NEXTeraM DUAN ENERG--YPA ýARNOLD February 28, 2013 NG-1 3-0085 10 CFR 2.202 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Duane Arnold Energy Center Docket No. 50-331 Renewed Op. License No. DPR-49 NextEra Energy-Duane Arnold, LLC's Overall Integrated Plan in Response to March 12, 2012 Commission Order Modifying Licenses with Regard to Requirements for Reliable Hardened Containment Vents (Order Number EA-12-050) References: 1. NRC Order Number EA-12-050, Order Modifying Licenses with Regard to Requirements for Reliable Hardened Containment Vents, dated March 12, 2012, Accession No. ML12054A694 2. NRC Interim Staff Guidance JLD-ISG-2012-02, Compliance with Order EA-12-050, Order Modifying Licenses with Regard to Requirements for Reliable Hardened Containment Vents, Revision 0, dated August 29, 2012, Accession No. ML12229A475 3. Letter, R. Anderson (NextEra Energy Duane Arnold, LLC) to U.S. NRC, "NextEra Energy Duane Arnold, LLC's Initial Status Report in Response to March 12, 2012 Commission Order Modifying Licenses with Regard to Reliable Hardened Containment Vents (Order Number EA-12-050)," NG-12-0427, dated October 29, 2012, Accession No. ML12305A375 On March 12, 2012, the Nuclear Regulatory Commission ("NRC" or "Commission") issued an Order (Reference 1) to NextEra Energy Duane Arnold, LLC (hereafter, NextEra Energy Duane Arnold). Reference 1 was immediately effective and directs NextEra Energy Duane Arnold to have a reliable hardened vent (RHV) installed at its Boiling Water Reactor (BWR) with a Mark I Containment to remove decay heat and maintain control of containment pressure within acceptable limits following events that result in the loss of active containment heat removal capability or prolonged Station Blackout (SBO). Specific requirements are outlined in Attachment 2 of Reference 1. Reference 1 requires submission of an Overall Integrated Plan by February 28, 2013. The NRC Interim Staff Guidance (Reference 2) was issued August 29, 2012, which provides direction regarding the content of this Overall Integrated Plan. NextEra Energy Duane Arnold, LLC, 3277 DAEC Road, Palo, IA5 2324 Document Control Desk NG-13-0085 Page 2 of 2 Reference 3 acknowledged NextEra Energy Duane Arnold's receipt of Reference 2 and provided the initial status report regarding the RHV, as required by Reference 1. The purpose of this letter is to provide the Overall Integrated Plan pursuant to Section IV, Condition C.1, of Reference 1. Reference 2, Section 4.0 contains the specific reporting requirements for the Overall Integrated Plan. The Enclosure to this letter provides NextEra Energy Duane Arnold's Overall Integrated Plan in accordance with Section 4.0 of Reference 2. For the purposes of compliance with Order EA-1 2-050 (Reference 1), NextEra Energy Duane Arnold plans to use a wetwell vent system. The potential addition of a hardened drywell vent system will not be determined until additional review of industry studies of severe accidents is completed. The Enclosure contains the current design information as of the writing of this letter, much of which is still preliminary, pending completion of on-going evaluations and analyses. Due to the synergy between the design of the RHV system and the equipment to be utilized in the Mitigating Strategies (so called FLEX) required by Order EA-12-049, some of the design details, in particular those regarding backup DC power and pneumatic supplies for the RHV, are still being developed. As further design details and associated procedure guidance are finalized, that additional information, as well as any revisions to the information contained in the Enclosure, will be communicated to the Staff in the 6-month updates required by the Orders. This letter contains no new regulatory commitments. If you have any questions regarding this report, please contact Ken Putnam at 319-851-7238. I declare under penalty of perjury that the foregoing is true and correct. Executed on February 28, 2013 Richard L. Anderson Vice President, Duane Arnold Energy Center NextEra Energy Duane Arnold, LLC Enclosure: Duane Arnold Energy Center Overall Integrated Plan for the Reliable Hardened Vent System cc: NRC Regional Administrator (Region Ill) NRC Resident Inspector (DAEC) NRC Licensing Project Manager (DAEC) Enclosure to NG-13-0085 Duane Arnold Energy Center Overall Integrated Plan for the Reliable Hardened Vent System 25 Pages to Follow Duane Arnold Energy Center Overall Integrated Plan for the Reliable Hardened Vent System Table of Contents: Section 1: System Description Section 2: Design Objectives Requirement 1.1.1 - Minimize the Reliance on Operator Actions Requirement 1.1.2 - Minimize Plant Operators' Exposure to Occupational Hazards Requirement 1.1.3 - Minimize Radiological Consequences Section 3: Operational Characteristics Requirement 1.2.1 - Capacity to Vent Equivalent of 1% Requirement 1.2.2 - HCVS Shall be Accessible to Plant Operators Requirement 1.2.3 - Prevent Inadvertent Actuation Requirement 1.2.4 - Monitor the Status of the Vent System Requirement 1.2.5 - Monitor the Effluent Discharge for Radioactivity Requirement 1.2.6 - Minimize Unintended Cross Flow of Vented Fluids Requirement 1.2.7 - Provision for the Operation, Testing, Inspection and Maintenance Requirement 1.2.8 - Design Pressures Requirement 1.2.9 - Discharge Release Point Section 4: Applicable Quality Requirements Requirement 2.1 - Containment Isolation Function Requirement 2.2 - Reliable and Rugged Performance Section 5: Procedures and Training Requirement 3.1 - Develop, Implement, and Maintain Procedures Requirement 3.2 - Train Appropriate Personnel Section 6: Implementation Schedule Milestones Section 7: Changes/Updates to this Overall Integrated Implementation Plan Section 8: Figures/Diagrams References: 1 Generic Letter 89-16, Installation of a Hardened Wetwell Vent, dated September 1, 1989 2 Order EA-049, Mitigation Strategies for Beyond-Design-Basis External Events, dated March 12, 2012 3 Order EA-050, Reliable Hardened Containment Vents, dated March 12, 2012 4 JLD-ISG-2012-02, Compliance with Order EA-12-050, Reliable Hardened Containment Vents, dated August 29, 2012 5 NRC Responses to Public Comments, Japan Lessons-Learned Project Directorate Interim Staff Guidance JLD-ISG-2012-02: Compliance with Order EA-12-050, Order Modifying Licenses with Regard to Reliable Hardened Containment Vents, dated August 29, 2012, ADAMS Accession No. ML12229A477 6 NEI 12-06, Diverse and Flexible Coping Strategies (FLEX) Implementation Guide, Revision 0, dated August 2012 Page I of 25 Duane Arnold Energy Center Overall Integrated Plan for the Reliable Hardened Vent System Section 1: System Description ISG Criteria: Licensees shall provide a complete description of the system, including important operational characteristics.T he level of detail generally considered adequate is consistent with the level of detail containedi n the licensee's Final Safety Analysis Report. Response: System Overview: The Hardened Containment Vent System (HCVS) will be designed to mitigate loss-of-decay- heat removal by providing sufficient containment venting capability to limit containment pressurization and maintain core cooling capability. The vent will be designed with sufficient capacity to accommodate decay heat input equivalent to approximately 1% of current licensed thermal power and will be capable of venting greater than the decay heat present when venting must be initiated to ensure the containment does not exceed design pressure. And thus, the hardened vent capacity will be adequate to relieve decay heat for a prolonged station blackout (SBO) event. The HCVS is intended for use as one element of core damage prevention strategies The HCVS flow path from the containment to an elevated release point is shown in the simplified diagram below. No ductwork will be used in the flow path. Page 2 of 25 Duane Arnold Enerav Center Overall Integrated Plan for the Reliable Hardened Vent System Figure 1 Simplified Vent Line Connections to Wetwell and Other Systems System Connection Options Option 1 - Dedicated wetwell vent-Not Currently Selected Option Vent %D etail Option 2 - Wetwell vent interfacing with another wetwell-connected system, dedicated release point-Currently Selected Option Vent To other sy st e ms P Option 3 -Wetwell vent interfacing with another wetwell-connected system and with an existing release point-Not Currently Selected Option To Stack A9 ~~ To othe4 syste ms Detail Options Option A - No control valve or rupture disk (Not Currently Selected Option) Option B - Rupture disk (Currently Selected Option) Option C - Control valve ii± 1 (Not Currently Selected Option) Page 3 of 25 Duane Arnold Enerqy Center Overall Integrated Plan for the Reliable Hardened Vent System Equipment and components: The following equipment and components will be provided: i. HCVS Mechanical Components - a) Containment isolation piping, valves and controls - The HCVS vent piping and supports up to and including the second containment isolation are designed in accordance with existing design basis. Containment isolation valves (CIVs) are provided consistent with the plants primary containment isolation valve design basis. The valves are air-operated valves (AOV) operated by a DC powered solenoid valve (SOV), and can be operated from switches in the Main Control Room. b) Other system valves and piping - The HCVS piping and supports downstream of the second containment isolation valve, including valve actuator pneumatic supply components, will be designed/analyzed to conform to the requirements consistent with the applicable design codes for the plant and to ensure functionality following a design basis earthquake. c) The interface valves provide isolation to the interconnected system. The HCVS shares part of its flow path with the Standby Gas Treatment System (SGTS). Prior to initiating the HCVS, the valve to the SGTS must be isolated. However, since SGTS isolation valves are fail-close AOV(s), with air-to-open and spring to shut, the containment isolation signal will automatically isolate the valve(s) upon any abnormal containment pressure. d) A rupture disk is currently provided in the vent line downstream of the CIVs. It is anticipated that this rupture disk will be retained following the modifications to improve the reliability of the hardened vent. Provisions will be made to pressurize the disk from Main Control Room as directed by applicable procedures to allow venting earlier in the event if desired. The final design may elect to remove the rupture disk or replace it with a rupture disk with a different pressure set. ii. Instrumentation to monitor the status of the HCVS - a) Instrumentation indications will be available in the Main Control Room b) Effluent radiation monitor will be located external to the vent piping. c) HCVS vent flow path valves position indication, temperature and pressure instrumentation will monitor the status of the HCVS to aid the operator to ensure verification of proper venting operation. A failure of the position indication instrumentation would not prevent opening and closing the valves. iii. Support systems - a) Existing power for the HCVS DC valve solenoids is provided from the 125 Volt Essential DC Batteries. b) Motive air/gas supply for HCVS operation under the current plant design are adequate for at least three strokes of the valves during the first 24 hours during operation under prolonged SBO conditions is provided from an accumulator in the Atmosphere Control System (1T429). If the final containment analysis Page 4 of 25 Duane Arnold Energy Center Overall Integrated Plan for the Reliable Hardened Vent System supporting the HCVS determines that additional valve cycles are needed, the accumulator capacity will be upgraded to match the required number of cycles. c) Under DAEC implementation of NRC Order EA-12-049 for Mitigation of Strategies for Beyond -Design-Bases External Events, FLEX equipment will have the capability to provide back-up support equipment for reliable HCVS operation. Power will be supplied from a portable 480 volt generator connected to the applicable battery chargers. Motive air/gas for HCVS operation can be supplied from a portable cylinder if needed. Power for instrumentation will be supplied from the same batteries as the solenoids. In addition, alternate means to power critical indicators of containment parameters will be provided under the FLEX program. System control: Active: Control Valves are operated in accordance with EOPs to control containment pressure. The CIVs are currently designed for 3 open / close cycles. Current procedures call for operation of the valves to maintain a containment pressure band between 45 PSIG and 53 PSIG (PCPL) unless otherwise directed by the Technical Support Center. ii. Passive: Inadvertent actuation protection will be provided by key lock switches for the CIV's that must be opened to permit flow. Page 5 of 25 Duane Arnold Energy Center Overall Integrated Plan for the Reliable Hardened Vent System Section 2: Design Obiectives Order EA-050 1.1.1 Requirement: The HCVS shall be designed to minimize the reliance on operatora ctions. ISG 1.1.1 Criteria: During events that significantly challenge plant operations,i ndividual operators are more prone to human error.I n addition, the plant operationss taff may be required to implement strategies and/ort ake many concurrent actions that further places a burden on its personnel. During the prolonged SBO condition at the Fukushima Dai-ichi units, operators faced many significant challenges while attempting to restore numerous plant systems that were necessary to cool the reactorc ore, including the containment venting systems. The difficulties faced by the operatorsr elated to the location of the HCVS valves, ambient temperaturesa nd radiologicalc onditions, loss of all alternating currente lectrical power, loss of motive force to open the vent valves, and exhausting dc battery power. The NRC staff recognizes that operatora ctions will be needed to operate the HCVS valves; however, the licensees shall considerd esign features for the system that will minimize the need and reliance on operatora ctions to the extent possible during a variety of plant conditions, as further discussed in this ISG. The HCVS shall be designed to be operated from a control panel located in the main control room or a remote but readily accessible location. The HCVS shall be designed to be fully functional and self sufficient with permanently installed equipment in the plant, without the need for portable equipment or connecting thereto, until such time that additionalo n-site or off-site personnel and portable equipment become available. The HCVS shall be capable of operatingi n this mode (i.e., relying on permanently installed equipment) for at least 24 hours during the prolonged SBO, unless a shorterp eriod is justified by the licensee. The HCVS operation in this mode depends on a variety of conditions, such as the cause for the SBO (e.g., seismic event, flood, tornado, high winds), severity of the event, and time requiredf or additional help to reach the plant, move portable equipment into place, and make connections to the HCVS. When evaluating licensee justification for periods less than 24 hours, the NRC staff will considert he number of actions and the cumulative demand on personnel resources that are needed to maintain HCVS functionality (e.g., installation of portable equipment during the first 24 hours to restore power to the HCVS controls and/ori nstrumentation)a s a result of design limitations. For example, the use of supplemental portable power sources may be acceptable if the supplementalp ower was readily available, could be quickly and easily moved into place, and installed through the use of pre-engineeredq uick disconnects, and the necessary human actions were identified along with the time needed to complete those actions. Conversely, supplemental power sources located in an unattended warehouse that require a qualified electrician to temporarily wire into the panel would not be considereda cceptable by the staff because its installation requires a series of complex, time-consuming actions in ordert o achieve a successful outcome. There are similar examples that could apply to mechanical systems, such as pneumatic/compresseda ir systems. Response (ref. ISG Item 1.1.1): The operation of the HCVS will be designed to minimize the reliance on operator actions in response to hazards identified in NEI 12-06, Diverse and Flexible Coping Strategies (FLEX) Implementation Guide. The design will allow immediate operator actions to be completed by reactor operators in the Main Control Room (MCR) or other accessible location. The operator actions that will be required to open a vent path are: Operator Actions Necessary to Vent the Containment during a Prolonged SBO Task Location Close interfacing system valves (new) MCR or Other Accessible Location Override containment isolation signal for CV4300 MCR Page 6 of 25 Duane Arnold Energy Center Overall Integrated Plan for the Reliable Hardened Vent System Open Containment Isolation Valve CV4300 MCR Open HCVS control valve CV4357 MCR Isolation or cycling of the vent path can be directly performed from the MCR by operating either of the containment isolation valves (CV4300 or CV4357). The HCVS will be designed to allow initiation, control, and monitoring of venting from the MCR or other accessible location. The location minimizes plant operators' exposure to adverse temperature and radiological conditions and is protected from hazards consistent with the existing plant design. In addition, an alternate capability to open the valves from a location outside the main control room in the essential switchgear room or another accessible location will be provided that allows applying portable pneumatic supply to directly actuate the HCVS valves in the event normal operation from the MCR is not available. Permanently installed power and motive gas capability will be available to support operation and monitoring of the HCVS in the modified design. The current motive gas accumulator is sized for three cycles of the HCVS valves. In the event final containment analysis and procedure concludes addition cycle capacity is needed the accumulator will be upgraded accordingly. DC power will be maintained throughout the event using portable generators under the FLEX program and NEI 12-06. If for any reason, DC power or installed motive gas is unavailable, a back up capability will be provided to open the HCVS remotely from the essential switchgear room or other accessible location using a portable pneumatic supply. Order EA-050 1.1.2 Requirement: The HCVS shall be designed to minimize plant operators'e xposure to occupationalh azards, such as extreme heat stress, while operating the HCVS system. ISG 1.1.2 Criteria: During a prolonged SBO, the drywell, wetwell (torus), and nearby areasi n the plant where HCVS components are expected to be located will likely experience an excursion in temperatures due to inadequatec ontainment cooling combined with loss of normal and emergency building ventilation systems. In addition, installed normal and emergency lighting in the plant may not be available. Licensees should take into considerationp lant conditions expected to be experienced during applicable beyond design basis external events when locating valves, instrumenta ir supplies, and other components that will be required to safely operate the HCVS system. Components requiredf or manual operation should be placed in areas that are readily accessible to plant operators,a nd not require additionala ctions, such as the installationo f ladders or temporary scaffolding, to operate the system. When developing a design strategy, the NRC staff expects licensees to analyze potentialp lant conditions and use its acquired knowledge of these areas, in terms of how temperatures would react to extended SBO conditions and the lighting that would be available during beyond design basis external events. This knowledge also provides an input to system operatingp rocedures, training,t he choice of protective clothing, required tools and equipment, and portable lighting. Response (ref. ISG Item 1.1.2): The HCVS design will allow operating the HCVS from the MCR or other accessible location which minimizes plant operators' exposure to adverse temperature and radiological conditions. The MCR is protected from hazards consistent with the existing plant design and will be evaluated for acceptable temperature and radiological conditions. In order to minimize operator exposure to temperature excursions due to the impact of the prolonged SBO (i.e., loss of normal and emergency building ventilation systems and/or containment temperature changes) procedures will not require access to suppression pool Page 7 of 25