ML19163A176
| ML19163A176 | |
| Person / Time | |
|---|---|
| Site: | Nuclear Energy Institute |
| Issue date: | 06/06/2019 |
| From: | True D Nuclear Energy Institute |
| To: | Ho Nieh Office of Nuclear Reactor Regulation |
| Williams, Donna | |
| References | |
| Project Number: 689 | |
| Download: ML19163A176 (13) | |
Text
NRR-DRMAPEm Resource From: TRUE, Doug <det@nei.org>
Sent: Thursday, June 6, 2019 4:20 PM To: Nieh, Ho Cc: Doane, Margaret; McDermott, Brian; Benner, Eric; Williams, Donna
Subject:
[External_Sender] Industry Initiative on Open Phase Condition, Revision 3 Attachments: 06-06-19_NRC_Industry Initiative on OPC Rev 3.pdf; 06-06-19_NRC_Industry Initiative on OPC Rev 3 - Attachment.pdf June 6, 2019 Mr. Ho Nieh, Jr.
Director, Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, DC 20555-0001
Subject:
Industry Initiative on Open Phase Condition, Revision 3 Project Number: 689
Dear Mr. Nieh:
On March 16, 2015, the Nuclear Energy Institute (NEI)[1] informed the U.S. Nuclear Regulatory Commission (NRC) that the industry had formally approved revision one to the Open Phase Condition (OPC) Initiative to address the OPC in the off-site power circuits.[2] Since that time, many plants have completed initial installation of their Open Phase Isolation System (OPIS) with the remaining plants scheduled to complete initial installation this year. In September 2018, Revision 2 to the industry initiative was approved. Revision 2 was initiated to provide for an extended monitoring period before implementing the automatic trip function. This was in response to monitoring data indicating that some installed OPIS would have experienced spurious actuations if the automatic trip functions had been activated and the uncertainty that all existing and potentially new plant and/or grid configurations could be reliably handled by the various OPIS designs without inducing spurious actuations.
In parallel with implementation of Revision 2 to the industry initiative, alternatives to enabling the automatic isolation of OPC were also pursued. As a result, risk assessment guidance was developed based on the premise that the risk associated with an OPC event is significantly reduced through the implementation of detection and alarm circuits. This guidance is being issued for industry use as NEI 19-02, Guidance for Assessing Open Phase Condition Implementation Using Risk Insights.
Revision 3 to the NEI OPC initiative incorporates an option for plants to perform a risk evaluation under certain boundary conditions to support manual response to an OPC. This option provides the opportunity for stations to more broadly consider the potential impacts of an OPC on equipment and plant configurations prior to taking actions that isolate or transfer loads. The initiative revision and drafts of the risk-informed guidance have been discussed with NRC staff in three public meetings held on February 20, 2019, March 20, 2019, and May 7, 2019. NEI greatly appreciates the staffs input on this change to the OPC initiative and has made efforts to address all comments received on the initiative revision and the guidance document during these interactions.
1
Additional changes in the revision include removal of historical statements that were no longer applicable and updating several actions that have been completed.
The industrys chief nuclear officers have voted to approve this revision to the NEI Open Phase Conditions Initiative. A copy of the approved initiative revision is attached for your information. The initiative is a formal commitment by NEI member companies that operate nuclear power plants to follow a specific policy or plan of action.
If you or your staff members have any questions, please feel free to contact Stephen Geier at (202) 739-8111 or seg@nei.org, or me.
Sincerely, Douglas E. True Senior Vice President and Chief Nuclear Officer Nuclear Energy Institute 1201 F St NW, Suite 1100 Washington, DC 20004 www.nei.org P: 202.739.8093 E: det@nei.org This electronic message transmission contains information from the Nuclear Energy Institute, Inc. The information is intended solely for the use of the addressee and its use by any other person is not authorized. If you are not the intended recipient, you have received this communication in error, and any review, use, disclosure, copying or distribution of the contents of this communication is strictly prohibited. If you have received this electronic transmission in error, please notify the sender immediately by telephone or by electronic mail and permanently delete the original message. IRS Circular 230 disclosure: To ensure compliance with requirements imposed by the IRS and other taxing authorities, we inform you that any tax advice contained in this communication (including any attachments) is not intended or written to be used, and cannot be used, for the purpose of (i) avoiding penalties that may be imposed on any taxpayer or (ii) promoting, marketing or recommending to another party any transaction or matter addressed herein.
Sent through www.intermedia.com
[1]
The Nuclear Energy Institute (NEI) is responsible for establishing unified policy on behalf of its members relating to matters affecting the nuclear energy industry, including the regulatory aspects of generic operational and technical issues. NEIs members include entities licensed to operate commercial nuclear power plants in the United States, nuclear plant designers, major architect and engineering firms, fuel cycle facilities, nuclear materials licensees, and other organizations involved in the nuclear energy industry.
[2]
Hearing Identifier: NRR_DRMA Email Number: 45 Mail Envelope Properties (55fd389175234bf48e9e06716c1327c6)
Subject:
[External_Sender] Industry Initiative on Open Phase Condition, Revision 3 Sent Date: 6/6/2019 4:19:41 PM Received Date: 6/6/2019 4:19:54 PM From: TRUE, Doug Created By: det@nei.org Recipients:
"Doane, Margaret" <Margaret.Doane@nrc.gov>
Tracking Status: None "McDermott, Brian" <Brian.McDermott@nrc.gov>
Tracking Status: None "Benner, Eric" <Eric.Benner@nrc.gov>
Tracking Status: None "Williams, Donna" <Donna.Williams@nrc.gov>
Tracking Status: None "Nieh, Ho" <ho.nieh@nrc.gov>
Tracking Status: None Post Office: nei.org Files Size Date & Time MESSAGE 5171 6/6/2019 4:19:54 PM 06-06-19_NRC_Industry Initiative on OPC Rev 3.pdf 76796 06-06-19_NRC_Industry Initiative on OPC Rev 3 - Attachment.pdf 64765 Options Priority: Standard Return Notification: No Reply Requested: No Sensitivity: Normal Expiration Date:
Recipients Received:
DOUGLAS E. TRUE Senior Vice President and Chief Nuclear Officer 1201 F Street, NW, Suite 1100 Washington, DC 20004 P: 202.739.8083 det@nei.org nei.org June 6, 2019 Mr. Ho Nieh, Jr.
Director, Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, DC 20555-0001
Subject:
Industry Initiative on Open Phase Condition, Revision 3 Project Number: 689
Dear Mr. Nieh:
On March 16, 2015, the Nuclear Energy Institute (NEI) 1 informed the U.S. Nuclear Regulatory Commission (NRC) that the industry had formally approved revision one to the Open Phase Condition (OPC) Initiative to address the OPC in the off-site power circuits. 2 Since that time, many plants have completed initial installation of their Open Phase Isolation System (OPIS) with the remaining plants scheduled to complete initial installation this year. In September 2018, Revision 2 to the industry initiative was approved. Revision 2 was initiated to provide for an extended monitoring period before implementing the automatic trip function. This was in response to monitoring data indicating that some installed OPIS would have experienced spurious actuations if the automatic trip functions had been activated and the uncertainty that all existing and potentially new plant and/or grid configurations could be reliably handled by the various OPIS designs without inducing spurious actuations.
In parallel with implementation of Revision 2 to the industry initiative, alternatives to enabling the automatic isolation of OPC were also pursued. As a result, risk assessment guidance was developed based on the premise that the risk associated with an OPC event is significantly reduced through the implementation of detection and alarm circuits. This guidance is being issued for industry use as NEI 19-02, Guidance for Assessing Open Phase Condition Implementation Using Risk Insights.
Revision 3 to the NEI OPC initiative incorporates an option for plants to perform a risk evaluation under certain boundary conditions to support manual response to an OPC. This option provides the opportunity for 1
The Nuclear Energy Institute (NEI) is responsible for establishing unified policy on behalf of its members relating to matters affecting the nuclear energy industry, including the regulatory aspects of generic operational and technical issues. NEIs members include entities licensed to operate commercial nuclear power plants in the United States, nuclear plant designers, major architect and engineering firms, fuel cycle facilities, nuclear materials licensees, and other organizations involved in the nuclear energy industry.
Mr. Ho Nieh, Jr.
June 6, 2019 Page 2 stations to more broadly consider the potential impacts of an OPC on equipment and plant configurations prior to taking actions that isolate or transfer loads. The initiative revision and drafts of the risk-informed guidance have been discussed with NRC staff in three public meetings held on February 20, 2019, March 20, 2019, and May 7, 2019. NEI greatly appreciates the staffs input on this change to the OPC initiative and has made efforts to address all comments received on the initiative revision and the guidance document during these interactions.
Additional changes in the revision include removal of historical statements that were no longer applicable and updating several actions that have been completed.
The industrys chief nuclear officers have voted to approve this revision to the NEI Open Phase Conditions Initiative. A copy of the approved initiative revision is attached for your information. The initiative is a formal commitment by NEI member companies that operate nuclear power plants to follow a specific policy or plan of action.
If you or your staff members have any questions, please feel free to contact Stephen Geier at (202) 739-8111 or seg@nei.org, or me.
Sincerely, Douglas E. True Attachment c: Ms. Margaret M. Doane, OEDO, NRC Mr. Brian J. McDermott, NRR, NRC Mr. Eric J. Benner, NRR/DE, NRC Ms. Donna Williams, NRR/DE/EEOB, NRC
Open Phase Condition Initiative June 2019, Revision 3 Goal An open phase condition (OPC) will not prevent functioning of important-to-safety structures, systems and components. An OPC is defined as one or two open phase(s), with or without a ground, which is located on the high voltage side of a transformer connecting a general design criterion (GDC) 17 off-site power circuit to the transmission system.
Objectives x Operating nuclear power plant licensees demonstrate that important-to-safety functions remain available given an OPC or install plant modifications to detect and isolate from the OPC. If the OPC prevents the functioning of important-to-safety structures, systems and components, the engineered safeguard buses should be transferred to an alternate source.
x New reactor licensees, combined license (COL) applicants and design centers for active safety features plant designs demonstrate that important-to-safety functions remain available given an OPC or install plant modifications to detect and isolate from the OPC. If the OPC prevents the functioning of important-to-safety structures, systems and components, the engineered safeguard buses should be transferred to an alternate source.
Criteria Notes:
x This section will only address the criteria for dealing with an adverse OPC. The design features (if not yet available) will be developed to meet the criteria noted below.
x Based on recent operating experience, two open phases must be considered when addressing the criteria below. Thus, the term open phase in the remainder of this document will mean one or two open phases.
x The risk associated with an OPC event is significantly reduced through the implementation of detection circuits such that the use of risk screening techniques as an alternative to enabling the automatic isolation of OPCs can be applied. See Attachment 1 for the modified information used for the risk-informed evaluation method.
Detection, Alarms and General Criteria An OPC must be detected and alarmed in the control room unless it can be shown that the OPC does not prevent functioning of important-to-safety structures, systems and components. For example, some licensees believe they can show no impact due to transformers that are oversized for their loading conditions. Sufficient robust calculational bases or tests must be provided to show that the OPC will not adversely affect important-to- safety equipment performance. Testing is preferred if this is possible without challenging on line shutdown risk profiles.
June 2019, Revision 3 If the licensee can demonstrate that the OPC does not prevent the functioning of important-to-safety structures, systems and components, then detection of the OPC should occur within a reasonably short period of time (i.e., 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />). The licensee must document how detection and correction of the OPC will occur.
Detection circuits for the OPC, which prevents the functioning of important-to-safety structures, systems and components, must be sensitive enough to identify an OPC for credited loading conditions (i.e., high and low loading).
Note: It is recognized that some transformers have very low or no loading when in the standby mode. Automatic detection may not be reliable in this condition; however, automatic detection must happen as soon as loads are transferred to this standby source. Additionally, if automatic detection is not reliable, shiftly monitoring requirements should be established to look for evidence of an open phase.
If OPC actuation circuits are required, the design should minimize misoperation or spurious action that could cause separation from an operable off-site GDC 17 source. Additionally, the protective scheme should not separate the operable off-site GDC 17 source in the range of voltage unbalance normally expected in the transmission system. Licensees must demonstrate that the additional actuation circuit design does not result in lower overall plant operation reliability.
These devices must be coordinated with other protective devices in both the transmission system and the plants electrical system (e.g., fault protection, overcurrent, etc.).
OPC detection and actuation circuits may be non-Class-1E. A non-Class-1E solution will enable timely implementation and will provide reasonable levels of reliable functionality given the low likelihood of adverse impacts from open phase events. Additionally, there is regulatory precedent in using non-Class-1E circuits in newly identified nuclear plant vulnerabilities (e.g., anticipated transient without scram (ATWS) circuits). New non-Class-1E circuits will not be allowed to replace existing Class-1E circuits.
The Updated Final Safety Analysis Report (UFSAR) must be reviewed to determine if updates to discuss the design features and analyses related to the effects of, and protection for, any OPC design vulnerability are required. This update would typically be to chapter 8.
2
June 2019, Revision 3 Protective Actions If an OPC occurs, 1 the following design requirements are to be satisfied:
- 1. With no accident condition signal present, the licensee must demonstrate that:
1.1.The OPC does not adversely affect the function of important-to-safety structures, systems and components; or 1.2.Technical Specification (TS) Limiting Conditions for Operation (LCOs) are maintained or the associated TS Actions are met without entry into TS LCO 3.0.3 (or the equivalent). This provision applies to TS equipment affected by the OPC (i.e., not just the specifications related to the off-site power source); and 1.3.Important-to-safety equipment is not damaged by the OPC; and 1.4.Shutdown safety is not compromised.
Notes:
x Provision 1.1 or provisions 1.2, 1.3 and 1.4 must be maintained.
x For operating modes where power is supplied from the main generator through unit auxiliary transformers, the licensee must evaluate provisions 1.1, 1.2 and 1.3 assuming that the main generator is lost and loads must be transferred to the alternate source(s). Load transfer cases will include reactor trips without accident conditions present.
x Operator action may be credited in the evaluation of provisions 1.3 and 1.4 if existing regulations and guidelines are met for the use of manual actions in the place of automatic actions.
x Item 1.4 is intended to ensure that an open phase event will not challenge fuel cooling during hot shutdown, cold shutdown and refueling modes of operation.
Power supplied to spent fuel pool cooling systems must also be considered. The limiting conditions will be those where power is supplied from a single source or an alternate source is used that does not have open phase protection (such as a main power transformer back-feed source).
x Provision 1.2 must consider situations where alternate sources are removed from service if allowed by the Technical Specifications.
1 For plants that have evaluated their specific designs and installations and have determined that there is no single credible failure that could cause an OPC, a full engineering evaluation must be developed and issued to document the basis for an OPC as a non-credible event. The Bruce Power and Forsmark operating experience must be considered as part of this analysis.
3
June 2019, Revision 3 x If provision 1.1 or provisions 1.2, 1.3 and 1.4 cannot be met with the existing plant design features, modifications will be required to provide automatic features to ensure the provisions can be met.
- 2. With an accident condition signal present, the licensee must demonstrate:
2.1.Automatic detection and actuation will transfer loads required to mitigate postulated accidents to an alternate source and ensure that safety functions are preserved, as required by the current licensing bases.
2.2.Alternatively, a licensee may show that all design basis accident acceptance criteria are met with the OPC, given other plant design features. Accident assumptions must still include licensing provisions associated with single failures. Typically, licensing bases will not permit consideration of the OPC as the single failure since this failure is in a non-safety system.
Note:
x It is not expected that accident analyses are updated when licensees add additional detection and mitigation circuitry. Actuation times needed to maintain equipment safety functions should be short enough to provide reasonable assurance that accident mitigation functions are maintained.
Periodic tests, calibrations, setpoint verifications or inspections (as applicable) must be established for any new OPC protective features. The surveillance requirements must be added to the plant Technical Specifications if necessary to meet the provisions of 10CFR50.36.
Interim Actions (Operating Plants)
The Institute of Nuclear Power Operations (INPO) staff performed reviews of the industry action plans in response to the Level 2 INPO Event Report (IER) L2-12-14, Automatic Reactor Scram Resulting from a Design Vulnerability in the 4.16-kV Bus Undervoltage Protection Scheme, and ensured that plant operators had identified compensatory actions needed to detect degraded off-site power sources due to open phase circuit conditions. INPO also ensured that plant operating procedures were either sufficient or actions were taken to enhance the procedures to help operators promptly diagnose and respond to open phase circuit conditions on off-site power supplies to Class- 1E vital buses. The reviews were completed and satisfactory industry responses were received in the 4th Quarter 2012.
INPO Follow-up Actions (Operating Plants)
Starting in 1st Quarter 2014, the engineering evaluators will review all recommendation responses in IER L2-12-14 during the plant evaluations and verify that the recommendations are fully implemented or that there is a reasonable due date and plan to fully implement the recommendations. Evaluators will verify that the compensatory measures originally taken are still in place and being effective. Evaluators will also review progress made and the milestones developed for the long-term corrective actions to provide automatic protection from open phase circuit conditions for off-site power sources supplying Class-1E vital buses. They 4
June 2019, Revision 3 will also ensure a review and study of the station design basis and that modeling has been conducted to obtain a complete understanding of plant and equipment response following an open phase event. Also, the final station configuration will be reviewed to ensure that the probability of losing the off-site (preferred) and the on-site power source is not increased. The evaluator review and conclusion of IER recommendations will be documented in evaluation products.
Regulatory Requirements GDC 17 provides criteria for the electric design of nuclear power plants for which a construction permit application was submitted after the Commission promulgated the GDC. The PSAR, FSAR and UFSAR document the implementation of the design criteria.
GDC 17 states:
An on-site electric power system and an off-site electric power system shall be provided to permit functioning of structures, systems, and components important to safety. The safety function for each system (assuming the other system is not functioning) shall be to provide sufficient capacity and capability to assure that: (1) specified acceptable fuel design limits and design conditions of the reactor coolant pressure boundary are not exceeded as a result of anticipated operational occurrences, and (2) the core is cooled and containment integrity and other vital functions are maintained in the event of postulated accidents.
The on-site electric power supplies, including the batteries, and the on-site electric distribution system, shall have sufficient independence, redundancy and testability to perform their safety functions assuming a single failure.
Electric power from the transmission network to the on-site electric distribution system shall be supplied by two physically independent circuits (not necessarily on separate rights of way) designed and located so as to minimize to the extent practical the likelihood of their simultaneous failure under operating and postulated accident and environmental conditions. A switchyard common to both circuits is acceptable. Each of these circuits shall be designed to be available in sufficient time following a loss of all on- site alternating current power supplies and the other off-site electric power circuit, to assure that specified acceptable fuel design limits and design conditions of the reactor coolant pressure boundary are not exceeded. One of these circuits shall be designed to be available within a few seconds following a loss-of-coolant accident to assure that core cooling, containment integrity and other vital safety functions are maintained.
Provisions shall be included to minimize the probability of losing electric power from any of the remaining supplies as a result of, or coincident with, the loss of power generated by the nuclear power unit, the loss of power from the transmission network, or the loss of power from the on-site electric power supplies.
Pre-GDC plants have their principal design criteria specified in their UFSAR.
5
June 2019, Revision 3 Schedule for Operating Plants (for Plants where License Amendments (LA) are not required to install any design changes. For plants where LAs are required, the design change schedule will be as directed by the LA process.)
May 15, 2013 NSIAC endorsement of the industry direction to resolve the OPC issue. Complete.
July 31, 2013 Draft NEI Initiative (what is required; industry criteria to address the OPC issue). Complete.
Aug. 31, 2013 NSIAC approval of the NEI Initiative by a vote of 80% of CNOs. Complete.
Dec. 31, 2013 Draft NEI guidance document (how to meet industry criteriacontaining industry research, developments, pilots, technology, etc.to address the OPC issue). Complete.
Dec. 31, 2014 Demonstration of compliance with the OPC criteria through analysis or identify appropriate actions required to demonstrate compliance. Complete.
March 2015 NSIAC approval of Revision 1 to the NEI Initiative. Complete.
September 2018 NSIAC approval of Revision 2 to the NEI Initiative. Complete.
Dec. 31, 2018 Implementation of design changes, if necessary, to comply with the OPC criteria.
The active actuation features of new technology designs may be installed in a monitoring mode, with adequate justification, to demonstrate reliability. During the monitoring period, further defined below, stations must implement an alarm response process for operators to take appropriate action if the system detects the presence of an OPC.
Monitoring Period If a monitoring period was deemed necessary, the period will run for at least 24 months. In order to capture industry-wide operating experience, the monitoring period for all plants will extend until December 31, 6
June 2019, Revision 3 2019. Plants that have not accumulated 24 months of monitoring time by December 31, 2019, may extend the monitoring period into 2020 until they reach 24 months. This period of monitoring will ensure the collection and application, including completion of any design adjustments, of station-specific operating experience through one operating cycle and two seasonal periods and ensure that industry-wide operating experience can be evaluated and applied.
Upon completion of the monitoring period, design adjustments identified during the monitoring period will have been performed and all active actuation features needed to demonstrate compliance with the OPC criteria will be enabled. During the monitoring period, stations must implement an alarm response process for operators to take appropriate action if the system detects the presence of an OPC.
As an alternative to enabling the automatic isolation of OPCs, the application of risk screening techniques (see Attachment 1) can be performed to determine that the risk associated with an OPC event is significantly reduced through the implementation of detection circuits. Completion of the risk analysis under the boundary conditions in Attachment 1 will have been performed by the completion of the monitoring period.
Additional Actions UFSAR Updates: Completion in conjunction with the timelines noted above and as required per the stations modification process.
Technical Specification Updates - Submitted by December 31, 2018, if required. If a TSTF Traveler is available, submitted within six months of issuance of an NRC approved TSTF Traveler.
Note 1: If Technical Specification updates are required for modification implementation, the schedule is expected to change based on NRC required review times; however, the station schedule should be maintained as closely as possible with the timelines noted above.
Note 2: If a Technical Specification Bases-only change is identified, implementation of the change by stations is expected to be completed as required per the stations modification process.
Schedule for New Reactors COL Licensees Complete design changes and plant modifications, as needed, prior to fuel load.
COL Applicants Describe design features in the FSAR, if change to certified design is required. Design Centers Provide design features in the Design Control Document/FSAR.
7
Open Phase Condition Initiative, June 2019, Revision 3 Attachment 1 - Risk Informed Evaluation Method Purpose To demonstrate that operator manual actions will be sufficient to mitigate the impact of an OPC.
Background
The previous revisions of the OPC Initiative employ a design condition based on the improbable concurrence of a DBA, which in turn drives the need to prevent loss of equipment important to mitigate such an event. 2 Consequently, the automatic trip function design requirement was a direct result of applying this design condition. The risk associated with an OPC event is significantly reduced through the implementation of detection circuits such that the use of risk-screening techniques as an alternative to enabling the automatic isolation of OPCs can be applied.
A probabilistic method of implementation of OPC solutions has been developed using the OPC Initiative framework. The risk evaluation of operator response to an OPC is predicated on use of the method outlined in NEI 19-02. The evaluation of a manual response to an OPC relies on the already conservative open phase detection circuit design which employed deterministic criteria combined with a probabilistic approach that characterizes the likelihood of the potential impact on plant equipment across a wide spectrum of potential plant conditions. Applying risk methods to support the application of manual actions to respond to an OPC provides nuclear plant operators an opportunity to more broadly consider the potential impacts of an OPC on equipment and plant configurations prior to taking actions that isolate or transfer loads.
Boundary Conditions Validate equipment recovery provisions to support the risk evaluation.
An OPC must be detected and alarmed in the control room.
Detection circuits for OPCs must be sensitive enough to identify an OPC for credited loading conditions (i.e.,
high and low loading).
For stations where transformers have very low or no loading when in the standby mode, automatic detection may not be reliable in this condition. The OPC solution must ensure automatic detection happens as soon as loads are transferred to this standby source. For this configuration, manual detection requirements must be documented in the risk evaluation and procedurally established to monitor for an OPC on a shiftly basis.
Written response procedures that allow operators to diagnose and take manual action to mitigate an OPC must be provided. Operator response should minimize action that could result in separation from an operable off-site GDC 17 source.
Licensees must demonstrate that the additional detection circuit design does not result in lower overall plant operation reliability.
2 ML13052A711 - NRC Bulletin 2012-01, Design Vulnerability in Electric Power System, Summary Report.