ML18151A712
| ML18151A712 | |
| Person / Time | |
|---|---|
| Site: | Surry  |
| Issue date: | 08/03/1998 |
| From: | Edison G NRC (Affiliation Not Assigned) |
| To: | NRC (Affiliation Not Assigned) |
| References | |
| NUDOCS 9808100037 | |
| Download: ML18151A712 (53) | |
Text
e August 3, 1998 LICENSEE:
FACILITY:
Virginia Electric and Power Company Surry Power Station, Unit 1
SUBJECT:
MEETING
SUMMARY
- RISK-INFORMED INSERVICE INSPECTION (RI-ISi)
On July 23, 1998, a meeting was held at NRG headquarters in Rockville, MD, to discuss Virginia Electric and Power Company's (VEPCO's) plans to convert to an RI-ISi program.
VEPCO is serving as a pilot plant to develop and implement RI-ISi based on Westinghouse Owners Group (WOG) technology.
On July 10, 1998, the NRG staff issued a letter requesting additional information from VEPCO, in the form of 32 questions, as part of the ongoing review of VEPCO's RI-ISi submittal. The purpose of the July 23, 1998, meeting was for VEPCO to explain their preliminary thinking in developing their response to the 32 questions, and for NRG to clarify the intent of various questions. It was agreed that a formal response to the questions will be provided by VEPCO by August 15, 1998. (Overview) and Enclosure 2 (Expert Panel Guidance) were distributed and discussed during the meeting. Enclosure 3 is the meeting attendance list.
Original signed by Gordon Edison, Sr. Project Manager Project Directorate 11-1 Division of Reactor Projects 1/11 Office of Nuclear Reactor Regulation Docket No. 50-280
Enclosures:
As stated cc w/enclosures: See next page Distribution:
Docket File PUBLIC PD 11/1 rf OGG ACRS eMail:
SCollins (SJC1)
FMiraglia (FJM)
BBoger (RPZ)
JZwolinski (JAZ)
TMartin (SLM3)
SAli SHou SDinsmore RHermann THiltz RRY\\RISK.INF
. OFFICE PM:PDII-1 LA:PDI I-1.
NAME GEdison EDunnington DATE
- 07.
98 Official Record Copy 9808:io0037 980803-~-----~---,
PDR ADOCK 05000280 P
/98
~
-~
e e
August 3, 1 998 LICENSEE:
FACILITY:
Virginia Electric and Power Company Surry Power Station, Unit 1
SUBJECT:
MEETING
SUMMARY
- RISK-INFORMED INSERVICE INSPECTION (RI-ISi)
On July 23, 1998, a public meeting was held at NRC headquarters in Rockville, MD, to discuss Virginia Electric and Power Company's (VEPCO's) plans to convert to an RI-ISi program. Surry Unit 1 is serving as a pilot plant to develop and implement RI-ISi based on Westinghouse Owners Group (WOG) technology.
On July 10, 1998, the NRC staff issued a letter requesting additional information from VEPCO, in the form of 32 questions, as part of the ongoing review of VEPCO's RI-ISi submittal. The purpose of the July 23, 1998, meeting was for VEPCO to explain their response to the 32 questions, and for NRC to clarify the intent of various questions. It was agreed that a formal response to the questions will be provided by VEPCO by August 15, 1998. (Overview) and Enclosure 2 (Expert Panel Guidance) were distributed and discussed during the meeting. Enclosure 3 is the meeting attendance list.
Docket No. 50-280
Enclosures:
As stated Original signed by Gordon Edison, Sr. Project Manager Project Directorate 11-1 Division of Reactor Projects 1/11 Office of Nuclear Reactor Regulation cc w/enclosures: See next page Distribution:
Docket File PUBLIC PD 11/1 rf OGC ACRS eMail:
SCollins (SJC1)
FMiraglia (FJM)
BBoger (RPZ)
JZwolinski (JAZ)
TMartin (SLM3)
SAli SHou SDinsmore RHermann THiltz Y\\RISK.INF
- see previous concurrence OFFICE PM:PDII-1 LA:PDII-1
- BC:ECGB AD:PDll/1 NAME GEdison EDunnington DATE 07
/98 Official Record Copy
'-*\\
NAME Edison, Gordon Bagchi, Gautam Ali, Syed Hou, Shou-nien Trainer, Jack Porter, Allen M.
Dinsmore, Stephen Closkey, Nancy McNeil!, Alex Weakland, Dennis Bucheit, Dave Hermann, Bob Miller, Gary Bishop, Bruce Haessler, Richard West, Ray Hiltz, Tom e
e JULY 23, 1998 MEETING ATTENDANCE ORGANIZATION NRC NRC/NRR/DE NRC/NRR/DE NRC/NRR/DE LMITCO INEEULMITCO NRC/NRR/DSSA WESTINGHOUSE VIRGINIA POWER DUQUESNE LIGHT/WOG VIRGINIA POWER NRC/NRR/DE VIRGINIA POWER WESTINGHOUSE WESTINGHOUSE NORTHEAST UTILITIES/WOG NRC/NRR/SPSB
Vi~ inia Power!WOG
- 1111 Overview of WOG Risk-Informed ISi Process and Surry
.Unit 1 Results 7/17/98 July 23, 1998 Alex McNeil!, Dave Bucheit Virginia Power Dennis Weakland Duquesne Light/WOG Nancy Closky, Richard Haessler, Bruce Bishop Westinghouse 1
~
~
- e.
Purpose of lnservice Inspection Vir inia Power!WOG
- 1111
. 11 To identify conditions, such as flaw indications, that are precursors to leaks and ruptures, which violate pressure boundary integrity principles 7/17/98 e1 I
ASME Section XI Enhanced by Risk-informed ISi Vi~ inia Power/WOG ASME Section XI
- Process
\\ Consequence Class 1, 2 and 3
- 1111 Risk-Informed ISi Exercising of PSA model (CDF, LERF, others) r**r=a1itirEi.................................................... **Ricih**aesign***stress..................... f.Exe.rcisirig***at.. sR*RA************ ** ****
! Probability and fatigue locations I model, including augmented by random I design, experience and
- selection
- operations - focused on.
areas of highest failure
- 1........ ?.t~.!.1.~.~............................................................................................................................................................................ P9.l~r~.!i.~,.....................................................................
- I
. Overall WOG Risk-Informed ISi Process Vi~ inia Power!WOG Scope and Segment Definition 7/17/98 Consequence Evaluation.
Structural Element Failure Probability Assessment Risk-Evaluation Expert Panel Categorization
- 1111 Element/
NOE 1==~ Implement Selection Program Feedback Loop 4
Overall Risk-Informed ISi Process (Can't)
Vifi in/a Power!WOG 11111 Scope and Segment Definition
. 11 Definition of piping sy.stems to be included consistent with. ISi, PSA and maintenance rule efforts 11 Definition of system boundaries 11 Structural elements to be included for examination
- Definition of piping segments 7/17/98 5
I
~
I i
e
Surry Pilot Plant Results Surry Segment Definition Summary
- Vi~ inia Power/WOG System Number of System Number of Segments Segments ACC 15 FC 9
AS 2
HHI 27 BO 12 LHI 18 cc 66 MS 38 CH 44 RC 96 CN 9
RH 11 cs 16 RS 13 cw 16 SW 54 ECCS 8
vs 2
EE 7
TOTAL 515 7/17/98
- 1111 6
Overall Risk-Informed ISi Process (Can't)
Vi~ inia Power/WOG 11111 Consequence Evaluation
. a Direct and indirect (spatial) effects a U.se of PSA to quantify impact of piping failures
- Consideration of multiple impacts
- Indirect effects - flood, spray, pipe whip, jet impingement - need for plant walkd.own 7/17/98 7
I e*
e
Overall Risk-Informed ISi Process (Can't)
Vir, inia Power/WOG
- 1111 Structural Element Failure Probability Assessment
- Industry failure experience
- Identification of potential failure modes and cau*ses
- Specific-plant information - layout, materials, operating conditions and experience
- Use of structural reliability/risk assessment (SRRA).
tool
- Estimation of leak and break probabilities by engineering team 7/17/98 8
Structural Element Failure Probability Assessment Process Vi~ inia Power/WOG
- 1111 INDUSTRY EXPERIENCE 7/17/98 IDENTIFICATION OF POTENTIAL FAILURE MODES AND CAUSES H
ENGINEERING TEAM ESTIMATED LEAK AND BREAK PROBABILITIES PLANT INFORMATION (LAYOUT, MATERIALS, OPERATING CONDITIONS, PLANT OPERATING EXPERIENCE)
SARA TOOL Engineering Team
-ISi/NOE Engineering
-Materials Engineering
-Design Stress Engineering (Engineering Mechanics) 9 e
Overall Risk-Informed ISi Process (Can't)
Vi~ inia Power/WOG
- 1111 Risk Evaluation
- Integrate PSA consequences and SRRA failure probabilities via a spreadsheet to estimate piping CDF/LERF results
- Determine risk importance measure determination
- Evaluate operator recovery actions and impact of augmented programs 7/17/98 10
Surry Risk Results Summary Vir inia Power!WOG
- 1111
- Piping CDF/LERF Results (not plant total)(point estimates)
- CDF No Operator Action ~ 6.28E-05/year
- CDF Operator Action = 4.05E-06/year
- LERF No Operator Action = 5.18E-06/year
- LERF Operator Action = 4.46E-07/year 7/17/98 11 I
I
Overall Risk-Informed ISi Process (Can't)
Vir inia Power/WOG
- 1111 Expert Panel Categorization
- Review risk evaluation results, including sensitivity studies
- Review basis for failure probability estimates
- Review other safety and deterministic insights
- Categorize into high safety significant (HSS) and low safety significant (LSS) pipe segments 7/17/98 12 e
Plant Expert Panel Process Vi~ inia Power/WOG RISK EVALUATION
- IMPACT
- RRW
- RAW
- INDIRECT EFFECTS
~
7/17/98 I
PRESSURE BOUNDARY FAILURE PROBABILITY
- MECHANISM
- PROBABILITY
- BASIS EXPERT PANEL HIGH AND LOW SAFETY-SIGNIFICANT PIPING SEGMENTS
- CONTAINMENT PERFORMANCE
- EXTERNAL EVENTS
- SHUTDOWN RISK
- OTHER SCENARIOS
-* MAINTENANCE/OPERATION INSIGHTS
- DESIGN BASIS/DEFENSE-IN-DEPTH
- OTHER DETERMINISTIC INSIGHTS e
~~~
Surry RI-ISi Results Summary Vir inia Power/WOG
- 1111
- 515 segments defined
- Risk evaluation prior to expert panel review
- 64 segments = RRW > 1.005
- .... 451 segments= RRW < 1.005 (85 segments between 1.001-and 1.004)
- Expert panel final categorization
- 108 segments = High safety significant
- 407 segments = Low safety significant 7/17/98 14
Overall Risk-Informed ISi Process (Can't)
Vir inia Power!WOG 11111 Element I NDE Selection Place pipe segments into structural element selection matrix -
failure importance vs. safety significance Define areas to receive 100°/o examination in HSS pipe segments with high failure potential Perform statistical evaluation of HSS segments.with low failure potential to determine minimur:n number of exams Relate required exams to augmented programs, as appropriate
- Select locations in pipe segments based on engineering insights and select appropriate exam method(s) and intervals 7/17/98 15
,..i
- e.
e
Inspection Location Selection Process.
Vi~ inia Power/WOG
- 1111
- Statistical model used to define how many structural elements to be inspected in each segment based on reliability criterio.n for Regions 1 b and 2
- Engineering team identifies the specific locations to inspect based on plant information(postulated failure mechanisms
- Engineering team also. ide11tifies the inspection method consistent with ASME Section XI Code Case N-577 guidance 7/17/98 16
Mapping of Surry Segments on Structural Element Selection Matrix Vir in/a Power/WOG
- 1111 7/17/98 HIGH FAILURE IMPORTANCE SEGMENT LOW FAILURE IMPORTANCE SEGMENT 3
4 0 W N ER DEFINED PROGRAM 153 SEGMENTS 0 N LY SYSTEM PRESSURE TEST & VISUAL EXAMINATION 254 SEGMENTS LOW SAFETY SIGNIFICANT SEGMENT (a) SUSCEPTIBLE LOCATIONS (100%)
1 2
(b) INSPECTION LOCATION SELECTION PROCESS 70 SEGMENTS INSPECTION LOCATION SELECTION PROCESS 38 SEGMENTS HIGH SAFETY SIGNIFICANT SEGMENT 17
.... \\
e e
Overall Risk-Informed ISi Process (Can't)
Vi~ inia Power!WOG
- 1111 Implement Program I Feedback
- Evaluate impact on risk
- Determine implementation of 'program in relation to current period of the station's Code interval
- Evaluate program relative to current commitments (e.g., relief requests)
- Submit program for approval and maintain appropriate documentation
- Develop and maintain feedback process for updates and changes to program 7/17/98 18
Pilot Plant Results Vi~ inia Power!WOG 11111 WOG-Sponsored Studies e
Current RI-ISi O/o 10yrRem Plant.
No. Exams(1) Exams(2)
Reduction Saved Millstone-3 753 107 86°/o 75R Surry-1 385 136 65°/o 60R Notes: (1) Majority of exams are Class 1 with r~mainder in Class 2 (2) More*than 50°/o of exams are Class 1 with the balance of exams 7/17/98 in Class 2 and 3 and some non-Code Class 19
Comparison of Risk for Surry Vi~ inia Power/WOG 100%
'C 90o/o
~80%
en ~70%
- g60%
~50%
840%
e>30%
r::
'a.20%
~10%
0%
/
T/ -
II f
J
~
~
~-
/-
/
--~
y I
~ -
y y
y
- 1111
~
y y
y y
y RC FW BD MS CH AFW HHI CW SW RH CC CS AS LHI ECC RS ACC CN EE FC VS System
-+-%CDF AUG ONLY
-a-%CDF SXI +XI-AUG
-.-%CDF RI-ISi +RI AUG 7/17/98 20
Vir inia Power/WOG 11111 Surry Structural Element Sele*ction 7/20/98 21 I
I I,,
,~
- e.
Some Key Insights From Risk-Informed ISi Pilot-Plants Viri inia Power!WOG *
- 1111
- Current ASME Class 1, 2, and 3 boundaries do not contain all the HSS piping segments, some are non-Code class
- Augmented programs address a significant
, portion of the HSS piping segments
- Indirect effects tend to dominate in the higher consequence piping segments
- Quantitative analysis cannot be used alone, expert panel and engineering team provide other valuable safety. and deterministic insights 7/17/98 22 e
Risk-Informed ISi Summary Vi~ inia Power!WOG -
- 1111
- Risk-informed ISi process will benefit utilities, industry, standards organizations and* regulators
- Provide* better focus and allocation of limited resources
-- Reduce overall plant operation and maintenance costs
- Reduce person-rem exposure
- Maintain-a high level of safety 7/17/98 23 e
~-
e Purpose and Scope RISK-INFORMED EXPERT PANEL GUIDANCE DOCUMENT Titis guidance document will be used to support the Surry Unit l risk-informed inservice inspection program. The guideline applies to piping ~egments on systems identified in the scope of the program.
The final safety determination (high and low safety significance) of each piping segment will be made by the expert panel using both probabilistic and deterministic insights.
Expert Panel Membership The expert panel shall be made from personnel who have expertise in the following fields; probabilistic safety assessment. inservice examination. nondestructive examination. stress and material considerations.
plant operations. plant and industry maintenance. repair. and failure history. and system design and operation. Members do not need to be experts in every field. however diversify of expertise shall be considered to prevent heavy reliance on any one member's judgment. Use of members associated with the maintenance rule shall be considered to ensure consistency with the other PSA applications. Alternates may be used if their expertise and training is sufficient.
Expert Panel Quorum The expert panel shall have the following positions represented by either the permanent or alternate member at all times during an expert panel meeting.
Probabilistic Safety Assessment (PSA engineer)
Operations (Senior Reactor Operator or Shift Teclmical Advisor)
Inservice Inspection (ISI)
Plant & Industry Maintenance. Repair, and Failure History (System Engineer)
As such. a minimum of 4 members or alternates filling the above positions constitutes a quorum.
Expert Panel Leader The expert panel chairperson shall be appointed by the Nuclear Engineering Manager. The chairperson shall conduct and rule on the proceedings of the meeting. The chairperson shall appoint an alternate chairperson from the panel if unable to attend a meeting.
Expert Panel Training Members and alternates shall receive training and indoctrination in the risk-informed inservice inspection selection process. It shall include indoctrination in the application of risk analysis teclmiques (risk importance measures, threshold values. failure probability models, failure mode assessments. PSA modeling limitations and the use of expert judgment) for ISi. Training documentation shall be main tamed with the expert panel's records.
Responsibility The expert panel shall meet as necessary to establish and maintain the risk-informed inservice inspection program. The expert panel shall approve the scope of the systems included in the project. the piping segment safety significance. and the final nondestructive examination program. including specific areas (structural elements) to be examined.
e e
RISK-INFORMED EXPERT PANEL GUIDANCE DOCUMENT (Continued)
Meeting Decision Making Process An initial scope of systems was separately detennined. The expen panel may add to the system scope. but may not delete any systems already considered. The piping segments or structural elements to be examined that have been detennined by quantitative methods to be high safety significant or requiring examination (by any one method) shall not be classified lower or eliminated from examination by the expen panel. Again the expen panel may only add piping segments to the higher classification or structural elements to be examined. The expen panel may feedback comments to the appropriate engineering personnel which may cause an adjustment of the numerical results. Adjusted numerical results require review by the expen panel.
Worksheets will be provided to the panel on each system for each piping segment. containing information peninent to the. panel's selection process. This information in conjunction with the panel member's own expenise and other documents as appropriate shall be used in determining the safety significance of a piping segment. Documentation supponing the expen panel process shall be provided to the panel in advance in a timely manner to allow appropriate preparation for the meeting.
An engineering team is used to determine a piping segments failure probability and which structural elements will be examined. At least one member of the team shall be present to answer questions to the expen panel as necessary when this portion of the process is being discussed.
The consensus process shall be used by the expen panel. Consensus is defined as unanimous during first consideration and 2/3 (rounding conservatively) of members or alternates present in the second or subsequent considerations. The chairperson shall allow appropriate time duration between considerations for deliberation. The chairperson may make the final determination. if consensus cannot be reached. by cc;mservatively selecting the system within the scope or by determining the piping segment or structural element to be high safety significant. whichever is appropriate.
Records The chairperson shall appoint someone to record the minutes of each meeting. The minµtes shall include the names of members and alternates in attendance and whether a quorum is present The minutes shall contain relevant discussion summaries and the results of membership voting. These minutes shall be maintained as program records. The minutes shall be provided for review at a subsequent meeting and approved by the expen panel. The signature of the chainnan indicates approval of the minutes.
A master listing of the systems within the scope of the program shall be maintained as a program record.
A master set of worksheets for each piping segment shall be maintained as a program record indicating the safety significance of the piping segment and a summary of the basis of the expen panel's classification. A master listing of the structural elements and selected examination techniques shall also be maintained as a program record.
Documentation of required training for*an expen panel member and the member's experience shall be maintained as a program record.
e Initial Expert Panel Chainnan - Jack Manin.(Primary) Alternate as designated PSA - Ron Thomas (Primary) Dave Bucheit (Alternate)
Operations - Jim Simpson (Primary) Alternate to be named lnservice Inspection - Dave Rogers (Primary) John Paul (Alternate) e Plant & Industry Maintenance. Repair, and Failure History - Gary Thompson (Primary) Spencer Semmes (Alternate)
Engineering Mechanics - Nitin Shah NDE - Dave Dodson Failure Lab/ Materials - Leslie L. Spain
e Surry Unit 1 Risk Informed Expert Panel Meeting Minutes 8/13/97 The following expert panel members were in attendance:
Jack Martin (Chair), Ron Thomas (PSA Primary), Gary Thompson (System Engineer Primary), Dave Rogers (ISI Primary), Jim Simpson (Ops Primary), Nitin Shah (Engineering Mechanics), David Dodson (NDE), Les Spain (Materials/Failure Lab). Additionally alternates John Paul (ISI) and Spencer Semmes (System Engineer) were in attendance. The required quorum was met.
The following guests were in attendance of the meeting:
Alex McNeill (appointed secretary for the expert panel), and Westinghouse employees Nancy Closky and Ken Balkey.
The purpose of the meeting was to receive WOG training on the Risk Informed ISI program at Surry and the expert panel application.
Training was given by Ken Balkey, Nancy Closky and Alex McNeill to the expert panel.
The guidelines for the expert panel received in training were accepted by the expert panel. Direction was given to the secretary to include panel minority opinions in the minutes if 100% agreement could not be reached.
The chairman requested that the Maintenance Rule system functions be reviewed to determine if all systems have been included in the Risk Informed ISI program for Surry. Alex McNeill took that responsibility and will report back.
Ron Thomas wanted to know if internal events such as flooding should be added to the CDF being calculated for the piping? Dave Bucheit was assigned responsibility and will report back.
A question was asked as to why MER-4 was not on Table 10-1 of the indirect analysis? Dave Bucheit was assigned responsibility and will report back.
The eves system was started using Segment CH-001 as an instructional segment. The numerical results indicated that the segment was Low Risk Significant. Deterministic insights were reviewed. The panel agreed with the postulated failure mechanism and proposed disabling leak of 2 gpm as being the most plausible scenario. Discussion discounted the probability of a much larger leak occurring and causing air bounding and loss of the charging pumps. The radiological release was determined bounded by the already analyzed rupture of the VCT.
The expert panel unanimously voted segment CH-001 Low Risk Significant The chairman requested that system information be supplied to the panel at least one week prior to their meeting on the system.
The next meeting of the expert panel would be on August 14, 1997 at 8:30am. at Surry..
The meeting was closed.
Respectfully submitted,
~;)t~
Alex McNeill Secretary
- ~t~
Jack Martin Chairman
e Surry Unit 1 Risk Informed Expert Panel Meeting Minutes 8/14/97 The following expert panel members were in attendance:
Jack Martin (Chair), Ron Thomas (PSA Primary), Dave Rogers (ISI Primaxy), Jim Simpson (Ops Primaxy), Nitin Shah (Engineering Mechanics), David Dodson (NDE), Les Spain (Materials/Failure Lab).
Additionally alternates John Paul (ISI), Dave Bucheit (PSA) and Spencer Semmes (System Engineer) were in attendance. Gary Thompson (System Engineer Primary) was absent, however alternate Spencer Semmes was present. The required quorum was met.
The following guests were in attendance of the meeting:
Alex McNeill (appointed secretary for the expert panel), Ernie Throckmorton, Westinghouse employees Nancy Closky and Ken Balkey, NRC representatives, Jack Guttmann, Stephen Dinsmore and Syed Ali, ASME Representatives, Ray Art, Robin Graybeal and Jerry Phillips, Northeast utilities employee Glen Gardner, and Japanese representatives Tetsuji Kumano, Hiroshi Nakamura, Shigeki Suzuki and Tomoaki Yoshida.
The purpose of the meeting was to continue the Risk Informed ISI expert panel evaluation process.
Discussion on the eves system continued.
Segment CH-002: The numerical results of the segment indicated Low Risk Significance. Deterministic insights were reviewed. The panel noted that the simplified drawing did not accurately show the single tap arrangement on the VCT. Charging pump cavitation was again discussed. The operator in the control room could receive misleading information as to the VCT level leading to cavitation of the pumps*.
The panel agreed that the 2 gpm leak modeled was more probable and would be detected prior to emptying the VCT. A quick bounding calculation was performed to access the effects of losing the 3 charging pumps. The added consequence did not numerically make the segment high risk significant.
The panel unanimously voted the segment Low Risk Significant.
Segment CH-003: The numerical results of the segment indicated Low Risk Significance. Deterministic insights were reviewed. The panel determined that the discussion for CH-00 I was applicable to the segment with the addition of added isolation capability. The panel unanimously voted the segment Low Risk Significant.
Segment CH-004 & CH-005: These segments were addressed together. The numerical results of the segments indicated Low Risk Significance. Deterministic insights were reviewed. The panel noted that the assumption that MOV-1373 closed on SI signal was in error. The valve closure would require operator action. Leakage could be as much as 180 gpm without the valve closure, being bmited by flow orifices. The panel *decided that the assumed leakage of 2 gpm was again more credible and the right assumption. The panel noted that the assumed failure of the MSTV SO Vs leading to a reactor trip due to indirect effects was not plausible and represented an overconservatism. The panel requested that the numerical results be corrected. The panel unanimously voted segment CH-004 as Low Risk Significant.
The panel was concerned about the single containment isolation afforded by segment CH-005. The panel pointed out that the design of the relief valve for the system inside containment made it highly probable that the barrier inside containment would be breached. This would leave segment CH-005 as a single barrier for containment integrity. The panel unanimously voted the segment High Risk Significant..
Segment CH-006: The numerical results of the segment indicated Low Risk Significance. Deterministic insights were reviewed. The panel noted that seal return failure would require operator action to isolate the leak. The HCVs were noted as designed to fail open. The loss of seal return would require RCP shutdown and a manual reactor trip. The panel unanimously voted the segment Low Risk Significant.
)
e e
Segment CH-007: The numerical results of the segment indicated Low Risk Significance. The panel noted that the seal bypass line could have different consequences compared to the seal leak-off line on the segment. The leak-off line failure would lead to a manual reactor trip as described in segment CH-006, however the bypass line failure could lead to a small break LOCA. Additionally the assumed pressure on the segment should be RCS pressure (2235 psig.). The panel requested that the numerical results be corrected. The panel unanimously voted that the segment was Low Risk Significant.
CH-008, 009, 010: These segments were evaluated together. The numerical results indicated that these segments were High Risk Significant. Deterministic insights were reviewed. It was noted that North Anna and V.C. Summer had both experienced through-wall leakage at these locations. The panel unanimously voted segments CH-008, 009, 010 as High Risk Significant.
CH-011, 012, 013: These segments were evaluated together.
- The numerical results indicated that these.
segments were Low Risk Significant. Deterministic insights were reviewed. The panel noted that a single check valve isolated the segments from High Risk Significant segments. The check valves were not currently leak tested. The panel unanimously voted segments CH-011, 012, 013 as High Risk Significant.
The next meeting of the expert panel was set for August 20, 1997 at 2:00pm. at Surry.
The meeting was closed.
Respectfully submitted,
~rn~
Alex McNeill Secretary
-~---
e Surry Unit 1 Risk Informed Expert Panel Meeting Minutes 8/20/97 The following expert panel members were in attendance:
Jack Martin (Chair), Gaiy Thompson (System Engineer Primacy), Jim Simpson (Ops Primacy), Nitin Shah (Engineering Mechanics), David Dodson (NDE), Les Spain (Materials/Failure Lab). Additionally alternates John Paul (ISI) and Dave Bucheit (PSA) were present. The required quorum was met.
The following guests were in attendance of the meeting:
Alex McNeill (appointed secretary for the expert panel), Ernie Throckmorton, Westinghouse employees Nancy Closky and Ken Balkey.
The purpose of the meeting was to continue the Risk Informed ISI expert panel evaluation process.
The meeting began by reviewing the feedback verbally received from the NRC observers at the last meeting. Generally, the feedback called for improvements in the information presentation to the expert panel. The Chairman, Jack Martin, added that a general write-up of deterministic insights for the entire plant would be useful to aid looking at the insights on a segment by segment basis. This was assigned to Ken Balkey. Nancy Closky, Alex McNeill and Dave Bucheit.
Feedback from the expert panel on check valve separation of segments suggested that inspection expansion could be used in lieu of higher classification if there are reliable differences in failure probabilities between the segments. Previously, a numerically low safety significant segment had been made high since it was separated only by one untested check valve from a high safety significant segment.
The suggested alternative was to examine the high safety significant segment and expand into the low safety significant segment only if problems were identified in the high safety significant segment. The panel thought this was an acceptable alternative, however they felt previous classifications were appropriate based upon the failure probabilities reported and their uncertainties.
The panel reviewed the definitions ofRRW and RAW, these follow:
a) RRW (Risk Reduction Worth) indicates the reduction factor in risk if the piping is assumed perfectly*
reliable for all failure modes. The RRW is calculated by reevaluating the PSA model and substituting a value of zero for the component unavailability for each piping segment of interest.
b) RAW (Risk Achievement Worth) indicates the increase factor in risk if the piping is assumed failed for all failure modes. The RAW is calculated by reevaluating the PSA model and substituting a value of unity for the component unavailability for each piping segment of interest.
Discussion on the eves system continued.
A general system overview of the eves was read to the panel.
Segment eH-014: This segment was Low Risk Significant numerically. Deterministic insights were reviewed. The panel noted that the segment supplied seal injection to the RePs and provided containment isolation. The panel noted multiple check valve containment isolation inside the containment, flow restriction outside containment and potential needle valve use, and MOVs and manual valves further upstream of the segment for containment isolation outside containment. The panel unanimously voted the segment as Low Risk Significant.
Segment eH-015: This segment was Low Risk Significant numerically. Deterministic insights were reviewed. The segment was a continuation of the seal injection header. The discussion for CH-014 was
e e
applicable. It was noted that seal injection is important in Appendix R considerations in that if a fire results in a loss of component cooling function only seal injection remains to prevent RCP seal failure and the resultant seal LOCA. The panel unanimously voted the segment as Low Risk Significant.
Segments CH-016 & 017: These segment were considered together. The segments were considered Low Risk Significant numerically. Deterministic insights were reviewed. The segments are used for RCS loop filling and could be used for alternate safety injection flow path and emergency borate flow path. The segments are normally isolated. The panel unanimously voted the segment as Low Risk Significant.
Segments CH-018, 019, 020, 021, 022, 023 and 041 were tabled pending numerical results which included failure of auxiliary spray. Numerical result update assigned to Dave Bucheit.
Segment CH-024: The segment was considered Low Risk Significant numerically. Deterministic insights were reviewed. The segment is part of letdown. It was noted that AP-16 requires operator isolation of letdown for RCS leakage greater than 24 gpm. Letdown was noted as important in shutdown with solid pressurizer operations. Discussion centered around repair options if leakage occurs and use of excess
- letdown. The panel unanimously voted the segment as Low Risk Significant.
Segments CH-025, 026, 027: These segments were considered together. The segments were considered Low Risk Significant numerically. Deterministic insights were reviewed. The discussion for CH-024 was applicable. The panel unanimously voted the segments as Low Risk Significant.
Segment CH-028A:. The segment was considered Low Risk Significant numerically. Deterministic insights were reviewed. The failure of this piping on Sony Unit 2 was discussed. The difficulty of shutting down the unit without Letdown was also reiterated. The panel unanimously voted the segment as Low Risk Significant, however noted that the company may want to incorporate some sort of inspection here for plant reliability.
Segments CH-028B to CH-040: These segments were evaluated together. The numerical results indicated the segments were Low Risk Significant. Deterministic insights were reviewed. It was noted that the basis for the low categorization had been fully discussed on similar segments previously. It was noted that segment CH-040 had hydrogen. Leakage from the segment could result in a fire. Additionally leakage could cause misleading information concerning VCT level. The panel unanimously voted the segments as Low Risk Significant.
The next meeting was tentatively established for Wednesday, August 27, 1997 at 2:00pm. at Surry.
The meeting was closed.
Respectfully sub~tted,
~Vt\\~
Alex McNeill Secretal)'
~?A~
Jack Martin Chairman
e Surry Unit 1 Risk Informed Expert Panel Meeting Minutes 8/27/97 The following expert panel members were in attendance:
Jack Martin (Chair), Jim Simpson (Ops Primary), Nitin Shah (Engineering Mechanics), Les Spain (Materials/Failure Lab). Additionally alternates John Paul (ISI), Dave Bucheit (PSA) by conference phone and Spencer Semmes (System Engineer) were present. ~e required quorum was met.
The following guest was in attendance of the meeting:
Alex McNeill (appointed secretaiy for the expert panel).
The purpose of the meeting was to continue the Risk Informed ISI expert panel evaluation process.
The minutes of August 13 and 14 were reviewed by the panel.
AS-001 & AS-002: These segments were c.onsidered together. The numerical results indicated that these segments were High Risk Significant. Deterministic insights were reviewed. The segments were modeled.
for indirect affects only. The safety significance appears to be driven by a high failure probability due to the piping being nonsafety-related. The conditional consequence appears to be reversed for each segment (i.e., AS-001 conditional consequence should be for AS-002 and vice versa). As both segments had similar high failure probabilities the results appeared to be unaffected by the error as both segments were classified high. The panel requested that the numerical results be corrected, however. Dave Bucheit was assigned the numerical correction. The expert panel unanimously voted the segments High Risk Significant.
VS-001 & VS-002: These segments were considered together. A VS system overview was read to the panel. It was pointed out that a design change incorporated at Surry now prevents total failure of the system by having two independent trains for chill water cooling. Additionally bearing cooling now provides make-up to the trains which may cause more accelerated corrosion on the system. The panel tabled the segments pending an update of the numerical results. Dave Bucheit and Alex McNeill were assigned the numerical update.
BD-001, 004, 007, 002A, 005A, 008A: These segments were evaluated together. A BD system overview was read to the panel. The segments were considered Low Risk Significant numerically. Deterministic insights were reviewed. The segments had only direct impacts associated with steam generator tube rupture. It was noted that the inside trip valves close on high flow in blowdown. There were no indirect effects. *The failure probability took credit for the augmented erosion/corrosion program, but was still considered high. It was noted that the risk-informed process would not affect the augmented program.
The panel unanimously voted the segments Low Risk Significant.
BD-002B, 005B, 008B, 003, 006, 009: These segments were evaluated together. The segments were considered High Risk Significant numerically. Deterministic insights were reviewed. The segments differ from the previous blowdown discussion in that the indirect effects of the segments failure contribute highly to the conditional consequence. It was reported that the conditional consequence for these segments were three orders of magnitude higher. The failure probability due to wastage was approximately the same. The panel unanimously voted the segments High Risk Significant.
The next meeting of the panel was scheduled for September 15, 1997, Monday at 8:30am. at Surry.
The meeting was closed.
Respectfully submitted,
~ty\\~
Alex McNeill Secretary
- rd'~
Jack Martin Chairman
~
e e
Surry Unit 1 Risk Informed Expert Panel Meeting Minutes 9/15/97 The following expert panel members were in attendance:
Spencer Semmes (Designated Chair and alternate System Engineer), Jim Simpson (Ops Primary), Nitin Shah (Engineering Mechanics), Les Spain (Materials/Failure Lab). Additionally alternates John Paul (ISI), Dave Bucheit (PSA) were present. The required quorum was met.
The following guests were in attendance at the meeting:
Alex McNeill (appointed secretary for the expert panel), Nancy Closky (Westinghouse), Ken Balkey (Westinghouse), Dick Haessler (Westinghouse) and attending for the Reactor Coolant system Jack Guttmann (NRC), Vince Dandini (Sandia) and Donnie Whitehead (Sandia).
The purpose of the meeting was to continue the Risk Informed ISI expert panel evaluation process.
CH-018, 019, 020, 021, 022, 023, 041: These segments were previously tabled to evaluate the effect of the loss of auxiliary spray resulting from the loss of these segments. Previously the loss of auxiliary spray had not been considered in the consequence evaluation. Dave Bucheit reported that a sensitivity study was performed on these segments adding the additional loss of auxiliary spray. The study indicated that the affect of adding the loss of auxiliary spray was very small change to the consequence. The numerical analysis previously performed was in his opinion still valid. Numerically each of these segments were considered low risk significant. The panel voted unanimously each of these segments Low Risk Significant.
VS-001, 002: These segments were previously tabled by the panel because of concerns associated with the consequence modeling. They indicated that new design modifications would make the consequence much lower than what was modeled. It was requested that the panel allow the segments to remain high while the modeling is updated in the PSA model to reflect the design change. If after updating the model the numerical results indicate a lower classification is warranted then it would be brought back for reconsideration. The panel voted unanimously each of these segments as High Risk Significant.
The panel had previously requested a plant overview which would provide information such as system functions, maintenance rule insights, shutdown risk considerations, external events. and other deterministic and probabilistic insights on a generic basis to aid the panel in it's decision process. As a result system overviews have been developed in response to this request.
Fuel Pool Cooling A system overview was read to the panel (attached to minutes).
FC-001, 002, 003: The panel pointed out that the fire protection water can be used as a back-up to the fuel cooling system: Leaks would be identified by increased liquid waste collection from the fuel building sump. The failure probability was determined to be low. The panel voted unanimously each segment Low Risk significant.
FC-004, 005: These segments were similar to FC-001, 002 & 003. Low failure probability noted. The panel voted unanimously each segment Low Risk significant.
FC-006: The segment had a higher failure probability due to vibration. The panel voted unanimously the segment Low Risk significant.
FC-007, 008: The failure probability due to stress corrosion cracking was considered conservative. The panel voted unanimously each segment Low Risk significant.
e FC--009: The panel pointed out a drawing error and ask that it be corrected. The failure probability was considered low. The panel voted unanimously the segment Low Risk significant.
Residual Heat Removal A system overview was read to the panel (attached to minutes).
RH--002: The segment was found to be numerically in the grey area (LERF OA). The segment had a low failure probability based on SCC. The panel noted that the PSA model was for at power conditions. The panel discussed the difficulty in providing alternate shutdown cooling (AP-27, Loss ofRHR.) to the plant.
The panel voted unanimously the segment High Risk significant.
RH--003, 003B: These segments were found to be numerically high risk significant (CDF OA, LERF OA, and CDF No OA). The discussion for RH--002 was applicable here. The panel voted unanimously each segment High Risk significant.
RH--003A, 010, 012, 013: These segments were found to be numerically low risk significant. The failure probability based upon SCC was considered conservative. The panel voted unanimously each segment Low Risk significant.
RH--011: The segment was found to be numerically low risk significant. The failure probability was based upon SCC. Surry has experienced problems on this segment previously at the corresponding location on Unit 2. Additionally the segment includes a contajrunent penetration. The panel voted unanimously the segment High Risk significant.
RH--008, 009: These segments were found to be numerically low risk significant. The failure probability of these segments is low. The piping is thicker wall type 316 material. The accumulators (Sn constantly pressurize this piping during normal operation to about 660 psig. A leak would be readily detectable by a change in accumulator level which is monitored in the control room. The panel voted unanimously each segment Low Risk significant.
RH--014: The segment was found to be numerically low risk significant. The discussion for RH--008 and 009 is applicable to this segment. The panel voted unanimously the segment Low Risk significant.
Auxiliary Feedwater A system overview was read to the panel (attached to minutes).
AFW--001, 002, 003: These segments were found to be numerically low risk significant. In general the auxiliary feedwater piping has a relatively high failure potential due to general corrosion. The panel noted that there are several redundant water sources for the system. The emergency CST constantly pressurizes the segments. A leak would be detected over time by a change in the tank level which is monitored. The panel requested that the segments include piping up to the suction of the auxiliary feedwater pumps and requested a drawing change. The panel voted unanimously each segment Low Risk significant.
AFW--004, 005, 006: These segments were found to be numerically high risk significant (CDF OA, LERF OA). The segments now included piping from the pump to the first discharge check valve due to the panel's request on AFW--001, 002, and 003. The panel voted unanimously each segment High Risk significant.
AFW--007, 008, 009: These segments were found to be numerically in the grey area (CDF OA). The segments were included in the augmented erosion corrosion program. The panel voted unanimously each segment Low Risk significant if included in augmented E/C program.
e AFW-010, Qll: These segments were found to be numerically in the grey area (CDF OA. LERF OA).
The discussion was similar to segments AFW-007, 008, 009. The panel voted unanimously each segment Low Risk significant if included in augmented E/C program.
AFW-012: This segment was numerically found to be low risk significant. The line functions only during pump periodic testing. The panel voted unanimously the segment Low Risk significant.
AFW-013, 014: These segments were found to be numerically in the grey area (CDF OA. LERF OA).
The panel noted that this was a containment penetration segment. The panel voted unanimously each segment Low Risk significant if included in augmented E/C program.
AFW-015, 016: These segments were found to be numerically high risk significant (CDF No OA. LERF No OA). The panel noted that the failure mechanism associated with general corrosion was similar to previous segments, but that the conditional consequence offailure was much higher due to loss of auxiliary feedwater without operator action. The panel voted unanimously each segment High Risk significant.
AFW-017, 018, 019: These segments were found to be numerically high risk signifi_cant (CDF No OA.
LERF No OA). The discussion on AFW-015 and 016 applied to these segments. The panel voted unanimously each segment High Risk significant.
AFW-020, 021, 022: These segments were found to be numerically low risk significant. The panel noted that the segment loss would not cause a loss of all auxiliary feedwater by design. The loss would be restricted to one steam generator. Additionally it was assumed that loss of the iine would not result in loss offeedwater due to the small size of the auxiliary feedwater line (3: 1 ratio line size not exceeded). The panel voted unanimously each segment Low Risk significant if included in augmented E/C program.
AFW-023: This segment was found to be numerically lo'Y risk significant. The panel noted that the segment provided a flow path from CN-TK-3. The panel noted that there are several potential water sources for the auxiliary feedwater system. The loss of this segment would have minimal consequences.
The panel voted unanimously the segment Low Risk significant.
AFW-024, 025, 026: These segments were found to be numerically low risk significant. The consequence discussion for AFW-023 applies to these segments. Additionally the pumps are tested monthly and discovery of leakage would be highly probable. The panel voted unanimously these segments Low Risk significant.
AFW-027: This segment was found to be numerically low risk significant. It was noted that the PSA model does not take credit for the fire protection system with regard to supplying water to the auxiliary feedwater system. The panel again.noted that the system has several redundant water supply capabilities and the loss of this segment should have minimal consequences. The panel voted unanimously the segment Low Risk significant.
AFW-028: This segment was found to be numerically in the grey area (CDF OA). The panel noted the segment's role in common mode failures of auxiliary feed water scenarios such as fire in cables. The segment consequence again appears to be reduced by the built in redundancy of the system. The panel
- voted unanimously the segment Low Risk significant if included in augmented E/C program.
AFW-030, 031, 032: These segments were found either to be in the grey area (31, 32, CDF OA) or low risk significant (30). The panel noted that a leak in the lube oil cooler lines could result in similar indirect effects (spray disabling pumps) given to AFW-004, 005 and 006. The numerical analysis had not taken this possibility into account. The panel voted unanimously each segment High Risk significant.
e Reactor Coolant A system overview was read to the panel (attached to minutes).
RC-001, 002, 003, 004, 005, 006: These segments were found to be numerically in the grey area (CDF OA). The panel noted that the numerical results did not credit leak detection in the analysis of the RCS system. The panel discussed the leak detection capabilities associated with the RCS (radiological alarms, containment sump level monitoring, RCS leak rate calculations). The panel voted unanimously these segments Low Risk significant.
RC-007, 008, 009: These segments were found to be numerically iµ the grey area (CDF OA). The discussion previously concerning leak detection applies to these segments. The panel voted unanimously these segments Low Risk significant.
RC-010, 011, 012, 013, 014, 015: These segments were found to be numerically in the grey area (CDF OA). The discussion previously concerning leak detection applies to these segments. The panel noted that loss of segments 013, 014, and 015 would lead to a faster core uncovery in shutdown conditions. It was noted however that mechanisms causing failure of the line during shutdown conditions would be greatly reduced. The panel voted unanimously these segments Low Risk significant RC-016, 017, 018: These segments were found to be numerically high risk significant (CDF OA). The segments provide hot leg safety injection water. The panel noted that the failure mechanism postulated (thermal striping) had occurred in the industry, though on the cold leg SI lines. The panel voted unanimously each segment High Risk significant.
RC-019: This segment was found to be numerically high risk significant (CDF OA). The panel noted that the failure probability for this segment was based upon thermal stratification in the pressurizer surge line. The panel noted that operational controls had been instituted preventing this occurrence in addition to the pressurizer heaters always being on now. They requested that the segment be analyzed using a failure probability that did not include potential thermal stratification. The new failure probability calculated lowered the failure probability an order of magnitude. Analyzing the results with the new failure probability appeared to place the segment in the grey area similar to the loop piping. The panel voted unanimously the segment Low Risk significant.
RC-020: This segment was found to be numerically low risk significant. The panel discussed whether the segment had good mixing flow since an SCC concern was raised for the attaching RH segment (RH-002).
The panel decided that the segment did receive good mixing flow. The panel voted unanimously these segments Low Risk significant.
RC-021, 022, 023: These segments were found to be numerically low risk significant. The segments had a low failure probability. The panel voted unanimously these segments Low Risk significant.
RC-024, 025, 026: These segments were found to be numerically low risk significant. These segments had a higher failure probability since the lines were smaller (2" pressure equalization lines). No active failure mechanism was identified. The panel voted unanimously these* segments Low Risk significant.
RC-027, 028, 029: These segments were found to be numerically in the grey area (CDF OA). The failure probability was higher due to vibration concerns. No previous problems were identified for the lines. The panel voted unanimously these segments Low Risk significant.
RC-30: The segment was found to be numerically low risk significant. The segment failure resulted in little or no consequence since the segment is isolated by a normally closed valve. The panel voted unanimously the segment Low Risk significant.
e RC-031, 032, 033: These segments were found to be numerically low risk significant. The discussion on segments RC-027, 028, and 029 was applicable to these segments. The panel voted unanimously these segments Low Risk significant.
RC-034, 035, 036: These segments were found to be numerically low risk significant. The segments had a low failure probability. The panel voted unanimously these segments Low Risk significant.
RC-037, 038, 039: These segments were found to be numerically high risk significant. The segments had a high failure probability due to vibration as a result of their proximity to the reactor coolant pumps. The panel voted unanimously each segment High Risk significant.
RC-040: The segment was found to be numerically low risk significant. The attaching CH segment (letdown) was also low risk significant. The panel voted unanimously the segment Low Risk significant.
RC-041, 042, 043: These segments were found to be numerically high risk significant. The high failure probability was due to postulated problems in the industry for thermal striping in the cold leg safety injection piping. The panel voted unanimously each segment High Risk significant.
RC-044, 045, 051: These segments were found to be numerically low risk significant. The failure probability took credit for the augmented inspection program for the SCC mechanism lowering the failure probability. The piping is sensitized. The panel voted unanimously these segments Low Risk significant with augmented program.
RC-046, 04 7, 048: These segments were found to be numerically low risk significant. The segments had a low failure probability. The panel voted unanimously these segments Low Risk significant.
RC-049: The segment was found to be numerically low risk significant. The segment has a low failure probability. The segment is separated by a check valve from the CH (normal charging) system but both segments are low. The panel voted unanimously the segment Low Risk significant.
RC-050: The segment was found to be numerically low risk significant. The panel discussed potential indirect effect concerns in this area (RX vessel head). Nothing significant was identified. The panel voted unanimously the segment Low Risk significant.
RC-052, 053, 054: These segments were found to be numerically low risk significant. The segments were associated with the code safety valves. The panel discussed indirect effect concerns in this area. Nothing significant was identified. The panel discussed the affects of failure on pressure control in the RCS. The panel voted unanimously these segments Low Risk significant.
RC-055: The segment was found to be numerically low risk significant. The segment had a low failure probability. The panel voted unanimously the segment Low Risk significant.
RC-056: The segment was found to be numerically low risk significant. The segment is normally isolated and therefore failure would have no consequence. The panel discussed potential concerns associated with water spillage if the safeties or PORVs lift coincident with the segment failure. Nothing significant was identified. The panel voted unanimously the segment Low Risk significant.
RC-057: The segment was found to be numerically in the grey area (CDF OA). Discussed potential indirect effect impacts and role in overpressure mitigation. Nothing significant was identified. The panel unanimously voted to make the segment Low Risk significant.
RC-058, 059: These segments were found to be numerically low.risk significant. The discussion for RC-057 was applicable to these segments. The panel originally voted to make these segments low risk significant.
e e
Note: On September 17, 1997 the panel reconsidered RC-058 and RC-059. The panel was concerned with high stress to allowable stress ratios. The panel voted unanimously each segment High Risk significant.
RC-060A: The segment was found to be numerically in the grey area (CDF OA). The line is smaller resulting in a higher failure probability. The panel unanimously voted to make.the segment Low Risk significant.
RC-060B: The segment was found to be numerically low risk significant. The segment is normally isolated resulting in little or no consequence as a result of it's failure. The panel unanimously voted to make the segment Low.Risk significant.
RC-061: The segment was found to be numerically in the grey area (CDF OA). The segment is not normally used being attached to auxiliary spray (CH). The possibility of a temperature shock was discussed, charging water being cooler. It was noted that the use of the system would be a one-time type event. The panel unanimously voted to make the segment Low Risk significant.
RC-062 through RC-095: These segments were found to be numerically low risk significant. The segments were discussed as a group as all the segments were 1 nps or smaller. The consequence of failure of these segments were either low or none (isolated). The panel discussed potential loss of instrumentation. Nothing significant was identified. The panel voted unanimously these segments Low Risk significant.
The RCS system being :finished, guests were asked to comment on the process. The NRC noted that RAW did not appear to be used significantly by the panel. The panel noted that the RAW values were provided but they did not provide any meaningful discriminator for the selection process. The NRC requested that our submittal address the lack of RAW usage.
The next meeting of the panel was scheduled for September 17, 1997, Wednesday at 8:30am. at Surry.
The meeting was closed.
Respectfully submitted,
~ht~
Alex McNeill Secretary APPJ,~z*
b, /
- ,1... I:__,~* -1:u~
t: {,(.
_{:;>-
Spencer Se es
~
Acting Chairman Py f... /tc "'r 11
/C/l=;/t:; 7
e Surry Unit 1 Risk Informed Expert Panel Meeting Minutes 9/17 /97 The following expert panel members were in attendance:
Spencer Semmes (Designated Chair and alternate System Engineer), Jim Simpson (Ops Primary), Nitin Shah (Engineering Mechanics). Additionally alternates John Paul (ISi), Dave Bucheit (PSA) were present. The required quorum was met.
The following guests were in attendance at the meeting:
Alex McNeill (appointed secretary for the expert panel), Dick Haessler (Westinghouse)
The purpose of the meeting was to continue the Risk Informed ISi expert panel evaluation process.
The panel decided to reevaluate segments RC-056, 058 and 059. Nitin Shah was concerned about the high stress to code allowable stress ratio in these segments.
RC-058, 059: The high stress is located at the PORV connection. Nitin Shah indicated that the stress approaches 80% of code allowable. This would not include stresses associated with external events. The panel was not comfortable with a small leak in this location. The panel voted unanimously to change each of the segments to High Risk significant.
RC-056: The panel discussed similar stress concerns at header and at the PORVs. The panel again noted that the segment has very little consequence functioning only to deliver water/steam that is released by the Code Safeties or PORVs to the PRT. The panel reconfirmed the segment as Low Risk significant.
Feedwater The feedwater system overview was read to the panel (attached).
FW-001: The segment was found to be numerically high risk significant (LERF OA). A discussion by the panel concerning the high LERF value ensued. The LERF value was attributed to the importance of the system as a back-up during steam generator tube ruptures. The PSA model has been determined to supply conseivative values in this failure scenario. The segment has a high failure probability due to the erosion/corrosion mechanism. Credit was given to the augmented inspection program improving the failure probability by a factor of 10, however the segment is still considered to have a high failure probability even after the inspection. The panel voted unanimously the segment as High Risk significant.
FW-002, 003, 004, 005, 006, 007: Segments FW-002 and FW-005 had similar numerical results to FW-001 and were considered numerically high risk significant (LERF OA). Segments FW-003, 004, 006, and 007 were numerically in the grey area (LERF OA). The difference was attributed to a lower failure probability for the segments in the grey area. The panel did not see a significant difference between FW-001 and these segments and voted unanimously each of the segments as High Risk significant.
FW-008: The segment was found to be numerically low risk significant. The difference between this segment and those previously was the segments failure probability. The probability offailure was approximately an order of magnitude lower. This lower probability was attributed to a class change in the piping (300# to 900#). The panel voted unanimously the segment as Low Risk significant but maintenance of the FAC program was required.
FW-009, 010, Oll: These segments were found to be numerically low risk significant. The low numerical value was attributed again to a very low failure probability. The segments are comprised of
e chrome-moly piping material which is not susceptible to the erosion/corrosion damage mechanism. The panel voted unanimously each segment as Low Risk significant.
FW-012, 013, 014: These segments were found to be numerically high risk significant (LERF OA, CDF OA). The segments were high because of high indirect consequences attributed to failure of components in the main steam valve house (i.e., auxiliary feedwater pumps, etc.) as a result of the feedwater piping failure. The segment is susceptible to the erosion/corrosion failure mechanism and credit was taken for the E/C augmented program. The panel voted unanimously each segment High Risk significant.
FW-015, 016, 017: These segments were in the grey area numerically (CDF OA). The difference between these segments and the previous (FW-012, 013, 014) was attributed to a lower failure probability.
The panel noted that the consequences would be similar; however. The panel voted unanimously each segment as High Risk significant.
FW-018, 019, 020: These segment were found to be numerically low risk significant. The segments are located in containment and had no indirect effects attributed. The erosion/corrosion mechanism is still present as well as the augmented inspection program. The panel voted unanimously each segment as Low Risk significant but maintenance of the F AC program was required.
Les Spain (Failure Lab/Materials) joined the meeting at this time.
Senice Water The system overview was read to the panel (attached).
SW-00 I, 002, 003: These segments were found to be numerically low risk significant. The segments a low failure probability and were part of a redundant system. The panel noted that the electric motor drive to one of the pumps was not attached. The panel also noted credit was being taken for the station's coatings program, lowering the failure probability. The panel voted unanimously each segment as Low Risk significant.
SW-004, 005, 006: These segments were found to be numerically high risk significant (CDF OA). The failure probability was determined without the SRRA due to the materials not being modeled in the SRRA. A conservatively high failure probability was determined by the engineering team. The panel voted unanimously each segment as High Risk significant.
SW-007, 008: These segments were found to.be numerically low risk significant. The !;:ngineering team took credit for the coatings program on this portion of the system. The team assumed the coatings program would be maintained, as such wastage resulting from corrosion would be very localized and not lead to catastrophic_ problems. The team used the fatigue failure probabilities as a result which are much lower failure probabilities than those generated from wastage. The panel voted unanimously each segment as Low Risk significant but the coatings program must be maintained on the piping.
SW-009, 010: These segments were found to be numerically in the grey area (CDF OA). The discussion on SW-007 and SW-008 was applicable to these segments. The failure probability was slightly higher than the previous segments due to a conservative selection of a small line to base the failure probability on. The small line may not lead to the same consequences (flooding), however. The panel voted unanimously that each segment was Low Risk significant but the coatings program must be maintained on the piping.
SW-Oll, 012, 013, 014, 015, 016, 017: These segments were found to be numerically. low risk significant. The failure probability again takes credit for the coatings program. The panel voted unanimously that each segment was Low Risk significant but the coatings program must be maintained on the piping.
/
SW-018, 019, 020, 021, 022,. 023, 024, 025: These segments were found to be numerically high risk significant. The higher classification was due to the increased failure probability. The engineering team had postulated a wastage mechanism on the segments. The panel noted that the piping was maintained chy and disagreed with the assumed wastage. The panel requested that a new failure probability be calculated with no wastage since the component was maintained dry. The probability was calculated as large leak 2.68 E-7 (no 1sn. The old probability was 1.3 E-4. The lower failure probability was determined to be enough to make the segments numerically low risk significant or in the grey area. The panel voted unanimously that each segment was Low Risk significant but the coatings program must be maintained on the piping.
SW-026, 027: These segments were found to be numerically in the grey area (CDF No OA, LERF No OA). Again the coatings program was seen as the essential element in maintaining this piping. The panel voted unanimously that each segment was Low Risk significant but the coatings program must be maintained on the piping.
SW-028: The segment was found to be low risk significant. The piping is used to drain the heat exchangers (RS) and is normally isolated. The consequences of failure of the piping was seen as negligible. The panel voted unanimously each segment as Low Risk significant.
SW-029, 030, 031, 032, 033, 034, 035, 036, 037, 038: These segments were found to be numerically in the grey area (LERF OA). The failure probabilities for these segments were placed consetvatively high (1.0 E-2) by the engineering team as the SRRA tool was not used (material not in SRRA). The panel also noted that the consequence of failure of the segments was low or consetvatively stated due to modeling in the PSA (failed equipment in separate rooms, MER-3 & MER-4, simultaneously from indirect effects).
The panel voted unanimously each segment as Low Risk significant.
SW-039: The segment was found to be numerically low risk significant. Failure of the segment was described as having no consequence. The failure probability was consetvatively high (1.0 E-2) again derived by the engineering team not using the SRRA tool. The panel noted that the isolation valves for this segment are normally closed. The panel voted unanimously the segment as Low Risk significant.
SW-040, 041, 042, 043: These segments were found to be numerically in the grey area (LERF OA).
Again the failure probability was established by the engineering team consetvatively high (1.0 E-2) not using the SRRA tool. The panel again described the consequence of segment failure as low. The panel voted unanimously each segment as Low Risk significant.
SW-044, 045, 046, 047, 054: These segments were found to be numerically low risk significant. The panel discussed the indirect effects associated with loss of these segments. A concern developed over the loss of the charging. pump component cooling water pumps as a result of spray from the postulated failed segments. There is no physical separation between these segments and the pumps, making possible water introduction into the electrical components of the pumps possible, if the piping failed. The failure ofboth pumps would result in loss of cooling to all charging pumps and simultaneous loss of high head safety injection. The operator would have to use the Unit 2 crosstie charging capability. The panel voted unanimously each segment as High Risk significant.
SW-048, 049, 050, 051, 052, 053: These segments were found to be numerically low risk significant.
The panel discussed the indirect effects of these segments. They noted that the segments were confined to individual charging pump cubicles and would not cause the same spray problem discussed above. The panel voted unanimously each segment as Low Risk significant.
Circulating Water
- The system overview was read to the panel (attached).
~
--~-:: ___ --- -------------------------- -----------
e CW-001, 002, 003, 004: These segments were found to be numerically low risk significant. The panel confirmed the low consequence associated with these segments noti~g the redundancy of water supply from the James River. The panel voted unanimously each segment as Low Risk significant.
CW-005, 006, 007, 008: These segments were found to be numerically high risk significant (CDF OA).
The panel discussed the importance of the segments with regard to flooding issues in the turbine building basement. The importance of the coatings program was discussed. The panel voted unanimously each segment as High Risk significant.
CW-009, 010, 011, 012, 013, 014, 015, 016: These segments were found to be numerically low risk significant. The panel noted that these segments would be automatically isolated during a flooding scenario and that they had negligible consequences. The panel voted unanimously each segment as Low Risk significant.
Condensate A system overview was discussed with the panel (note: no written report only verbal).
CN-001, 002, 003, 004, 005: These segments were found to be numerically low risk significant. These segments failure probabilities are high due to the erosion/corrosion failure mechanism. The probabilities took credit for the augmented program. The panel voted unanimously each segment as Low Risk significant but maintenance of the FAC program was required.
CN-006: The segment was found to be numerically low risk significant. The segment is normally isolated, resulting in negligible consequence if it fails. The panel voted unanimously the segment as Low Risk significant.
CN-007: The segment was found to be numerically low risk significant. The failure probability was very low based upon fatigue. The panel voted unanimously the segment as Low Risk significant.
CN-008: The segment was found to be numerically high risk significant CDF No OA, CDF OA, LERF No OA). The panel decided to subdivide the segment into segments CN-008A and CN-008B. CN-008A comprises all of the original segment excluding the piping between valves 1-CN-150 and l-CN-151. CN-008B comprises the piping between the valves. The original analysis assumed that the entire segment did not get leak tested very often. This led to a high failure probability in the calculation of risk. CN-008A woµld be very similar in consequence and failure probability with AFW-001, 002, and 003. These segments were low risk significant. A quick numerical analysis confirmed that the segment would only be in ~e grey area at the most. The segment (CN-008A) would be constantly leak tested by the tank (CN-TK-2) pressure and the tank level is monitored. The panel voted unanimously the segment (CN-008A) as Low Risk significartt. CN-008B could still not be leak tested very often, leading to a higher failure probability, however the consequence of failure was limited to loss of make-up capability from the main condensate tank to the emergency condensate tank. This risk is considered minimal. Conservatively the consequences from AFW-001, 002, 003 were used in a quick analysis. The new results indicated at most the segment was numerically in the grey area. The panel voted unanimously the segment (CN-008B) as Low Risk significant.
CN-009: The segment was found to be numerically low risk significant. The panel noted failure of the segment resulted in minimal consequence. The panel voted unanimously the segment as Low Risk significant.
Emergency Diesel Fuel Oil The system overview was read to the panel (this was a verbal report no handout)
}
-~-------------------------
e EE-001, 002, 003, 004, 005-lA, 005-lB, 005-2A, 005-2B, 005-3A, 005-3B, 006-lA, 006-lB, 006-2A, 006-2B, 006-3A, 006-3B, 007-1, 007-2, 007-3: These segments were found to be numerically low risk significant. The panel evaluated the deterministic insights provided such as shutdown risk, but did not identify any problems. The panel noted that for fire considerations that there is a fire suppression system in the rooms. The panel voted unanimously each segment as Low Risk significant.
Main Steam The system overview was read to the panel (attached).
MS-001, 002, 003: These segments were found to be numerically low risk significant. The panel noted that these segments were located inside containment and had a low failure probability. The panel voted unanimously each segment as Low Risk significant.
MS-004, 005, 006, 007, 008, 009, 016, 017, 018, 019, 020, 021: These segments were found to be numerically low risk significant. The segments are found in the 1,llain steam valve house. The consequence of failure is affected by indirect effects on components within the building. The panel discussed the potential of loss of suction to the high head safety injection pumps due to the MSLB in the main steam valve house. It was pointed out that the RWST crosstie would still provide a water source to the high head pumps. The failure probability based upon large leak (500gpm) was considered low. The leak would need to approach rupture to account for this type consequence Qoss of high head suction) driving the failure probability even lower. The consequence was already high based upon the indirect effects already assigned. The panel voted unanimously each segment as Low Risk significant.
MS-010, 011, 012, 013, 014, 015: These segments were found to be numerically low risk significant.
The consequence of failure would again result in indirect effects inside the main steam valve house. The lines being smaller had a higher failure probability as a result of wastage due to the erosion/corrosion failure mechanism. The panel noted that an augmented program already addressed this failure mechanism. The panel voted unanimously each segment as Low Risk significant but maintenance of the F AC program was required.
MS-022, 023, 024, 025, 026, 027, 028: These segments were found to be numerically in the grey area (CDF OA). The segments were assigned a relatively high failure probability based upon the erosion/corrosion failure mechanism. The segments are in the station's augmented program for this mechanism. The panel noted that flow to the terry twbine was associated with the pump test. They also noted that the NRV-I02s were normally closed. The panel voted unanimously each segment as Low Risk significant but maintenance of the FAC program was required.
MS-029, 030, 031, 035, 036, 037: These segments were found to be numerically low risk significant.
The segments had a slightly lower failure probability from those directly above. The panel voted unanimously each segment as Low Risk significant but maintenance of the F AC program was required.
MS-032: The segment was found to be numerically in the grey area (CDF OA). The panel noted that loss of the segment would result in a three (all) steam generator cooldown. The panel was not comfortable
- with the potential reactivity change in the reactor that could result. The panel voted unanimously each segment as High Risk significant and maintenance of the FAC program was required. *
, MS-033, 034: These segments were found to be numerically high risk significant (CDF OA, LERF OA).
The panel discussed the high failure probabilities and determined that they were realistic even when considering the on-off nature of pump operation. The panel voted unanimously each segment as High Risk significant and maintenance of the F AC program was required.
MS-038: The segment was found to be numerically low risk significant. The segment consequence was considered low as the segment is located primarily in the turbine building. The segment did have a high
)-
e failure potential from erosion/corrosion. Low Risk significant but maintenance of the FAC program was required.
The next meeting of the panel was scheduled for September 18, 1997, Thursday at 8:30am. at Surry.
The meeting was closed.
Respectfully submitted, a1ut,m.M Alex McNeill Secretary App~oyed by,
)f' /' /
f:. L:. I~ -./j;;,... __..:_ /.o Spencer Semmes 1
-:,* _ /
Acting Chairman I>'/ " * " t',- * *,
IC/? -::;;,/17
~-'
)
- * -i,*
e Surry Unit l Risk Informed Expert Panel Meeting Minutes 9/18/97 The following expert panel members were in attendance:
Spencer Semmes (Designated Chair and alternate System Engineer), Jim Simpson (Ops Primary), Nitin Shah (Engineering Mechanics), Les Spain (Materials/Failure Lab). Additionally alternates John Paul (ISI), Dave Bucheit (PSA) were present. The required quorum was met.
The following guests were in attendance at the meeting:
Alex McNeill (appointed secretary for the expert panel), Nancy Closky (Westinghouse), Ken Balkey (Westinghouse), Dick Haessler (Westinghouse)
The purpose of the meeting was to continue the Risk Informed ISi expert panel evaluation process.
. The system overview was read to the panel (attached).
The panel discussed the containment spray design basis versus the requirements found in the PSA based upon best estimate for overpressure. The best estimate allows for more time at overpressure conditions.
The panel discussed the short and long term effects oflack ofNaOH introduction and it's lack of modeling in the PSA.
CS-001, 002: These segments were found to be numerically in the grey area (CDF OA). The failure
- probability was considered to be conservatively high based upon pitting. The panel noted that the segment was constantly at pressure from normal RWST head. The panel noted that leakage would be identified based upon RWST level monitoring. The panel voted unanimously each segment as Low Risk significant.
CS-003, 004: These segments were found to be numerically low risk significant. The segments have sensitized stainless steel piping sections. The failure probability was adjusted to credit the augmented inspection program for sensitized stainless steel. The failure probability is considered low as a result. The panel voted unanimously each segment as Low Risk significant, but maintenance of the augmented inspection program is required.
CS-005, 006: These segments were found to be numerically in the grey area (CDF No OA, LERF No OA). The segments have a low failure probability. They are tested as part of the type C (appendix J) program. The panel voted unanimously each segment as Low Risk significant.
CS-007, 008: These segments were found to be numerically in the grey area (LERF OA). The segments have a low consequence of failure. The concern for the Containment Spray system from a PSA inJpact is delivering the RWST water to containment. These segments are entirely in containment and failure would only deliver water inside containment. The panel voted unanimously each segment as Low Risk significant, but maintenance of the augmented inspection program is required.
CS-009: The segment was found to be numerically low risk significant. The panel noted the discussion for CS-007 & 008 applied to this segment. The panel voted unanimously the segment as Low Risk significant.
CS-010, 011, 012: These segments were found to be numerically low risk significant. The PSA modeled minimal consequences offailure for these segments (CS-010 & 011 are part of the test line and CS-012 is associated with the CAT). The panel voted unanimously each-segment as Low Risk significant.
~--*
L" I e
CS-013, 014: These segments were found to be numerically low risk significant. The segments deliver water to the recirculation spray pumps to assure net positive suction head. The segments have a low failure probability. The panel voted unanimously each segment as Low Risk significant.
CS-015, 016: These segments were found to be numerically low risk significant. The segments are part of the RWST cooler subsystem. The simplified drawing prepared for the panel was determined to be incorrect. The panel directed the drawing be corrected. The panel voted unanimously each segment as Low Risk significant.
Safety Injection (accumulators)
The system overview applicable to the accumulators was read to the panel (attached).
ACC-001, 002, 003, 004, 005, 006, 007, 008, 009, 010, Oll, 012, 013, 014, 015, 016: These segments were found to be numerically low risk significant. The segments are pressurized using nitrogen as part of the passive accumulator function. The accumulators are pressurized to approximately 660 psig. and are individually alarmed in the control room if leakage occurs resulting in pressure loss. The consequence of loss is low due to the redundancy of the accumulators. The panel voted unanimously each segment as Low Risk significant.
Safety Injection (common low head & high head segments)
The system overview applicable to the common SI segments was read to the panel (attached).
ECC-000: The segment was found to be numerically low risk significant. The Panel was concerned about,
the failure of the line resulting in a common mode failure of Low Head and High Head SI. A question was asked about segments CS-001 & CS-002 previously discussed as to whether the concern should be assigned to those segments also. The panel indicated that loss of the CS segments would still allow some SI flow where as loss ofECC-000 would result in an instantaneous loss. The panel voted unanimously the segment as High Risk significant.
ECC-001, 002, 003, 005, 006, 007: These segments were found to be numerically low risk significant.
The panel identified that the low numerical ranking was based upon qualitative insights (3 train redundancy) as the PSA does not model each individual SI train. Additionally the panel identified that _
the segments are separated from high risk significant segments (RC-041, 042, 043 & RC-016, 017, 018) by a single check valve. The potential for a common mode failure was discussed. The failure probability was high based upon thermal stratification concerns developing from a leaking check valve. The panel voted unanimously each segment as High Risk significant.
ECC-004: The segment was found to be numerically low risk significant. The panel noted that loss of the segment would result in loss of all hot leg safety injection flow. The panel discussed the use of the hot leg injection flow paths and the consequences of loss. The path is not used until later in the accident sequence. It was pointed out that an augmented inspection program for sensitized stainless steel was in place and would not be affected by this program. The panel voted unanimously the segment as Low Risk significant, but maintenance of the augmented program was required.
Safety Injection (high head segments)
The system overview applicable to the high head SI segments was read to the panel (attached).
HID-001, 002: These segments were found to be numerically low risk significant. The consequence of failure was described as high, however the failure probability was moderate due to snubber malfunction.
The panel noted that similar concerns expressed for ECC-000 would apply to these segments. The panel voted unanimously each segment as High Risk significant.
~~i HHI-003: The segment was found to be numerically low risk significant. The consequence offailure was again was described as high. The panel discussed leak detection capability. Again the panel was concerned about loss of SI flow. The panel voted unanimously the segment as High Risk significant.
HHI-004.A, 005.A, 006A: These segments were found to be numerically in the grey area (CDF No OA, LERF No OA, LERF OA). The panel noted that leakage would be detectable (charging pump amps, operator walkdown) and easily isolated. Segment HHI-004A was included in the augmented program for sensitized stainless steel. The panel voted unanimously each segment as Low Risk significant.
HHI-004B, 005B, 006B, 007: These segments were found to be numerically low risk significant. The segments are located downstream of the flow restricting orifices which would minimize the consequence if failure occurred. The panel voted unanimously each segment as Low Risk significant.
HHI-004C, OOSC, 006C, 008, 009: These segments were found to be numerically low risk significant.
The panel was again concerned about loss of high head flow failure. The segments have no check valves allowing loss of all flow if any segment fails. The panel was not comfortable with a consequence resulting from interrupted high head flow. The panel voted unanimously each segment as High Risk significant.
HHI-010, 013: These segments were found to be numerically high risk significant (LERF OA, CDF OA).
The numerical results reflect a concern for indirect effects caused by the piping failure. The panel voted unanimously each segment as High Risk significant.
HHI-011, 014: _These segments were found to be numerically low risk significant. The panel again noted a concern associated with interrupted high head flow through segmented HHI-011. Segment HHI-014 is normally isolated. The panel voted unanimously segment HHI-011 as High Risk significant. The panel voted unanimously segment HHI-014 as Low Risk significant.
Hlll-012A: The segment was found to be numerically high risk significant (LERF OA, CDF OA). The segment had a high failure probability even with credit given to the augmented inspection program for sensitized stainless steel. The consequence of failure was loss of all high head injection to the cold legs (common header). The panel voted unanimously the segment as High Risk significant.
HHI-012B, 012C, Ol2D: These segments were found to be numerically low risk significant. The panel noted that the consequence was qualitatively assessed since the PSA did not model individual trains of SI.
The panel also noted that the failure probability should take credit fcir the augmented inspection program for sensitized stainless steel. The panel discussed the separation of these segments from the high safety significant segments on the RCS. Where as the ECC segments only had one check valve separation these segments had two check valves for separation. The panel voted unanimously each segment as Low Risk significant, but maintenance of the augmented inspection program was required.
HHI-015, 017: These segments were found to be numerically high risk significant (LERF OA, CDF OA).
The segments had indirect effects leading to a high consequence of failure. The panel noted that the consequence assumed may be conservative since these lines were for hot leg safety injection and components being failed for indirect effects may not be needed once hot let injection is used (approx. 8-9 hours after accident). It was explained that the consequence determination was based upon the possible need to use the lines (i.e., in use when fails). The panel voted unanimously each segment as High Risk significant.
HHI-016, 018: These segments were found to be numerically low risk significant. The segments provide hot leg safety injection water. The segments feed ECC-004 which was found to be low risk significant.
The panel noted that the consequence of failure was low, since cold leg injection remained. The panel voted unanimously each segment as Low Risk significant.
. t \\)'
\\.r~
______ :---------------------------*-----~--- ---
Safety Injection Oow head segments)
The system overview applicable to the low head SI segments was read to the panel (attached).
LHI-001,002: These segments were found to be numerically low risk significant. The segments had a low failure probability. Additionally there were two identical trains providing redundancy of capability.
The panel voted unanimously each segment as Low Risk significant.
LHI-003,004: These segments were found to be numerically low risk significant. The segments had a low failure probability. The panel noted that the segments were part of the containment boundary and that there was only a single isolation valve. The segment starts at the containment sump and there is no valve for isolation inside containment. The panel voted unanimously each segment as High Risk significant.
LHI-005,006: These segments were found to be numerically low risk significant. The panel discussed the same containment boundary issue (LHI-003,004). These segments are on the other side of the containment isolation valve. The panel decided thatthe segments were riot a containment boundary concern. The panel voted unanimously each segment as Low Risk significant.
LHI-007,008,009: These segments were found to be numerically low risk significant. The panel thought that the modeled consequence (loss of charging pump) was conservati\\_'e. The panel was more concerned with the potential loss of all low head safety injection since the segments are tied together by segment LHI-009. The panel noted that the drawing provided did not reflect the normally open valves (MOV-1864A & B). A break in either LHI-007, LHI-008 or LHI-009 would result in interrupted low head flow without operator intervention. The panel voted unanimously each segment as High Risk significant.
LHI-010: The segment was found to be numerically low risk significant. The panel noted that the segment failure will also cause a low head flow interruption. The panel noted that the drawing provided should indicate that the segment penetrates containment. The panel voted unanimously the segment as High Risk significant.
LHI-011,012: These segments were found to be numerically low risk significant. The panel noted that.
the segments are normally isolated providing low head injection to the hotlegs. The segments would not be used until 9 hours1.041667e-4 days <br />0.0025 hours <br />1.488095e-5 weeks <br />3.4245e-6 months <br /> aftex: the accident. The panel voted unanimously each segment as Low Risk significant.
LHI-013,014,015,016,017: These segments were found to be numerically low risk significant. The panel noted that the segments were used for pump recirculation when full flow was not required from the pumps. The panel noted that the segments could be isolated if leakage occurred, preventing potential release paths. The panel voted unanimously each segment as Low Risk significant.
LHI-018: The segment was found to be numerically low risk significant. The panel noted that the segment was surrounded by high risk significantsegments. The panel voted unanimously the segment as High Risk significant..
Component Cooling Water The system overview was read to the panel (verbal report given only, no written attachment).
The panel noted that the consequences and the failure probabilities were very similar throughout the system. The panel decided to address the numerically high and g~cy areas initially.
CC-025,030,033: These segments were found to be numerically high risk significant (LERF OA). The high consequence was driven by conservative modeling ofRHR requirements in a steam generator tube
- +/--~~--------- --- ----------------------.-------
rupture event. Component Cooling is the rum. system heat sink. The segments in question have previously developed problems due to vibration in the reactor coolant pump shroud cooling coil area. The failure probability was correspondingly high as a result. The panel noted containment integrity concerns associated with the system as credit is taken for no penetration of the membrane barrier of the system.
The panel voted unanimously each segment as High Risk significant.
. CC-003,004,005,006,007,008,038,039,054,055: These segments were found to be numerically in the grey area (LERF OA). The system is low pressure and low temperature. Again the consequence was driven by the conservative application ofRHR in a steam generator tube rupture event. The panel noted that leakage could be identified by surge tank level changes which is monitored and operator walkdowns. The segments can be isolated if problems develop. The panel voted unanimously each segment as Low Risk significant.
CC-Balance of Segments: These segments were found numerically low risk significant. The panel addressed these segments together to see if there were any concerns not addressed in the numerical results.
Segments CC-028A, 028B, and 029 were discussed with regard to a RCP thermal barrier accident. The segments will be potentially called on to withstand a one-time overpressurization (RCS pressure) in this event. The panel decided that assurance of the integrity of the segments would be desirable based upon the overpressurization requirement. The panel voted unanimously segments CC-028A, 028B and 029 as High Risk significant. The panel discussed the other segments, noting the plant was designed for hot shutdown. They discussed spent fuel pit cooling alternatives, as component cooling is the heat sink for that system. The panel voted unanimously each of the remaining segments as Low Risk significant.
Recirculation Spray A system overview was read to the panel (verbal report given only, no written attachment).
RS-001,002: These segments were found to be numerically low risk significant. The segments were located inside containment and appear to concrete encased. The failure probability was considered low and the consequence of failure was low. The panel voted unanimously each of the segments as Low Risk significant.
RS-003A,004A: These segments were found to be numerically low risk significant. The panel noted that the segments served as a containment integrity boundary. The segments had no isolation capability inside containment. The panel voted unanimously each of the segments as High Risk significant.
RS-005: The segment was found to be numerically low risk significant. The panel noted that segment is encased in concrete and did not have the same failure concerns as RS-003 & RS-004. The panel voted unanimously the segment as Low Risk significant.
RS-003B,004B: These segments were found to be numerically low risk significant. The panel noted that the segments are only used during testing of the pumps and that the segments had a low failure probability. The penetrations were tested as part of the Type C Appendix J program. The panel voted unanimously each of the segments as Low Risk significant.
- RS-007,008,009,010,0l l,012: These segments were found to be numerically low risk significant. The panel agreed with the low classification noting the low failure probability for this standby system. The panel voted unanimously each of the segments as Low Risk significant.
This concluded the original scope of the expert panel meetings. The panel directed a subpanel of Alex McNeill, Les Spain, Nitin Shah, and John Paul or Dave Dodson to select the actual examination locations I
j
~
f
~
and methods. The panel was reminded that this was a living process and their services may be required in the future. A future meeting will be scheduled to report the final results to the expert panel.
The meeting was closed.
Respectfully submitted, *
~W\\~
Alex McNeill Secretary Ap~J"e~ J>y, /
~-/_,~~-
Spencer Se~es
_--1:...=__,i Acting Chairman I> 1 /,-, ~ / c, :
- c.*/.7 ?le;/