ML13163A258

Request for Additional Information - Response to March 12, 2012, Commission Order EA-12-049 to Modify Licenses Requirements for Mitigating Strategies for Beyond Design Basis External Events

ML13163A258
Person / Time
Site:	Vermont Yankee
Issue date:	06/17/2013
From:	Richard Guzman Plant Licensing Branch 1
To:	Entergy Nuclear Operations
Guzman R
References
EA-12-049, TAC MF0779
Download: ML13163A258 (17)

Text

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 June 17,2013 Site Vice President Entergy Nuclear Operations, Inc.

Vermont Yankee Nuclear Power Station P.O. Box 250 Governor Hunt Road Vernon, VT 05354

SUBJECT:

VERMONT YANKEE NUCLEAR POWER STATION - REQUEST FOR ADDITIONAL INFORMATION REGARDING OVERALL INTEGRATED PLAN IN RESPONSE TO MARCH 12,2012 COMMISSION ORDER TO MODIFY LICENSES WITH REGARD TO REQUIREMENTS FOR MITIGATION STRATEGIES FOR BEYOND-DESIGN-BASIS EXTERNAL EVENTS (ORDER NUMBER EA-12-049) (TAC NO. MF0779)

Dear Sir or Madam:

By letter dated February 28, 2013 (Agencywide Document Access and Management System (ADAMS) Accession No. ML13064A300), Entergy Nuclear Operations, Inc. submitted Vermont Yankee Nuclear Power Station's Overall Integrated Plan in response to the March 12, 2012, Commission Order to modify licenses with regard to requirements for mitigating strategies for beyond-design-basis external events (Order Number EA-12-049).

The Nuclear Regulatory Commission (NRC) staff is reviewing the information provided in your submittal and has determined that additional information is needed to support its review.

Enclosed is the NRC staffs request for additional information (RAI). The RAI was discussed with your staff on June 12, 2013. Please provide a response to the questions within 30 days of the date of this letter. If any part of this information is not available within 30 days of this request, please provide the date that this information will be provided.

Sincerely, Richard V. Guzman, Senior Project Manager Plant Licensing Branch 1-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-271

Enclosure:

As stated cc w/encl: Distribution via Listserv

REQUEST FOR ADDITIONAL INFORMATION REGARDING OVERALL INTEGRATED PLAN IN RESPONSE TO MARCH 12,2012 COMMISSION ORDER TO MODIFY LICENSES WITH REGARD TO REQUIREMENTS FOR MITIGATION STRATEGIES FOR BEYOND-DESIGN-BASIS EXTERNAL EVENTS (ORDER NUMBER EA-12-049)

ENTERGY NUCLEAR OPERATIONS, INC.

VERMONT YANKEE NUCLEAR POWER STATION DOCKET NO. 50-271 By letter dated February 28,2013 (Agencywide Document Access and Management System (ADAMS) Accession No. ML13064A300), Entergy Nuclear Operations, Inc. submitted Vermont Yankee Nuclear Power Station's (VY) Overall Integrated Plan in response to the March 12, 2012, Commission Order to modify licenses with regard to requirements for mitigating strategies for beyond-design-basis external events (Order Number EA-12-049). The Nuclear Regulatory Commission (NRC) staff is reviewing the license amendment request and has determined that additional information as requested below will be needed to support its review.

049-RAI-Vermont Yankee-1 Please identify any License Amendment Requests that are necessary for modifications proposed in the integrated plan.

049-RAI-Vermont Yankee-2 Generic Letter 89-16, "Installation of a Hardened Wetwell Vent," provided for the installation of wetwell vents in BWR Mark I containments "primarily to avoid exceeding the primary containment pressure limit." Installation of the hardened vents under the provisions of 10 CFR 50.59 was appropriate because there were no changes to procedures as described in the licensee's final safety analysis reports, as updated, that would allow opening the vents; opening the vents was to only occur at pressures exceeding peak calculated containment accident pressures. Opening of the hardened vent was primarily accepted as a last resort effort to be employed when exceeding the primary containment pressure limit was imminent and all other viable mitigation strategies had been exhausted without yielding a successful result. The portion of the VY response on page 24 follows directly from this position when it states, in part, It . . . if the maximum containment pressure is reached, EOP [Emergency Operating Plan]

requires operators to vent the containment."

The design pressure of the VY containment is 56 pounds per square inch gauge (psig), but page 24 of the response also states, in part, "torus venting is assumed to open at an approximate pressure of 30 psig .... "

The response does not propose venting at 30 psig as an extreme, last resort action to prevent the containment from experiencing an uncontrolled release. The staff has not previously Enclosure

-2 reviewed or accepted "early venting" as a mitigation strategy to compensate for limitations in core cooling caused by the use of existing equipment, e.g., reactor core isolation cooling (RCIC). In light of this, please provide a discussion of the technical and regulatory bases which were relied upon to justify this approach. In the response, please include a detailed discussion of whether any plant modifications were considered that would maintain both core cooling and preserve containment integrity during an Extended Loss of AC Power (ELAP) without employing "early venting"?

049-RAI-Vermont Yankee-3 Several of the time constraints identified in Attachment 1A are either identical or very close to analytically determined values. For example, the analytical value for operator action to stem the rise in the main control room temperature is 2.S hours and the time restraint is 2.4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> (pages 36, 47, and S). Another example is in order to remain in the safe region of the heat capacity temperature limit (HCTL) the analytical value of 7.S hours is cited as the time it takes to depressurize the reactor pressure vessel (RPV). This value is the same as the time restraint (pages 12 and 47). Similarly, the time constraint of 9.S hrs for refilling the condensate storage tank (CST) is the same as the analytically determined value (pages 12 and 48). Unless the analysis is conservative, the required action times have minimal or no margins when compared to the analytically determined values.

Provide a basis that describes how the time constraints can reasonably be met as described in Nuclear Energy Institute's (NEI) 12-06, Section 3.2.1.7, Principle 6.

049-RAI-Vermont Yankee-4 Page 7, Item 4.c states: "equipment needed for the station blackout (S80) coping duration is available at the site once Phase 2 is implemented." Identify equipment needed for the S80 coping duration that is being credited for ELAP during Phase 2. Specify if this equipment is permanently installed equipment or portable equipment.

049-RAI-Vermont Yankee-S On page 36, the Main Control Room Accessibility section indicates that the assumed maximum temperature for efficient human performance is 110°F, as described in NUMARC 87-00, It further states that through the use of smoke ejectors and by removing ceiling tiles, the main control room temperature can be maintained at this temperature for up to 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. However, NUMARC 87-00 also indicates that the technical basis for defining the habitability standard comes from MIL-STD-1472C, which concludes that 110 of is tolerable for light work for a 4 hour4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> period while dressed in conventional clothing with a relative humidity of -30 percent In light of these conflicting technical bases, please provide justification for the long term habitability of the main control room and/or please indicate what additional relief efforts for the main control room staff will be provided (e.g. short stay time cycles, use of ice vests/packs, supplies of bottled water, etc.).

049-RAI-Vermont Yankee-6 The integrated plan states that the engineered safety feature (ESF) switchgear rooms and the residual heat removal (RHR) rooms will exceed a limit of 110 of. In the case of the ESF switchgear rooms, the plan states that, without reference to a technical basis, the temperatures would be reduced to 108 OF and 10S of for the east and west switchgear rooms respectively, but relies on a maximum temperature of 114 OF determined in the switchgear room heatup

- 3 calculation. In the case of the RHR rooms, the plan states that the temperature will be below 148 of during the time in which the RHR pump and two RHR service water pumps would be placed into service. It discusses industrial safety procedures to prevent adverse impacts on personnel due to heat stress, but provides no further information on the provisions of protective clothing, other equipment provided to protect operators, or on the extent of potential local operator actions necessary in these locations. Please discuss planned provisions for access to these areas.

049-RAI-Vermont Yankee-7 The strategies for regulating the temperature in the main control room and the RCIC room, as well as ventilation strategies for the battery room and the spent fuel pool area involve propping open of doors to these rooms, or c;loors to stairways and equipment hatches. Please indicate what security measures have been considered or will be implemented in light of these open pathways.

049-RAI-Vermont Yankee-8 With regard to the load shedding of the DC bus in order to conserve battery capacity:

a. Provide the DC load profile for the mitigation strategies to maintain core cooling, containment, and spent fuel pool cooling during all modes of operation. In your response, describe any load shedding that is assumed to occur and the actions necessary to complete each load shed. Also provide a detailed discussion on the loads that will be shed from the dc bus, the equipment location (or location where the required action needs to be taken), and the required operator actions necessary and the time to complete each action. In your response, explain which functions are lost as a result of shedding each load and discuss any impact on defense-in-depth strategies and redundancy.

b. Identify any plant components that will change state if vital ac or dc power is lost or de-energized during the load shed. The staff are particularly interested in whether a safety hazard is introduced, such as de-energizing the DC-powered seal oil pump for the main generator and allowing hydrogen to escape, which could contribute to risk of fire or explosion in the vicinity from the uncooled main turbine bearings.

c. Identify DC breakers that must be opened as a part of the load shed evolution.

d. Identify whether the DC breakers that must be opened will be physically identified by special markings to assist operators in manipulating the correct breakers.

049-RAI-Vermont Yankee-9 The licensee states that their batteries can last at least 9 hours1.041667e-4 days <br />0.0025 hours <br />1.488095e-5 weeks <br />3.4245e-6 months <br />. The Institute of Electrical and Electronics Engineers (IEEE) Standard 535-1986, "IEEE Standard for Qualification of Class 1E Lead Storage Batteries for Nuclear Power Generating Stations;' as endorsed by Regulatory Guide 1.158, "Qualification of Safety-Related Lead Storage Batteries for Nuclear Power Plants;'

provides guidance for qualifying nuclear-grade batteries and describes a method acceptable to the NRC staff for complying with Commission regulations with regard to qualification of safety-related lead storage batteries for nuclear power plants. Provide documentation that shows that your battery cells fully comply with the qualification principles in clause 5 and meet the requirements in clause 8.2 of IEEE Standard 535, for the duration you are crediting the

-4 station batteries in your mitigating strategies integrated plan (See Agencywide Documents Access and Management System Accession No. ML13094A397 for additional information).

049-RAI-Vermont Yankee-10 In the discussion of safety relief valve (SRV) control on pages 5 and 6 of the integrated plan.

Entergy assumes that battery power for SRV control is available throughout Phases 1 and 2 by providing a FLEX diesel generator (DG) to power the battery chargers at approximately 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />.

Describe Entergy's basis for concluding that this time constraint can reasonably be met as specified in NEI 12-06. Section 3.2.1.7. Principle 6 given the potential limitation of battery capability as discussed above.

049-RAI-Vermont Yankee-11 Describe how the portable/FLEX diesel generators and the Class 1E diesel generators are isolated to prevent simultaneously supplying power to the same Class 1E bus in order to conform to NEI 12-06. Section 3.2.2. guideline (13). which specifies that appropriate electrical isolations and interactions should be addressed in procedures and guidance.

049-RAI-Vermont Yankee-12 Provide the minimum DC bus voltage that must be maintained to ensure proper operation of all required electrical equipment.

049-RAI-Vermont Yankee-13 The second bullet on page 5 of the Vermont Yankee (VY) integrated plan indicates that entry into ELAP will occur at one hour to conservatively reflect the need to verify the entry conditions and validate that emergency diesel generators are not available based on Plant procedure OPOT-3122-02. "Station Blackout:' Revision 1. The third bullet on page 5 indicates that load shed initiated by the SBO procedures will be completed by approximately one hour. This is documented in the VY Overall Integrated Plan, Attachment 1A as simultaneously occurring.

Explain how operators will simultaneously identify an ELAP condition and complete all DC load shedding. Is this an action to be performed by a dedicated operator? Describe the basis for concluding that these time constraints can reasonably be met as specified in NEI 12-06, Section 3.2.1.7, Principle 6.

049-RAI-Vermont Yankee-14 The licensee stated that"jf onsite diesel fuel reserves are needed to operate temporary equipment, there are two locations to obtain diesel fuel." The first option would be the fuel oil storage tank. The second option would be the two diesel generator (DG) day tanks:' Describe the design of these tanks (e.g., seismically qualified or robust?).

049-RAI-Vermont Yankee-15 The licensee stated that"in this case. the reliable hardened vent (RHV) system will be used as implemented per EA-12-050 to vent containment with control from the control room (CRP 9-25):'

Describe the power requirements for the valves and indication or instrumentation and how they power will be supplied.

049-RAI-Vermont Yankee-16 Regulatory Position C.6 in Regulatory Guide (RG) 1.128, "Installation Design and Installation of Vented Lead-Acid Storage Batteries for Nuclear Power Plants:' states that conformance with the IEEE Std. 484-2002 requirements (indicated by the verb "shall') for installation design and

- 5 installation of vented lead-acid storage batteries for nuclear power plants provides an adequate basis for complying with the design, fabrication, erection, and testing requirements set forth in GDCs 1, 17, and 18 of Appendix A to 10 CFR Part 50, as well as Criterion III of Appendix B to 10 CFR Part 50, subject to the following stipulation: In Subsection 5.4, 'Ventilation;' revise the second sentence to be consistent with RG 1.189, as follows: 'The ventilation system shall limit hydrogen accumulation to one percent of the total volume of the battery area:'

The licensee stated that 'the accumulation of hydrogen from the batteries located in the battery room would not exceed 4% [percent1 concentration in the battery room in 2.5 days (36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />) with a complete loss of the ventilation system (Reference 2, Section 8.6.4):' Discuss the accumulation of hydrogen with respect to national standards and codes which limit hydrogen concentration to less than 1percent according to the National Fire Code and Regulatory Guide 1.128, "Installation Design and Insta"ation of Vented Lead-Acid Storage Batteries for Nuclear Power Plants; which endorses IEEE Standard 484, with exceptions.

049-RAI-Vermont Yankee-17 The licensee stated that 'there are two strategies for venting the battery rooms. The primary strategy will be to repower the existing exhaust fan which is connected to the emergency power bus. The alternate strategy is to prop open doors and set up portable fans:' Provide a discussion on the hydrogen gas exhaust path for each strategy.

049-RAI-Vermont Yankee-18 The integrated plan contains insufficient information to support a conclusion that considerations 2 through 4 of NE112-06, Section 5.3.3, will be taken into account in the development of the mitigation strategies pursuant to Order EA-12-049. These considerations address the potential impacts of large internal flooding sources that are not seismically robust and do not require ac power, the potential reliance on ac power to mitigate ground water, and the potential impacts of non-seismically robust downstream dams. Please discuss the effects of these considerations on the strategies being developed at VY pursuant to EA-12-049.

049-RAI-Vermont Yankee-19 The response identifies the limiting source of external flooding as being regional preCipitation, which NEI 12-06 characterizes in Table 6-1 as having warning time in days and persistence in months. Failing to apply the longer warning time in the development of the strategies would not enable a licensee to make use of the allowances of NEI 12-06, Section 6.2.3.2, consideration 1 for pre-event preparations, which would be conservative to a set of strategies making use of that consideration. However, failing to characterize the persistence of an external flooding hazard prevents the staff from concluding that NEI 12-06, Section 6.2.3.2, Consideration 2 on the ability to move equipment and restock supplies during a flood with long persistence has been appropriately addressed. Please discuss the persistence of the external flooding hazard.

049-RAI-Vermont Yankee-20 The integrated plan response presents information on Entergy's partiCipation in the industry regional response centers for phase 3 equipment sufficient to allow the staff to conclude that there is reasonable assurance that Entergy will establish a capability to obtain equipment and commodities to sustain and backup the site's coping strategies as specified in NEI12-06, Section 12.2, item 1. However, Entergy has provided insufficient information to allow the NRC staff to conclude that items 2 through 10 of that section will be adequately addressed. Please discuss.

- 6 049-RAI-Vermont Yankee-21 ,

The integrated plan response presents no information on the identification of plant procedures and guidance of portable lighting such as flashlights, headlamps and communications systems necessary for ingress and egress to plant areas, which is required for deployment of the strategies as discussed in NEI 12-06, Section 3.2.2, paragraph (8). Please discuss.

049-RAI-Vermont Yankee-22 Page 8 of the integrated plan discusses programmatic controls that will be implemented, but it omits discussions of unavailability control for equipment and connections per NEI 12-06, Sections 3.2.2 and 11.5. Please discuss.

049-RAI-Vermont Yankee-23 The nitrogen gas supply to the safety relief valves is non-seismic and so may be lost. The plant operators will rely on backup N2 bottles that need to be replaced within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. Discuss access and protection of the connections for the nitrogen bottles.

049-RAI-Vermont Yankee-24 Page 11 also states, '.' re nitrogen storage bottles automatically supply backup pneumatic pressure for SRV operation with enough capacity to provide for 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> of operation':

Provide additional basis and supporting details for this statement. including the differences between ELAP and the orjginal basis for sizing of nitrogen storage bottles. Please focus your response on why the storage bottles are sufficient for 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> of operation under ELAP.

049-RAI-Vermont Yankee-25 Page 8 indicates that VY procedures and programs will be developed in accordance with NEI 12-06 to address storage structure requirements. However the submittal is silent on the securing of large portable equipment to protect the plant during a seismic event and the evaluation of stored equipment for seismic interactions. Please clarify the inclusion of these considerations in the planned procedures and programs.

049-RAI-Vermont Yankee-26 Page 8 indicates that identified paths and deployment areas will be accessible during all modes of operation. However, the submittal provides no information on considerations for the effects of ac power loss on access to the protected area and internal locked areas where remote equipment is necessary, as discussed in NEI 12-06, Section 3.2.2. paragraph (9).

049-RAI-Vermont Yankee-27 Pages 19. 20 and 34 indicate that plant piping and valves for connections, specifically valves V70-320AlB, V73-26, the 4' Storz splitter and the connection upstream of valve V19-50 will be within Seismic Class 1 structures, but insufficient information has been presented to confirm that access to these connections will only require access through seismically robust structures.

Please confirm that the path to access these connection points will not require entry into non-seismically robust structures.

049-RAI-Vermont Yankee-28 Page 44 identifies two vehicles with sufficient rating to tow the pumps and DGs during phase 2, but provides no information on the protection of the vehicles from external events. Please

-7 discuss the level of protection to be afforded the vehicles as discussed in NEI 12-06, Sections 5.3.2, 6.2.3.2, and 7.3.2.

049-RAI-Vermont Yankee-29 Pages 14 and 25 of the integrated plan indicates that key parameters can be determined from local readings using standard I&C instruments, but provides insufficient information for the NRC to determine whether a reference source currently exists for obtaining necessary instrument readings or whether one will be developed as discussed in NEI 12-06, Section 5.3.3. Please clarify.

049-RAI-Vermont Yankee-30 Page 46 indicates that debris clearing equipment will be provided during phase 3. Page 3 indicates that this equipment will be available within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> of the event. The goal of which is to maintain key safety functions for up to 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> using installed and onsite portable equipment. Given the potential need for debris removal in the context of a hurricane or tornado, discussed in NEI12-06, Section 7.3.2, and the identified time constraint of 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> for powering up both divisions of the Class 1E battery chargers using a portable DG, please discuss the basis for this being achievable without onsite debris removal equipment.

049-RAI-Vermont Yankee-31 The integrated plan response identifies that the administrative program for deployment of strategies will include elements that ensure pathways are clear or require actions to clear pathways, but does not provide sufficient information on the capabilities to remove snow and ice for NRC staff to come to a conclusion since such equipment is not listed in the tables on pages 44 through 46. Please discuss.

049-RAI-Vermont Yankee-32 The response includes information on the heat-up of a variety of enclosed rooms and spaces, but has no information on the potential effects of high ambient temperatures at the locations where portable equipment would operate in the event that mitigation strategies are implemented, as discussed in NEI 12-06, Section 9.3.3. Please discuss.

049-RAI-Vermont Yankee-33 The response does not contain sufficient analytical results to support the conclusions that the analytical predictions of the Modular Accident Analysis Program (MAAP) code are consistent with expected plant behavior and that core cooling is maintained. Please provide the relevant calculations which demonstrate adequate core cooling for NRC staff audit review.

049-RAI-Vermont Yankee-34 The actions reported in the integrated plan and their timing are based on analyses performed with version 4.05 of the MAAP code. The NRC staff has not conducted a detailed review of the capabilities of this code for application to an ELAP conditions. The staff is further aware that the MAAP code contains simplified models and correlations and allows user-specified inputs that can affect the accuracy of its predictions for significant parameters such as core two-phase level and system pressure. Therefore, please provide adequate technical basis to support the conclusion that the capability of the MAAP code is sufficient to predict whether the intended mitigating strategies would adequately cool the reactor core during an ELAP event. The justification may include discussion of the adequacy of the code's relevant models and

-8 correlations, benchmarking of code calculations against relevant experimental data, and relevant comparisons to calculations with state-of-the-art thermal-hydraulic codes.

049-RAI-Vermont Yankee-35 Please provide a summary of the techniques, assumptions, and boundary conditions for the MAAP evaluation model created for VY. For example, discuss important aspects of the evaluation model include the nodalization, two-phase flow modeling (e.g., homogeneity, equilibrium, or lack thereof, between phases), modeling of heat transfer and losses, vent line pressure losses, etc.

049-RAI-Vermont Yankee-36 Please discuss the quality assurance process under which the MAAP calculations were performed.

049-RAI-Vermont Yankee-37 Please identify and provide justification for the assumptions made regarding primary system leakage from the recirculation pump seals and other sources. Please include a discussion of the assumed pressure-dependence of the leakage rate. Please further clarify whether the leakage was determined or assumed to be single-phase liquid, two-phase mixture, or steam at the donor cell and discuss how mixing of the leakage flow with the drywell atmosphere is modeled.

049-RAI-Vermont Yankee-38 The ELAP analyses for VY generally appear to be based on the assumption that the RCIC system will be placed into service. However, the potential for the high pressure coolant injection (HPCI) system to provide backup capability is identified in several places, including the discussion of mitigating an ELAP event that occurs during cold shutdown mode when the operability of either system is not required. Please clarify whether use of HPCI instead of RCIC would significantly affect the analysis for VY (e.g., steam requirements, temperature qualification, etc.) and provide justification.

049-RAI-Vermont Yankee-39 Please provide confirmation that suppression pool water level remains adequately stable under long-term injection of external water sources.

049-RAI-Vermont Yankee-40 Describe whether any equipment protection features will interfere with the operation of RCIC during ELAP.

049-RAI-Vermont Yankee-41 Page 16 states: Providing defense in depth for RCIC pump is to deploy the diesel driven FLEX pump to the west deep basin. While taking suction from the deep basin, the diesel driven FLEX pump will then discharge to a 4" flexible hose which will be run approximately 500 feet through the Protected Area fences, by cutting a hole, to the south side of the reactor building. There, the hose will be run through the new penetration on the south wall of the reactor building (FLEX Connection #1) (Figure 1). Per Reference 6, approximately another 200 feet of 4" flexible hose will then be run from the interior side of this penetration in the reactor building, split into two, 2" hoses and tie into the 'A' loop RHR system via valves V70-320A and V70-320B. The system will be lined up per

- 9 existing plant procedure (Reference 1) and provide make up to the vessel using the RHR seismically qualified piping.

And'.'.Aportable diesel driven FLEX pump will supply the required flow rate of 120 gpm at 140 feet of head ~'

In the event that the described defense-in-depth configuration is needed, what is the timeframe for getting it staged and operating?

049-RAI-Vermont Yankee-42 Page 11 of the integrated plan states that the automatic depressurization system will either be placed in 'inhibif or closely monitored to prevent automatic initiation. Please clarify how the determination of placing the system in 'inhibif will be made and justified such that the planned monitoring approach is an acceptable alternative for preventing system actuation.

049-RAI-Vermont Yankee-43 Page 12 states: Raising the standpipes will allow the CST to last greater than the 7 hour8.101852e-5 days <br />0.00194 hours <br />1.157407e-5 weeks <br />2.6635e-6 months <br /> limit that is currently in effect due to the limited 75,000 reserve gallons (Reference 9, Section 4.7.5). The increased height of the standpipes allow for crediting another 11,000 gallons (a total of 86,000 gallons) and provide for the CST inventory to last approximately 9.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br />.

There was no reference provided supporting the statement that increasing the reserved storage by 11,000 gallons would support an additional duration of 2.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> of RCIC operation. Discuss whether this conclusion is based on a linear comparison or if any calculations were performed to support this conclusion, including sufficient details to support the conclusion.

049-RAI-Vermont Yankee-44 On page 16, the alternate strategy for maintaining core cooling using portable equipment for Phase 2 in lieu of RCIC indicates that the diesel driven FLEX pump will be deployed to the west deep basin. Then hose connections will be made to allow for injection via the 'P/. RHR loop in order to maintain/recover RPV inventory. According to Attachment 1A, the time at which injection begins is 9.5 hrs after RPV depressurization from 200 psig to 400 psig. However, according to page 44, the diesel-driven FLEX pump has a 500 ft dynamic head, which has a pressure of approximately 200 psig. As this is insufficient to overcome the pressure in the RPV, the RPV would need to be further depressurized for water injection to occur, but there is no mention of further RPV depressurization in the coping strategy. Please provide additional basis or analysis that supports the diesel-driven FLEX pump when considering the pressure within the RPV and the loss of pressure along the FLEX pump supply lines is capable of injecting water into the RPV with a sufficient rate to maintain and recover core inventory.

049-RAI-Vermont Yankee-45 Page 16 also describes an arrangement of hoses and hydraulic components that will be incorporated into the portable system which is intended to refill the CST.

What analyses or evaluations were done or are planned for confirming the ability of the diesel driven FLEX pumps to deliver the required flow through the system of flex hoses, wye splitters, valves, elevation changes, etc. Please discuss in terms of both the primary and alternate strategies.

- 10 049-RAI-Vermont Yankee-46 For the Phase 2 strategy for maintaining adequate core cooling, page 16 of the integrated plan response indicates that water from the west deep basin or Connecticut River may be supplied to cool the reactor core. Please discuss the quality of this water (e.g., suspended solids) and provide justification that its use will not result in blockage at the fuel assembly inlets to an extent that would inhibit adequate flow to the core. Alternately, if deleterious blockage at the fuel assembly inlets cannot be precluded, then please discuss alternate means for assuring adequate core cooling.

049-RAI-Vermont Yankee-47 Page 13 states: If an ELAP occurs during Cold Shutdown, water in the vessel will heatup. When temperature reaches 212°F (Hot Shutdown), the vessel will begin to pressurize. The turbine driven systems (RCIC and HPCI) are generally available for emergency use at the beginning and end of an outage, thus during the pressure rise RCIC can be returned to service, after testing, with suction from the CST to provide injection flow. When pressure rises to the SRV setpoints then pressure will be controlled by SRVs.

Provide an assessment of the timeline for pressure rise, including specific times when the minimum pressure required for RCIC operation is reached, testing is completed, and RCIC is available and aligned to inject. The assessment should consider the bounding case with respect to core heat up and demonstrate that adequate core cooling is maintained during the period without primary system makeup. Additionally, discuss whether portable equipment could be successfully used if the installed turbine-driven systems cannot be restored to service in adequate time for an ELAP event that occurs during cold shutdown mode.

049-RAI-Vermont Yankee-48 Page 13 states: The most limiting condition is the case in which the reactor head is removed and water level in the vessel is at or below the reactor vessel flange. If an ELAP/LUHS (loss of ultimate heat sink) occurs during this condition then (depending on the time after shutdown) boiling in the core occurs quite rapidly.

Provide a timeline for boiling to occur for the most limiting water level condition within the vessel when the reactor head is removed. Use the shortest historical time after shutdown in which the reactor head was able to be removed. Discuss the ability to place Phase 2 makeup measures in effect within this time and the basis for concluding that mitigating actions can be taken in time to satisfy the event acceptance criteria. Alternatively, provide the lowest RPV water level that could be reached before the Phase 2 measures are effective.

049-RAI-Vermont Yankee-49 Page 24 of the submittal (emphasis added) states: The containment design pressure is 56 psig (Reference 1, Section 5.2.3.2 and Table .2.1). Containment pressure limits are not expected to be reached during Phase 1 of the event. However, if the maximum containment pressure is reached, EOP requires operators to vent the containment (Reference 2). In this case, the RHV System will be used as implemented per EA-12-050 to vent containment with control from the Control Room (CRP 9-25).

- 11 Then continues to state, '!C\s determined by MAAP analysis (Reference 3), torus venting is assumed to open at an approximate pressure of 30 psig via the RHV system at approximately

=

time t 14 hours1.62037e-4 days <br />0.00389 hours <br />2.314815e-5 weeks <br />5.327e-6 months <br />."

Explain the inconsistency between the guidance in the EOPs quote #1, and the implementation of the Mitigation Strategies plan to vent the containment at approximately 30 psig (quote #2).

049-RAI-Vermont Yankee-50 Page 26 states: Containment pressure limits are not expected to be reached during the event as indicated by MAAP analYSis (Reference 1), because the hardened containment vent system HCVS is opened prior to exceeding any containment pressure limits.

Containment integrity is maintained throughout the event by permanently installed equipment.

Please confirm that the maintenance of containment integrity as described in the above statement is intended to demonstrate the ability to quickly restore containment integrity at some time in the future while supporting decay heat removal from containment in the meantime.

049-RAI-Vermont Yankee-51 Page 48 states: MAAP analysis indicates that the containment pressure limit would be exceeded at approximately 20 hours2.314815e-4 days <br />0.00556 hours <br />3.306878e-5 weeks <br />7.61e-6 months <br />. However, to keep from approaching this limit and the other containment limits (noted above), the vents are assumed to open early at approximately 30 psig which is reached at approximately 14 hours1.62037e-4 days <br />0.00389 hours <br />2.314815e-5 weeks <br />5.327e-6 months <br />.

Which parameter is the limiting factor in the analysis: 14 hours1.62037e-4 days <br />0.00389 hours <br />2.314815e-5 weeks <br />5.327e-6 months <br /> or 30 psig? If venting was done at 30 psig, will the containment ever reach the design pressure; if so, when?

049-RAI-Vermont Yankee-52 The essential containment instrumentation listed in the response (e.g., page 25) does not include instrumentation for measuring drywell temperature. Please provide the basis for concluding that monitoring drywell temperature is not required for purposes such as validating the qualification range of measurement instruments located in the drywell or establishing the survivability of penetration seals or other equipment. The basis should also consider the assumptions in light of the information provided in NEDC-33771P (e.g., Figures D-11 and G-11).

049-RAI-Vermont Yankee-53 The response appears to correlate containment integrity with ensuring containment pressure limits are not exceeded (e.g., discussion on page 26). Please clarify whether the calculated containment temperatures would remain within design values during an ELAP event. If not, please clarify whether excessive temperatures could result in a loss of containment integrity due to the failure of containment penetration seals or other portions of the containment boundary and provide justification.

049-RAI-Vermont Yankee-54 Provide the range of plant states that will require venting, and describe the information and parameter values used by the operator to make the decision to vent.

- 12 049-RAI-Vermont Yankee-55 Page 7 states (emphasis added):'The guidance provided in [NEDC-33771 P, Revision 1]

was utilized as appropriate to develop coping strategies and for prediction of the plant's response."

Page 46 of the subject NEDC document states, Therefore, the analyses results presented herein are not deemed to be bounding. Plant-specific justification or detailed analysis is required:'

To what extent do VYs Integrated Plan and the time constraints depend on NEDC-33771 P, Revision 1? To the extent that the NEDC report was relied upon, were any plant specific analyses performed to support the applicability of the document to VY?

Identify each instance where a plant parameter or time constraint for VY was based on the data and/or analyses from the subject NEDC document and provide a technical justification for its applicability to VY.

049-RAI-Vermont Yankee-56 In conjunction with the request immediately above, provide the VY, plant-specific ELAP analysis information commensurate with the level of detail contained in NEDC-33771 P, including analysis assumptions and results in their tabulated and plotted formats.

049-RAI-Vermont Yankee-57 Pages 5, 6, 12, and 24 of the integrated plan cite MAAP evaluations contained in a referenced ENERCON Calculation, ENTGVY033-CALC-002, 'Vermont Yankee Nuclear Power Station Containment Analysis of FLEX Strategies;' Revision O.

Page 26 cites a different MAAP evaluation applicable to Phase 2 contained in a referenced ENERCON Report, ENTGVY033-PR-002,"Diverse and Flexible Coping Strategies (FLEX) and Conceptual Design in Response to NRC Order EA-12-049,

'Mitigation Strategies for Beyond-Design-Basis External Events', Revision 1, but also refers the reader back to the '.' .R1ase 1 description for discussion of containment integrity applicable throughout the event:'

Explain the differences in the two cited MAAP calculations. If they are identical, describe the administrative controls in place to ensure that poth calculations are appropriately revised if/when the need arises.

049-RAI-Vermont Yankee-58 Page 24 states, "no non-permanently installed equipment will be required to maintain containment integrity. Therefore, there is no defined end time for the Phase 1 coping period for maintaining containment integrity:'

Confirm that deployment of FLEX portable equipment for replenishment of consumables (e.g.

compressed air/nitrogen bottles, power, etc.) is not relied upon to support continued operatiofl of the HCVS beyond the 24-hour duration, which is specified in NRC Order EA-12-050.

- 13 049-RAI-Vermont Yankee-59 As quoted in the request immediately above, page 24 states, "no non-permanently installed equipment will be required to maintain containment integrity:'

The following statement is applied several times on page 27 and referenced on page 29:

The HCVS will be implemented and enhanced in accordance with NRC Order EA-12-050, Issuance of Order to Modify Licenses with Regard to Reliable hardened Containment Vents and guidance in JLD-ISG-2012-02. The HCVS will meet the design requirements as specified for reasonable protection per NEI 12-06.

This section covers the storage and protection of portable equipment. If no portable equipment is required for HCVS operation, this section should state as such. If portable equipment is required, the statements in this section should be similar to those under the core cooling section. Please clarify the intent of this statement.

049-RAI-Vermont Yankee-60 Based on the discussion on page 31 of the integrated plan response, please clarify whether earthquake loads considered within the scope of the Order would result in sloshing losses from the spent fuel pool and whether these have been factored into the time to boil calculation.

049-RAI-Vermont Yankee-61 The integrated plan response states on page 39 that a high point vent should be created above the reactor building, 345 feet elevation, if possible. Please discuss the consequences of not establishing a high point vent and confirm that the analysis demonstrates that steam from boiling in the spent fuel pool can be adequately vented without adversely affecting other mitigation equipment or activities (e.g. preventing manual operation of valves or connection of hoses to provide spent fuel pool makeup) even if a high point vent is not established.

049-RAI-Vermont Yankee-62 On page 31, the Primary Strategy Method 1 for maintaining spent fuel pool cooling using portable equipment for Phase 2 indicates that the hose will be run from the 4inch Storz valve splitter, which is connected to the same FLEX pump used for RPV injection (via CST and RCIC or directly through '1\ RHR), to a new valve header installed upstream of valve V19-50. In the process of running this hose, valve X004 on the 4' Storz valve splitter will be closed, and the adjacent valve X002 will be opened. This will prevent the FLEX pump from supplying makeup water to the CST, when so aligned. Please clarify if maintaining spent fuel pool cooling requires closing off makeup to the CST and if so, discuss the basis for this. Additionally, if it is required for makeup to the CST be closed off, the CST may run dry and deprive RCIC of its primary injection source. This would then necessitate using the FLEX pump to supply RPV injection via the /\ RHR loop as discussed in the Maintain Core Cooling Alternate Strategy on page 16.

However, the need to align the FLEX pump to inject via the '/1\ RHR loop when spent fuel pool cooling begins is not indicated in the Spent Fuel Pool Cooling section of the coping strategy.

Please clarify whether the 'p.: RHR loop injection alignment will always be used with spent fuel pool cooling or whether the discharge of the FLEX pump would be alternated between the CST and spent fuel pool.

- 14 049-RAI-Vermont Yankee-63 On page 32, the Primary Strategy Method 3 for maintaining spent fuel pool cooling using portable equipment for Phase 2 indicates that the use of valve X006 will require a spray flow of 250 gpm over the spent fuel pool. Please provide justification that when the diesel-driven FLEX pump is providing injection to the RPV via 'p.: RHR loop that the loss of in-line pressure due to supplying a 250 gpm spray flow to the spent fuel pool does not adversely impact the pump's ability to inject and supply adequate flow rate to maintain and recover the RPV inventory.

Further, if flow is simultaneously supplied to the reactor vessel and spent fuel pool, please clarify whether adequate flow indications are available to ensure an adequate flow split.

049-RAI-Vermont Yankee-64 Page 31 indicates that for a full core offload, spent fuel pool boiling occurs at 8.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br />, and it takes 60.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> to boil off the 21 feet of water protecting the tops of the spent fuel. However, for a full core offload it is not clear if the intent is to begin cooling and maintaining the spent fuel pool at 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />, before boiling occurs, or, as a result of the 60.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> margin, to begin cooling and maintaining the spent fuel pool at 28 hrs, just as it would for the design basis conditions.

Please clarify when spent fuel pool cooling will begin for a full core offload. If the intent is to begin at 28 hours3.240741e-4 days <br />0.00778 hours <br />4.62963e-5 weeks <br />1.0654e-5 months <br />, this means there will be 19.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> of time during which the water level in the spent fuel pool is boiling and the inventory of water is lowering. In this case, please provide justification that the resulting reduction in water level does not result in an increase in exposure beyond acceptable levels.

049-RAI-Vermont Yankee-65 Page 17 states:

If onsite diesel fuel reserves are needed to operate temporary equipment, there are two locations to obtain diesel fuel. The first option would be the Fuel Oil Storage Tank. The second option would be the two DG day tanks. A minimum of 36,000 gallons of diesel fuel is stored in the Fuel Oil Storage Tank and two day tanks have a nominal capacity of 800 gallons each (Reference 5, Section 8.5.4). The fuel could be accessed through a hose connected to accessible drain valves of the day tanks. The oil in the Fuel Oil Storage Tank can be transferred to the day tanks using the fuel oil transfer pumps or with a portable transfer pump connected to the system. Adequate fuel supplies are available and accessible to operate emergency response equipment.

Page 44 includes a listing of 500 gallon diesel tank carts and fuel transfer pumps/carts.

Provide a discussion on fueling provisions for the portable equipment, including the level of protection afforded the diesel tank carts and fuel transfer pumps/carts and time constraints associated with fueling and refueling the portable equipment.

049-RAI-Vermont Yankee-66 Describe the instrumentation that will be used to monitor portable/FLEX electrical power equipment including their associated measurement tolerances/accuracy to ensure that: 1) the electrical equipment remains protected (from an electrical power standpoint-e.g., power fluctuations) and 2) the operator is provided with accurate information to maintain core cooling, containment, and spent fuel cooling.

- 15 049-RAI-Vermont Yankee-67 Provide details of the maintenance and testing plan for electrical equipment that is credited for events that require mitigating strategies. The staff is trying to understand how Regulatory Guidance documents, IEEE Standards, manufacturer recommendations, etc. will be utilized to establish the maintenance and testing programs for the portable/FLEX electrical equipment, especially for batteries and diesel generators.

Additional RAls resulting from SRM-SECY-12-0157 In Staff Requirements Memorandum SRM-SECY-12-057, "Consideration of Additional Requirements for Containment Venting System for Boiling Water Reactors with Mark I and Mark II Containments;' the Commission has approved Option 2 to issue a modification to Order EA-12-050, "Order Modifying Licenses With Regard to Reliable Hardened Containment Vents;'to require licenses for Boiling Water Reactors (BWRs) with Mark I and Mark II containments to upgrade or replace the reliable hardened vents required by Order EA-12-050, with a containment venting system designed and installed to remain functional during severe accident conditions. The revision to Order EA-12-050 and the revised interim staff guidance JLD-ISG-2012-02, "Compliance with Order EA-12-050, Reliable Hardened Containment Vents; are scheduled to be issued in the near future. The revised order nominally expands the scope of the reliable hardened vent from preventing core damage to mitigating an ELAP after severe core damage with vessel breach to the drywell floor. The expanded scope will have an impact on Mark I and Mark II BWR responses to comply with Order EA-12-049, 'Order Modifying Licenses with Regard to Requirements for Mitigation Strategies for Beyond-Design Basis External Events:' As a result of this change, please address the following questions:

049-RAI-Vermont Yankee-68 How are the mitigating actions proposed by VY affected by the severe accident environment, including high temperature, radiation, and combustible gases that could be present in the reactor building, as well as the routing of the severe accident containment vent line?

For example, page 2 states, ~.c:r:srator actions to open MCR doors, remove ceiling tiles and deploy smoke ejectors (Item 6) to ventilate the MCR:'

Is this strategy still feasible with an accident source term in the drywell and a vent sending radiation out of the containment?

049-RAI-Vermont Yankee-69 How are the Mitigation Strategies Phase 1 and Phase 2 responses, including the transporting of FLEX equipment to their intended locations, and the response times affected by the severe accident environment and the location of the vent releases?

049-RAI-Vermont Yankee-70 What additional FLEX equipment, including permanent FLEX connections and additional mitigation actions, would be required for drywell flooding to maintain containment integrity?

June 17, 2013 Site Vice President Entergy Nuclear Operations, Inc.

Vermont Yankee Nuclear Power Station P.O. Box 250 Governor Hunt Road Vernon, VT 05354 SUB..IECT: VERMONT YANKEE NUCLEAR POWER STATION - REQUEST FOR ADDITIONAL INFORMATION REGARDING OVERALL INTEGRATED PLAN IN RESPONSE TO MARCH 12, 2012 COMMISSION ORDER TO MODIFY LICENSES WITH REGARD TO REQUIREMENTS FOR MITIGATION STRATEGIES FOR BEYOND-DESIGN-BASIS EXTERNAL EVENTS (ORDER NUMBER EA-12-049) (TAC NO. MF0779)

Dear Sir or Madam:

By letter dated February 28, 2013 (Agencywide Document Access and Management System (ADAMS) Accession No. ML13064A300), Entergy Nuclear Operations, Inc. submitted Vermont Yankee Nuclear Power Station's Overall Integrated Plan in response to the March 12, 2012, Commission Order to modify licenses with regard to requirements for mitigating strategies for beyond-design-basis external events (Order Number EA-12-049).

The Nuclear Regulatory Commission (NRC) staff is reviewing the information provided in your submittal and has determined that additional information is needed to support its review.

Enclosed is the NRC staff's request for additional information (RAI). The RAI was discussed with your staff on June 12, 2013. Please provide a response to the questions within 30 days of the date of this letter. If any part of this information is not available within 30 days of this request, please provide the date that this information will be provided.

Sincerely, IRAJ Richard V. Guzman, Senior Project Manager Plant Licensing Branch 1-1 Division of Operating Reactor licensing Office of Nuclear Reactor Regulation Docket No. 50-271

Enclosure:

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