L-MT-13-015, Plant'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)
| ML13060A411 | |
| Person / Time | |
|---|---|
| Site: | Monticello  |
| Issue date: | 02/28/2013 |
| From: | Schimmel M Northern States Power Co, Xcel Energy |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| EA-12-050, L-MT-13-015 | |
| Download: ML13060A411 (32) | |
Text
{{#Wiki_filter:Xc el Energy@ Monticello Nuclear Generating Plant 2807 W County Road 75 Monticello, MN 55362 L-MT 015 February 28, 2013 10 CFR 2.202 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Monticello Nuclear Generating Plant Docket No. 50-263 Renewed Facility Operating License No. DPR-22 Commission Order MNGP 's Overall Integrated Plan in Response to March 12. 2012 ned Containment Modifying Licenses with Regard to Reguirements for Reliable Harde Vents (Order Number EA-12-050)
References:
Licenses with Regard to
- 1. NRC Order Number EA-12-050, "Issuance of Order to Modify March 12, 2012 Requirements for Reliable Hardened Containment Vents," dated (ADAMs Accession Number ML12054A694).
with Order EA-12-050,
- 2. NRC Interim Staff Guidance JLD-ISG-2012-02, "Compliance le Hardened Order Modifying Licenses with Regard to Requirements for Reliab s Accession Number Containment Vents," Revision 0, dated August 29, 2012 (ADAM ML12229A475).
nse to March 12, 2012
- 3. NSPM Letter to NRC, "MNGP's Initial Status Report in Respo s for Reliable Commission Order Modifying Licenses with Regard to Requirement October 29,20 12 Hardened Containment Vents (Order Number EA-12-050)," dated (ADAMs Accession Number ML12305A384).
) issued an Order On March 12, 2012, the Nuclear Regulatory Commission (NRC construction permits in (Reference 1) to all NRC power reactor licensees and holders of ive and directs Northern active or deferred status. Reference 1 was immediately effect Xcel Energy to require States Power Company (NSPM), a Minnesota corporation, d/b/a Reactor (BWR) with a the Monticello Nuclear Generating Plant (MNGP), a Boiling Water nality of reliable Mark I containment, to take certain actions to ensure the functio in control of hardened vent (RHV) systems to remove decay heat and mainta containment heat containment pressure following events that result in loss of active fic requirements are removal capability or prolonged Station Blackout (SBO). Speci outlined in Attachment 2 of Reference 1.
Document Control Desk Page 2 by February 28, 2013. Reference 1 requires submission of an Overall Integrated Plan pursuant to Section The purpose of this letter is to provide the Overall Integrated Plan (Refer ence 2) was issued IV, Condition C.1, of Reference 1. The interim staff guidance of this Overall August 29, 2012 which provides direction regarding the content ic reporting Integrated Plan. Section 4.0 of Reference 2 contains the specif the enclosure to this requirements for the Overall Integrated Plan. The information in nce 2. For the purposes letter aligns with the guidance provided in this section of Refere ll vent. of compliance with Order EA-12-050, NSPM plans to use a wetwe information. Final The enclosed Overall Integrated Plan is based on conceptual design revisions to the design details and associated procedure guidance, as well as any nth status reports information contained in the Enclosure, will be provided in the six-mo required by Reference 1. Summary of Commitments g commitments. This letter makes no new commitments and no revisions to existin correct. I declare under penalty of perjury that the foregoing is true and Executed on February 28, 2013. Mark A. Schimmel Site Vice President, Monticello Nuclear Generating Plant Northern States Power Company - Minnesota Enclosure cc: Administrator, Region III, USNRC Director of Nuclear Reactor Regulation (NRR), USNRC NRR Project Manager, MNGP, USNRC Senior Resident Inspector, MNGP, USNRC
ENCLOSURE Mont icello Nuclear Generating Plant NRC Order EA-12-050 Overall Integrated Plan (29 Pages to Follow)
Enclosure Monticello Nuclear Generating Plant NRC Order EA-12-050 Overa ll Integr ated Plan Table of Contents
........................................................ 3 Section 1: System Description............................................................
................. .......... .................. ............ 6 Section 2: Design Objectives... ..................... .... ..... ................. ...........
................................................ '" 6 Requirement 1.1.1 - Minimize the Reliance on Operator Actions 8 tional Hazards... ........... .......
Requirement 1.1.2 - Minimize Plant Operators' Exposure to Occupa 9 Requirement 1.1.3 - Minimize Radiological Consequences...........
.................................. ......................... ...... 10 Section 3: Operational Characteristics...................... ...... ...........
.................... ........................ 10 Requirement 1.2.1 - Capacity to Vent Equivalent of 1 Percent....... 11 Operat ors...... ..... ....................................
Requirement 1.2.2 - HCVS Shall be Accessible to Plant 12 on ........... ...... '" ........ ,. ........ .... .............................. Requirement 1.2.3 - Prevent Inadvertent Actuati 13 of the Vent System ....... ........... ........... .............................. Requirement 1.2.4 - Monitor the Status 14 Requirement 1.2.5 - Monitor the Effluent Discharge for Radioactivity.. 14 Fluids........................................ Requirement 1.2.6 - Minimize Unintended Cross Flow of Vented 16 tion and Maintenance................ Requirement 1.2.7 - Provision for the Operation, Testing, Inspec 17 Requirement 1.2.8 - Design Pressures....................................... 18 Requirement 1.2.9 - Discharge Release Point. .. '" ...........
................................ ................................. 20 Section 4: Applicable Quality Requirements............. ...... ...........
..................................................... 20 Requirement 2.1 - Containment Isolation Function.................... 20 Requirement 2.2 - Reliable and Rugged Performance...... ........
................................................................. 22 Section 5: Procedures and Training. .......................... ..... ...........
. ....... .................. ........ ...... .... 22 Requirement 3.1 - Develop, Implement, and Maintain Procedures.... 23 Requirement 3.2 - Train Appropriate PersonneL...........................
.......... ........................................ ............ 24 Section 6: Implementation Schedule Milestones................. .........
entation Plan...... ............. ............. .... ........ 24 Section 7: Changes/Updates to this Overall Integrated Implem
................................... .............................. 25 Section 8: Additional Tables and Figures..... ..... .... .....................
Figures:
..... ...... ....... ............ ... ................ ... ......... .... 3 Figure 1 - HCVS Flow Path.... ..... ... ..... .............. ....... ..... ......... .......... ......
.......................................................... 18 Figure 2 - Side and Top View of the HCVS..................................................
.................................................................. 26 Figure 3 - HCVS Connection to Torus...................................................
.............................................................. 27 Figure 4 - HCVS Piping................. ............................................................
.......................................................... 28 Figure 5 - Alternate Nitrogen System............................................................
.............. '" '" ... ... ........... ... .......... ..... ....... 29 Figure 6 - Electrical Drawing for the HCVS Valves ....................................
Tables: an S80.................................................. 7 Table 1 - Operator Actions Necessary to Vent the Containment during
....................................................... 17 Table 2 - Testing and Frequencies..................................................................
........................................................... 26 Table 3 - Failure Evaluation Table...............................................................
Page 1 of 29
Enclosure Monti cello Nucle ar Generating Plant NRC Order EA-12-050 Overall Integrated Plan
References:
l Vent," dated September 1, 1989.
- 1. NRC Generic Letter 89-16, "Installation of a Hardened Wetwel Licenses with Regard to Requirements for Mitigation
- 2. NRC Order Number EA-12-049, "Issuance of Order to Modify l Events, " dated March 12, 2012 (Accession Number ML12054A736).
Strategies for Beyond-Design-Basis Externa Licenses with Regard to Requirements for Reliable
- 3. NRC Order Number EA-12-050, "Issuance of Order to Modify ion Number ML12054A694).
Hardened Containment Vents," dated March 12,201 2 (Access with Order EA-12-050, Order Modifying Licenses with
- 4. NRC Interim Staff Guidance JLD-ISG-2012-02, "Compliance Revision 0, dated August 29,201 2 (Accession Regard to Requirements for Reliable Hardened Containment Vents,"
Numbe r ML12229A475). d Project Directorate Interim Staff Guidance JLD-ISG-
- 5. NRC Responses to Public Comments, "Japan Lessons-Learne Licenses with Regard to Reliable Hardened Containment 2012-02: Compliance with Order EA-12-050, Order Modifying Vents," dated August 29, 2012 (Accession No. ML12229A477).
Implementation Guide," Revision 0, dated August, 2012.
- 6. NEI12- 06, "Diverse and Flexible Coping Strategies (FLEX)
Page 2 of 29
Enclosure Monticello Nucle ar Generating Plant NRC Order EA-12-050 Overa ll Integr ated Plan Section 1: System Description (FSAR Level of Detail) ISG Criteria: including important operational characteristics. The level Licensees shall provide a complete description of the system, of detail contained in the licensee's Final Safety of detail generally considered adequate is consistent with the level Analysi s Report.
Response
System Overview: to mitigate loss-of-decay-heat removal by The Hardened Containment Vent System (HCVS) is designed nment pressurization and maintain core providing sufficient containment venting capability to limit contai to accommodate decay heat input cooling capability. The vent is designed with sufficient capacity percent planned power uprate above the equivalent to one percent of 2004 MWt which accounts for a 13 capacity is adequate to relieve decay current licensed thermal power (CLTP). Thus, the hardened vent intended for use as one element of core heat for a prolonged station blackout (S80) event. The HCVS is damage prevention strategies. e point is shown in the simplified The HCVS flow path from the containment to an elevated releas diagram below. No ductwork is used in the flow path. Vent Radiation Monitor o Rupture disc Torus Figure 1 - HCVS Flow Path*
*Note: See Figures in Section 8 for more detail.
Page 3 of 29
Enclosure Monticello Nuclear Generating Plant NRC Order EA-12-050 Overall Integrated Plan Equipment and Components: The following equipment and components are or will be provided:
- i. HCVS Mechanical Components -
vent piping and supports up a) Containment isolation piping, valves and controls - The HCVS ed in accordance with to and including the second containment isolation valve are design consistent with the existing design basis. Containment isolation valves are provided air-operated valves (AOV) plants containment isolation valve design basis. The valves are controls on the Alternate operated by solenoid valves (SOV), and can be operated from Shutdown System Panel. rts downstream of the b) Other system valves and piping - The HCVS piping and suppo ed to conform to the second containment isolation valve have been designed and analyz plant and to ensure requirements consistent with the applicable design codes for the functionality following a design basis earthquake. vent line downstream of c) A rupture disc of 44 to 50 psig capability is provided in the HCVS onally breached from the the containment isolation valves. The rupture disc can be intenti ble procedures. Alternate Shutdown System (ASDS) Panel as directed by applica ii. Instrumentation to monitor the status of the HCVS - a) Instrumentation indications are available at the ASDS Panel. with indication on the ASDS b) An effluent radiation monitor is located outside the vent line panel. status of the HCVS c) HCVS vent flow path valves position indication monitors the tion of proper venting containment isolation valves to aid the operator to ensure verifica not prevent opening operation. A failure of the position indication instrumentation would and closing the valve. iii. Support systems - the Division II 480V busses. a) Normal power for the HCVS valve solenoids is provided from II 250V Battery System will b) In the event of a loss of Division II 480V power, the Division quantify this time. provide power for an estimated 8 hours. A future evaluation will will be modified as necessary c) The Alternate Nitrogen System supply for HCVS operation to operate for 24 hours under prolonged SBO conditions. support equipment for reliable d) FLEX equipment will have the capability to provide back-up will be supplied from HCVS operation. For example, power to the Division II 250 V battery nal motive nitrogen for a FLEX 480V portable diesel generator (to be procured). If additio on-site. HCVS operation is needed, additional nitrogen bottles are stored System control: Operating Procedures
- i. Active: HCVS valves are operated in accordance with Emergency prolonged SBO (EOP). The HCVS is designed for rupturing the rupture disc under ary, to ensure the conditions. The Alternate Nitrogen System will be modified, if necess EOPs allow opening the valves will be able to cycle multiple times (at least five cycles).
Page 4 of 29
Enclosure Monticello Nuclear Generating Plant NRC Order EA-12-050 Overa ll Integr ated Plan ession Pressure (PSP), HCVS vent when drywell pressure is above the Pressure Suppr A manual valve will be which is approximately 17 to 34 psig, depending on Torus level. valves in the event of a added to allow the Alternate Nitrogen System to open the HCVS loss of DC power or solenoid failure. disc in the vent line ii. Passive: Inadvertent actuation protection is provided by a rupture ion of HCVS is controlled downstream of the containment isolation valves. Remote operat Panel. by key lock switches located in the Alternate Shutdown System Page 5 of 29
Enclosure Monticello Nuclear Generating Plant NRC Order EA-12-050 Overall Integrated Plan ined in Order EA-050 Attachment 2, Section 2: A description of how the design objectives conta Requirements 1.1.1, 1.1.2, and 1.1.3, are met. Order EA-050 1.1.1 Requirement: r actions. The HCVS shall be designed to minimize the reliance on operato ISG 1.1.1 Criteria: al operators are more prone to human error. In During events that significantly challenge plant operations, individu strategies and/or take many concurrent actions that addition, the plant operations staff may be required to implement ed sao condition at the Fukushima Dai-ichi units, further places a burden on its personnel. During the prolong es while attempt ing to restore numerous plant systems that were necessary operators faced many significant challeng
. The difficulties faced by the operators related to to cool the reactor core, including the containment venting systems tures and radiolog ical conditions, loss of all alternating current the location of the HCVS valves, ambien t tempera exhausting dc battery power. The NRC staff electrical power, loss of motive force to open the vent valves, and the HCVS valves; however, the licensees shall conside r recognizes that operator actions will be needed to operate on operato r actions to the extent possible during design features for the system that will minimize the need and reliance a variety of plant conditions, as further discussed in this ISG.
located in the main control room or a remote but The HCVS shall be designed to be operated from a control panel be designe d to be fully functional and self sufficient with permanently readily accessible location. The HCVS shall ent or connecting thereto, until such time that installed equipment in the plant, without the need for portable equipm ent become available. The HCVS shall be capable of additional on-site or off-site personnel and portable equipm relying on perman ently installed equipm ent) for at least 24 hours during the prolonged operating in this mode (i.e., HCVS operatio n in this mode depends on a variety of sao, unless a shorter period is justified by the licensee. The , high winds), severity ofthe event, and flood, tornado conditions, such as the cause for the sao (e.g., seismic event, equipm ent into place, and make connections to the time required for additional help to reach the plant, move portable HCVS. the NRC staff will consider the number of actions When evaluating licensee justification for periods less than 24 hours, to maintain HCVS functionality (e.g., installation of and the cumulative demand on personnel resources that are needed to the HCVS controls and/or instrumentation) as a result portable equipment during the first 24 hours to restore power the use of supplem ental portable power sources may be acceptable if the of design limitations. For example, easily moved into place, and installed through the use supplemental power was readily available, could be quickly and necessa ry human actions were identifie d along with the time needed to of pre-engineered quick disconnects, and the ded warehouse that require a located in an unatten complete those actions. Conversely, supplemental power sources ble by the staff because its would not be conside red accepta qualified electrician to temporarily wire into the panel ful outcome. There are in order to achieve a success installation requires a series of complex, time-consuming actions air systems . as pneuma tic/com pressed similar examples that could apply to mechanical systems, such Response (ref. ISG Item 1.1.1 ): reliance on operator actions. The The operation of the HCVS has been designed to minimize the in Table 1 below. operator actions required to open a vent path are summarized Page 6 of 29
Enclosure Monticello Nuclear Generating Plant NRC Order EA-12-050 Overall Integrated Plan Table 1 - Operator Actions Necessary to Vent the Containment during an SSO Vent containment with Vent containment with Equipment Location containment pressure above containment pressure the rupture disc rupture below the rupture disc pressure rupture pressure
- 1. Open a manual valve to 1. Open a manual valve Turbine building supply nitrogen to the HCVS to supply nitrogen to the valves* HCVS valves*
- 2. Open valve to provide ASDS Panel (EFT bldg) nitrogen to pressurize area between rupture disc and closed valve
- 3. Shut valve to stop ASDS Panel (EFT bldg) nitrogen after 5 minutes
- 2. Open 1sl Containment 4. Open 1sl Containment ASDS Panel (EFT bldg)
Isolation Valve Isolation Valve
- 3. Open 2nd Containment 5. Open 2 nd Containment ASDS Panel (EFT bldg)
Isolation Valve Isolation Valve
*NOTE: The normal position of this valve is currently SHUT and will be changed to OPEN. This will eliminate step 1, which relies on an operator action.
No other operator actions are required to initiate venting. The HCVS is designed to allow initiation, control, and monitoring of venting from the Alternate Shutdown System Panel in the Emergency Filtration (EFT) Building. The EFT building is a Class I structure located away from the Reactor Building and contains no radioactive material or piping with contaminated material, thereby minimizing plant operators' exposure to adverse temperature and radiological conditions. Permanently installed equipment will supply nitrogen for an estimated 24 hours and power to HCVS for at least 8 hours. These times will be confirmed by future evaluations. Staffing studies, when completed in response to the NRC's 10 CFR 50.54(f) letter dated March 12, 2012, will demonstrate that sufficient manpower is available to ensure that supplemental DC control power can be re-established and any supplemental nitrogen bottles required can be installed in the required time. Connections for supplementing electrical power and motive nitrogen will be located in Class I areas of the turbine building, EFT or administration buildings. A failure evaluation table is included as Table 3 in Section 8. Page 7of29
Enclosure Monticello Nuclear Generating Plant NRC Order EA-12-050 Overall Integrated Plan Order EA-050 1.1.2 Requirement: e to occupational hazards, such as extreme heat The HCVS shall be designed to minimize plant operators' exposur stress, while operating the HCVS system. ISG 1.1.2 Criteria: areas in the plant where HCVS components are During a prolong ed sao, the drywell, wetwell (torus), and nearby tures due to inadequate containment cooling expected to be located will likely experience an excursion in tempera of normal and emerge ncy building ventilati on systems . In addition, installed normal and emergency combined with loss take into conside ration plant conditions expected to be lighting in the plant may not be available. Licensees should when locating valves, instrument air supplies, and experienced during applicable beyond design basis extema l events system. Components required for manual operation other components that will be required to safely operate the HCVS accessi ble to plant operato rs, and not require additional actions, such as the should be placed in areas that are readily installation of ladders or temporary scaffolding, to operate the system. s to analyze potentia l plant conditions and use its When developing a design strategy, the NRC staff expects licensee tures would react to extended sao conditions and the acquired knowledge of these areas, in terms of how tempera e during beyond design basis externa l events. This knowledge also provides an input to lighting that would be availabl clothing , required tools and equipment, and portable system operating procedures, training, the choice of protective lighting. Response (ref. ISG Item 1.1.2): System supply valve in the turbine Following the changing of the position of the Alternate Nitrogen ing and monitoring the HCVS from the building, the HCVS design will allow initiating and then operat e temperature and radiological ASDS panel, which minimizes plant operators' exposure to advers excursions due to the impact of the conditions. In order to minimize operator exposure to temperature tion systems and/or containment prolonged SBO (Le., loss of normal and emergency building ventila access the Torus area for HCVS temperature changes) procedures will not require personnel to systems. operations or for backup operation of electrical and pneumatic operation of the HCVS will be located in Connections for supplemental equipment needed for sustained Class I structures, as listed below: DC Power: chargers (primary)
- 480 V AC breakers in 4kV switch gear rooms to power battery
- Battery charger connections in the battery rooms (alternate)
Alternate Nitrogen System:
- Seismically protected area of turbine building mps or lighting alternatives like flashlights Tools required for sustained operation, such as portable headla in the FLEX equipment storage locations.
or portable lights, and connection specific tooling will be stored these connections or storage Neither temporary ladders nor scaffolding will be required to access locations. Page 8of29
Enclosure Monticello Nuclear Generating Plant NRC Order EA-12-050 Overall Integrated Plan Order EA-050 1.1.3 Requirement: The HCVS shall also be designed to minimize radiological consequences that would impede personnel actions needed for event response. ISG 1.1.3 Criteria: The design of the HCVS should take into consideration the radiological consequences resulting from the event that could negatively impact event response. During the Fukushima event, personnel actions to manually operate the vent valves were impeded due to the location of the valves in the torus rooms. The HCVS shall be designed to be placed in operation by operator actions at a control panel, located in the main control room or in a remote location. The system shall be designed to function in this mode with permanently installed equipment providing electrical power (e.g., dc power batteries) and valve motive force (e.g., N2/air cylinders). The system shall be designed to function in this mode for a minimum duration of 24 hours with no operator actions required or credited, other than the system initiating actions at the control panel. Durations of less than 24 hours will be considered if justified by adequate supporting information from the licensee. To ensure continued operation of the HCVS beyond 24 hours, licensees may credit manual actions, such as moving portable equipment to supplement electrical power and valve motive power sources. In response to Generic Letter (GL) 89-16, a number of facilities with Mark I containments installed vent valves in the torus room, near the drywell, or both. Licensees can continue to use these venting locations or select new locations, provided the requirements of this guidance document are satisfied. The HCVS improves the chances of core cooling by removing heat from containment and lowering containment pressure, when core cooling is provided by other systems. If core cooling were to fail and result in the onset core damage, closure of the vent valves may become necessary if the system was not designed for severe accident service. In addition, leakage from the HCVS within the plant and the location of the extemal release from the HCVS could impact the event response from on-site operators and off-site help arriving at the plant. An adequate strategy to minimize radiological consequences that could impede personnel actions should include the following:
- 1. Licensees shall provide permanent radiation shielding where necessary to facilitate personnel access to valves and allow manual operation of the valves locally. Licensee may use altematives such as providing features to facilitate manual operation of valves from remote locations, as discussed further in this guidance under Requirement 1.2.2, or relocate the vent valves to areas that are significantly less challenging to operator access/actions.
- 2. In accordance with Requirement 1.2.8, the HCVS shall be designed for pressures that are consistent with the higher of the primary containment design pressure and the primary containment pressure limit (PCPL), as well as including dynamic loading resulting from system actuation. In addition, the system shall be leak-tight. As such, ventilation duct work (i.e., sheet metal) shall not be utilized in the design of the HCVS. Licensees should perform appropriate testing, such as hydrostatic or pneumatic testing, to establish the leak-tightness of the HCVS.
- 3. The HCVS release to outside atmosphere shall be at an elevation higher than adjacent plant structures. Release through existing plant stacks is considered acceptable, provided the guidance under Requirement 1.2.6 is satisfied. If the release from HCVS is through a vent stack different than the plant stack, the elevation of the stack should be higher than the nearest building or structure.
Response (ref. ISG Item 1.1.3): The HCVS is designed for reliable, remote-manual operation. Operators will not be required to access the Torus area. The HCVS is designed to be independent of other ventilation systems, prevent steam flow into unintended areas, and provide containment isolation. No duct work is used in the HCVS. No actions are required in the Torus area. Therefore, shielding or other alternatives to facilitate manual actions are not required for operation of the HCVS. The containment valves are located in the Torus room and are tested per the 10 CFR Appendix J requirements. The vent piping is routed through the HPCI room roof, up the side of the reactor building, along the reactor plenum, to an elevated release point. The stack is higher than the nearest building or structure. See Section 1.2.8 for discussion of design pressure. Page 90f29
Enclosure Monticello Nuclear Generating Plant NRC Order EA-12-050 Overa ll Integr ated Plan how each of the Order's technical Section 3: Operational characteristics and a description of requirements are being met. Order EA-050 1.2.1 Requirement: nt of 1 percent of Iicensedlrated thermal power The HCVS shall have the capacity to vent the steam/energy equivale n containment pressure below the primary (unless a lower value is justified by analyses), and be able to maintai containment design pressure. ISG 1.2.1 Criteria: could result in the loss of active containment heat Beyond design basis extemal events such as a prolonged SBO is to provide sufficient venting capacity to prevent a long-removal capability. The primary design objective of the HCVS ment by keeping the contain ment pressure below the primary containment term overpressure failure of the contain other factors, such as the maximum containment design pressure and the PCPL. The PCPL may be dictated by and the HCVS valves can be opened and closed. pressure at which the safety relief valves (SRVs) ns of constant heat input at a rate equal to 1 percent The NRC staff has determined that, for a vent sized under conditio of the primary containment design pressure and of rated thermal power and containment pressure equal to the lower sufficien t to prevent the containment pressure from increasing. the PCPL, the exhaust-flow through the vent would be torus suppression capacity is typically sufficient to This determination is based on studies that have shown that the following the shutdown of the reactor with torus as absorb the decay heat generated during at least the first three hours typically less than 1 percent of rated thermal power three hours following the source of injection, that decay heat is e to well under 1 percent, thereafter. Licensees shall shutdown of the reactor, and that decay heat continues to decreas heat absorbi ng capacity of their torus, selection of venting pressure have an auditable engineering basis for the decay conditions to maintain containment pressure at or such that the HCVS will have sufficient venting capacity under such If required , venting capacity shall be increased to an below the primary containment design pressure and the PCPL. with the licensee 's venting strategy . License es may also use a venting capacity sized appropriate level commensurate of thermal power if it can be justified by analysis under conditions of constant heat input at a rate lower than 1 percent and the PCPL would not be exceede d. In cases where plants were granted, that primary containment design pressure shall use 1 percent thermal power corresponding to the have applied, or plan to apply for power uprates, the licensees shall give appropriate consideration of where venting is uprated thermal power. The basis for the venting capacity in pressure between the drywell and the suppression being performed from (i.e., wetwell ordrywe ll) and the difference ration simultaneous venting from all the units, and chamber. Vent sizing for multi-unit sites must take into conside negativ ely impact the ability to vent on the other units. ensure that venting on one unit does not Response (ref. ISG Item 1.2.1): at a capacity of 1 percent of 2004 MW The HCVS wetwell path is designed for venting steam/energy re is the containment design pressure, thermal power at containment pressure of 56 psig. This pressu pressure value and the primary which is the lower value when comparing the containment design containment pressure limit (PCPL) value. nt to absorb the decay heat generated The one percent value assumes that the Torus capacity is sufficie t containment pressure from during the first three hours. The vent would then be able to preven is able to absorb the necessary decay increasing above the containment design pressure. The Torus heat for at least the first three hours. Page 10 of29
Enclosure Monticello Nuclear Generating Plant NRC Order EA-12-050 Overall Integrated Plan Order EA-050 1.2.2 Requirement: of remote operation and control, or manual operation, The HCVS shall be accessible to plant operators and be capable during sustained operations. ISG 1.2.2 Criteria: is from the main control room. However, alternate The preferre d location for remote operation and control of the HCVS d the licensee s take into consideration the following: locations to the control room are also acceptable, provide multiple times during the event. Licensees shall
- 1. Sustained operations mean the ability to open!Close the valves ose cycles necessa ry during the first 24 hours of operation and provide supporting determine the number of open/cl basis consistent with the plant-specific contain ment venting strategy operating personnel may encoun ter both in transit and
- 2. An assessment of temperature and radiological conditions that ives such as providin g features to facilitate manual operation of valves locally at the controls. Licensee may use altemat from remote locations or relocatinglreorienting the valves.
ions required to supplement the HCVS operation
- 3. All permanently installed HCVS equipment, including any connect above the maximum design basis external flood level during a prolong ed sao (electric power, N2Iair) shall be located or protecte d from the design basis externa l flood.
necessary to operate the HCVS. As demonstrated
- 4. During a prolonged sao, manual operation/action may become g electric power and pneumatic air supply to the valve during the Fukushima event, the valves lost motive force includin If direct access and local operation of the valves is not feasible due to operators, and control power to solenoi d valves.
features to facilitate remote manual operation of temperature or radiological hazards, licensees should include design hand wheels, and portable equipment to provide motive the HCVS valves by means such as reach rods, chain links, powere d compre ssors, and dc batterie s). The connections between the valves and force (e.g., air/N2 bottles, diesel If a portable motive force (e.g., air or N2 bottles, dc portable equipment should be designed for quick deployment. on of that equipment
, licensee s shall provide reasona ble protecti power supplies) is used in the design strategy 1 for Order EA-12-0 49.
consistent with the staff's guidance delineated in JLD-ISG-2012-0 ry ladders or operate from atop scaffolding to access
- 5. The design shall preclude the need for operators to move tempora the HCVS valves or remote operating locations.
Response (ref. ISG Item 1.2.2): ring the HCVS from the ASDS panel. The HCVS design allows initiating and then operating and monito en System valve in the turbine As discussed in Table 1, the position of the manual Alternate Nitrog operation of the HCVS from the ASDS building will be changed from closed to open to allow complete including the design basis external panel. This location is protected from adverse natural phenomena, flood. ng air-to-open and spring-to-
- 1. The HCVS flow path valves are air-operated valves (AOV) requiri ed valve (SOV) and providing shut. Opening the valves requires energizing a solenoid operat motive nitrogen.
Station battery power will be The station batteries will be used initially to power the solenoids. portable diesel generator will maintained by a portable diesel generator (FLEX equipment). The provide continuous power. System. The Alternate Nitrogen Motive nitrogen pressure is delivered from the Alternate Nitrogen for a minimum of five valve System will be confirmed to be able to provide a nitrogen supply operating cycles. functionality that are located The SOVs are the only electrical components required for valve S80. Should all power to the inside the area considered not-accessible following a prolonged the containment isolation valves SOV be lost or an SOV fail to open, a remote manual bypass for of any electric power. will be added to open the valves using nitrogen gas, independent Page 11 of 29
Enclosure Monticello Nuclear Generating Plant NRC Order EA-12-050 Overall Integrated Plan
- 2. All operations of the HCVS will occur in the EFT building, the turbine building or the battery rooms. None of these areas are near the HCVS piping. Also, no fuel damage has occurred per the event scenario. Therefore, no adverse radiological conditions will exist in these areas.
Due to the low heat loads in these areas during an S80, loss of ventilation is not expected to affect the local temperatures significantly. Should cooling be needed, portable FLEX equipment will be available after portable diesel generators are set up.
- 3. All permanently installed HCVS equipment, including any connections required to supplement the HCVS operation during a prolonged S80 (electric power, N2/air) will be located in areas reasonably protected from the defined hazards discussed in Section 1.1.1 above.
- 4. All valves required to open the flow path are designed for remote operation following a prolonged S80, i.e., no valve operation via handwheel, reach-rod or similar means that requires close proximity to the containment isolation valve. Supplemental connections will be pre-engineered to minimize man-power resources and any needed portable equipment will be reasonably protected from hazards defined in NEI 12-06.
- 5. Access to the locations described above will not require temporary ladders or scaffolding.
Order EA-050 1.2.3 Requirement: The HGVS shall include a means to prevent inadvertent actuation. ISG 1.2.3 Criteria: The design of the HGVS shall incorporate features, such as control panel key-locked switches, locking systems, rupture discs, or administrative controls to prevent the inadvertent use of the vent valves. The system shall be designed to preclude inadvertent actuation of the HGVS due to any single active failure. The design should consider general guidelines such as single point vulnerability and spurious operations of any plant installed equipment associated with HGVS. The objective of the HGVS is to provide sufficient venting of containment and prevent long-term overpressure failure of containment following the loss of active containment heat removal capability or prolonged SBO. However, inadvertent actuation of HGVS due to a design error, equipment malfunction, or operator error during a design basis loss-of-coolant accident (DBLOGA) could have an undesirable effect on the containment accident pressure (GAP) to provide adequate net positive suction head to the emergency core cooling system (EGGS) pumps. Therefore, prevention of inadvertent actuation, while important for all plants, is essential for plants relying on GAP. The licensee submittals on HGVS shall specifically include details on how this issue will be addressed on their individual plants for all situations when GAP credit is required. Response (ref. ISG Item 1.2.3): A rupture disc and key lock switches on the ASDS panel prevent inadvertent venting. The HCVS containment isolation valves are normally closed AOVs that are nitrogen-to-open and spring-to-shut. The SOV is energized by a key-locked switch to allow the motive nitrogen to open the AOV. Manual Alternate Nitrogen System valves that bypass the containment isolation valve solenoids will be installed, locked and controlled by procedure. EOPs provide supplementary instructions to point out that reducing primary containment pressure will affect Net Positive Suction Head (NPSH) margin. This administrative control, along with locked valves and a rupture disc, will prevent inadvertent vent opening. Page 12 of29
Enclosure Monticello Nuclear Generating Plant NRC Order EA-12-050 Overall Integrated Plan Order EA-050 1.2.4 Requirement: The HCVS shall include a means to monitor the status of the vent system (e.g., valve position indication) from the control room or other location(s). The monitoring system shall be designed for sustained operation during a prolonged sao. ISG 1.2.4 Criteria: Plant operators must be able to readily monitor the status of the HCVS at all times, including being able to understand whether or not containment pressure/energy is being vented through the HCVS, and whether or not containment integrity has been restored following venting operations. Licensees shall provide a means to allow plant operators to readily determine, or have knowledge of, the following system parameters: (1) HCVS vent valves' position (open or closed), (2) system pressure, and (3) effluent temperature. Other important information includes the status of supporting systems, such as availability of electrical power and pneumatic supply pressure. Monitoring by means of permanently installed gauges that are at, or nearby, the HCVS control panel is acceptable. The staff will consider altemative approaches for system status instrumentation; however, licensees must provide sufficient information and justification for alternative approaches. The means to monitor system status shall support sustained operations during a prolonged sao, and be designed to operate under potentially harsh environmental conditions that would be expected following a loss of containment heat removal capability and sao. Power supplies to all instruments, controls, and indications shall be from the same power sources supporting the HCVS operation. "Sustained operations" may include the use of portable equipment to provide an alternate source of power to components used to monitor HCVS status. Licensees shall demonstrate instrument reliability via an appropriate combination of design, analyses, operating experience, and/or testing of channel components for the following sets of parameters:
- radiological conditions that the instruments may encounter under normal plant conditions, and during and after a prolonged sao event.
- temperatures and pressure conditions as described under requirement 1.2.8, including dynamic loading from system operation.
- humidity based on instrument location and effluent conditions in the HCVS.
Response (ref. ISG Item 1.2.4): The existing HCVS was designed with containment isolation valve position indications and an inline radiation monitor. These instruments provide indirect system flow information. Valve position identifies when flow can occur and the radiation monitor is designed to detect when flow does occur. The instrument range will provide indication of flow at low levels such as conditions when all fuel is intact. The existing HCVS includes a primary containment pressure indicator in the ASDS panel where the HCVS controls are located. The pressure in the HCVS will be bounded by the containment pressure indication. Additional HCVS temperature and pressure monitors were evaluated and determined not be necessary, as existing HCVS instrumentation is adequate for plant operators to monitor venting status. The HCVS valve position indication, HCVS inline radiation monitor and containment pressure indicator are all powered from essential DC power. The range for the containment pressure indication is -5 to 250 psig. The upper limit is more than twice the required design containment pressure. The installed instruments for valve position indication and containment pressure are reliable for the radiological, temperature, pressure and humidity conditions as described in ISG 1.2.4. The instrument Page 13 of 29
Enclosure Monticello Nuclear Generating Plant NRC Order EA-12-050 Overall Integrated Plan detector for radiation monitoring is installed outside the reactor building and the radiation monitor instrumentation is in the ASDS panel in the EFT building. Due to the location of the equipment for the detector and monitor, it is not expected to experience abnormal radiological, temperature, pressure or humidity conditions as a result of the event. Order EA-050 1.2.5 Requirement: The HCVS shall include a means to monitor the effluent discharge for radioactivity that may be released from operation of the HCVS. The monitoring system shall provide indication in the control room or other location(s), and shall be designed for sustained operation during a prolonged sao. ISG 1.2.5 Criteria: Licensees shall provide an independent means to monitor overall radioactivity that may be released from the HCVS discharge. The radiation monitor does not need to meet the requirements of NUREG 0737 for monitored releases, nor does it need to be able monitor releases quantitatively to ensure compliance with Title 10 of the Code of Federal Regulations (10 CFR) Part 100 or 10 CFR Section 50.67. A wide-range monitoring system to monitor the overall activity in the release providing indication that effluent from the containment environment that is passing by the monitor is acceptable. The use of other existing radiation monitoring capability in lieu of an independent HCVS radiation monitor is not acceptable because plant operators need accurate information about releases coming from the containment via the HCVS in order to make informed decisions on operation of the reliable hardened venting system. The monitoring system shall provide indication in the control room or a remote location (i.e., HCVS control panel) for the first 24 hours of an extended sao with electric power provided by permanent DC battery sources, and supplemented by portable power sources for sustained operations. Monitoring radiation levels is required only during the events that necessitate operation of the HCVS. The reliability of the effluent monitoring system under the applicable environmental conditions shall be demonstrated by methods described under Requirement 1.2.4. Response (ref. ISG Item 1.2.5): A dedicated radiation monitor is installed in the HCVS. The approximate range of the radiation monitoring system is 0.1 mrem/hr to 10,000 mrem/hr. This range exceeds the NRC guidance provided in the NRC Responses to Public Comments document. The detector is physically mounted on the outside of the HCVS piping. The radiation level is indicated at the ASDS panel. The radiation monitoring system is powered from the same source as all other powered HCVS components. Refer to the response in Section 1.0, Equipment and Components, subpart iii, for a discussion on power supply. Order EA-050 1.2.6 Requirement: The HCVS shall include design features to minimize unintended cross flow of vented fluids within a unit and between units on the site. ISG 1.2.6 Criteria: At Fukushima, an explosion occurred in Unit 4, which was in a maintenance outage at the time of the event. Although the facts have not been fully established, a likely cause of the explosion in Unit 4 is that hydrogen leaked from Unit 3 to Unit 4 through a common venting system. System cross-connections present a potential for steam, hydrogen, and airbome radioactivity leakage to other areas of the plant and to adjacent units at multi-unit sites if the units are equipped with common vent piping. In this context, a design that is free of physical and control interfaces with other systems eliminates the potential for any cross-flow and is one way to satisfy this requirement. Regardless, system design shall provide design features to prevent the cross flow of vented fluids and migration to other areas within the plant or to adjacent units at multi-unit sites. The current design of the hardened vent at several plants in the U.S. includes cross connections with the standby gas treatment system, which contains sheet metal ducts and filter and fan housings that are not as leak tight as hard pipes. In addition, dual unit plant sites are often equipped with a common plant stack. Examples of acceptable means for prevention of cross flow is by valves, leak-tight dampers, and check valves, which shall be designed to automatically Page 14 of 29
Enclosure Monticello Nuclear Generating Plant NRC Order EA-12-050 Overa ll Integr ated Plan as long as the HCVS is in operation. Licensee's shall close upon the initiation of the HCVS and shall remain closed for at the damper locations during venting operations evaluate the environmental conditions (e.g. pressure, temperature) sufficien tly leak-tigh t, and if necessary, replace the dampers with to ensure that the dampers will remain functional and the interfacing valves to move to isolation position, it other suitable equipment such as valves. If power is required for tightnes s of any such barriers shall be periodically shall be from the same power sources as the vent valves. Leak verified by testing as described under Require ment 1.2.7. Response (ref. ISG Item 1.2.6): through two dedicated containment The HCVS fluid path starts at a dedicated Torus penetration, passes the reactor building, and then the pipe isolation valves, through a rupture disc, through a pipe that exits the top of the reactor building goes up the outside of the reactor building to an open pipe tee near nitrogen line to open the rupture disc, exhaust plenum. The only piping connections are a drain line, a ore, there are no connections with other and containment isolation leakage testing connections. Theref systems and no cross flow interactions with the HCVS. MNGP is a single unit site. Page 15 of29
Enclosure Monticello Nuclear Generating Plant NRC Order EA-12-050 Overall Integrated Plan Order EA-050 1.2.7 Requirement: The HCVS shall include features and provision for the operation, testing, inspection and maintenance adequate to ensure that reliable function and capability are maintained. ISG 1.2.7 Criteria: The HCVS piping run shall be designed to eliminate the potential for condensation accumulation, as subsequent water hammer could complicate system operation during intermittent venting or to withstand the potential for water hammer without compromising the functionality of the system. Licensees shall provide a means (e.g., drain valves, pressure and temperature gauge connections) to periodically test system components, including exercising (opening and closing) the vent valve(s). In situations where total elimination of condensation is not feasible, HCVS shall be designed to accommodate condensation, including applicable water hammer loads. The HCVS outboard of the containment boundary shall be tested to ensure that vent flow is released to the outside with minimal leakage, if any, through the interfacing boundaries with other systems or units. Licensees have the option of individually leak testing interfacing valves or testing the overall leakage of the HCVS volume by conventional leak rate testing methods. The test volume shall envelope the HCVS between the outer primary containment isolation barrier and the vent exiting the plant buildings, including the volume up to the interfacing valves. The test pressure shall be based on the HCVS design pressure. Permissible leakage rates for the interfacing valves shall be within the requirements of American Society of Mechanical Engineers Operation and Maintenance of Nuclear Power Plants Code (ASME OM) - 2009, Subsection ISTC - 3630 (e) (2), or later edition of the ASME OM Code. When testing the HCVS volume, allowed leakage shall not exceed the sum of the interfacing valve leakages as determined from the ASME OM Code. The NRC staff will consider a higher leakage acceptance values if licensees provide acceptable justification. When reviewing such requests, the NRC staff will consider the impact of the leakage on the habitability of the rooms and areas within the building and operability of equipment in these areas during the event response and subsequent recovery periods. Licensees shall implement the following operation, testing and inspection requirements for the HCVS to ensure reliable operation of the system. Testing and Inspection Requirements Description Frequency Cycle the HCVS valves and the interfacing system Once per year valves not used to maintain containment integrity during operations. Perform visual inspections and a walkdown of Once per operating cycle HCVS components Test and calibrate the HCVS radiation monitors. Once per operating cycle Leak test the HCVS. (1) Prior to first declaring the system functional; (2) Once every five years thereafter; and (3) After restoration of any breach of system boundary within the buildings Validate the HCVS operating procedures by Once per every other operating cycle conducting an open/close test of the HCVS control logic from its control panel and ensuring that all interfacing system valves move to their proper (intended) positions. Page 16 of 29
Enclosure Monticello Nuclear Generating Plant NRC Order EA-12-050 Overall Integrated Plan Response (ref. ISG Item 1.2.7): Condensation accumulation resulting from intermittent venting will be evaluated. The HCVS Containment Isolation Valves will be tested in accordance with the licensing and design basis. The test pressure shall be based on the HCVS design pressure 62 psig. When testing the HCVS volume, the allowed leakage will not exceed ASME Operations and Maintenance (OM) Code unless a higher leakage acceptance value is justified to the NRC. The test types and frequencies will conform to Table 2 below: Table 2 - Testing and Frequencies Description Frequency Cycle the HCVS valves and the HCVS valves Once per year used to rupture the rupture disc. Perform visual inspections and a walkdown of Once per operating cycle HCVS components. Test and calibrate the HCVS radiation monitor. Once per operating cycle Leak test the HCVS boundary valves. Per Appendix J requirements Validate the HCVS operating procedures by Once per every other operating cycle conducting an open/close test of the HCVS control logic from its control panel and ensuring that all interfacing system valves move to their proper (intended) positions. Rupture discs will be replaced at manufacturer's recommendations not to exceed 10 years, per the NRC Responses to Public Comments document. Order EA-050 1.2.8 Requirement: The HCVS shall be designed for pressures that are consistent with maximum containment design pressures, as well as, dynamic loading resulting from system actuation. ISG 1.2.8 Criteria: The vent system shall be designed for the higher of the primary containment design pressure or PCPL, and a saturation temperature corresponding to the HCVS design pressure. However, if the venting location is from the drywell, an additional margin of 50 of shall be added to the design temperature because of the potential for superheated conditions in the drywell. The piping, valves, and the valve actuators shall be designed to withstand the dynamic loading resulting from the actuation of the system, including piping reaction loads from valve opening, concurrent hydrodynamic loads from SRV discharges to the torus, and potential for water hammer from accumulation of steam condensation during multiple venting cycles. Response (ref. ISG Item 1.2.8): The HCVS design pressure is 62 psig and design temperature is 30goF. The HCVS design pressure is the higher of the containment design pressure and the PCPL value. The HCVS design temperature is the saturation temperature corresponding to the design pressure. Page 17 of29
Enclosure Monticello Nuclear Generating Plant NRC Order EA-12-050 Overall Integrated Plan The internal piping is Class I and located in a Class I structure. The piping, supports, torus penetrations, and valves were designed to withstand loads from a seismic event, Mark I/LOCA loads, rupture disc opening loads, deadweight, thermal, and dynamic loads, including piping reaction loads and hydrodynamic loads from SRV discharges to the Torus. Condensation accumulation resulting from intermittent venting will be evaluated for water hammer potential. The external piping is Class II that meets Class I seismic requirements to prevent it from impacting any safety related equipment. Order EA-050 1.2.9 Requirement: The HCVS shall discharge the effluent to a release point above main plant structures. ISG 1.2.9 Criteria: The HCVS release to outside atmosphere shall be at an elevation higher than adjacent plant structures. Release through existing plant stacks is considered acceptable, provided the guidance under Requirement 1.2.6 is satisfied. If the release from HCVS is through a stack different than the plant stack, the elevation of the stack should be higher than the nearest building or structure. The release point should be situated away from ventilation system intake and exhaust openings, and emergency response facilities. The release stack or structure exposed to outside shall be designed or protected to withstand missiles that could be generated by the external events causing the prolonged sao (e.g., tornadoes, high winds). Response (ref. ISG Item 1.2.9): The HCVS discharge path is routed next to the reactor building plenum with the vent three feet above the top of the reactor building plenum (see drawing below). This is above the main plant structures as required by the Order. The vent is located above ground level by over 100 feet, providing an elevated release point that will not affect personnel staging any portable equipment needed for the station blackout event. Side View Top View Reactor Building Roof
"'111--------__ Reactor Building Plenum Reactor Building Reactor Building Exhaust fans Reactor Building Roof Figure 2 - Side and Top View of the HCVS Page 18 of 29
Enclosure Monticello Nuclear Generating Plant NRC Order EA-12-050 Overall Integrated Plan The vent is not near the reactor building intake, control room intake, or any of the emergency response facilities, but is in the vicinity of the reactor building exhaust path through the reactor building plenum. A negative pressure could be developed in the reactor building plenum exhaust in one of three ways:
- 1. Running Standby Gas Treatment System
- 2. Running the stack dilution fans
- 3. Wind creating a negative pressure on one side of the reactor building Standby Gas treatment fans are also powered from 480 V AC Motor Control Centers (MCC) which are not backed up with any DC power supply. The stack dilution fans are powered from 480 V AC MCCs which are not backed up with any DC power supply. None of these fans will have power in a station blackout event. The geometry of the vent exhaust, and the fact that the HCVS exhaust will be heated to 212°F or greater and therefore, less dense than the surrounding air, and three feet elevation above the plenum exhaust, make it very unlikely that the HCVS venting gases will be drawn into the reactor building. In conclusion, the existing HCVS vent configuration meets the requirements of the Order and is acceptable as installed.
The piping outside safety-related structures is designed to Class II and supported to meet Class I seismic requirements to prevent the piping from affecting other safety related structures or equipment. This piping is designed to withstand the design basis flood and tornado winds forces. The piping may experience plastic deformation during a tornado, but has been analyzed to not become a missile. The vent piping is not designed to withstand tornado missiles. Page 19 of29
Enclosure Monticello Nuclear Generating Plant NRC Order EA-12-050 Overall Integrated Plan Section 4: Applicable Quality Requirements (Order EA-050 requirements 2.1 and 2.2) Order EA-050 2.1 Requirement: The HCVS system design shall not preclude the containment isolation valves, including the vent valve from performing their intended containment isolation function consistent with the design basis for the plant. These items include piping, piping supports, containment isolation valves, containment isolation valve actuators and containment isolation valve position indication components. ISG 2.1 Criteria: The HCVS vent path up to and including the second containment isolation barrier shall be designed consistent with the design basis of the plant. These items include piping, piping supports, containment isolation valves, containment isolation valve actuators and containment isolation valve position indication components. The HCVS design, out to and including the second containment isolation barrier, shall meet safety-related requirements consistent with the design basis of the plant. The staff notes that in response to GL 89-16, in many cases, the HCVS vent line connections were made to existing systems. In some cases, the connection was made in between two existing containment isolation valves and in others to the vacuum breaker line. The HCVS system design shall not preclude the containment isolation valves, including the vent valve from performing their intended containment isolation function consistent with the design basis for the plant. The design shall include all necessary overrides of containment isolation signals and other interface system signals to enable the vent valves to open upon initiation of the HCVS from its control panel Response (ref. ISG Item 2.1 ): The HCVS vent path, from the dedicated Torus penetration up to and including the second containment isolation valve, piping and supports, are designed in accordance with the existing design basis. The containment isolation valves do not open or shut on any automatic signals. The only controls are remote key locked switches in the ASDS panel. These valves are considered "sealed-closed barriers" as defined by NUREG-0800, Standard Review Plan, 6.2.4, Containment Isolation System. The control circuit will allow operation of the HCVS from its control panel regardless of containment isolation signals. Order EA-050 2.2 Requirement: All other HCVS components shall be designed for reliable and rugged performance that is capable of ensuring HCVS functionality following a seismic event. These items include electrical power supply, valve actuator pneumatic supply, and instrumentation (local and remote) components. ISG 2.2 Criteria: All components of the HCVS beyond the second containment isolation barrier shall be designed to ensure HCVS functionality following the plant's design basis seismic event. These components include, in addition to the hardened vent pipe, electric power supply, pneumatic supply and instrumentation. The design of power and pneumatic supply lines between the HCVS valves and remote locations (if portable sources were to be employed) shall also be designed to ensure HCVS functionality. Licensees shall ensure that the HCVS will not impact other safety-related structures and components and that the HCVS will not be impacted by non-seismic components. The staff prefers that the HCVS components, including the piping run, be located in seismically qualified structures. However, short runs of HCVS piping in non-seismic structures are acceptable if the licensee provides adequate justification on the seismic ruggedness of these structures. The hardened vent shall be designed to conform to the requirements consistent with the applicable design codes for the plant, such as the American Society of Mechanical Engineers Boiler and Pressure Vessel Code and the applicable Specifications, Codes and Standards of the American Institute of Steel Construction. To ensure the functionality of instruments following a seismic event, the NRC staff considers any of the following as acceptable methods:
- Use of instruments and supporting components with known operating principles that are supplied by manufacturers with commercial quality assurance programs, such as IS09001. The procurement specifications shall include the seismic requirements and/or instrument design requirements, and specify the need for Page 20 of 29
Enclosure Monticello Nuclear Generating Plant NRC Order EA-12-050 Overall Integrated Plan consistent with design basis values at the commercial design standards and testing under seismic loadings instrument locations. through methods that predict performance by
- Demonstration of the seismic reliability of the instrumentation conditions, a combination of testing and analysis, or the use analysis, qualification testing under simulated seismic 10 of IEEE Standard 344-2004, "IEEE of experience data. Guidance for these is based on sections 7, 8, 9, and ent for Nuclear Power Generating Stations,"
- Recommended Practice for Seismic Qualification of Class 1E Equipm or a substantially similar industrial standard could be used.
in design to instrumentation that has been
- Demonstration that the instrumentation is substantially similar the plant design basis at the location where the previously tested to seismic loading levels in accordance with frequen cy ranges) . Such testing and analysis should be similar to that instrument is to be installed (g-Ievels and performed for the plant licensing basis.
Response (ref. ISG Item 2.2): isolation valve up to the HPCI room roof The HCVS components downstream of the second containment safety-related structures is designed to are routed in seismically qualified structures. The piping outside Class 1\ and supported to meet Class I seismic requirements. including piping and supports, The HCVS downstream of the second containment isolation valve, nment pressure indication, up to the electrical power supply, valve actuator pneumatic supply, and contai tent with the applicable design HPCI room roof was designed to conform to the requirements consis basis earthquake. codes for the plant and to ensure functionality following a design nment pressure indication, and The HCVS instruments, including valve position indication, contai d by using one of the three radiation monitoring, were installed as safety-related or will be qualifie methods described in the ISG, which includes: operating principles from
- 1. Purchase of instruments and supporting components with known IS090 01) where the manufacturers with commercial quality assurance programs (e.g.,
ble seismi c require ments , design requirements, procurement specifications include the applica and applicable testing. performance described in
- 2. Demonstration of seismic reliability via methods that predict IEEE 344-2004.
the design of instrumentation
- 3. Demonstration that instrumentation is substantially similar to previously qualified.
Instrument Qualification Method Containment Pressure . Installed instrument is safety-related HCVS Process Radiation Monitor To be determined* HCVS Process Valve Position Installed instrument is safety-related
.. .. Instrument Will be reported In
- The specific qualification method used for each required HCVS future six month status reports.
not safety-related components nor do The HCVS radiation detector and radiation monitor are currently will be analyzed and qualified via they currently meet the ISG 2.2 guidance for instruments. They to instrumentation that has been demonstration that the instrument is substantially similar in design plant design basis as described in ISG previously tested to seismic loading levels in accordance with the ments. 2.2, or will be replaced with components that meet ISG 2.2 require Page 21 of 29
Enclo sure Monti cello Nucle ar Gener ating Plant NRC Order EA-12-050 Overa ll Integr ated Plan ts 3.1 and 3.2) Sectio n 5: Proce dures and Traini ng (Orde r EA-050 requir emen Order EA-050 3.1 Requirement: necessary for the safe operation of the HGVS. Licensees shall develop, implement, and maintain procedu res when normal and backup power is available, and during SBO Procedures shall be established for system operations conditions. ISG 3.1 Criteria: the HGVS in operation, the location of system Procedures shall be developed describing when and how to place and backup power supplies, directions for sustain ed operation, components, instrumentation available, normal operating the portable equipment, and testing of including the storage location of portable equipment, training on conditio ns and criteria for use of the HGVS. The procedures shall equipment. The procedures shall identify appropriate clearly state the nexus between GAP and EGGS pumps during a DBLOGA and how an inadvertent opening of the vent procedu res shall be developed and implemented in the valve could have an adverse impact on this nexus. The HGVS necess ary to support the executio n of the Emergency Operating Procedures same manner as other plant procedures (EOPs). ents of the HGVS and compensatory measures. These Licensees shall establish provisions for out-of-service requirem ments Manual (TRM) or similar document. The allowed provisions shall be documented in the Technical Require shall not exceed 30 days during modes 1, 2, and 3. If the unavailability time exceeds unavailability time for the HGVS ent and take the necessary actions to restore 30 days, the TRM shall direct licensees to perform a cause assessm consiste nt with plant procedu res and prevent future unavailability for similar HGVS availability in a timely manner, causes. Response (ref. ISG Item 3.1): and backup power is available and during Procedures are established for system operation when normal te method that could be used to operate prolonged SSO conditions. Current procedures provide an alterna These operator actions are unnecessary the vent valves locally, but requires an entry into the Torus room. s will be eliminated after completion of a if all systems perform as designed. Also, these operator action id bypass. Procedures for providing the modification to install a manual containment isolation valve soleno ed operation and available instrumentation backup DC power, location of equipment, directions for sustain will be generated as part of FLEX. re for NPSH for ECCS pumps. A Some Monticello design bases accidents rely on containment pressu primar y contai nment pressure affects margin to comment in the EOPs states that while venting, "Reducing NPSH limits." nsatory measures will be provided in Provisions for out-of-service requirements of the HCVS and compe the Technical Requirements Manual (TRM), as follows: d 30 days during modes 1, 2, and 3.
- The allowed unavailability time for the HCVS shall not excee
- If the unavailability time exceeds 30 days o The condition will be entered into the corrective action system with plant procedures, o The HCVS availability will be restored in a manner consistent ilability for similar causes.
o A cause assessment will be performed to prevent future unava Page 22 of 29
Enclo sure Monti cello Nucle ar Gener ating Plant NRC Order EA-12-050 Overa ll Integr ated Plan Order EA-050 3.2 Requirement: The training curricula shall include system Licensee shall train appropriate personn el in the use of the HCVS. operations when normal and backup power is available, and during sao conditions. ISG 3.2 Criteria: in the use of plant procedures developed for system All personnel expected to operate the HCVS shall receive training operations when normal and backup power is availabl e, and during sao conditions consistent with the plants on a periodic basis and as any changes occur to the systematic approach to training. The training shall be refreshed HCVS. Response (ref. ISG Item 3.2): received necessary training in the use Personnel expected to perform direct operation of the HCVS have ed on a periodic basis and as any of plant procedures for system operations. Training will be refresh following the creation of procedures to changes occur to the HCVS. Additional training will be provided training will utilize the systematic provide backup DC power during prolonged SSO conditions. The approach to training. to supplement trained personnel. In addition, per NEI 12-06, untrained personnel on-site will be used Page 23 of 29
Enclosure Monticello Nuclear Generating Plant NRC Order EA-12-050 Overall Integrated Plan Section 6: Implementation Schedule Milestones The following milestone schedule is provided. The dates are target dates and are subject to change as design and implementation details are developed. Any changes to the following target dates will be reflected in the subsequent six month status reports, as required by the Order. Original Target Activity Status Date (including any target date revisions) October 2012 Submit 60 Day Status Report Complete February 2013 Submit Overall Integrated Implementation Plan Completed by this submittal August 2013 Submit six month status report January 2014 Commence engineering design February 2014 Submit six month status report July 2014 Commence installation August 2014 Submit six month status report February 2015 Submit six month status report End of 2015 HCVS Operational Refueling Outage August 2015 Submit Completion Report Section 7: Changes/Updates to this Overall Integrated Implementation Plan Consistent with the requirements of NRC Order EA-12-050, the six month status reports will delineate progress made, any proposed changes in NSPM's compliance methods, updates to the schedule, and if needed, requests for relief and the bases for these requests. Page 24 of29
Enclosure Monticello Nuclear Generating Plant NRC Order EA-12-050 Overall Integrated Plan Section 8: Additional Tables and Figures Table 3 - Failure Evaluation Table Functional Failure Failure Cause Alternate Action Alternate Action Mode Corrects Failure One or Both Loss of Normal AC power to DC power supplied to inverter Yes Containment Isolation solenoid valve supplying Valve Fails to Open on nitrogen gas Demand Loss of AC and DC power Recharge DC batteries with FLEX Yes diesel generator or open manual bypass (future installation) Loss of safety-related Add additional gas bottles to the Yes Alternate Nitrogen System Alternate Nitrogen System (on site FLEX equipment) Solenoid valve fails to open Open manual bypass (future Yes installation) Mechanical valve problem None No One Containment Any failure Close alternate valve Yes Isolation Valve Fails to Close on Demand Both Containment Both solenoid valves fail to De-pressurize alternate nitrogen Yes Isolation valves Fail to close for any reason supply to solenoids Close and Rupture Disc Open Mechanical problems in both None No valves Spurious Containment Not creditable as key locked NA NA Isolation Valve Opening switches prevent mis-positioning. Also, the installed rupture disc prevents flow, if it has not be ruptured as part of the event Automatic Containment No automatic closure signals NA NA Isolation Closure from other signals Failure to be able to Loss of safety-related Add additional gas bottles to the Yes open rupture disc at a Alternate Nitrogen System Alternate Nitrogen System (on site containment pressure FLEX equipment) below the rupture pressure Solenoid valve fails to open Open manual bypass (future Yes installation) Page 25 of29
Enclosure Monticello Nuclear Generating Plant NRC Order EA-12-050 Overall Integrated Plan Figure 3 - HCVS Connection to Torus L rr\V1Vl (~'L
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Page 26 of 29
Enclosure Monticello Nuclear Generating Plant NRC Order EA-12-050 Overall Integrated Plan Figure 4 - HCVS Piping
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Enclosure Monticello Nuclear Generating Plant NRC Order EA-12-050 Overall Integrated Plan Figure 5 - Alternate Nitrogen System
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