ML20135D270
| ML20135D270 | |
| Person / Time | |
|---|---|
| Site: | 05200003 |
| Issue date: | 12/06/1996 |
| From: | Martin T NRC (Affiliation Not Assigned) |
| To: | Liparulo N WESTINGHOUSE ELECTRIC COMPANY, DIV OF CBS CORP. |
| References | |
| NUDOCS 9612090316 | |
| Download: ML20135D270 (12) | |
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Decesaber 6,1996 l
Mr. Nicholas J. Liparulo, Manager Nuclear Safety and Regulatory Activities Nuclear and Advanced Technology Division Westinghouse Electric Corporation P.O. Box 355 Pittsburgh, Pennsylvania 15230 i
SUBJECT:
LIST OF KEY LICENSING ISSUES ON THE AP600 DESIGN
Dear Mr. Liparulo:
The staff has updated its March 1995, list of issues that it believes are l potential critical path issues on the design of the AP600. Enclosed is the l list with a description of the issue and the lead Nuclear Regulatory Commis-sion review branch.
The staff will work with Westinghouse to develop a common list to be used to monitor the progress of issue resolution in the months ahead. This list is a "living document," that will change as resolutions of issues are reached or new issues are identified. We are forwarding you this list so that we can l better focus our attention on obtaining prompt resolution of these issues.
If you have any questions, you can call Tom Kenyon at (301) 415-1120.
Sincerely, original signed by: Dave B. Matt 1xws I
l Thomas T. Martin, Director Division of Reactor Program Management !
Office of Nuclear Reactor Regulation i Docket No.52-003
Enclosure:
As stated cc w/ enclosure:
See next page DISTRIBUTION:
l See next page ff DOCUMENT NAME: S; TOP 30.LTR (9J AP600 DISK) !
T2,eceive a copy of this doperment. iracete in the bon: "C" = Copy without attechmeh6:@h se 'E' = Copy wth attechmentlenclosure *N' = No copy 0FFICE PM:PpSTYDRPM D:PDST:D8PK D:DR$M/ f l l l NAME TJK6nybn:sg TRQuay Wrd TTMartin JA Y~
l DATE 12/3196 12/)/96 12/b /96 V l OFFICIAL RECORD COPY l
l 9612090316 961206 l
PDR ADOCK 05200003 ,,
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Mr. Nicholas J. Liparulo Docket No.52-003 Westinghouse Electric Corporation AP600 cc: Mr. B. A. McIntyre Mr. Ronald Simard, Director Advanced Plant Safety & Licensing Advanced Reactor Programs Westinghouse Electric Corporation Nuclear Energy Institute
, Energy Systems Business Unit 1776 Eye Street, N.W.
l P.O. Box 355 Suite 300
! Pittsburgh, PA 15230 Washington, DC 20006-3706 l
l Mr. John C. Butler Ms. Lynn Connor l Advanced Flant Safety & Licensing Doc-Search Associates l Westinghouse Electric Corporation Post Office Box 34 l Energy Systems Business Unit Cabin John, MD 20818 l Box 355 l Pittsburgh, PA 15230 Mr. James E. Quinn, Projects Manager l LMR and SBWR Programs Mr. M. D. Beaumont GE Nuclear Energy Nuclear and Advanced Technology Division 175 Curtner Avenue, M/C 165 l
Westinghouse Electric Corporation San Jose, CA 95125 One Montrose Metro 11921 Rockville Pike Mr. Robert H. Buchholz l Suite 350 GE Nuclear Energy i
Rockville, MD 20852 175 Curtner Avenue, MC-781 San Jose, CA 95125
- Mr. Sterling Franks l U.S. Department of Energy Barton Z. Cowan, Esq.
l NE-50 Eckert Seamans Cherin & Mellott l 19901 Germantown Road 600 Grant Street 42nd Floor l Germantown, MD 20874 Pittsburgh, PA 15219 l
l Mr. S. M. Modro Mr. Ed Rodwell, Manager Nuclear Systems Analysis Technologies PWR Design Certification Lockheed Idaho Technulogies Company Electric Power Research Institute Post Office Box 1625 3412 Hillview Avenue Idaho Falls, ID 83415 Palo Alto, CA 94303 i Mr. Frank A. Ross Mr. Charles Thompson, Nuclear Engineer 4 i
U.S. Department of Energy, NE-42 AP600 Certification '
Office of LWR Safety and Technology NE-50 19901 Germantown Road 19901 Germantown Road j Germantown, MD 20874 Germantown, MD 20874 l
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! Consolidated AP600 " Key Issues" List I November 26, 1996 l 1. Content of the SSAR (All branches)
J 10 CFR 52.47(b)(2)(1) states that Certification of a standard design which.... utilizes simplified, inherent, passive, or other innovative means to accomplish its safety functions will be granted only if....
! (4) The scope of the design is complete except for site-specific elements....
The staff has stated that applications for the evolutionary and passive l LWRs must be for an essentially complete plant. SECYs-90-241 and 90-377, l and the subsequent February 15, 1991 SRM, address the level of detail required for the staff to complete its safety review.
Between March and August 1996, Westinghouse removed design information from the AP600 SSAR that had been approved in the 1994 DSER without prior notification. In addition, Westinghouse has notified the staff that it l no longer intends to include responses to RAls as a separate section of the SSAR. Because of the amount of missing information, the staff no i longer believes that the AP600 design application is essentially com-l plete. The staff continues its rereview of the SSAR to ensure that I necessary information, including design descriptions, P& ids, and tables,
- that have either been removed or were never included are (re) inserted
! into the SSAR.
- 2. Regulatory Treatment of Non-Safety Related Systems (RTNSS) (SRXB lead) l l
The issue includes several related issues, including:
l a. Passive System Thermal-Hydraulic Performance Reliability (SRXB) l (Discussed in SECY-96-128, dated June 12, 1996) (see Item 21) i b. Acceptability of Baseline & Focused Probabilistic Risk Assessment l (SPSB,SCSB) l The staff is having difficulty coming to agreement on issues to
! achieve a Baseline PRA that the staff can approve. The Focused PRA l (basically a sensitivity study using the Baseline PRA where only the l passive safety systems work) effort should follow after an acceptable l Baseline PRA is approved.
- c. Adverse Systems Interactions (SRXB) (see Item 25)
- d. Post ~2 Hour Support Actions (Discussed in SECY-96-128, dated June 12, 1996) (SRXB) (see Item 9)
Enclosure l
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, e. Safe Shutdown End-State (Discussed in SECY-96-128, dated June 12, 1996) (SRXB, OTSB) (see Item 19)
- f. Other RTNSS Concerns protection of RTNSS and Defense-in-Depth systems from internal and external floods, internally-generated missiles (inside and outside containment), externally-generated missiles and missiles generated by natural phenomena, and pipe failures. '
The staff needs to define the criteria for what type of oversight is appropriate for a system that falls under the RTNSS process.
- 3. Inspections, Tests, Analyses, and Acceptance Criteria (ITAAC) (All branches)
The ITAAC for passive safety systems include inspection of the as-built system configuration (sizing and elevation); functional testing to verify isolation valve operation upon receipt of actuation signals, valve stroke time and valve operation at design differential pressures, tests to verify correct divisional power supply to each valve; hydraulic test to determine piping flow resistance; and heat removal performance test for PRHR heat exchanger heat transfer rate. The AP600 is the first passive plant for ITAAC development. Westinghouse submitted a complete replace-ment for the ITAAC on November 7, 1996. It appears that Westinghouse has :
taken a significantly different approach from that of the evolutionary LWRs based on the staff's preliminary review. The staff has the follow-ing preliminary concerns with the ITAAC:
- a. Certain phenomena such as natural circulation, need a heat source for proper testing. Because ITAAC are performed before fuel loading, the staff needs to evaluate the relationship between ITAAC, Chapter 14 initial tests, and the vendor's test program, including scaling effects,
- b. The passive systems that have relatively small driving forces are sensitive to certain parameters, such as (1 'effect of relative elevations and piping configurations on grav)ity injection and natural circulation capability, and (2) effect of surface roughness, coating, striping, and water coverage on the containment exterior shell on passive containment cooling system heat transfer capability. West-inghouse will need to perform sensitivity analyses of these parame-ters to develop acceptable bands for ITAAC verification.
- c. ITAAC will have to be developed for certain non-safety-related defense-in-depth systems based on their importance to the safe operation of the plant.
- d. Inconsistencies with the evolutionary plant precedents need to be addressed by Westinghouse.
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The Instrumentation and Control-related ITAAC provided by Westing-house is not consistent with draft SRP Section 14.3. The needed detail has not been provided. i
- f. The Human Factors-related ITAAC provided by Westinghouse is not consistent with draft SRP Section 14.3. The needed detail has not j been provided.
Westinghouse proposes to apply LBB methodology to its feedwater piping system. The staff indicated in the DSER and a letter to Westinghouse dated November 4,1996, that this proposal was not acceptable, and that LBB should not be applied to the feedwater piping system.
- 5. Soil / Structure / Seismic Interactions (ECGB) ,
In its November 4,1996 letter, the staff informed Westinghouse that the AP600 seismic design capacity could be established through the use of a sufficient and necessary set of minimum seismic design response spectra
- by the COL applicant to complete its seismic desinn within the scope of the certified design. Suit- ability of a future site would then have to be established by demonstrating that the seismic demand spectra for the i site are lower than the capacity spectra. l I
- 6. Site-Soil Variability (Basemat) (ECGB) l l
Westinghouse is proposing to use a 6-foot thick basemat versus a typical l
10-foot or thicker structure. In its November 4, 1996 letter, the staff informed Westinghouse that the thinness of the basemat makes it unaccept- l able for the likely soil stiffness variability that can be reasonably 1 l expected to exist at a site.
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- 7. DBA Radiological Consequences (PCRB lead) I Westinghouse uses the EPRI source term for the AP600 10 CFR Part 100 calculations. Issues include
- fission product release fraction iodine chemical form aerosol deposition in containment pH control of water in containment
- use of floating window (Discussed in SECY-96-128, dated June 12, 1996, also see Section 15.3 of the DSER.)
- 8. Prevention and Mitigation of Severe Accidents (SCSB lead, PERB)
The AP600 does not have a containment spray, which could be used to reduce containment pressure and atmospheric radioactivity concentrations
. during a severe accident event. In lieu of a containment spray system, Westinghouse has proposed that natural processes for fission product removal, in combination with certain mitigative equipment, are sufficient for mitigation of the consequences of a severe accident. The staff disagrees, and has identified its concerns and potential alternatives in SECY-96-128, dated June 12, 1996. This matter is currently before the Commission for guidance.
- 9. Post-72 Hour Support Actions (SRXB lead)
The passive safety systems are designed with sufficient capability to mitigate all design basis events for 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> without operator actions and without non-safety-related onsite or o'fsite power. For long-term safety (post-72 hours), Westinghouse str.tes that the AP600 design includes safety-related connections for use with transportable equipment and supplies to provide the extended support actions for safety-related functions. These support actions include, for example, using portable engine-driven pumps and ac generators that connect to safety-related connections for water makeup to passive cooling control system (PCS) and spent fuel pool inventories and electrical power to supply the post l accident and spent fuel pool (SFP) monitoring instrumentation and air for control room habitability. In addition, these extended support actions are implemented as part of the combined license applicant's " Site Emergency Response Plan" to provide support for continued long-term operation of the passive safety systems. These actions are accomplished by the site support personnel, in coordination with the main control room operators, and are performed separate from but in parallel with other actions taken by the plant operators to directly mitigate the consequenc-es of an event. j In SECY-96-128, the staff stated that local communities struggling with !
disaster response should not be given the additional burden of providing l for nuclear power safety. In addition, the staff is concerned that equipment not under the plant operator's control may be susceptible to damage from environmental conditions. The staff recommended the Commis- !
sion approve the position that the site be capable of sustaining all '
design basis events with onsite equipment and supplies for the long term.
After 7 days, replenishment of consumables such as diesel fuel oil from offsite suppliers can be credited.
- 10. Containment Isolation (SCSB)
Many systems that have traditionally been safety-related systems are now non-safety-related systems in the AP600. Non-safety-related systems are typically automatically isolated on a containment isolation signal. The AP600 design does not isolate certain non-safety-related systems, such as the normal RHR. The staff is concerned with the potential for contain-l ment bypass because a non-safety-related system fails to isolate. (See DSER Open Items 3.11.3.1-1, 6.2.4.2-1, and 7.6.1-1.)
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t h . 11. Systems Reliability of Hydrogen Mitigation Systems (SCSB)
The AP600 design uses passive hydrogen recombiners for design-basis i
accident (DBA) hydrogen control. The staff is reviewing the acceptability of the design.
For severe accident hydrogen control, the AP600 relies on 58 igniters.
The staff is concerned with the adequacy of igniter coverage within the containment, and diversity of power supplies to the igniters. In a l November 4, 1996 letter, Westinghouse has proposed a modification to the design of the ac power supplies.
l 12. Fire Protection Program (SPLB) l l
The staff has identified four key issues pertaining to the fire protec-tion program for the AP600:
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- a. The staff is concerned that the containment fire water supply will compete with the water supply for the passive containment cooling I system.
- b. Zone-of-Influence Inside Containment - Westinghouse has not demon-strated that at least one shutdown path will be free of fire damage for a number of fire zones.
- c. Westinghouse has not provided an adequate technical bases for why SSE l is not needed to go to cold shutdown.
- d. The staff is concerned with smoke control for the AP600 design.
l l 13. Spent Fuel Pool Cooling System (SPLB)
The SFP cooling system is not safety-related and does not meet the alter-nate criteria of Section 9.1.3 of the standard review plan. Sec-tion 9.1.3 acceptance criteria for compliance with GDC 2 and 4 calls for
! a safety-related SFP cooling system, or a non-safety-related SFP cooling system with safety-related makeup and safety-related ventilation. The AP600 SFP cooling system is non-safety-related and has neither safety-related makeup or ventilation. Westinghouse states that the passive heat l capacity of the water in the SFP is sufficient to cool the spent fuel for
- 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. Non-safety-related makeup can be obtained from the IRWST or the demineralizer tank. (Discussed in SECY-96-128, dated June 12,1996)
- 14. Overspeed Protection l The staff believes that the AP600 design should include mechanical l overspeed protection for the turbine. Westinghouse believes that the electrical overspeed design that they propose is more reliable, and the AP600 design does not include a mechanical overspeed trip.
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- 15. Proposed AP600 Security Plan (PSGB)
Westinghouse has submitted a revised securi'< plan and vulnerability analysis employing a simplified safeguards concept using the plant structures as part of their security perimeters.
- 16. Initial Test Program (HQMS lead, All branches)
The staff believes that a rigorous initial test program (ITP) is required for the unique AP600 systems that are different from operating plants.
Revision 9 of the SSAR (August 9, 1996) substantially modifies the content, format, and approach for the AP600 ITP. Major concerns identi-fied thus far include:
- b. acceptability of Westinghouse's new approach for the criteria of SSCs to be tested versus that of Position C.2 of RG 1.68;
- c. treatment of SSCs not considered safety-related, defense-in-depth, or RTNSS-related;
- d. ensuring that the scope of the ITP captures all AP600 passive design !
features or those not present in traditional designs;
- e. the acceptability of test abstracts designated as first-plant-only by Westinghouse; and
- f. the acceptability of the ITP for water hammer in the secondary l systems.
- 17. Code Documentation and Qualification (V&V of Codes) Review Incorporating ;
Testing Data Results (SCSB/SRXB) '
The supplement to the DSER on Codes and Testing identified approximately 120 open issues concerning the AP600 testing and code validation program.
Although the reactor system code effort is currently on an acceptable path to resolution, the staff continues to identify many significant '
problems with the documentation for the WG0THIC containment analysis j code. ;
- 18. Chapter 15 Accident Analysis (SRXB lead) !
Although a preliminary Chapter 15 accident analysis was submitted by i Westinghouse, the final revision to the SSAR is not expected until '
February 1997. The staff continues to review Code V&V reports and other supporting documentation. Because the review of the codes took prece-
- dence ever the Chapter 15 review, there has been a hiatus in this area, j and many open items remain.
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- 19. Westinghouse's Proposed LC0 3.0.3 (OTSB)
In accordance with the staff's position in SECY-96-128, Westinghouse has proposed that, for unanticipated configurations, the safe shutdown end l state for the AP600 should be defined as MODE 5 (cold shutdown). In l addition, Westinghouse has agreed to include the use of the normal l
residual heat removal system (NRHR) in technical specification (TS) 3.0.3, in response to the staff's position for a " cold shutdown" l default state. However, TS 3.0.3 specifically (by design) excludes any statement about the availability or operability of the NRHR system or any of its necessary support systems (i.e., ac power, cooling water, etc.).
Although the staff concludes this is unacceptable, guidelines regarding l
' the type of regulatory controls that should be applied to these RTNSS-identified systems need to be established. (See Item 2, RTNSS) l l 20. Integrated Use of PRA Insights (lead SPSB, HQMB)
Westinghouse must use insights from the sensitivity, uncertainty, and importance analyses in an integrated fashion, in conjunction with assump-tions from the entire PRA, to identify design certification and opera-tional requirements (such as ITAAC, RAP, TSs, administrative controls, procedares) as well as COL and interface requirements. The staff has not l
l l yet received the insights chapter from Westinghouse (See DSER Open ~
l Item 19.1.3.1-26.)
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- 21. Passive System Thermal-Hydraulic Performance Reliability (formerly Passive System Reliability (SRXB)
Westinghouse has stated that the AP600 can respond in an acceptable j manner to risk-significant PRA accident sequences by using only passive safety systems and that as a result, no reguictory oversight of active,
! , non-safety-related systems is required. To support this statement, l Westinghouse has proposed using the NOTRUMP small-break loss-of-coolant-l accident (LOCA) computer code to perform sensitivity studies on accident sequences that are risk-significant in the focused PRA (which assumes no availability of active systems), using conservative, bounding inputs and assumptions, and to demonstrate thereby that there are large margins to core damage. The sequences to be analyzed will be selected using the MAAP4 computer code to " screen" sequences from the focused PRA. The margins approach is undertaken in lieu of attempting to quantify thermal-l hydraulic uncertainties in the PRA, related to passive system perfor-i mance.
! The staff has requested further information from Westinghouse detailing l how the approach will be implemented, including (1) complete documenta-l tion on how the NOTRUMP sensitivity analyses will be performed; (2) the i basis by which the risk-significant sequences will be screened and selected; and (3) documentation of and justification for the selection of the bounding parameters for the sensitivity analyses. The staff is continuing to discuss this issue with Westinghouse and to review Westinghouse's documentation. Westinghouse has also agreed to address
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how uncertainties associated with long-term cooling will be evaluated, ;
but the staff has not yet received any information related to this issue.
(Discussed in SECY-96-128, dated June 12,1996)
- 22. Shutdown and Low Power Operations (SPSB) i
, Experience with events occurring during shutdown operation indicates that
- substantial safety improvements are warranted for low power and shutdown operations. Westinghouse responses to RAls regarding the shutdown risk issue are mostly qualitative without quantitative analysis. The staff has also requested Westinghouse to provide a systematic evaluation of the AP600 design against the issues identified in NUREG-1449. Included in
' this issue is whether the proposed AP600 TS comply with SECY-93-190,
" Regulatory Approach to Shutdown and Low-Power Operations," and NUREG-1449, " Shutdown and Low Power Operation at Commercial Nuclear Power Plants in the United Stated." (See Section 19.1 of the DSER.)
- 23. External Cooling of the Reactor Pressure Vessel / Severe Accidents (SCSB/ECGB)
The AP600 is the first of the advanced plants to take credit for external cooling cf the reactor pressure vessel. The success (or failure) of this cooling mechanism has major implications concerning the progression of severe accident sequences. The staff's concerns include heat transfer correlations, reactor vessel insulttion, timing of flooding, and consid-eration of debris superheat and crust formation in the transient analy-ses. Because of its proposal, Westinghouse felt that they did not need to address severe accident issues raised by the staff in SECYs-90-016 and 93-087, including ex-vessel cooling, hydrogen, core retention, and core-on-the-floor issues. The staff disagreed. In SECY-96-128, the staff recommended that the Commission approve the position that Westinghouse use a balanced approach, involving reliance on in-vessel retention of the core complemented with limited analytical evaluation of ex-vessel-
, phenomena, to address the adequacy of the AP600 design for ex-vessel events. Westinghouse has since agreed to address ex-vessel phenomena, but this information has not yet been provided.
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- 24. Containment Bypass /SGTR (SRXB)
SECY-93-087, " Policy, Technical, and Licensing Issues Pertaining to Evolutionary and Advanced Light-Water Reactor (ALWR) Designs," required design certification applicants to assess design features to mitigate cont.ainment bypass due to : team generator tube rupture (SGTR) events, and recommended 3 fe:tures for consideration. Westinghouse provided an I
analysis of SGTR events involving up to 5-tube ruptures in August 1995.
Westinghouse provided a qualitative description of levels of defense available for SGTR events (AP600 systems / event operation matrix), and stated that its severe accident mitigation design alternatives (SAMDA) evaluation of design alternatives showed a risk reduction of 6.7E-4 man-rem /yr. None of the design alternatives provided a risk reduction that meets severe accident screening criteria. The staff will require Westinghouse to provide a detailed analysis and evaluation with respect
. to mitigating design features, diagnostic instrumentation, available time for operator actions, ERG, TS, and ITAAC. (See DSER Open_ Items 15.3.5-;
and 19.2.3.3-8.) '
- 25. Adverse Systems Interactions (SRXB)
Westinghouse should demonstrate that the AP600 design prevents adverse systems interactions between the non-safety-related systems and the safety-related systems. In addition, Westinghouse should demonstrate 4
that the AP600 is designed to prevent adverse systems interactions from water intrusion, internal floods, seismic events, and pipe ruptures.
Westinghouse has submitted WCAP-14477, "The AP600 Adverse Systems :
Interactions Evaluation Report," on which the staff has provided comments to Westinghouse. (See DSER Open Items 1.2.2.7-1, 7.3.2-1, and 20.2-5.)
- 26. Technical Specifications Review (OTSB)
Because issue preclusion for technical specifications is not provided by the design certification process, the staff must decide the extent of the i review that it will perform on Westinghouse's proposed Technical Specifi-cations.
! 27. Quality Classification of Systems (SPLB, ECGB)
Westinghouse proposes to use Quality Group E instead of Quality Group D for systems that could potentially contain radioactive material. This is not consistent with the SRP, and the staff does not believe that accept-
- able justification for deviation has been provided.