ML120090242
| ML120090242 | |
| Person / Time | |
|---|---|
| Site: | River Bend  |
| Issue date: | 02/08/2012 |
| From: | Wang A Plant Licensing Branch IV |
| To: | Entergy Operations |
| Wang, A B, NRR/DORL/LPLIV, 415-1445 | |
| References | |
| TAC ME6514 | |
| Download: ML120090242 (23) | |
Text
UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 February 8, 2012 Vice President, Operations Entergy Operations, Inc.
River Bend Station 5485 US Highway 61 N St. Francisville, LA 70775
SUBJECT:
RIVER BEND STATION, UNIT 1 - ISSUANCE OF AMENDMENT re: TECHNICAL SPECIFICATION CHANGES CONSISTENT WITH TSTF-427, REVISION 2, "ALLOWANCE FOR NON TECHNICAL SPECIFICATION BARRIER DEGRADATION ON SUPPORTED SYSTEM OPERABILITY (TAC NO. ME6514)
Dear Sir or Madam:
The U.S. Nuclear Regulatory Commission (NRC) has issued the enclosed Amendment No. 173 to Facility Operating License No. NPF-47 for the River Bend Station, Unit 1. The amendment consists of changes to the Technical Specifications (TSs) in response to your application dated June 10,2011, as supplemented by letter dated July 27, 2011.
The amendment revises the TSs to add a new limiting condition for operation (LCO)
Applicability requirement, LCO 3.0.9, and its associated Bases, relating to the modification of requirements regarding the impact of unavailable barriers, not explicitly addressed in the TSs, but required for operability of supported systems in the TSs. This change is consistent with NRC-approved Technical Specification Task Force (TSTF) Improved Standard Technical Specification Change Traveler, TSTF-427, Revision 2, "A"owance for Non Technical Specification Barrier Degradation on Supported System OPERABILITY," using the consolidated line item improvement process.
A copy of our related Safety Evaluation is enclosed. The Notice of Issuance will be included in the Commission's next biweekly Federal Register notice.
Sincerely,
~w Alan B. Wang. ~Manager Plant Licensing Branch IV Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-458
Enclosures:
- 1. Amendment No. 173 to NPF-47
- 2. Safety Evaluation cc w/encls: Distribution via Listserv
UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 ENTERGY GULF STATES LOUISIANA, LLC AND ENTERGY OPERATIONS, INC.
DOCKET NO. 50-458 RIVER BEND STATION, UNIT 1 AMENDMENT TO FACILITY OPERATING LICENSE Amendment No. 173 License No. NPF-47
- 1.
The Nuclear Regulatory Commission (the Commission) has found that:
A.
The application for amendment by Entergy Operations, Inc. (the licensee), dated June 10, 2011, as supplemented by letter dated July 27, 2011, complies with the standards and requirements of the Atomic Energy Act of 1954, as amended (the Act), and the Commission's rules and regulations set forth in 10 CFR Chapter I; B.
The facility will operate in conformity with the application, as amended, the provisions of the Act, and the rules and regulations of the Commission; C.
There is reasonable assurance (i) that the activities authorized by this amendment can be conducted without endangering the health and safety of the public, and (ii) that such activities will be conducted in compliance with the Commission's regulations; D.
The issuance of this license amendment will not be inimical to the common defense and security or to the health and safety of the public; and E.
The issuance of this amendment is in accordance with 10 CFR Part 51 of the Commission's regulations and all applicable requirements have been satisfied.
- 2
- 2.
Accordingly, the license is amended by changes to the Technical Specifications as indicated in the attachment to this license amendment, and Paragraph 2.C.(2) of Facility Operating License No. NPF-47 is hereby amended to read as follows:
(2)
Technical Specifications and Environmental Protection Plan The Technical Specifications contained in Appendix A, as revised through Amendment No. 173 and the Environmental Protection Plan contained in Appendix B, are hereby incorporated in the license. EOI shall operate the facility in accordance with the Technical Specifications and the Environmental Protection Plan.
- 3.
The license amendment is effective as of its date of issuance and shall be implemented within 60 days from the date of issuance.
FOR THE NUCLEAR REGULATORY COMMISSION Michael T. Markley, Chief Plant Licensing Branch IV Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation
Attachment:
Changes to the Facility Operating License No. NPF-47 and Technical Specifications Date of Issuance:
February 8, 2012
ATTACHMENT TO LICENSE AMENDMENT NO. 173 FACILITY OPERATING LICENSE NO. NPF-47 DOCKET NO. 50-458 Replace the following pages of the Facility Operating License No. NPF-47 and Appendix A Technical Specifications with the attached revised pages. The revised pages are identified by Amendment number and contain marginal lines indicating the areas of change.
Facility Operating License Remove -3 Technical Specifications Remove 3.0-1 3.0-1 3.0-3 3.0-3
-3 (3)
EOI, pursuant to the Act and 10 CFR Part 70, to receive, possess and to use at any time special nuclear material as reactor fuel, in accordance with the limitations for storage and amounts required for reactor operation, as described in the Final Safety Analysis Report, as supplemented and amended; (4)
EOI, pursuant to the Act and 10 CFR Parts 30, 40 and 70, to receive, possess, and use at any time any byproduct, source and special nuclear material as sealed neutron sources for reactor startup, sealed sources for reactor instrumentation and radiation monitoring equipment calibration, and as fission detectors in amounts as required; (5)
EOI, pursuant to the Act and 10 CFR Parts 30, 40 and 70, to receive, possess, and use in amounts as required any byproduct, source or special nuclear material without restriction to chemical or physical form, for sample analysis or instrument calibration or associated with radioactive apparatus or components; and (6)
EOI, pursuant to the Act and 10 CFR Parts 30, 40 and 70, to possess, but not separate, such byproduct and special nuclear materials as may be produced by the operation of the facility.
C.
This license shall be deemed to contain and is subject to the conditions specified in the Commission's regulations set forth in 10 CFR Chapter I and is subject to all applicable provisions of the Act and to the rules, regulations and orders of the Commission now or hereafter in effect; and is subject to the additional conditions specified or incorporated below:
(1 )
Maximum Power Level EOI is authorized to operate the facility at reactor core power levels not in excess of 3091 megawatts thermal (100% rated power) in accordance with the conditions specified herein. The items identified in Attachment 1 to this license shall be completed as specified. Attachment 1 is hereby incorporated into this license.
(2)
Technical Specifications and Environmental Protection Plan The Technical Specifications contained in Appendix A, as revised through Amendment No. 173 and the Environmental Protection Plan contained in Appendix 8, are hereby incorporated in the license. EOI shall operate the facility in accordance with the Technical Specifications and the Environmental Protection Plan.
Amendment No. 173
LCO Applicablity 3.0 3.0 LIMITING CONDITION FOR OPERATION (LCO) APPLICABILITY LCO 3.0.1 LCOs shall be met during the MODES or other specified conditions in the Applicability, except as provided in LCO 3.0.2, LCO 3.0.7, and LCO 3.0.9.
LCO 3.0.2 Upon discovery of a failure to meet an LCO, the Required Actions of the associated Conditions shall be met, except as provided in LCO 3.0.5 and LCO 3.0.6.
If the LCO is met or is no longer applicable prior to expiration of the specified Completion Time(s), completion of the Required Action(s) is not required, unless otherwise stated.
LCO 3.0.3 When an LCO is not met and the associated ACTIONS are not met, an associated ACTION is not provided, or if directed by the associated ACTIONS, the unit shall be placed in a MODE or other specified condition in which the LCO is not applicable. Action shall be initiated within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> to place the unit, as applicable, in:
- a.
MODE 2 within 7 hours8.101852e-5 days <br />0.00194 hours <br />1.157407e-5 weeks <br />2.6635e-6 months <br />;
- b.
MODE 3 within 13 hours1.50463e-4 days <br />0.00361 hours <br />2.149471e-5 weeks <br />4.9465e-6 months <br />; and
- c.
MODE 4 within 37 hours4.282407e-4 days <br />0.0103 hours <br />6.117725e-5 weeks <br />1.40785e-5 months <br />.
Exceptions to this Specification are stated in the individual Specifications.
Where corrective measures are completed that permit operation in accordance with the LCO or ACTIONS, completion of the actions required by LCO 3.0.3 is not required.
LCO 3.0.3 is only applicable in MODES 1, 2, and 3.
LCO 3.0.4 When an LCO is not met, entry into a MODE or other specified condition in the Applicability shall only be made:
- a.
When the associated ACTIONS to be entered permit continued operation in the MODE or other specified condition in the Applicability for an unlimited period of time; (continued)
RIVER BEND 3.0-1 Amendment No. 81,156,173
LCO Applicablity 3.0 3.0 LCO APPLICABILITY (continued)
LCO 3.0.7 Special Operations LCOs in Section 3.10 allow specified Technical Specifications (TS) requirements to be changed to permit performance of special tests and operations. Unless otherwise specified, all other TS requirements remain unchanged. Compliance with Special Operations LCOs is optional. When a Special Operations LCO is desired to be met but is not met, the ACTIONS of the Special Operations LCO shall be met.
When a Special Operations LCO is not desired to be met, entry into a MODE or other specified condition in the Applicability shall only be made in accordance with the other applicable Specifications.
LCO 3.0.8 Not Used LCO 3.0.9 When one or more required barriers are unable to perform their related support function(s), any supported system LCO(s) are not required to be declared not met solely for this reason for up to 30 days provided that at least one train or subsystem of the supported system is OPERABLE and supported by barriers capable of providing their related support function(s), and risk is assessed and managed. This specification may be concurrently applied to more than one train or subsystem of a multiple train or subsystem supported system provided at least one train or subsystem of the supported system is OPERABLE and the barriers supporting each of these trains or subsystems provide their related support function(s) for different categories of initiating events.
For the purposes of this specification, the High Pressure Core Spray system, the Reactor Core Isolation Cooling system, and the Automatic Depressurization System are considered independent subsystems of a single system.
If the required OPERABLE train or subsystem becomes inoperable while this specification is in use, it must be restored to OPERABLE status within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> or the provisions of this specification cannot be applied to the trains or subsystems supported by the barriers that cannot perform their related support function(s).
At the end of the specified period, the required barriers must be able to perform their related support function(s) or the supported system LCO(s) shall be declared not met.
RIVER BEND 3.0-3 Amendment No. 84-, 173
UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. 173 TO FACILITY OPERATING LICENSE NO. NPF-47 ENTERGY OPERATIONS, INC.
RIVER BEND STATION, UNIT 1 DOCKET NO. 50-458
1.0 INTRODUCTION
By application dated June 10, 2011 (Reference 1), as supplemented by letter dated July 27, 2011 (Reference 2), Entergy Operations, Inc. (Entergy, the licensee), requested changes to the Technical Specifications (TSs) for the River Bend Station, Unit 1 (RBS).
The amendment would revise the TSs by adding a new limiting condition for operation (LCO)
Applicability requirement, LCO 3.0.9, and its associated Bases, relating to the modification of requirements regarding the impact of unavailable barriers, not explicitly addressed in the TSs, but required for operability of supported systems in the TSs. This change is consistent with U.S. Nuclear Regulatory Commission (NRC)-approved Technical Specification Task Force (TSTF) Improved Standard Technical Specification Change Traveler, TSTF-427, Revision 2, "Allowance for Non Technical Specification Barrier Degradation on Supported System OPERABILITY," using the consolidated line item improvement process.
The supplemental letter dated July 27,2011, provided additional information that clarified the application, did not expand the scope of the application as originally noticed, and did not change the NRC staff's original proposed no significant hazards consideration determination as published in the Federal Register on July 26,2011 (76 FR 44616).
On May 3, 2006, the industry owners group TSTF submitted a proposed change, TSTF-427, Revision 2, to the standard technical specifications (STS) (NUREGs 1430-1434) on behalf of the industry (TSTF-427, Revisions 0 and 1 were prior draft iterations) (Reference 3). TSTF-427, Revision 2, is a proposal to add an STS LCO 3.0.9, allowing a delay time for entering a supported system TS, when the inoperability is due solely to an unavailable barrier, if risk is assessed and managed. The postulated initiating events which may require a functional barrier are limited to those with low frequencies of occurrence, and the overall TS system safety function would still be available for the majority of anticipated challenges. In its letter dated June 10, 2011, the licensee stated it was not proposing any variations or deviations from the TS changes described in TSTF-427, Revision 2.
-2 The proposed amendment is one of the industry's initiatives being developed under the risk informed TS program. These initiatives are intended to maintain or improve safety through the incorporation of risk assessment and management techniques in TSs, while reducing unnecessary burden and making TS requirements consistent with the Commission's other risk-informed regulatory requirements.
2.0 REGULATORY EVALUATION
In Section 50.36, "Technical specifications," of Title 10 of the Code of Federal Regulations (10 CFR), the Commission established its regulatory requirements related to the content of TSs.
Pursuant to 10 CFR 50.36, TSs are required to include items in the following five specific categories related to station operation: (1) safety limits, limiting safety system settings, and limiting control settings; (2) LCOs; (3) surveillance requirements (SRs); {4} design features; and (5) administrative controls. The rule does not specify the particular requirements to be included in a plant's TSs. The regulations in 10 CFR 50.36(c)(2), "Limiting conditions for operation,"
state, in part, that Limiting conditions for operation are the lowest functional capability or performance levels of equipment required for safe operation of the facility. When a limiting condition for operation of a nuclear reactor is not met, the licensee shall shut down the reactor or follow any remedial action permitted by the technical specifications until the condition can be met.
TS Section 3.0, on "LCO and SR Applicability," provides details or ground rules for complying with the LCOs.
Barriers are doors, walls, floor plugs, curbs, hatches, installed structures or components, or other devices, not explicitly described in the TSs that support the performance of the functions of systems described in the TSs. For purposes of this TS, the term "barrier" refers to one or more devices which protect one train of a safety system from a given initiating event. A "degraded barrier" refers to a barrier that has been found to be degraded and must be repaired, or to a barrier that is purposefully removed or reconfigured to facilitate maintenance activities.
As stated in Nuclear Energy Institute (NEI) 04-08, "Allowance for Non-Technical Specification Barrier Degradation on Supported System OPERABILITY (TSTF-427), Industry Implementation Guidance," March 2006 (Reference 4), LCO 3.0.9 specifically does not apply to fire barriers, snubbers, barriers which support ventilation systems or non-TS systems, or barriers which support TS systems where the unavailability of the barrier does not render the supported system inoperable.
Some TS required systems may require one or more functional barriers in order to perform their intended function(s) for certain initiating events for which the barriers provide some protective support function. For example, there are barriers to protect systems from the effects of internal flooding, such as floor plugs and retaining walls, and barriers are used to protect equipment from steam impingement in case of high energy line breaks. Barriers are also used to protect systems against missiles, either internally generated, or generated by external events.
Barriers are not explicitly described in the TSs, but are required to be capable of performing their required support function by the definition of OPERABILITY for the supported system
- 3 which is described in the TSs. Therefore, under the current STS, the supported system must be declared inoperable when the related barrier(s) are unavailable. However, the magnitude of plant risk associated with the barrier which cannot perform its related support function is much less than the risk associated with direct unavailability of the supported system, since barriers are only required for specific, low frequency initiating events.
Some potential undesirable consequences of the current TS requirements include:
- 1.
When maintenance activities on the supported TS system require removal and restoration of barriers, the time available to complete maintenance and perform system restoration and testing is reduced by the time spent maneuvering the barriers within the time constraints of the supported system LeO;
- 2.
Restoration of barriers following maintenance may be given a high priority due to time restraints of the existing supported system LeO, when other activities may have a greater risk impact and should therefore be given priority; and
- 3.
Unnecessary plant shutdowns may occur due to discovery of degraded barriers which require more time than provided by the existing supported system LeO to complete repairs and restoration of the barrier.
To improve the treatment of unavailable barriers and enhance safety, the TSTF proposed a risk informed TS change that introduces a delay time before entering the actions for the supported equipment, when one or more barriers are found to be degraded, or are removed or reconfigured to support maintenance activities, if risk is assessed and managed. Such a delay time will provide needed flexibility in the performance of maintenance and at the same time will enhance overall plant safety by:
- 1.
Performing system maintenance and restoration activities, including post maintenance testing, within the existing TS LeO time, and allowing barrier removal and restoration to be performed outside of the TS LeO, providing more time for the safe conduct of maintenance and testing activities on the supported TS system;
- 2.
Requiring barrier removal and restoration activities to be assessed and prioritized based on actual plant risk impacts; and
- 3.
Avoiding unnecessary unscheduled plant shutdowns and thus minimizing plant transition and realignment risks.
-4
3.0 TECHNICAL EVALUATION
3.1 Proposed TS Changes
The licensee's proposed change adds new LCO 3.0.9 to the TSs. LCO 3.0.9 allows licensees to delay declaring an LCO not met for equipment supported by barriers unable to perform their associated support function, when risk is assessed and managed. In its letter dated June 10, 2011, the licensee proposed adding new LCO 3.0.9, which states:
When one or more required barriers are unable to perform their related support function(s), any supported system LCO(s) are not required to be declared not met solely for this reason for up to 30 days provided that at least one train or subsystem of the supported system is OPERABLE and supported by barriers capable of providing their related support function(s), and risk is assessed and managed. This specification may be concurrently applied to more than one train or subsystem of a multiple train or subsystem supported system provided at least one train or subsystem of the supported system is OPERABLE and the barriers supporting each of these trains or subsystems provide their related support function(s) for different categories of initiating events.
For the purposes of this specification, the High Pressure Core Spray system, the Reactor Core Isolation Cooling system, and the Automatic Depressurization System are considered independent subsystems of a single system.
If the required OPERABLE train or subsystem becomes inoperable while this specification is in use, it must be restored to OPERABLE status within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> or the provisions of this specification cannot be applied to the trains or subsystems supported by the barriers that cannot perform their related support function(s).
At the end of the specified period, the required barriers must be able to perform their related support function(s), or the supported system LCO(s) shall be declared not met.
In its letter dated July 27,2011, the licensee amended its initial application to adopt TSTF-427, Revision 2, by submitting an inadvertently omitted TS change to LCO 3.0.1, which currently
- states, LCOs shall be met during the MODES or other specified conditions in the Applicability, except as provided in LCO 3.0.2 and LCO 3.0.7.
Revised LCO 3.0.1 would state:
LCOs shall be met during the MODES or other specified conditions in the Applicability, except as provided in LCO 3.0.2, LCO 3.0.7, and LCO 3.0.9.
-5 3.2
NRC Staff Evaluation
The industry submitted TSTF-427, Revision 2 (Reference 3), in support of the proposed TS change. This submittal documents a risk-informed analysis of the proposed TS change.
Probabilistic risk assessment (PRA) methods are used, in combination with deterministic and defense-in-depth arguments, to identify and justify delay times for entering the actions for the supported equipment associated with unavailable barriers at nuclear power plants. The industry also submitted implementation guidance NEI 04-08, March 2006 (Reference 4). This submittal provides detailed guidance on assessing and managing risk associated with unavailable barriers. This is in accordance with guidance provided in Regulatory Guide (RG) 1.174, "An Approach for Using Probabilistic Risk Assessment in Risk-Informed Decisions on Plant-Specific Changes to the Licensing Basis,>> July 1998, and RG 1.177, "An Approach for Plant-Specific, Risk-Informed Decisionmaking: Technical Specifications," August 1998 (References 5 and 6, respectively).
The risk impact associated with the proposed delay times for entering the TS actions for the supported equipment can be assessed using the same approach as for allowed completion time (CT) extensions. Therefore, the risk assessment was performed following the three-tiered approach recommended in RG 1.177 for evaluating proposed extensions in currently allowed CTs:
- 1.
The first tier involves the assessment of the change in plant risk due to the proposed TS change. Such risk change is expressed (1) by the change in the average yearly core damage frequency (~CDF) and the average yearly large early release frequency (~LERF) and (2) by the incremental conditional core damage probability (ICCDP) and the incremental conditional large early release probability (ICLERP). The assessed ~CDF and ~LERF values are compared to acceptance guidelines, consistent with the Commission's Safety Goal Policy statement as documented in RG 1.174, so that the plant's average baseline risk is maintained within a minimal range. The assessed ICCDP and ICLERP values are compared to acceptance guidelines in RG 1.177, which provide assurance that the plant risk does not increase unacceptably during the period the equipment is taken out of service.
- 2.
The second tier involves the identification of potentially high-risk configurations that could exist if equipment in addition to that associated with the change were to be taken out of service simultaneously, or other risk-significant operational factors such as concurrent equipment testing were also involved. The objective is to ensure that appropriate restrictions are in place to avoid any potential high-risk configurations.
- 3.
The third tier involves the establishment of an overall configuration risk management program (CRMP) to ensure that potentially risk-significant configurations resulting from maintenance and other operational activities are identified. The objective of the CRMP is to manage configuration-specific risk by appropriate scheduling of plant activities and/or appropriate compensatory measures.
-6 A simplified risk assessment was performed to justify the proposed addition of LCO 3.0.9 to the TSs. This approach was necessitated by (1) the general nature of the proposed TS change (i.e., it applies to all plants and is associated with an undetermined number of barriers that are not able to perform their function), and (2) the lack of detailed modeling in most plant-specific PRAs which do not include passive structures such as barriers.
The simplified risk assessment considers three different parameters:
- 1.
The length of time the affected barrier is unavailable,
- 2.
The initiating event frequency for which the affected barrier is designed to mitigate, and
- 3.
The importance to CDF (or LERF) of the TS equipment (train, subsystem, or component) for which the affected barrier is designed to protect, measured by the risk achievement worth of the equipment.
The ICCDP can be calculated based on the following equation:
Tc lEt]
(
)
ICCDP = [ 8766 x lET x [ RAWj X CDFbase CDFbase ]
where:
Tc is the time the barrier is unavailable (hours),
Tc t 8766 is therefore the fraction of the year during which the barrier is unavailable, IE; tiEr is the ratio of the initiating event frequency for which the affected barrier is designed to mitigate, IE;, and the total initiating event frequency, IEr, RAWj is the risk achievement worth of the component(s) for which the barrier provides protection, and CDFbase is the baseline core damage frequency (per year).
ICLERP also may be similarly determined, using baseline LERF and RAW values with respect to LERF. It is assumed that the magnitude of the LERF risk resulting from the barrier unable to perform its related support function would be generally at least one order of magnitude less than the corresponding CDF risk. Containment bypass scenarios, which are typically the significant contributors to LERF, would not be uniquely affected by application of LCO 3.0.9, and initiating events which would be significant LERF contributors, such as steam generator tube rupture and interfacing systems loss-of-coolant accident, are not typically associated with barriers within the scope of LCO 3.0.9. Therefore, the assumption regarding LERF risk is reasonable and acceptable for the generic risk evaluation, provided that LERF risk impacts are considered on a plant-specific basis for unavailable barriers, as described in Section 3.3.3 of this safety evaluation.
- 7 The relevant initiating events (i.e., events for which barriers subject to LCO 3.0.9 provide protection) are:
internal and external floods, high energy line breaks, feedwater line breaks, loss-of-coolant accident (small, medium, and large),
tornados and high winds, and turbine missiles.
Generic frequencies for most of these initiating events were obtained from NUREG/CR-5750, "Rates of Initiating Events at U.S. Nuclear Power Plants," February 1999 (Reference 7). For external floods, turbine missiles, and tornados, other industry source documents were referenced. The most limiting (highest frequency) initiating event was obtained for a high energy line break from NUREG/CR-5750, with a frequency of 9.1 E-3 per year. The risk assessment is therefore based on this limiting frequency, and the proposed methodology to apply LCO 3.0.9 is similarly restricted to barriers protecting against initiating events whose total frequency is no more than 9.1 E-3 per year.
3.3 Risk Assessment Results and Insights The results and insights from the implementation of the three-tiered approach of RG 1.177 to support the proposed addition of LCO 3.0.9 to the TSs are summarized and evaluated in Sections 3.3.1 to 3.3.3 of this safety evaluation.
3.3.1 Risk Impact The bounding risk assessment approach, described in Section 3.0, was developed for a range of plant baseline CDF values and for a range of protected component RAW values. The maximum allowable 30-day outage time was used. The results are summarized below in Table 1.
Table 1 - Risk Assessment Results for a Postulated 30-Day Barrier Outage.
Baseline CDF =1 E-6 per year:
7.5E-10 7.5E-11 10 6.7E-09 6.7E-10 50 3.7E-08 3.7E-09 100 7.4E-08 7.4E-09
- 8 Baseline CDF =1 E-5 per year:
7.5E-09 7.5E-10 10 6.7E-08 6.7E-09 50 3.7E-07 3.7E-08 100 7.4E-07 7.4E-08 Baseline CDF =1 E-4 per year:
7.5E-08 7.5E-09 10 6.7E-07 6.7E-08 50 3.7E-06 3.7E-07 100 7.4E-06 7.4E-07 The above results represent a sensitivity analysis covering the expected range of plant baseline CDF values and component RAW values. The most limiting configurations involving very high risk components (RAW> 10) would not be anticipated to occur for most planned maintenance activities.
The calculations conservatively assume the most limiting (highest frequency) initiating event and the longest allowable outage time (30 days). Occurrence of the initiating event during unavailability of the barrier is conservatively assumed to directly fail the protected equipment; no credit is taken for event-specific circumstances which may result in the equipment remaining functional even with the barrier unavailable. (For example, a barrier required to protect equipment from steam impingement for high energy line breaks may only be required for breaks occurring in specific locations and orientations relative to the protected equipment, and only for large size breaks.) No credit is taken for avoided risk identified in Section 2.0 of this safety evaluation.
The risk assessment results of Table 1 were compared to guidance provided in the revised Section 11, "Assessment of Risk Resulting from Performance of Maintenance Activities," of Nuclear Management and Resources Council's (NUMARC, now NEI) NUMARC 93-01, Revision 2, "Industry Guideline for Monitoring the Effectiveness of Maintenance at Nuclear Power Plants," dated April 29, 2002 (Reference 8), endorsed by RG 1.182, "Assessing and Managing Risk Before Maintenance Activities at Nuclear Power Plants," May 2000 (Reference 9), for implementing the requirements of paragraph (a)(4) of the Maintenance Rule, 10 CFR 50.65. Such guidance is summarized in Table 2. Guidance regarding the acceptability of conditional risk increase in terms of CDF for a planned configuration is provided. This guidance states that a specific configuration that is associated with a CDF higher than 1 E-3 per year should not normally be entered voluntarily. The NRC staff notes that the higher risk configurations documented in Table 1 would exceed this guidance, and would therefore not be permitted to be entered voluntarily. For example, with a baseline CDF of 1 E-4 per year, a
- 9 component with a RAW greater than 10 would exceed the 1 E-3 per year criteria. Therefore, the sensitivity analyses presented in Table 1 are understood to include higher risk configurations which would not be permitted under the guidance of Reference 8.
Table 2 - Guidance for Implementing 10 CFR 50.65(a)(4).
~RCDF Guidance Greater than 1 E-3/year Configuration should not normally be entered voluntarily ICCDP Guidance ICLERP Greater than 1 E-5 Configuration should not normally be entered voluntarily Greater than 1 E-6 1E-6 to 1E-5 Assess non-quantifiable factors Establish risk management actions 1E-7 to 1E-6 Less than 1 E-6 Normal work controls Less than 1 E7 Guidance regarding the acceptability of ICCDP and ICLERP values for a specific planned configuration and the establishment of risk management actions is also provided in NUMARC 93-01. This guidance, as shown in Table 2, states that a specific plant configuration that is associated with ICCDP and ICLERP values below 1 E-6 and 1 E-7, respectively, is considered to require "normal work controls." Table 1 shows that for the majority of barrier outage configurations the conservatively assessed ICCDP and ICLERP values are within the limits for what is recommended as the threshold for the "normal work controls" region.
As stated in the implementation guidance for LCO 3.0.9 (Reference 4), plants are required to commit to the guidance of NUMARC 93-01, Section 11, and, therefore, the above limits would be applicable. Plant configurations including out of service barriers may therefore be entered voluntarily if supported by the results of the risk assessment required by 10 CFR 50.65(a)(4),
and by LCO 3.0.9.
RG 1.177 (Reference 6) provides guidance of 5E-7 incremental core damage probability and 5E-8 incremental large early release probability as the limit for a TS allowed outage time. As shown in Table 1, the guidance is met for the typically anticipated configurations, unless either the baseline CDF for the plant approaches 'I E-4 per year or the RAW of the protected components is well above 10. Such configurations may exceed the criteria described in Reference 6 (Table 2) and would not be voluntarily entered. Such configurations are not expected to be frequently encountered, and may be addressed on a case-by-case plant-specific basis by limiting the allowed outage time and by implementing plant-specific risk management actions, as per the implementing guidance (Reference 4).
RG 1.174 (Reference 5) provides guidance of 1 E-5 per year ~CDF and 1 E-6 per year ~LERF.
The ICCDP calculations demonstrated that each individual 30-day barrier outage is anticipated to be low risk. Although there is no explicit limit on the number of times per year that LCO 3.0.9 may be applied, even assuming barrier outages occurred continuously over the entire year, the risk incurred would still be anticipated to be below the limits of the guidance.
-10 The NRC staff concludes that the risk assessment results support the proposed addition of LCO 3.0.9 to the TSs. The risk increases associated with this TS change will be insignificant based on guidance provided in RGs 1.174 and 1.177 and within the range of risks associated with normal maintenance activities.
3.3.2 Identification of High-Risk Configurations The second tier of the three-tiered approach recommended in RG 1.177 involves the identification of potentially high-risk configurations that could exist if equipment, in addition to that associated with the TS change, were to be taken out of service simultaneously. Insights from the risk assessments, in conjunction with important assumptions made in the analysis and defense-in-depth considerations, were used to identify such configurations. To avoid these potentially high-risk configurations, specific restrictions to the implementation of the proposed TS changes were identified.
When LCO 3.0.9 is applied, at least one train or subsystem is required to be operable with required barriers in place, such that this train or subsystem would be available to provide mitigation of the initiating event. LCO 3.0.9 may be applied to multiple trains of the same system only for barriers which provide protection for different initiating events, such that at least one train or subsystem is available to provide mitigation of the initiating event. The use of LCO 3.0.9 for barriers which protect all trains or subsystems from a particular initiating event is not permitted. Therefore, potentially high-risk configurations involving a loss of function required for mitigation of a particular initiating event are avoided by the restrictions imposed on applicability of LCO 3.0.9.
LCO 3.0.9 also addresses potential emergent conditions where unplanned failures or discovered conditions may result in the unavailability of a required train or subsystem for a particular initiating event. Such conditions may result during application of LCO 3.0.9 from equipment failure on the operable train, such that all trains of a TS system are not protected from the same initiating event. In such cases, a 24-hour allowed time is provided to restore the conditions to permit continued operation with unavailable barriers, after which the applicability of LCO 3.0.9 ends, and the supported system LCO becomes effective. This allowed time is provided so that emergent conditions with low risk consequences may be effectively managed, rather than requiring immediate exit of LCO 3.0.9 and the potential for an unplanned plant shutdown.
A limit of 30 days is applied to the LCO 3.0.9 allowed outage time for each barrier, after which the barrier must be restored to an available status, or the supported system TSs must be applied. This 30-day backstop applies regardless of the risk level calculated, and provides assurance that installed plant barriers will be maintained available over long periods of time, and that the application of LCO 3.0.9 will not result in long-term degradation of plant barriers.
The NRC staff concludes that the restrictions on the applicability of LCO 3.0.9 assuring that one safety train remains available to mitigate the initiating event, along with the 30-day limit applicable to each barrier, assure that potentially high-risk configurations are avoided in accordance with the guidance provided in RGs 1.174 and 1.177.
- 11 3.3.3 Configuration Risk Management The third tier of the three-tiered approach recommended in RG 1.177 involves the establishment of an overall configuration risk management program (CRMP) to ensure that potentially risk significant configurations resulting from maintenance and other operational activities are identified. The objective of the CRMP is to manage configuration-specific risk by appropriate scheduling of plant activities and/or appropriate compensatory measures. This objective is met by licensee programs to comply with the requirements of paragraph (a}(4) of the Maintenance Rule (10 CFR 50.65) to assess and manage risk resulting from maintenance activities, and by LCO 3.0.9 requiring risk assessments and management using (a}(4) processes if no maintenance is in progress. These programs can support licensee decision making regarding the appropriate actions to manage risk whenever a risk-informed TS is entered.
The implementation guidance for LCO 3.0.9 (Reference 4) requires that the allowed outage time determination for an unavailable barrier be performed using the plant-specific configuration.
Further, the risk determinations are to be updated whenever emergent conditions occur. These requirements assure that the configuration-specific risk associated with unavailable barriers is assessed and managed prior to entry into LCO 3.0.9 and during its applicability as conditions change.
These evaluations for the unavailable barrier are performed as part of the assessment of plant risk required by 10 CFR 50.65(a)(4). The numerical guidance identified in Table 2 is applicable to implementation of LCO 3.0.9, using the results of the configuration-specific risk assessment which addresses the risk impact of the unavailable barrier along with all other out-of-service components and plant alignments.
Risk management actions are required to be considered when the calculated risk exceeds specific thresholds per NUMARC 93-01 Section 11, as identified in Table 2. Additional guidance on risk management actions are provided in the implementation guidance for LCO 3.0.9.
The allowed outage time for a barrier is calculated based on an ICCDP limit of 1 E-6. This is the NUMARC 93-01, Section 11, guidance for applicability of normal work controls, and is conservatively lower than the guidance of 1 E-5 for voluntary maintenance activities. The use of 1 E-6 will result in conservatively short allowed outage times for barriers compared to allowed times for other maintenance activities.
If the scope of the PRA model used to support the plant-specific CRMP does not include the initiating event for which a barrier provides protection, then LCO 3.0.9 applicability is limited to one barrier on a Single train. Multiple barriers for such initiating events may not be unavailable under LCO 3.0.9, and in such situations, the LCO(s) associated with the protected components would be applicable. Applicability of LCO 3.0.9 to the single barrier for an initiating event that is not modeled in the plant PRA is acceptable based on the generic risk analysis provided by TSTF-427, Revision 2, as described in Section 3.2 of this safety evaluation.
Assessment of the LERF risk impact on an unavailable barrier is required to be performed in accordance with NUMARC 93-01, Section 11. If an unavailable barrier provides protection to equipment which is relevant to the containment function, or which protects equipment from the
- 12 effects of an initiating event which is a contributor to LERF, then applicability of LCO 3.0.9 must be limited to that one barrier unless a quantified assessment of LERF is performed.
The NRC staff concludes that the risk evaluations necessary to support the applicability of LCO 3.0.9 appropriately consider the risk from unavailable barriers in an integrated manner based on the overall plant configuration. Therefore, potentially high-risk configurations can be identified and managed in accordance with the guidance provided in RGs 1.174 and 1.177.
3.4 Summary and Conclusions The unavailability of barriers which protect TS required components from the effects of specific initiating events is typically a low-risk configuration which should not require that the protected components be immediately declared inoperable. The current TSs require that when such barriers are unavailable, the protected component LCO is immediately entered. Some potential undesirable consequences of the current TS requirements include:
- 1.
When maintenance activities on the supported TS system requires removal and restoration of barriers, the time available to complete maintenance and perform system restoration and testing is reduced by the time spent maneuvering the barriers within the time constraints of the supported system LCO;
- 2.
Restoration of barriers following maintenance must be given a high priority due to time restraints of the existing supported system LCO, when other more risk important activities may have a greater risk impact and should therefore be given priority; and
- 3.
Unnecessary plant shutdowns may occur due to discovery of degraded barriers which may require more than the existing supported system LCO time to complete repairs and restoration.
To remove the overly restrictive requirements in the treatment of barriers, licensees are proposing a risk-informed TS change which introduces a delay time before entering the actions for the supported equipment when one or more barriers are found degraded or removed to facilitate planned maintenance activities. Such a delay time will provide needed flexibility in the performance of maintenance during power operation and at the same time will enhance overall plant safety by (1) performing system maintenance and restoration activities, including post maintenance testing, within the existing TS LCO time, and allowing barrier removal and restoration to be performed outside of the TS LCO, providing more time for the safe conduct of maintenance and testing activities on the supported system; (2) requiring barrier removal and restoration activities to be assessed and prioritized based on actual plant risk impacts; and (3) avoiding unnecessary unscheduled plant shutdowns, thus minimizing plant transition and realignment risks.
The risk impact of the proposed TS changes was assessed following the three-tiered approach recommended in RG 1.177. A simplified bounding risk assessment was performed to justify the proposed TS changes. This bounding assessment was selected due to the lack of detailed plant-specific risk models for most plants which do not include failure modes of passive
- 13 structures such as barriers. The impact from the addition of the proposed LCO 3.0.9 to the TSs on defense-in-depth was also evaluated in conjunction with the risk assessment results.
Based on this integrated evaluation, the NRC staff concludes that the proposed addition of LCO 3.0.9 to the TSs would lead to insignificant risk increases as stipulated by RG 1.177 and depicted in Table 1 above. This conclusion is true without taking any credit for the removal of potential undesirable consequences associated with the current conservative treatment of barriers. Therefore, the NRC staff concludes that the proposed change provides adequate protection of public health and safety and is, therefore, acceptable.
4.0 REGULATORY COMMITMENTS Consistent with the NRC staff's approval and inherent in the implementation of TSTF-427, Revision 2, the licensee provided the following regulatory commitments in its letter dated June 10,2011:
- 1.
Entergy will establish the Technical Specification Bases for LCO 3.0.9 as adopted with the applicable license amendment.
- 2.
Entergy commits to the guidance of NUMARC 93-01 Section 11, which provides guidance and details on the assessment and management of risk during maintenance.
- 3.
Entergy will revise procedures to ensure that the risk assessment and management process described in NEI 04-08 is used whenever a barrier is considered unavailable and the requirements of LCO 3.0.9 are to be applied, in accordance with an overall configuration risk management program to ensure that potentially risk-significant configurations resulting from maintenance and other operational activities are identified and avoided.
The licensee will complete the above commitments within 60 days of the issuance of the amendment. The NRC staff considers the above to be a regulatory commitment and concludes it is acceptable.
5.0 STATE CONSULTATION
In accordance with the Commission's regulations, the Louisiana State official was notified of the proposed issuance of the amendment. The State official had no comments.
6.0 ENVIRONMENTAL CONSIDERATION
The amendment changes a requirement with respect to the installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20 and change surveillance requirements. The NRC staff has determined that the amendment involves no significant increase in the amounts and no significant change in the types of any effluents that may be released offsite, and that there is no significant increase in individual or cumulative occupational radiation exposure. The Commission has previously issued a proposed finding that
- 14 the amendment involves no significant hazards considerations, and there has been no public comment on the finding published in the Federal Register on July 26,2011 (76 FR 44616).
Accordingly, the amendment meets the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9). Pursuant to 10 CFR 51.22(b), no environmental impact statement or environmental assessment need be prepared in connection with the issuance of the amendment.
7.0 CONCLUSION
The Commission has concluded, on the basis of the considerations discussed above, that (1) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, (2) such activities will be conducted in compliance with the Commission's regulations, and (3) the issuance of the amendments will not be inimical to the common defense and security or to the health and safety of the public.
8.0 REFERENCES
- 1.
Olson, E., Entergy Operations, Inc., letter to U.S. Nuclear Regulatory Commission, "License Amendment Request, Application for Technical Specification Changes Technical Specification Task Force (TSTF) Improved Standard Technical Specification Change Traveler, TSTF-427, 'Allowance for Non Technical Specification Barrier Degradation on Support System OPERABILITY,' River Bend Station, Unit 1," dated June 10, 2011 (ADAMS Accession No. ML11168A077).
- 2.
Roberts, J. C., Entergy Operations, Inc., letter to U.S. Nuclear Regulatory Commission, "Supplement to License Amendment Request, Application for Technical Specification Changes Technical Specification Task Force (TSTF) Improved Standard Technical Specification Change Traveler, TSTF-427, 'Allowance for Non Technical Specification Barrier Degradation on Support System OPERABILITY,' River Bend Station, Unit 1,"
dated July 27, 2011 (ADAMS Accession No. ML11214A092).
- 3.
Technical Specifications Task Force, letter to U.S. Nuclear Regulatory Commission, "TSTF-427, Revision 2, 'Allowance for Non Technical Specification Barrier Degradation on Supported System OPERABILITY'," dated May 3,2006 (ADAMS Accession No. ML061240055).
- 4.
Pietrangelo, A. R., Nuclear Energy Institute, letter to U.S. Nuclear Regulatory Commission, transmitting NEI 04-08, "Allowance for Non-Technical Specification Barrier Degradation on Supported System OPERABILITY (TSTF-427), Industry Implementation Guidance," March 2006," dated April 4, 2006 (ADAMS AcceSSion No. ML061220426).
- 5.
U.S. Nuclear Regulatory Commission, "An Approach for USing Probabilistic Risk Assessment in Risk-Informed Decisions on Plant-Specific Changes to the Licensing Basis," Regulatory Guide 1.174, July 1998 (ADAMS Accession No. ML003740133).
- 6.
U.S. Nuclear Regulatory Commission, "An Approach for Plant-Specific, Risk-Informed Decisionmaking: Technical Specifications," Regulatory Guide 1.177, August 1998 (ADAMS Accession No. ML003740176).
- 15
- 7.
U.S. Nuclear Regulatory Commission, "Rates of Initiating Events at U.S. Nuclear Power Plants," NUREG/CR-5750, Idaho National Engineering and Environmental Laboratory, February 1999 (not publicly available).
- 8.
Nuclear Management and Resources Council (now Nuclear Energy Institute), "Industry Guideline for Monitoring the Effectiveness of Maintenance at Nuclear Power Plants",
NUMARC 93-01, Revision 2, Section 11, "Assessment of Risk Resulting from Performance of Maintenance Activities," dated April 29, 2002 (ADAMS Accession No. ML101020466).
- 9.
U.S. Nuclear Regulatory Commission, "Assessing and Managing Risk before Maintenance Activities at Nuclear Power Plants," Regulatory Guide 1.182, May 2000 (ADAMS Accession No. ML003699426).
Principal Contributor: A. Wang Date: February 8, 2012
February 8, 2012 Vice President, Operations Entergy Operations, Inc.
River Bend Station 5485 US Highway 61 N St. Francisville, LA 70775
SUBJECT:
RIVER BEND STATION, UNIT 1 -ISSUANCE OF AMENDMENT re: TECHNICAL SPECIFICATION CHANGES CONSISTENT WITH TSTF-427, REVISION 2, "ALLOWANCE FOR NON TECHNICAL SPECIFICATION BARRIER DEGRADATION ON SUPPORTED SYSTEM OPERABILITY (TAC NO. ME6514)
Dear Sir or Madam:
The U.S. Nuclear Regulatory Commission (NRC) has issued the enclosed Amendment No. 173 to Facility Operating License No. NPF-47 for the River Bend Station, Unit 1. The amendment consists of changes to the Technical Specifications (TSs) in response to your application dated June 10,2011, as supplemented by letter dated July 27,2011.
The amendment revises the TSs to add a new limiting condition for operation (LCO)
Applicability requirement, LCO 3.0.9, and its associated Bases, relating to the modification of requirements regarding the impact of unavailable barriers, not explicitly addressed in the TSs, but required for operability of supported systems in the TSs. This change is consistent with NRC-approved Technical Specification Task Force (TSTF) Improved Standard Technical Specification Change Traveler, TSTF-427, Revision 2, "Allowance for Non Technical Specification Barrier Degradation on Supported System OPERABILITY," using the consolidated line item improvement process.
A copy of our related Safety Evaluation is enclosed. The Notice of Issuance will be included in the Commission's next biweekly Federal Register notice.
Sincerely, IRN Alan B. Wang, Project Manager Plant Licensing Branch IV Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-458
Enclosures:
- 1. Amendment No. 173 to NPF-47
- 2. Safety Evaluation cc w/encls: Distribution via Listserv DISTRIBUTION:
PUBLIC LPLIV r/f RidsAcrsAcnw_MailCTR Resource RidsNrrDorlDpr Resource RidsNrrDorlLpl4 Resource RidsNrrDssStsb Resource RidsNrrLAJBurkhardt Resource RidsNrrPMRiverBend Resource RidsOgcRp Resource RidsRgn4MailCenter Resource er ML072980209 NRR/LPL4/BC NRR/LPL4/PM
- AWang 2/8/12