ML20137G861
| ML20137G861 | |
| Person / Time | |
|---|---|
| Site: | 05200003 |
| Issue date: | 03/21/1997 |
| From: | Mcintyre B WESTINGHOUSE ELECTRIC COMPANY, DIV OF CBS CORP. |
| To: | Quay T NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| CON-NRC-NSD-97-5034, RTR-REGGD-01.097, RTR-REGGD-1.097 NUDOCS 9704010552 | |
| Download: ML20137G861 (5) | |
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l Westinghouse Energy Systems Itjs[]Eh Pennsylvania 15230-0355 3
Electric Corporation NRC-NSD-97-5034 DCP/NRC0781 Docket No.: STN-52-003 March 21,1997 Document Control Desk U. S. Nuclear Regulatory Commission i
Washington, DC 20555 ATTENTION: T. R. QUAY
SUBJECT:
Response to AP600 SSAR Chapter 18 Minimum Inventory NRC Review Comments
Dear Mr. Quay:
Attached are the Westinghouse responses to NRC questions regarding categorization of the steam i
generator wide range level variable and meeting R.G.1.97 for the letdown radiation monitor. These i
questions were asked during the NRC review of minimum inventory requirements in AP600 SSAR Chapter 18 and relate directly to SSAR Chapter 7. The attached response closes OITS item 5027 as shown on the attached OITS report, where Westinghouse status is Closed and NRC status is Resolved, as discussed in a telephone call with Mr. Iluffman on March 21,1997.
Please contact Robin K. Nydes at (412) 374-4125 if you have any questions regarding this letter or SSAR Chapters 7 or 18.
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Brian A. McIntyre, Manager Advanced Plant Safety and Licensing jml Attachment cc:
W. C. Iluffman, NRC (w/ Attachment)
N. J. Liparulo, Westinghouse (w/o Attachment)
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NRC Question:
"Should steam generator wide range level be a D1 or a D2 variable? What is the basis for leaving it as a D2 or making it a Dl? And, should it also be a B variable (it is noted as an Al in PAMS for Vogtle); why or why not?"
i Westinghouse Response:
The Westinghouse position for post-accident monitoring (PAMS) variables is that there are no Category 1, Types D n iables. This position has been accepted by the NRC and licensed for Westinghouse PWRs.
The basis for this approach is that when considering all PAMS variables, Type D variables j
fundamentally provide indirect or backup indication related to the satisfaction of true design safety goals, identified as critical safety functions and fission product barrier challenges that are monitored by Type B and C variables. From this overall perspective, the Type D variables provide backup indication to the Type B and C variables, by monitoring the operation of l
safety-related systems and equipment that are used to achieve the critical safety functions and protect the fission product barriers.
If no Type D variables were available'following an event at a Westinghouse PWR, the operators would still have the total inventory of Category I and 2, Type B and C variables to directly monitor the status of the entical safety functions and the fission product barriers. In addition, the Type B and C variables indirectly confirm the satisfactory operation of the safety-related systems (that are used to achieve the critical safety functions and protect the fission product barriers) monitored by the Type D variables.
The inventory of Type D variables in Westinghouse PWRs essentially serve as " backup indications" for the more important Type B and C variables. Therefore, the Westinghouse approach, which has been accepted by the NRC, is not to mandate the imposition of Category 1 design requirements for Type D variables which only monitor the operation of the safety-related systems and equipment. (The primary differences between Category 1 and ?
variables are related to classification of power supplies, seismic qualification, and single failure response.) Therefore, there have been no D1 variables for the Westinghouse plants.
SG wide range level is not a Type B variable for the AP600 for two reasons. First, the design of the AP600 is fundamentally different from current plants where SGs and auxiliary feedwater provide the core heat sink and SG level.is used to monitor the status of this heat sink.
For AP600, the Passive Residual Heat Removal heat exchanger (PRHR Hx), not the SGs, is the safety-related heat sink. There is no safety-related Auxiliary Feedwater System in the AP600. The startup feedwater system that provides steam generator feedwater is nonsafety-related and does not provide the design basis heat sink monitored by the Type B variables for the AP600. The PRHR Hx parameters (such as flow and outlet temperature) and IRWST level are the AP600 B1 variables used to monitor the status of the safety-related heat sink. These are listed in SSAR Table 7.5-5 for heat sink, equivalent to the SG level and associated variables (auxiliary feedwater flow, etc.) in current plant PAMS.
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' a Secondly, SG wide range level could be considered a Type B variable for monitoring RCS inventory (e.g., to monitor for SG overfill following a SG tube rupture event with the SG safety valves sticking open). Some older plants have included SG wide range level as a Type B variable under RCS inventory. However, the current licensing approach approved by the NRC for recent plants.does NOT list SG wide range level as a backup variable for RCS inventory.
Westinghouse has adopted the most current licensing approach for AP600 and, therefore, SG wide range level is NOT included as a Type B variable for RCS ir,ventory control.
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NRC Question:
"How does Westinghouse meet R.G.1.97 on the letdown radiation monitor?"
Westinghouse Response:
Table 2 of RG 1.97 identi6es the following variables to monitor for a fuel cladding Gssion product barrier breach during and following an accident:
Core Exit Temperature (Type C, Category I) a Radioactivity Concentration or Radiation Level in Circulating Primary Coolant a
(Type C, Category 1)
Analysis of Primary Coolant (Type C, Category 3)
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The AP600 specines the following post-accident monitoring variables for fuel cladding barrier integrity:
Core Exit Temperatures (Type C, Catesory I)
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Analysis of Primary Coolant (. manual sample)(Type C, Category 3)
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l The AP600 takes credit for measurement of primary coolant radioactivity levels in the analysis of the primary coolant and does not speci6cally include this second item in the RG 1.97 PAMS variables. This is consistent with the approach licensed in other recent Westinghouse plants.
Traditionally, nuclear power plants designed by Westinghouse have taken exception to the second item in RG 1.97 as a PAMS variable and this has been accep'ed by the NRC in the most recent licensing submittals. In particular, recent plants have not included the
" radioactivity concentration or radiation level in circulating primary coolant" as a separate PAMS variable. Instead, they have taken credit for the primary coolant analysis to determine the " radioactivity concentration in circulating primary coolant."
These recent plants include another backup variable, Reactor Vessel Level Indication (RVLIS) as a backup indication to monitor for fuel cladding breach. Comparably, the AP600 has reactor vessel-hot leg water level indication that is used as a Type B, Category 2 variable for Reactor Core Cooling and a Type B, Category 3 for Reactor Coolant Inventory Control. This
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. variable is not identified as a Type C, Category 2 variable for monitoring Fuel Clad Breach i
since it cannot be used to satisfy the monitoring requirement associated with radioactivity levels in the coolant. While hot leg level can function as a backup to indicate potential to establish conditions where a cladding breach could develop, as in current plants that use RVLIS, hot leg level need not be included as a Type C variable in the AP600 PAMS since primary sampling is an adequate backup indication to core exit thermocouples.
Further, as discussed during a recent Westinghouse /NRC telecon, AP600 does not have a radiation monitor in the purification loop (equivalent to the chemical and volume control system letdown line in current plants). While some Westinghouse plants have a radiation monitor installed in the letdown line for the chemical and volume control system, this monitor is unavailable to provide post-accident indication for current plants since the letdown line has safety-related automatic isolation following certain design basis plant events. Therefore, this monitor cannot be credited for post-accident monitoring of circulating reactor coolant radioactivity levels.
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AP600 Opea item Trcckirg Sytt:m Dat base: Execttive S:mmary '
prtr: 3/26/97 Selection:
l item no] between 5027 And 5027 Sorted by item #
Item
' DSLR Seuion/
Title / Description Resp (W)
NRC
=
No-Branch Question Type Detail Status Engineer Status Status i.etter No /
Date 5027 NRR/litCB 7.5 M fG-OI Nydes Closed Resolved l1he steam generator wide range level instrument is considered a D2 variable in the AP600 SSAR Should it be a Dl? Should it also be a B?
hcam deseloping respcnse to be issued by >/14. rkn 3/l187 Response provided by Iax on 3/19 for NRC concurrence prior to formal issuance. rkn 3/21 Via 3/21 telecent with Bill IlutTman NRC concurs with response. Comments incorporated into formal submittal provided in NRC.NSD-97-5034.
NRC status changed to Resolved. rkn 3/25B7
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