3F0498-17, Submits Addl Info Clarifying post-LOCA Boron Precipitation Plan to Facilitate NRC Review of LAR 223,dtd 980227. Calculation 86-1266272-02, Post-LOCA Boron Concentration Mgt for CR-3, Encl
| ML20217G678 | |
| Person / Time | |
|---|---|
| Site: | Crystal River  |
| Issue date: | 04/24/1998 |
| From: | Grazio R FLORIDA POWER CORP. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| Shared Package | |
| ML20217G681 | List: |
| References | |
| 3F0498-17, 3F498-17, TAC-M99892, NUDOCS 9804290186 | |
| Download: ML20217G678 (6) | |
Text
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8 CORPORATION Finrida Power j
Dock N 56402 Operating LJcense No. DPR-72 l
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April 24,1998 3F0498-17 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555-0001
Subject:
Clarification of Post-LOCA Boron Precipitation Prevention - License Amendment l
Request #223 (NRC TAC Number M99892) - Crystal River Unit 3 l
References:
1.
FPC to NRC letter (3F0298-12) dated Febmary 27,1998, " Finalized Summary Report for License Amendment Request #223 - Post-LOCA Boron Precipitation Prevention (NRC TAC Number M99892)"
l 2.
FPC to NRC letter (3F1297-43) dated December 13,1997, " Additional j
Information on License Amendment Request # 220 - Revision of Operating l
License Condition 2.C.(5)"
j 3.
Babcock and Wilcox Owners Group to NRC letter dated March 27,1997,
" Post-LOCA Boron Concentration Management" (OG-1644) l
Dear Sir:
The purpose of this letter is to submit additional information to clarify the post-Loss of Coolant Accident (LOCA) boron precipitation prevention plan for the Crystal River Unit 3 Nuclear Generation Station (CR-3). This information is provided in response to telephone conferences with the NRC Staff held on March 5 and 25, and April 17, 1998, and is to facilitate NRC review of License Amendment Request (LAR) #223, Post-LOCA Boron Precipitation Prevention.
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Attachment A provides information regarding (a) implementation of boron precipitation prevention concurrent with a single failure; (b) use of the factor of safety in core boron concentration control limits; and (c) results of maximizing Auxiliary Pressurizer Spray (APS) flow. Attachment B is Florida Power Corporation (FPC) calculation M97-0146, Revision 2,
" Post-LOCA Boron Concentration Management for CR-3," with supporting Framatome Technologies Inc. (FTI) Document 86-1266272-02. The FTI report was revised from that i
submitted by Reference 1 in order to address modified APS flow alignment. Attachment C is a list of acronyms and abbreviations used in this submittal.
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Based on discussion with the NRC Staff, FPC understands that there is a remaining open issue g
with regard to satisfying single failure criterion when relying on active mitigation methods. FPC t
CRYSTAL RIVER ENFRGY COMPI FX-M7Rn w Power une Street a Crystal River, Flonda 34428-6708 * (352) 7954488 9804290186 980424 i Progress company PDR ADOCK 05000302 P
U.S. Nuclear Regulatory Commission 3F0498-17
- Page 2 of 2 is evaluating options that will lead to a timely resolution of this issue. One option is the work
. that the B&W Owners Group (BWOG) is pursuing to evaluate the core barrel flow holes as a passive method that will reliably prevent core boron precipitation. FPC is actively involved in discussing this option with the BWOG and ' monitoring progress of the work. It is FPC's understanding that the NRC Staff will be kept informed of the progress of the core barrel flow i
holes analysis by means of monthly updates by telephone from the BWOG. Completion of this-analysis is projected for early June 1998, at which time FPC desires a meeting with the NRC Staff to discuss issue resolution.
There are no new commitments made in this submittal. If you have any questions regarding this submittal, please contact Ms. Sherry Bernhoft, Manager, Nuclear Licensing at (352) 563-4566.
Sincerely, YW R. E. Grazio
/
l Director Nuclear Regulatory Affairs REG:rer xc:
Regional Administrator, Region II NRR Project Manager -
Senior Resident Inspector Attachments:
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'A.
Response to NRC Request for Additional Information Regarding Post-LOCA Boron j
Precipitation Prevention Submittal l
B.
FPC Calculation M97-0146, Revision 2
" Post-LOCA Boron Concentration Management for CR-3," with supporting FTl Document 86-1266272-02 C.
Acronyms and Abbreviations j
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r U.S. Nuclear Regulatory Commission Attachment A 3F0498-17 Page 1 of 4 l
ATTACHMENT A RESPONSE TO NRC REQUEST FOR ADDITIONAL INFORMATION REGARDING POST-LOCA BORON PRECIPITATION PREVENTION SUBMITTAL CRYSTAL RIVER UNIT 3 NUCLEAR GENERATION STATION i
NRC Reauest #1 Provide additional discussion regarding the ability of CR-3 to initiate an active method of core boron concentration control in the event of a single failure. This discussion should include the credible single failure (s), the process for repairing or repowering affected components, and the expected duration of any corrective actions.
FPC Response The following clarifies CR-3's position on single failure as discussed in FPC's February 27, 1998 submittal (Reference 1). The following discusses some conservati:ms inherent in the analyses that would provide time to repair a single failure before precipitation becomes a concern, and concludes with a description of a common mode single failure that renders both active dilution methods unavailable.
l The Reference 1 submittal discussed CR-3's position on addressing single failures. In that submittal, it was stated that teams would be dispatched to repair a failure (e.g., ES MCC-3AB motor control center) when it becomes apparent that such a failure has occurred, even well before boron precipitation becomes a concern. This position is unchanged. The dilution mechanism provided by the hot leg nozzle gaps was only mentioned in the context that its operation can be realistically expected during the time of repair. It is important to note that the analyses performed take no credit for any dilution flow that could be realistically expected from I
the gaps or reactor vessel vent valve (RVVV) overflow.
In addition to neglecting any benefit from gap flow, the analysis in the submittal has other inherent conservatisms to ensure that time will be available to address any single failure. For example, as discussed in Reference 3, the boron solubility curve (precipitation concentration as a function of Reactor Coolant System (RCS) saturation temperature) used in the analysis is
)
assumed to be based on pure boric acid (H BO ). No credit is taken for the presence of buffer 3
4 compounds, such as trisodium phosphate (Na3PO ), which tends to increase the solubility limit.
4 This would have a beneficial effect in that it would increase the available time to act.
l The times involved for boron precipitation control are discussed in the demonstration cases provided in Section 5.4 of FPC Calculation M97-0146, both Revision 1 (provided as Attachment B of Reference 1) and Revision 2 (provided as Attachment B of this submittal). These case studies examine LOCA scenarios and how each could be managed with the Technical Support Center (TSC) guidance. Despite the inherent conservatisms, the studies indicate that time would be available before initiation of an active method would be needed.
b.h. Nuclear Regulatory Commission Attachment A 3F0498-17 Page 2 of 4 There is a common mode single failure that would temporarily result in both active post-LOCA core boron dilution methods being unavailable. The failure of Engineered Safeguards (ES) motor control center ES MCC-3AB could de-power valves that must be opened to initiate either the Auxiliary Pressurizer Spray (APS) method or the drop line to the Reactor Building Sump (DIeRB Sump) method. This single failure cannot be accommodated by means of system design redundancy, rather, manual repair actions would be needed. In the event of this very unlikely single failure FPC will repower ES MCC-3AB and valves (e.g., RCV-53) from an alternate source. Emergency Plan Implementing Procedure EM-225B, " Post-Accident Boron Concentration Management," contains the necessary guidance for repowering the MCC and nives. A risk evaluation performed by FPC indicates that the frequency of this failure mode, in combination with the postulated accident scenario, is extremely low, having an order of magnitude of 104 / year.
Given these considerations, the measures that FPC has taken to ensure that its post-LOCA boron precipitation management strategy will be successful are considered to be adequate.
NRC Reauest #2 Provide discussion of whether the 25% safety factor margin in the core boron concentration curves is addressed in the analysis provided in FPC's letter dated February 27,1998, and how it is incorporated into the implementing procedures.
FPC Response The December 13,1997 submittal (Reference 2) included an analysis that should be considered a design basis analysis. The 25% safety factor was not included in the figures provided in the analysis. Instead, the factor was included in the figures for the implementing procedure, EM-225B, which would be used by the TSC for post-LOCA boron precipitation prevention management.
The February 27,1998 submittal (Reference 1) included the safety factor, as reflected in Table 4 of FTI document 86-1266272-02 (FPC calculation M97-0146, Revision 2). FPC requested preparation of Table 4 to concisely document the key input assumptions and variables for the analytical effort. As such, the sump concentration difference curve in the analyses conservatively reflects the application of the safety factor. The curve has been incorporated into EM-225B.
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U.S. Nuclear Regulatory Commission Attachment A 3F0498-17 Page 3 of 4 NRC Reauest #3 Determine the benefit that can be derived from the following configuration: A and B low pressure injection (LPI) trains operating, DHV-5 closed, and the A-train only providing high pressure injection (HPI) and APS flow. This configuration helps to maximize APS flow and may increase APS effectiveness. It also addresses a single failure on the decay heat drop line.
FPC Response A hydraulic analysis was performed to determine the flow characteristics of this configuration.
The system alignment is shown in Figure 1. The results were then provided to FTI as input to the actual boron precipitation analysis. The results of this analysis showed that with Appendix K assumptions (1.2 multiplier on ANS 1971 decay heat standard), this configuration can provide adequate boron dilution any time after a minimum of 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />. In comparison, if only the A LPI train is operating, adequate dilution is available after a minimum of 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />. Figure 11 of FPC Calculation M97-0146, Revision 2, with FTI document 86-1266272-02, (provided as Attachment B) shows the associated effectiveness curve for this configuration. As a further comparison, the configuration provides full APS effectiveness for realistic decay heat (1.0 multiplier). This is best illustrated in Figure 12 of FPC Calculation M97-0146, Revision 2.
Although a benefit can be derived from this configuration (i.e., DHV-5 closed), a single failure of ES MCC-3AB concurrent with the initiation of any active method would require time to complete repairs, as discussed in the response to Request #1. However, also discussed in the calculations are the conservatisms assumed in the supporting analysis, including no credit for any passive dilution mechanisms (i.e., hot leg nozzle gap or RVVV overflow). These conservatisms, in addition to procedural measures to facilitate single failure mitigation, provide reasonable assurance of long term cooling availability.
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U.S. Nuclear Regulatory Commission Attachment A 3F0498-17 Page 4 of 4 FIGURE 1 Auxiliary Pressurizer Spray (Flow Schematic)
DHV-5 closed,2 LPI Trains Operating m
(Flow path is indicated by dashed line)
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