ML18352B233
| ML18352B233 | |
| Person / Time | |
|---|---|
| Issue date: | 08/15/2018 |
| From: | NRC/NRR/DSS |
| To: | |
| Wilkin L | |
| Shared Package | |
| ML18352B238 | List: |
| References | |
| TAC ME4565, TAC MF8075, Y020100159 | |
| Download: ML18352B233 (24) | |
Text
Enclosure OFFICE OF NUCLEAR REACTOR REGULATION ACTION PLAN GAS MANAGEMENT TAC NOS.:
08/26/2010 - 06/02/2016: ME4565 Last Update: July 2017 05/09/2016 - Present: MF8075 Lead Division: Safety Systems (DSS)
Yellow Ticket No.: Y020100159 Supporting Divisions: Policy and Rulemaking (DPR)
The U.S. Nuclear Regulatory Commission (NRC), Office of Nuclear Reactor Regulation (NRR)
Gas Management Action Plan consists of actions to (1) close Generic Letter (GL) 2008-01, (2) create a comprehensive gas management document, (3) address Technical Specification (TS) issues, and (4) address vortexing, gas transport, operability, and Design Basis (DB) issues that were not covered in Item 2. Items 1 and 2 have been completed. Selected schedule information is provided in the following table:
Item No.
Milestone1 Date (T=target)
(C=Complete)
Lead Support 1
Close GL 2008-01 (Individual Plants) 07/07/11 (C)
Reactor Systems Branch (SRXB)
J. Whitman Generic Communications Branch (PGCB)
E. Bowman Nuclear Energy Institute (NEI) gas management workshop with over 200 attendees 01/08 (C)
SRXB W. Lyon Issue GL 2008-01 (GL, January 11, 2008) 01/11/08 (C)
W. Lyon Receive Licensee 3-Month Responses 04/11/08 (C)
Division of Reactor Licensing (DORL) Project Manager (PM)
Review 3-Month Responses 08/11/08 (C)
W. Lyon Receive Licensee 9-Month Responses 11/11/08 (C)
DORL PM Industry meeting at Westinghouse offices 12/05/08 (C)
SRXB D. Woodyatt W. Lyon Industry meeting at Westinghouse offices 01/30/09 (C)
D. Woodyatt W. Lyon NEI workshop at Dana Point, California 02/09(C)
D. Woodyatt W. Lyon Industry meeting at Westinghouse Rockville, Maryland offices 03/19/09 (C)
D. Woodyatt W. Lyon Issue Assessment Guidance to Industry (Ruland, May 28, 2009) 05/28/09 (C)
W. Lyon 1 The list of meetings is incomplete and is provided to illustrate continued Nuclear Energy Institute (NEI) /
industry / NRC interactions in support of gas-related issues.
Item No.
Milestone1 Date (T=target)
(C=Complete)
Lead Support Issue Temporary Instruction (TI) 2515/177 (NRC, June 9, 2009) 06/09/09 (C)
W. Lyon Regulatory Improvements Branch (IRIB)
S. Vaughn NEI / Industry / NRC meeting 01/06/10 (C)
W. Lyon Workshop 01/21/10 (C)
W. Lyon Industry meeting at NEI 06/02/10 (C)
W. Lyon Complete Initial GL 2008-01 Response Reviews, Provide Requests for Additional Information (RAIs) 12/30/10 (C)
J. Whitman Receive RAI Responses 05/17/11 (C)
DORL PM TI 2515/177 Inspection Guidance to Regions (NRC, May 23, 2011) 05/25/11 (C)
W. Lyon Complete GL Response Reviews 06/09/11 (C)
J. Whitman Send Individual Closure Memos to Licensees 06/30/11 (C)
DORL PM Complete GL Closure Memo (Ulses, July 5, 2011) 07/05/11 (C)
J. Whitman 2
Create Comprehensive Gas Management Document (See also Item 4.)
05/27/14 (C)
W. Lyon Define Acceptable Pump Suction Void Fractions 06/30/10 (C)
W. Lyon Regulatory Information Conference (RIC) session 03/11/13 (C)
J. Whitman C. Jackson W. Lyon Issue Safety Evaluation Report (SER) that endorses NEI-09-10 (NRC, April, 2013) 03/19/13 (C)
J. Whitman W. Lyon Licensing Processes Branch (PLPB)
S. Stuchell Issue Regulatory Issue Summary (RIS) that announces endorsement of NEI 09-10 (NRC, August 23, 2013) 03/23/13 (C)
W. Lyon S. Stuchell Issue Comprehensive Gas Assessment update report (Proprietary) 05/27/14 (C)
W. Lyon J. Whitman C. Jackson 3
Develop TSTF as a Generic Approach to Address Gas Accumulation Ongoing Technical Specification Branch (STSB)
M. Hamm Receive TSTF-523 Rev. 0 (Schrader, June 29, 2010) 06/29/10 (C)
Item No.
Milestone1 Date (T=target)
(C=Complete)
Lead Support TSTF-523 Meetings with Industry2 09/30/10 (C) 01/12/11 (C)
J. Whitman Radiation Protection Branch (PRPB)
M. Honcharik Accept Industry TSTF for Review (Honcharik, March 2, 2011) 03/02/11 (C)
J. Whitman M. Honcharik SRXB RAIs 05/10/12 (C)
W. Lyon A. Ulses Reject Proposed TSTF (Jolicoeur, May 25, 2011) 05/25/11 (C)
J. Whitman M. Honcharik SE on TSTF-523 Rev. 1 (NRC, December, 2012) 12/12 (C)
J. Whitman W. Lyon M. Hamm TSTF-523 Rev. 2 (TSTF, February 21, 2013) 02/21/13 (C)
M. Hamm Publish FRN for public comment 09/02/13 (C)
M. Hamm Resolve any comments, issue Notice of Availability in Federal Register 12/23/13 (C)
M. Honcharik M. Hamm 4
Gas Transport and Vortexing Issues Exclusive of Regulatory Guide (RG) 1/16/19 (T)3 W. Lyon D. Woodyatt J. Holonich SRXB inspection support for Millstone4 10/08 (C)
W. Lyon Meeting with Industry to review Purdue Tests 07/07/09 (C)
G. Cranston D. Woodyatt W. Lyon NRC Information Notice 2010-11 06/16/10 (C)
D. Garmon W. Lyon Byron inspection support regarding GOTHIC 01/04/11 (C)
W. Lyon Tele-conference covering planning to discuss computational methodologies 05/17/11 (C)
D. Woodyatt W. Lyon SRXB inspection support for Prairie Island 06/05/11 (C)
W. Lyon NRC Information Notice 2011-17 07/26/11 (C)
J. Whitman W. Lyon Initial Farley vortex assessment 05/02/12 (C)
W. Lyon SRXB support for DC Cook inspection 06/03/12 (C)
W. Lyon Observe aux feedwater pump test 11/12 (C)
J. Miller W. Lyon 2 This item provided to illustrate early TSTF-523 meetings. Later meetings are not listed.
3 This date assumes planned NEI/Industry support schedule is met and is subject to change if additional SRXB inspection support is requested.
4 Identification of inspection support activities is provided to illustrate continuing involvement. The list is not complete.
Item No.
Milestone1 Date (T=target)
(C=Complete)
Lead Support SRXB support for Kewaunee inspection 01/13 (C)
J. Miller W. Lyon SRXB support for Byron inspection 02/15/13 (C)
W. Lyon NEI/Industry/NRC meeting to discuss vortexing 04/18/13 (C)
W. Lyon S. Stuchell Prairie Island TI-177 SRXB support 07/23/14 (C)
W. Lyon Robinson inspection support report (Lyon, September 24, 2013) 09/27/13 (C)
W. Lyon SRXB support for Ft. Calhoun inspection 03/06/14 (C)
W. Lyon Complete Farley vortex assessment 05/25/14 (C)
R. Nease W. Lyon SRXB support for McGuire inspection 07/22/14 (C)
W. Lyon C. Jackson SRXB support for N. Anna Vortex inspection 08/02/14 (C)
W. Lyon NEI/Industry/NRC meeting to discuss gas issues 08/19/14 (C)
W. Lyon J. Holonich Draft NUREG that addresses gas issues 10/05/14 (C)
W. Lyon J. Whitman SRXB support for Summer inspection 12/20/14 (C)
W. Lyon NEI/Industry/NRC meeting to discuss gas issues 01/15/15 (C)
W. Lyon J. Whitman C. Jackson 2015 RIC Session 03/11/15 (C)
W. Lyon J. Whitman C. Jackson SRXB Peach Bottom TSTF-523 Review 03/31/15 (C)
W. Lyon SRXB Calvert Cliffs, Ginna, Nine Mile Point TSTF-523 Reviews 07/15/15 (C)
W. Lyon C. Jackson SRXB Wolf Creek TSTF-523 Review 07/28/15 (C)
W. Lyon NEI/Industry/NRC meeting to discuss gas issues 08/04/15 (C)
W. Lyon J. Whitman C. Jackson NEI/Industry Topical Report.
05/10/16 (C)
NEI, J. Riley SRXB Millstone, Surry, Hatch, Oconee, McGuire, Catawba, Brunswick, Harris, Prairie Island, Farley, Vogtle, TSTF-523 Reviews 04/16 (C)
W. Lyon SRXB support for Farley inspection 09/27/17 (C)
W. Lyon Final SE for NEI/Industry Topical Report 9/30/18 (T)
W. Lyon J. Holonich Item No.
Milestone1 Date (T=target)
(C=Complete)
Lead Support Draft RIS Status of Regulatory Issues Identified through GL 2008-01 Federal Register notice 02/13/17 (C)
D. Woodyatt A. Garmoe Rescind Draft RIS Federal Register notice 09/21/17 (C)
D. Woodyatt N. Martinez 5
Regulatory Guide Number of days after submission of RG for publishing (N) +
155 (T)
W. Lyon D. Woodyatt J. Whitman M. Eudy Decision regarding publication of NUREG, RG, or other guidance documents 09/30/16 (C)
E. Oesterle W. Lyon J. Whitman Draft RG to NEI for proprietary review 03/30/2019 (T)
J. Whitman W. Lyon D. Woodyatt M. Eudy Receive NEI proprietary review response 04/27/2019(T)
Submit RG to FRN for publishing 07/27/2019 (T)
D. Woodyatt M. Eudy Publish RG in FRN N
Receive comments on RG N+60 J. Holonich Address comments and modify RG as necessary N+100 D. Woodyatt M. Eudy Submit RG for final publishing N+150 ADMIN M. Eudy
==
Description:==
A review of operating experience and NRC inspection results showed that gas accumulation events involving systems that are important to safety have rendered or potentially rendered these risk-significant systems inoperable. The number of identified gas accumulation events and their significance at some facilities raised concerns about whether similar unrecognized design, configuration, and operability problems existed at additional facilities.
System designs vary widely regarding potential gas sources and capability to control gas. It is important that the subject systems are sufficiently filled with water to ensure that they can reliably perform their intended functions under all loss-of-coolant accident (LOCA) and non-LOCA conditions that require makeup to the reactor coolant system (RCS). The final safety analysis reports (FSARs) at many facilities state that some systems are full of water and TSs often require periodic surveillances to confirm this condition. Some plant TSs have incomplete Surveillance Requirements (SRs) that cover only portions of a system. The current staff position is that standard SRs are needed to ensure compliance and adequate protection to the health and safety of the public. The staff is pursuing TS changes with industry through the TSTF process.
Regulatory Requirements:
The regulations in Appendix A to Title 10 of the Code of Federal Regulations (10 CFR) Part 50 or similar plant-specific principal design criteria provide design requirements.5 Appendix B to 10 CFR Part 50, the TSs, and licensee quality assurance programs provide operating requirements.
10 CFR 50 Appendix A requirements include the following:
General Design Criterion (GDC) 1 requires that the subject systems be designed, fabricated, erected, and tested to quality standards.
GDC 34 requires a residual heat removal (RHR) system designed to maintain specified acceptable fuel design limits and to meet design conditions that are not exceeded if a single failure occurs simultaneous with failure of specified electrical power systems.
GDCs 35, 36, and 37 require an emergency core cooling system (ECCS) design that meets performance, inspection, and testing requirements.
GDCs 38, 39, and 40 require a containment heat removal system design that meets performance, inspection, and testing requirements.
Quality assurance criteria provided in Appendix B to 10 CFR Part 50 include:
Criteria III and V require measures to ensure that applicable regulatory requirements and the DB, as defined in 10 CFR 50.2, Definitions, and as specified in the license application, are correctly translated into controlled specifications, drawings, procedures, and instructions.
Criterion XI requires a test program to ensure that the subject systems will perform satisfactorily in service and requires that test results shall be documented and evaluated to ensure that test requirements have been satisfied.
Criterion XVI requires measures to ensure that conditions adverse to quality, such as failures, malfunctions, deficiencies, deviations, defective material and equipment, and nonconformances, are promptly identified and corrected, and that significant conditions adverse to quality are documented and reported to management.
Criterion XVII requires maintenance of records of activities affecting quality.
Regulatory requirements covering TSs are provided in 10 CFR 50.36(c). Categories covered include (1) safety limits, limiting safety systems settings, and limiting control settings; (2)
Limiting Conditions of Operations (LCOs); (3) SRs; (4) design features; and (5) administrative controls. Of particular interest here with respect to operability is 10 CFR 50.36(c)(2) that defines the LCO as the lowest functional capability or performance levels of equipment required for safe 5 The Atomic Energy Commission (AEC) published the rule that added 10 CFR Part 50, Appendix A, "General Design Criteria for Nuclear Power Plants," in the Federal Register (36 FR 3255) on February 20, 1971, with the rule becoming effective on May 21, 1971. Appendix A was not applied to plants with construction permits issued prior to May 21, 1971. Such plants were licensed in accord with plant-specific principal design criteria that are generally similar to Appendix A requirements.
operation of the facility. When an LCO of a nuclear reactor is not met, the licensee shall shut down the reactor or follow any remedial action permitted by the TSs until the condition can be met. A purpose of the correlations addressed in this program is to provide methodologies to predict gas accumulations in pump suction piping that have the potential to impact operability.
This information may then be used to determine if SRs are satisfied.
Plants typically are designed and licensed so that systems, such as the ECCS and RHR system, are to be in a water-solid condition.6 Consequently, for most licensees, whether stated or not, the current DB for the subject systems is a water-solid condition. This was reiterated in NEI 09-10 and the accompanying NRC Safety Evaluation (SE) (NEI, April, 2013), which stated If there is no specified design limit then the design limit is no gas present. It is also identified in TSTF-523 Revision 2 (NRC, February 21, 2013) by such statements as The NRC was concerned that the design condition, with some exceptions, is water-solid and the system may not be restored to this condition. To be completely consistent with the DB, the subject systems should be water-solid when transitioning from an outage into power operation.
It is not always practical to maintain a water-solid condition in existing nuclear power plant systems and voids may be acceptable provided operability is reasonably maintained and the voids are removed as soon as is practical.7 This is consistent with (1) Task Interface Agreement (TIA) 2008-03 (NRC, October 21, 2008) that stated that system piping can be considered filled with water if system operability has been established, (2) TSs such as 3.5 that require the ECCS to be operable in MODES 1 and 2 and in MODE 3 if the RCS is pressurized above a stated level, and (3) TSs such as 3.4 that require RHR loop locations susceptible to gas accumulation are sufficiently filled with water.
With respect to operability, the objective is to reasonably ensure that subject system operability is achieved and a reasonable expectation test applies. This means that a high degree of confidence applies but absolute assurance is not necessary. The determination can be based on analyses, test or partial test, experience, and/or engineering judgment (NRC, January 31, 2014).
A typical SR 3.0.4 states that Entry into a MODE or other specified condition in the applicability of an LCO shall only be made when the LCO's surveillances have been met within their specified frequency, except as provided by SR 3.0.3.
Also of interest are the regulations in 10 CFR 50.46 that provide specified ECCS performance criteria pertaining to peak cladding temperature, cladding oxidation, hydrogen generation, core cooling, long-term core temperature, and long-term decay heat removal that could potentially be impacted by ECCS rendered inoperable due to gas accumulation.
Background:
Instances of gas accumulation in plant systems have occurred since the beginning of commercial nuclear power plant operation. The NRC has published 21 Information Notices (INs), three GLs, and NUREG and NUREG/CRs related to this issue. NRC has also 6 Voids that have no effect on operation, such as isolated bubbles or voids in heat exchangers that cannot be removed and will not affect operation, are allowed to exist under water-solid conditions.
7 As soon as is practical may be (1) at the time of discovery, (2) the next outage, or (3) it may not be practical to remove gas. However, operability must be maintained or the plant must be shut down as required by applicable TSs.
interacted with the nuclear industry many times in relation to these publications and in response to gas accumulation events. Despite this history, and in many instances inconsistent with the above regulatory requirements, licensees continued to inadequately address gas accumulation issues. This situation changed as a result of plant shutdowns due to gas issues, workshops to address the issues, and following publication of GL 2008-01 and the Institute of Nuclear Power Operations Significant Operating Event Report (SOER) 2-05 (INPO, January 9, 2008).
GL 2008-01 requested that each addressee evaluate its ECCS, Decay Heat Removal system, and containment spray system licensing basis, design, testing, and corrective actions to ensure that gas accumulation is maintained less than the amount that challenges system operability.
The INPO SOER 2-05 Rev. 1 also recommended that licensees take appropriate action when conditions adverse to quality are identified. The combination of inspections, plant shutdowns, workshops, meetings, GL 2008-01, and INPO SOER 2-05 Rev. 1 resulted in an in-depth industry effort to address many of the issues. This resulted in a significant and continuing improvement in addressing gas management issues, although further NRC guidance is needed for some issues, such as gas transport, vortexing, and addressing the DB.
NEI 09-10 Revision 1a-A (NEI, April, 2013), hereafter referred to as NEI 09-10, addressed issues that were identified in GL 2008-01 and INPO SOER 2-05 Rev. 1 during evaluations of industry operations, and in meetings and workshops. It provided recommendations and guidance to nuclear power plant licensees for development and implementation of programs and processes to prevent and manage gas intrusion and gas accumulation in plant systems.
The focus was on aspects necessary to maintain operability. NEI 09-10 Revision 1a was endorsed in an NRC SE and announced in RIS 13-09.
The NRC is aware of many potentially significant gas intrusion events that have occurred since GL 2008-01 was issued for comment.8 To assess the licensee's evaluations and actions, the NRC requested that the licensees submit information to demonstrate that the subject systems are in compliance with the current licensing and design bases and applicable regulatory requirements, and that suitable design, operational, and testing control measures are in place for maintaining this compliance. The NRC further stated that it would collect the requested information to determine if additional regulatory action is required. The licensees were requested to submit a written response consistent with the requested actions and information within 9 months of the issuance of the GL. A preliminary assessment of each 9-month licensee response was completed by the NRC staff to determine whether sufficient information was provided to complete the review and close out the GL.
The reviews determined that the FSARs at many facilities stated that the subject systems were full of water and plant TS often required periodic surveillances to confirm this condition. Most plant DBs require a water-solid condition.9 Some plant TSs have incomplete SRs that cover only portions of the systems. Since the subject systems could be rendered inoperable or degraded by gas accumulation in any section of piping or by ingestion of gas while draining 8 39 instances of discovery of gas at one site were identified in one licensee document during an inspection at a two unit site. The document also identified multiple cases of unexpected accumulator level changes. A significant increase in the discovery and response to gas voids occurred after the NRC started pursuing this issue, an indication of increased licensee recognition of the potential impact.
9 Water-solid, gas-free, and free-of gas mean there is no gas with the exception of isolated gas bubbles or gas accumulation in locations that cannot affect operability that cannot be removed by practical means. Other terms, such as filled with water, mean there is sufficient water to reasonably ensure system operability. (TIA, October 21, 2008) tanks or from sumps, the regulations require assessment of gas issues to establish operability.
In recognition of practical operation considerations, some level of gas accumulation may not affect operability as determined by licensee void acceptance criteria that are acceptable to the NRC staff. However, the NRC staff position is that such gas accumulation should be corrected at the earliest practical times.
Criterion III of Appendix B to 10 CFR Part 50 and the plants operating license identify regulatory requirements for the design of systems that are important for safety. The failure to translate the DB (such as the system being maintained full of water) into drawings, specifications, procedures, and instructions would be contrary to Criterion III. System designs vary widely regarding potential gas sources and capability to control gas. Potential gas sources and symptoms of gas leakage from those sources should be identified and potential gas accumulation locations should be known and provisions made to address gas accumulation at those locations. Additionally, Criteria V and XI and the plant operating license require licensees to perform testing using written test procedures that incorporate the requirements and acceptance limits contained in applicable design and licensing documents. Criterion XVII requires keeping appropriate records. Testing of portions of piping and components in systems where unacceptable gas accumulation may occur is necessary to confirm acceptance limits and operability unless it has been acceptability established that some portions may be excluded.
Surveillance and testing that do not reasonably ensure operability prior to the next surveillance are not consistent with this testing requirement.
Lastly, the reviews identified that some licensees have treated the accumulation of substantial gas quantities as an expected condition rather than a nonconforming condition and have not documented the condition when discovered even when it involved a substantial volume of gas that clearly constituted a significant condition adverse to quality and safety.
Meetings were conducted with the NEI, owners groups, several industry organizations, and licensees to identify additional information needed to be submitted to the NRC. On May 28, 2009, the NRC issued an assessment guidance document to clarify to the licensees what information was needed to be submitted to the NRC to facilitate close out of the GL (Ruland, May 28, 2009). Licensees used this assessment guidance to determine if they wanted to supplement their original submittals.
The NRC staff has completed the detailed reviews of the licensee responses to GL 2008-01.
The reviews assessed the information provided by the licensees to support a conclusion that there is a reasonable assurance that the subject systems are operable. The NRC staff issued individual plant closure letters after plant responses were received, reviewed, and accepted.
After all individual plant closure letters were issued, the NRC staff issued a GL 2008-01 individual plant closure memorandum (Rosenberg, July 7, 2011).
The NRC staff issued TI 2515/177 (NRC, May 23, 2011) to provide background information and guidance for inspectors to verify that the onsite documentation, system hardware, and licensee actions were consistent with the information provided in the licensees response to GL 2008-01.
The staff also provided the regions with generic10 and plant-specific inspection guidance for TI 2515/177.
The individual plant closure of GL 2008-01 closed the immediate operability issue as defined in the GL. Licensee responses to the GL demonstrated that the systems subject to gas 10 (NRC, May 23, 2011) is the latest version of the generic guidance.
accumulation are in compliance with the current licensing and design bases and applicable regulatory requirements, and that suitable design, operational, and testing control measures are in place to maintain this compliance. NRC issued letters to each licensee documenting closure of GL 2008-01 for their facilities. Documentation of the closeout of multi-plant action (MPA)-L803 Managing Gas Accumulation in Emergency Core Cooling, Decay Heat Removal, and Containment Spray Systems, Generic Letter 2008-01, is provided in ADAMS Accession No. ML111860007. However, staff efforts beyond the closure of GL 2008-01 to provide durable guidance for gas management continue as discussed below.
Regulatory Outcome:
As stated above, individual plant closure of GL 2008-01 closed the immediate operability issue as defined in GL 2008-01. It did not, however, complete the staffs efforts to develop durable guidance for all of the gas accumulation and management issues. The staff continued to work with industry through NEI to develop a revised NEI 09-10 that was found acceptable via an SER (NRC, April, 2013). This was followed by RIS 2013-09 to announce endorsement of the revision (NRC, August 23, 2013). These documents:
conformed to and reinforced previously established NRC regulations, reinforced previously issued guidance such as contained in GL 2008-01, various inspection guidance documents [(NRC, May 23, 2011), (NRC, April 16, 2008), (NRC, February, 1978), and (NRC, April 16, 2008)], and discussed in meetings such as those identified in the table at the beginning of this document, documented in one location practices that are in widespread use, provided insights and attributes to implement aspects of an acceptable approach to effectively prevent and manage gas intrusion and accumulation in plant systems, provided an aid in the identification of susceptible systems, outlined principles and practices designed to effectively prevent, identify, manage and monitor accumulation of gas that would challenge the capability of a system to perform its functions as designed, identified training to ensure plant personnel can readily recognize and effectively respond to gas intrusion and accumulation in susceptible systems, provided guidance for addressing gas management issues, added value to NRC and industry activities by detailing methods of resolving gas accumulation issues, and will improve the efficiency of licensing processes such as associated with license amendment requests since licensees can reference NEI 09-10, the accompanying SE, and RIS 2013-09 in the same manner as they can reference previously approved NRC documents such as SEs.
With respect to application of computer codes, NEI 09-10 stated that any computer code used to develop a system specific model should be verified to be applicable to solve problems involving gas transport in piping systems via comparisons with laboratory test data or other appropriate methods. Further, a suitable safety factor should be added to predicted results to reasonably ensure the predictions encompass actual behavior. Details associated with entrance of gas into systems due to gas ingestion from hot leg pipes, storage tanks, and recirculation sumps were outside of the NEI 09-10 scope.
Application of computer codes to assess gas movement, associated gas movement methodologies, and gas ingestion have been addressed by preparing additional guidance documents and providing inspection support. Completion of this Action Plan includes addressing these by completing ongoing reviews and issuing a RG.
With respect to TSs, 10 CFR 50.36(c)(3) states that SRs are requirements relating to test, calibration, or inspection to assure that the necessary quality of systems and components is maintained, that facility operation will be within safety limits, and that the limiting conditions for operation will be met. The Standard TSs, NUREGs 1430 - 1434, currently include a SR for ensuring the ECCS is full of water consistent with the NRC staff concluding that this is a necessary requirement to reasonably ensure ECCS operability.11 Operating experience, industry investigations, and NRC activities such as inspections have demonstrated that the TSs and Standard TS are incomplete since they do not address all systems that are important to safety where gas accumulation could cause inoperability. Consequently, Standard TSs and TSs must be improved consistent with NRC Administrative Letter 98-10 that addresses response to TSs that may not assure safety (Roe, December 29, 1998).
The goal of gas management TSs is to address system SRs and acceptance criteria for gas voiding in an enforceable manner. Industry submitted TSTF-523 Revision 0 on June 29, 2010.
In a July 15, 2010, meeting, the Technical Specifications Branch staff stated that entirely removing the gas volume SR from the TSs, as included in TSTF-523, was not acceptable. In September 30, 2010, and January 12, 2011, meetings, the staff raised questions about the TSTF but no changes were made in TSTF-523. The staff accepted TSTF-523 for review on March 2, 2011, and determined that it would remove the SRs from the TSs and only insert gas management operability information into the LCO Bases. TSTF-523 would also add a gas management program to the updated FSAR.
Following a determination that the proposed TSTF was unacceptable, the NRC staff continued to work with industry through the TSTF to develop acceptable gas management TSs to further ensure adequate protection of the public. The model SE for plant-specific adoption of TSTF 523, Revision 2, is available in ADAMS under Accession No. ML13255A169. Minor editorial comments were received from the Notice of Opportunity for Public Comment announced in the Federal Register on August 2, 2013. (78 FR 47010). Disposition of comments received is available in ADAMS under Accession No. ML13255A403. On January 15, 2014, the staff issued a Notice of Availability in the Federal Register for TSTF-523, Revision 2.
Current Status:
GL 2008-01 responses have been reviewed, individual plant closure memos have been transmitted to licensees. The individual plant GL review was closed (Rosenberg, July 7, 2011).
TI 2515/177 inspections are complete. SRXB staff continues to provide inspection support when requested and will complete review of a topical report that addresses gas movement 11 Some licensees have less TS coverage than provided in the Standard TSs.
(Swantner, August, 2015). It is anticipated with the completion of Milestone 4, there will be a decrease in regional requests for inspection support assistance.
The NRC staff will continue to meet with industry to address follow-up items such as gas ingestion, void transport methodologies, and DB issues on an as-needed basis, to support development of the RG. Staff is reviewing industry guidance (PWROG-15060, Pump Suction Gas Accumulation Operability Criteria Guidance) to inform development of the RG.
CONTACTS: Diana Woodyatt (SRXB) 415-1245 Jennifer M. Whitman (Chief, SRXB) 415-3253
REFERENCES:
NRC. (January 11, 2008). Managing Gas Accumulation in Emergency Core Cooling, Decay Heat Removal, and Containment Spray Systems, NRC Generic Letter 2008-01, ML072910759, January 11, 2008.
Honcharik, M. C. (March 2, 2011). ACCEPTANCE FOR REVIEW OF TRAVELER TSTF-523, REVISION 0, GENERIC LETTER 2008-01, MANAGING GAS ACCUMULATION (TAC NO.
ME4177).
INPO. (January 9, 2008). Gas Intrusion in Safety Systems, SOER 2-05, Revision 1.
Jolicoeur, J. R. (May 25, 2011). Review of Traveler TSTF-523, Revision 0, Generic Letter 2008-01, Managing Gas Accumulation (TAC No. ME4177), NRC Letter to Technical Specifications Task Force (TSTF), ML111430832.
Lyon, W. (September 24, 2013). "Office of Nuclear Reactor Regulation (NRR) Reactor Systems Branch (SRXB) Support of Region II Inspection of H. B. Robnson Treatment of Voids in Systems that are Important," ML13270A176.
NEI. (April, 2013). Guidelines for Effective Prevention and Management of System Gas Accumulation, Rev 1a-A, ML13136A129.
NRC. (April 16, 2008).... Revision to Guidance Formerly Contained in NRC Generic Letter 91-18, Information to Licensees Regarding Two NRC Inspection Manual Sections on Resolution of Degraded and Nonconforming Conditions and on Operability, RIS-2005-20-Rev-1, ML07344010.
NRC. (April 16, 2008). Part-9900, Operability Determinations & Functionality Assessments for Resolution of Degraded or Nonconforming conditions Adverse to Quality or Safety, NRC Inspection Manual, Part 9900: Technical Guidance, Attachment to RIS 2005-20 Rev 1.
NRC. (April, 2013). Guidelines for Effective Prevention and Management of System Gas Accumulation, Rev 1a-A, ML13136A129.
NRC. (August 23, 2013). "NRC REGULATORY ISSUE
SUMMARY
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