ML080660652
| ML080660652 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 03/06/2008 |
| From: | Gerald Bichof Dominion, Dominion Nuclear Connecticut |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| 07-0023A | |
| Download: ML080660652 (8) | |
Text
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Dominion Nuclear Connecticut, Inc.
\ 1il]s!lllll' Power Station
.:"" Dominion" l~, 'pc ITIT\' Road
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March 6, 2008 U. S. Nuclear Regulatory Commission Serial No. 07-0023A Attention: Document Control Desk NL&OS/MLC R2 One White Flint North Docket No. 50-336 11555 Rockville Pike License No. DPR-65 Rockville, Maryland 20852-2738 DOMINION NUCLEAR CONNECTICUT, INC.
MILLSTONE POWER STATION UNIT 2 RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION DELETION OF ECCS SUBSYSTEM TECHNICAL SPECIFICATION SURVEILLANCE REQUIREMENT 4.5.2.e In a February 20, 2007 letter (Serial No. 07-0023), Dominion Nuclear Connecticut, Inc.
(DNC) requested a change to the Millstone Power Station Unit 2 (MPS2) Technical Specifications to eliminate Surveillance Requirement 4.5.2.e. On February 15, 2008, the NRC forwarded a request for additional information (RAJ). The response to the RAI is provided in the attachment to this letter.
The information provided in this letter does not affect the conclusions of the Significant Hazards Consideration provided in DNC's February 20, 2007 submittal.
Should you have any questions about the information provided or require additional information, please contact Ms. Margaret Earle at (804) 273-2768.
Sincerely, t~!rn?c;6 VICKI L. HULL Vice President - Nuclear Engineering NotaIy N
- COINnOIaw.... of WIIfIICI COMMONWEALTH OF VIRGINIA Convntilion . . . . . MOy II, . . .
COUNTY OF HENRICO The foregoing document was acknowledged before me, in and for the County and Commonwealth aforesaid, today by Gerald T. Bischof, who is Vice President - Nuclear Engineering of Dominion Nuclear Connecticut, Inc. He has affirmed before me that he is duly authorized to execute and file the foregoing document in behalf of that Company, and that the statements in the document are true to the best of his knowledge and belief.
Acknowledged before me this & "'!' day of /;J(a/l.fA. J ,2008.
My Commission Expires: dltLy 3 4 ,JOto. K ~. /} I 1(/(/& ~,.=>4JdL.
Notary ublic
Serial No. 07-0023A Docket No. 50-336 Resp. to Request for Add. Info.
Page 2 of 2 Attachment Commitments made in this letter: None cc: U.S. Nuclear Regulatory Commission Region I 475 Allendale Road King of Prussia, PA 19406-1415 Mr. J. D. Hughey Project Manager U.S. Nuclear Regulatory Commission One White Flint North 11555 Rockville Pike Mail Stop 8C2 Rockville, MD 20852-2738 NRC Senior Resident Inspector Millstone Power Station Director Bureau of Air Management Monitoring and Radiation Division Department of Environmental Protection 79 Elm Street Hartford, CT 06106-5127
Serial No. 07-0023A Docket No. 50-336 ATTACHMENT RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION DELETION OF ECCS SUBSYSTEM TECHNICAL SPECIFICATION SURVEILLANCE REQUIREMENT 4.5.2.e MILLSTONE POWER STATION UNIT 2 DOMINION NUCLEAR CONNECTICUT, INC.
Serial No. 07-0023A Docket No. 50-336 Resp. to Request for Add. Info.
Attachment Page 1 of 5 RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION DELETION OF ECCS SUBSYSTEM TECHNICAL SPECIFICATION SURVEILLANCE REQUIREMENT 4.5.2.e NRC RAI By letter dated February 20, 2007 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML070510599) Dominion Nuclear Connecticut, Inc. (DNC), the licensee, submitted a request for changes to the Millstone Power Station, Unit No. 2 (MPS2) Technical Specifications (TS). The requested change would revise the Millstone Power Station, Unit No.2 (MPS2) TS to eliminate Surveillance Requirement (SR) 4.5.2.e from the TS.
The Nuclear Regulatory Commission (NRC) staff has reviewed the information the licensee provided that supports the proposed amendment and would like to discuss the following issues to clarify the submittal.
Background
The licensee's application dated February 20, 2007, makes the following statements that indicate that charging pump flow is not credited with mitigating any design basis accidents for MPS2:
a) Section 5.1 of Attachment 1 to the application states in the response to Question 1 of the "No Significant Hazards Consideration," that "[t]he [Final Safety Analysis Report] FSAR Chapter 14 accident analyses for MPS2 take no credit for the flow delivered by the charging pumps."
b) Section 5.2 of Attachment 1 to the licensee's application states that "the function of the charging pumps no longer satisfy the requirements of 10 CFR 50.36(c)(2)(ii) and consequently are no longer required to be addressed under [Limiting Condition for Operation] LCO 3.5.2."
c) Section 5.2 of Attachment 1 to the licensee's application states that "[t]he proposed change to delete SR 4.5.2.e and thereby the requirement for an OPERABLE charging pump as part of an [Emergency Core Cooling System]
ECCS subsystem, does not involve any modification to, or change in method of operation of, any system, structure or component required for safe operation of the facility or mitigation of design basis accidents assumed in the facility safety analysis."
Based on NRC staff review of Chapter 14 of the MPS2 FSAR, and contrary to the above statements in the application, it appears that charging pump flow is credited in the MPS2 accident analyses. Specifically, with respect to an
Serial No. 07-0023A Docket No. 50-336 Resp. to Request for Add. Info.
Attachment Page 2 of 5 inadvertent opening of a pressurizer relief valve event, Page 7 of FSAR Table 14.0.9-1, "Overview of Plant Systems and Equipment Available for Transient and Accident Conditions," lists the charging and Safety Injection System (SIS) as available equipment for this event. The asterisk note for Table 14.0.9-1 states, "All of the systems and equipment listed for an event would normally be available to mitigate the event consequences." In addition, the discussion for this event in FSAR, Section 14.6.1.6, states:
The charging and SISs have been shown to have sufficient capacity to easily compensate for the loss of primary coolant mass through the inadvertent opening of the pressurizer pressure relief valves. Therefore, the core is not expected to uncover during this event.
In addition, although not explicitly discussed in the accident analysis shown in FSAR Section 14.2-7 for a loss of normal feedwater flow, FSAR Tables 14.2.7-3 and 14.2-7-4 associated with this FSAR section list charging flow initiation as part of the sequence of events.
Also, Appendix 1A of the FSAR provides a discussion of the design of MPS2 as it relates to the General Design Criteria (GDC) shown in Appendix A to Part 50 of Title 10 of the Code of Federal Regulations (10 CFR). GDC 33, "Reactor Coolant Makeup," specifies, in part, that "[a] system to supply reactor coolant makeup for protection against small breaks shall be provided. The system safety function shall be to assure that specified acceptable fuel design limits are not exceeded as a result of reactor coolant loss due to leakage from the reactor coolant boundary and rupture of small piping or other small components which are part of the boundary." Appendix 1A, Page 1.A-23, of the MPS2 FSAR states, in part, the following regarding GDC 33:
Reactor Coolant System (RCS) makeup during normal operation is provided by the Chemical and Volume Control System (CVCS) which includes three positive displacement charging pumps rated at 44 gpm each. Two operating CVCS pumps are capable of making up the flow loss for leaks in the reactor coolant boundary of up to 0.250 inches equivalent diameter. Two CVCS pumps are sufficient to makeup for a 0.250 inch equivalent diameter RCS break assuming either: 1) minimum letdown with no RCS leakage, or 2) letdown isolated with maximum TS allowed leakage. This CVCS design results in a substantial RCS steady state pressure that is well above the shutoff head of the high pressure safety injection (HPSI) pumps. The above described CVCS capability fulfills the intent of Criterion 33.
NRC Question No.1.
Provide an explanation for the apparent discrepancy between the three statements in the application cited above (items a, b, and c) and the information currently
Serial No. 07-0023A Docket No. 50-336 Resp. to Request for Add. Info.
Attachment Page 3 of 5 shown in the FSAR regarding whether the charging pumps are credited in mitigating any design basis accidents.
ONC Response As discussed in FSAR Section 14.6.1.6, charging and SIS have been shown to have sufficient capacity to easily compensate for the loss of primary coolant mass through the inadvertent opening of the pressurizer power-operated relief valves (PORVs). Although this is a true statement, ONC recognized that this statement could be interpreted that both charging and SIS are required to prevent core uncovery following inadvertent opening of the PORVs. Although ONC's initial assessment was that HPSI, by itself, was adequate to compensate for the inventory loss through the PORVs and prevent core uncovery, a condition report (CR-07-08295) was generated on August 7, 2007, to provide the technical documentation to support this assessment and revise the FSAR accordingly to prevent future misinterpretations. At the time this condition report was being generated, this license amendment request was concurrently undergoing review.
It was ONC's initial assessment, that previous docketed correspondence, which indicated that charging was not credited for the mitigation of any FSAR Chapter 14 accident, remained valid.
On February 15, 2008, an engineering evaluation was completed, demonstrating that HPSI, by itself, remains adequate to prevent core uncovery following an inadvertent opening of the PORVs. This evaluation provides the bases for an FSAR change which is planned to be completed in conjunction with the FSAR change for the Cycle 19 reload safety analysis. This FSAR change is scheduled for the end of April 2008.
Table 14.0.9-1 lists all the systems and equipment normally available to mitigate the consequences of Chapter 14 events. As the footnote to the table indicates, this table was not intended to indicate that these normally available systems are required to mitigate the FSAR Chapter 14 events. FSAR Chapter 14 assumes normal automatic control of control systems if this condition either worsens the event consequences or does not have any significant impact on the event consequences. Table 14.2.7-3 provides the sequence of events for the loss of normal feedwater event analyzed to determine the minimum steam generator inventory. In this scenario, normal automatic operation of the charging pumps is assumed. This action has no impact on the minimum steam generator inventory results of this analysis. Table 14.2.7-4 provides the sequence of events for the loss of normal feedwater event analyzed to determine the maximum pressurizer water level. As noted in this table and Figure 14.2.7-8, the maximum pressurizer water level occurs prior to the start of the charging pumps on level deviation.
As such, the automatic operation of the charging pumps does not impact the results of this event.
ONC has reviewed the remaining instances in FSAR Chapter 14 where mention is made of charging pump operation. For the main steam line break and loss of coolant accident, FSAR Sections 14.1.5 and 14.6.5 identify that the charging pumps are not credited for
Serial No. 07-0023A Docket No. 50-336 Resp. to Request for Add. Info.
Attachment Page 4 of 5 event mitigation. For the following three FSAR Chapter 14 events, the assumption is that charging pump operation worsens the event consequences. FSAR Section 14.4.6, Boron Dilution Accident, the charging pumps deliver unborated water, causing the reduction in the RCS boron concentration. Table 14.4.8.3 provides the event summary for the control rod ejection maximum RCS pressurization case. This table identifies that the charging pumps start at the initiation of the event. This results in a modest increase in the pressurizer level which increases the RCS pressure consequences of this event.
For the FSAR Section 14.6.3, Steam Generator Tube Rupture Analyses, operation of all three charging pumps is assumed, as this increases the primary-to-secondary leak rate and the radiological consequences of the accident.
Based upon the above discussion, DNC believes the statements in the proposed license amendment remain valid, and that the charging pumps are not credited for the mitigation of any FSAR Chapter 14 accident. However, the charging pumps are appropriately addressed when considering any potential negative effects as a result of their operation.
NRC Question No.2.
Item c cited above indicates that the proposed amendment does not involve any modification to any system, structure or component required for safe operation of the facility. However, the discussion in FSAR Appendix 1A, with respect to GDC 33, indicates that the charging pumps support the safety function to assure that specified acceptable fuel design limits are not exceeded as a result of reactor coolant loss due to leakage from the reactor coolant boundary and rupture of small piping or other small components which are part of the boundary. Provide an explanation for the apparent discrepancy.
DNC Response The GDC 33 design bases function described above (Le., a system to supply reactor coolant makeup for protection against small breaks in the reactor coolant pressure boundary) is a function that the MPS2 charging pumps are currently required to satisfy.
This system assures that specified acceptable fuel design limits are not exceeded as a result of reactor coolant loss due to leakage from reactor coolant boundary and rupture of small piping or other small components which are part of the boundary. The charging pumps will continue to be required to satisfy this GDC 33 design bases function should the proposed license amendment be approved. The proposed license amendment has no impact on this design function.
Appendix B to NEI 97-04, Revision 1, endorsed by Regulatory Guide 1.186, defines design basis functions as functions performed by systems, structures and components that are (1) required by, or otherwise necessary to comply with regulations, license conditions, orders or T3, or (2) credited in the licensee safety analysis to meet NRC requirements. This GOC 33 design basis function is necessary to comply with
Serial No. 07-0023A Docket No. 50-336 Resp. to Request for Add. Info.
Attachment Page 5 of 5 regulations and fits Category (1) of this definition. This design basis function is not credited in the safety analysis to meet NRC requirements and does not fit Category (2) of this definition.
As discussed in ONC's February 20, 2007 submittal, the charging pumps are not required to satisfy any of the 10 CFR 50.36(d)(2)(ii) criteria requiring a TS LCO. As such, ONC believes it is appropriate to eliminate the charging pumps from the TS LCO.
ONC is not planning any changes that would diminish the ability of the charging pumps to perform the design basis function described in the current MPS2 FSAR Appendix 1A discussion.