), P315 K. Perkins, RV T. Quay R. Jones, 8E23 OGC, 15B18 J. Mitchell, 17G21 C. Carpenter V. McCree, 17G21 L. Plisco,17G21 G. Grant, 17G21 g
R. Hall l
Mr. George J. Beck, Chairman Regulatory Response Group Boiling Water Reactor Owners' Group c/o Southern Nuclear Operating Company P.O. Box 1295, Bin B052 Birmingham, AL 35201 Mr. Paul Blanch 135 Hyde Road.
W._ Hartford, CT 06117 Mr. Ernest Hadley.
414 Main Street P.O. Box 3121 u
Wareham,';MA 02571 I
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ENCLOSURE 1 2 1ober 29. 1992 NRC/BWROG MEETING Mr Level Instrumentation _fff_gn List of Atteden tLA11E IJ1LE ORGAN 12ATION Jim Clifford Senior PM NRC/NRR/PDV Robert Jones Chief NRC/NRR/SRXB Gary Holahan Deputy Director NRC/NRR/DSSA Amy Cubbage Reactor Systems Engr.
NRC/NRR/DSSA Scott Newberry Chief NRC/NRR/HICB Fred Moody Consulting Engineering GE Nuclear Energy David Weber Engineer PECO Steven Hudson Elec. Systems Engineering Div. Mgr. Boston Edison Pat Harriott Mgr. Safety & Licensing GENE /BWROG J. H. Munchausen Mgr. 1 & C Maintence EPRl/PSE Bob NcKillip Associate EPRI Ben Hayes Director 01 Edward Fiegler Mech. Engineering Project Mgr.
~ RSB/NRR-ABB/CE Ron Frahm Section Chief Ronald Eaton Sr. Project Mgr.
NRR/PDl-3 Brenda Whitare Reactor Engineer NRR/SRXB William Ruland Section Chief Electrical Section Region 1/DRS Lawrence Vick Reattur Engineer NRR/DRCH/0LB Wayne Hodges Director, Reactor Safety NRC/ Region 1 Chuck Johnson Consultant to Boston Edison SLEVY_Inc Serge Deshraukh
.I & C Engineer GPU Nuclear Jose Ibarra Sr. 1 & C-AE0D/NRC Richard Znerchez Associate Editor Nuclear-Alan Bilanin Senior Associate CDl/EPRI Gerald Seay Engineer PEC0/BWROG.
George Beck Chairman BWROG/(PECo)
Richard Zuercher Associate Editor Nucleonics week I. Ahmed Sr. Electrical Engineer NRR/NRC-W. Swenson Section Chief NRR/HHFB Jim Wade Sr. Engineer Southern Nuclear Bruce Veazie Sr. Resu'Its Eng.
Penna Pwr & Light Peter Miner Sr. Scientist Northeast-Utilities Girija Shukla Sr. Lic. Engineer Detroit Edison Paul Blanch.
I &_C Eng. SOPV SELF David Desaulniers Engineering Psychologist NRR/HHFB Lamont Youngbord Principal' Engineer GENE Lambros.Lois Sr. Nuc'iear Engineer NRR/DSSA/SRXB 3
George Thomas Nuclear Engineer NRR/DSSA/SRXB Harold Fossett inspector NRC/OlG Andrew Kugler Reactor Engineer NRC/0GCB y
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e NAME IJJ1E PRGANIZATION Vince SanAngelo Licensing Engineer Bechtel Power Tom Collins Technical Assistant OCH/FR Richard'Zuercher Associate Editor Nucleonics week Taggart Rogers Exec. Consultant OEI (BWROG)-
A. Q. Howard Researcher Tokyo Electric Pwr.
Jocelyn Mitchell Sr. Regional Coordinator NRC/0EDO Dob Dennig Section Chief, BWR Events NRC/NRR/ DORS-Bill Berg Senior Staff Engineer PSE & G/BWROG/EPC
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BWR Owners' Group Regulatory Response Group INTRODtiCTION o
. Attendees o
Agenda o
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Program overview o
Purpose of requesting this meeting c
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BWR Owners' Group Regulatory Response Group AGENDA Introduction G. J. Beck Purpose of this Meeting RRG Chairman Issues o
" Notching" S. D. Hudson (BECO) o Rapid Depressurization G. 'R. Sealy (PECO)
Steering Comittee Chairman
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W. 'F. Berg (PSE&G)
EPC Vice-Chairman S. T. Rogers (0EI)
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Test Program Status A.Bilanin(EPRI/CDI) o Analytical Model' Status D. S. Weber (PECO)
Model & Test Comittee Chairman Acceptance Criteria W. F. Berg (PSE&G)
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l Potential Modifications J.A. Wade (SNC)
Modifications & Procedures Committee Chairman TECHAGND-3
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o Barsebeck/Swedish-' Data F. J. Moody (GENE)'
' (Proprietary) 1 Schedule / Conclusions'.
G. J. Beck-(PECO)
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HISTORY (CONT'D)
NRC Letter - Sept 9
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' Questions on Generic Report RRG/ Committee' Formation - Sept 15-17 Reaffirm the Program Plan Steering Committee Model & Test Committee Modifications & Procedures Committee BWROG/ Utility Letter - Sept 24 GL 92-04; Utility Responses - Sept 27 TECHGJB1-4
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1 NOTCHING Introduction Steve.-Hudson, Boston Edison Company Pilgr' m Nuclear. Power Station '- BWR.3 i
Cold: Reference Legs.&;Rosemount Transmitters -
. Level Error due to!" Notching".is different than< the. level Error. due to-Rapid Depressurization S
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' Notching-Seen.during-Normal Depressurization Following Reactor Shutdown Indicated Leveljis Momenta'rily. Greater than the' Actual Level Level Returns to: Actual Level Observable on both Level-Recorders and Plant Computer 4
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. NOTCHING Cont'o Experience Instruments on "A" & "B" Racks Respond Differently Begins at - 450 psig on "B" side Typically, Square Wave shape.approximately 4"-6".High
.and 20-30 Secon'ds Duration
-Amplitude' Increases.as Pressure Decreases At. Low Pressure (< 60..psig), Shape becomes more Irregular Maximum Recorded Notch Size > 29" (Limited by Instrument Range)
MSIV Isolations have occurred!during Cooldown -in '90, '91, & '92 TECHSDH1-3
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NOTCHING CONT'D Cause l
Non-Condensable Gases Collect in the Condensing Chambers Gas-Laden Water Migrates Down the Reference Leg due to Seepage at the~ Instrument Racks During Depressurization, Gas comes out of Solution and eventually Forms a Bubble Supported by Ultrasonic Monitoring With a Bubble in a Vertical Section of Piping, the Weight of the Water-is? Reduced.
Therefore, the Indicated Level.is Greater than the Actual Level When the Bubble reaches:a Horizontal Section of Piping, the Indicated Level Returns to the Actual: Level TECHSDH1-6
.x BWR Owners' Group ' Regulatory Response-Group-NOTCHING CONT'O Factors 1.
Non-condensable Gases build up in the Condersing Chambers 2.
Horizontal section in the Reference Leg Piping 3.
Small seepage at the Instrument Racks causes the gas-laden water to migrate 6wn the Reference Leg TECHSDH1-7
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BWR Owners' Group Regulatory Response: Group NOTCHING' CONT'D' Future Actions-Fix Identified Seepage; on. "B L Rack-during_ Mid Cycle
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Measure As-Left External Seepage after Start-up
- Measure instrument. Bypass Valve Seepage. on "A" &~ "B" Racks -
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' Support BWROG' Action! Plan to increase. Understanding L off Rapid".Depressurization Phenomenon-fA '
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RAPID DEPRESSURIZATION
..j Generic Concern
.i Non-condensable gases may dissolve in cold reference leg
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RAPID DEPRESSURIZATION CONT'D
- BWROG/NRC Discussion on July.29,1992
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RAPID DEPRESSURIZATION Cont'o i0 pen: Issues / Actions Taken' o
Determination of '" Actual" Possible Level Indication Error
< Analyzed Depressurization' Rates
- . Realistic Pipe Geometries
'BWROG Reactor Water-Level Program o
DefinitionLof-" Indeterminate" Water Level a
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BWR Owners' Group Regulatory Response Group OPERATOR GUIQA_RGE I
Two guidance /information packages to utilities August 14 October 16 l
-o Ensure adequate core cooling j
l Core submergence 1
Steam cooling o
Maintain EPG philosophy Best-available guidance Any mechanistic event o
Bad and good level instruments o
-o Loss of injection - Containment flood L:
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o Normal cooldown Lottom of notch o
' Rapid depressurization Stable pressure Trend on instrument with tap above TAF O
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BWR Owners' Group Regulatory Response Group SWROG ACTION PLAN BWROG Reactor Water Level Instrumentation Program 4
A comprehensive plan which embodies prototypical testing, o
analytical modeling, plant unique testing, analysis, and hardware and/or procedure modifications o
Developed by a team of utility and industry experts o
A resource intensive program that will produce the most expeditious and technically appropriate resolution of this issue TECHGJB2-1
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Objectives of Full Scale Tests De-Gas Condensing Chamber Description of Tests 1
De-Gas 1
Condensing Chamber-Status of Ongoing Activities-
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Figure 1 BWROG Reactor Water LevelInstrumentation Long Term Action Plan o
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? i~ j,>,$ Eo0 5 1 4 t e L L Condensing Chamber Tests i j; Object - Determine performance of condensing chambers !i currently in use on BWRs b . Primary data is to measure dissolved gas species and concentration present in the cold reference leg L Empirically determine nominal design geometries for l condensing chamber and steam inlet piping-l- Data to be used in conjunction with de-gas tests to i - evaluate plant unique level error [ Data to be used.to validate steam inlet condensing + chamber analytic model i L i. I 4 -1 m .ir .e m---- r ~,- ., -~. Condensing Chamber Performance Test Thermocouple Sample Connection F 1000 PSIA Steam Inlet Piping Condensing ' Steam Source Chamber (simulating RPV) L Thermocouples control gg,P, " H and O concentration 2 2 m' L Sampic Connection j m steam length i f jp Cold Leg Mout I Figure 2.1. Test steam inlet geometries as well as CC geometry to obtain data for the concentradon of non-condensible gases entering the cold leg. Generic Steam Inlet Leg i Characterization L. cc A ' fh h i = RPV A B C t J k C B h (ft) A m V l s(ft) ^ .y ,--s. _.,.....,-.,m-, Status of Ongoing Activities " Scope of Work for Testing of BWR Condensing Chamber Performance Characteristics" " Scope of Work Testing Protypical BWR Water Level Instrumentation Reference Leg Geometries During Rapid Depressurization Events" Final utility approval by 11/6/92 1 l identification of Generic % Complete ~ Steam Leg inlet Geometries 50 % Cold Leg Geometries 70% Test Organization Location De-Gas EPRI Charlotte, NC l Cond. Chamber TBD TBD O BWR Owners' Group Regulatory Response Group g) DEL AND TEST C0fMITTEE MISSION STATEMENT o-To oversee and direct the analytic model development and test programs which ' consist of: a). The condensing chamber test program b) -The cold reference leg de-gas test program c)- The detail analytic model development and validate against ' test data. L TECHDSW1-1' 1 BWR Owners' Group Regulatory Response Group l STATUS Functional requirements documents have been drafted and o reviewed o Detail analytic model development continues Qualitative results of detail analytic model confirm results o presented at July 29th meeting with NRC were conservative l l Analytic model requires validation using data from test programs o prior to plant unique predictions i i TECHDsW1-2 O-BWR Owners' Group Regulatory Response Group ANALYTICAL MODEL o Two computer mathematical models in development a) Model of inlet steam piping and condensing chamber b) Cold reference leg model o Inlet 3 team piping / condensing chamber mode 1 a) De-gassing effect b) Insulation c) Inlet piping geometry d) Chamber / inlet piping heat transfer characteristics e) Solubility, diffusion, seepage TECHDSWl-3 ^ BWR Owners' Group Regulatory Response Group - _ s ANALYTICAL MODEL (CONT'D) o Cold -reference leg model-a) Two phase thermal hydraulics (drift flux) 'l b) Solubility-4 c) Gas coming out of solution (source term) d) Piping geometry .e) - Hydrostatic head
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BWR Owners' Group Regulatory Response Group-r ACCEPTANCE CRITERIA o
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METERED FLOW FROM THE FUEL ZONE VARIABLE LEG (USES JETPUMP FLOW)
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