ML17102B607
| ML17102B607 | |
| Person / Time | |
|---|---|
| Site: | Diablo Canyon  |
| Issue date: | 04/12/2017 |
| From: | Balwant Singal Plant Licensing Branch IV |
| To: | Richardson M Pacific Gas & Electric Co |
| References | |
| MF8528, MF8529 | |
| Download: ML17102B607 (16) | |
Text
NRR-PMDAPEm Resource From: Singal, Balwant Sent: Wednesday, April 12, 2017 3:02 PM To: 'Richardson, Michael' Cc: Hoffman, Raymond
Subject:
Request for Additional Information (RAI) - Revised Emergency Action Level Schemes Pursuant to Nuclear Energy Institute (NEI) 99-01, Revision 6 (CAC Nos. MF8528 and MF8529)
Attachments: MF8528-Diablo-EAL-RAIs.docx By letter dated October 25, 2016 (Agencywide Documents Access and management System (ADAMS)
Accession No. ML16315A184), Pacific Gas and Electric Company (PG&E) requested approval for an Emergency Action Level (EAL) scheme change for Diablo Canyon Power plant, Units 1 and 2 (DCPP). DCPP proposed to revise their current EAL scheme to one based upon NEI 99-01, Revision 6.
The U.S. Nuclear Regulatory Commission (NRC) staff has identified additional information provided in the attachment to this e-mail needed to complete its review. Draft request for additional information (RAI) was transmitted to PG&E on March 17, 2017. The NRC staff was unable to have the clarification call due to non-availability of the PG&E staff. The NRC staff was advised by Mr. Michael Richardson to issue the official RAIs on April 12, 2017 and also requested for additional time to respond to the RAIs. You are requested to provide your response within 45 days of the date of this e-mail. Please treat this e-mail as official transmittal of RAIs.
Please let me know if you have any additional questions.
Thanks.
Balwant K. Singal Senior Project Manager (Diablo Canyon and Wolf Creek)
Nuclear Regulatory Commission Division of Operating Reactor Licensing Balwant.Singal@nrc.gov Tel: (301) 415-3016 Fax: (301) 415-1222 1
Hearing Identifier: NRR_PMDA Email Number: 3436 Mail Envelope Properties (60aac3ea3bd44bc6af5b4b47ed85f48e)
Subject:
Request for Additional Information (RAI) - Revised Emergency Action Level Schemes Pursuant to Nuclear Energy Institute (NEI) 99-01, Revision 6 (CAC Nos. MF8528 and MF8529)
Sent Date: 4/12/2017 3:01:35 PM Received Date: 4/12/2017 3:01:36 PM From: Singal, Balwant Created By: Balwant.Singal@nrc.gov Recipients:
"Hoffman, Raymond" <Raymond.Hoffman@nrc.gov>
Tracking Status: None
"'Richardson, Michael'" <MJRm@pge.com>
Tracking Status: None Post Office: HQPWMSMRS02.nrc.gov Files Size Date & Time MESSAGE 1339 4/12/2017 3:01:36 PM MF8528-Diablo-EAL-RAIs.docx 45128 Options Priority: Standard Return Notification: No Reply Requested: No Sensitivity: Normal Expiration Date:
Recipients Received: ZZZ
REQUEST FOR ADDITIONAL INFORMATION LICENSE AMENDMENT REQUEST EMERGENCY ACTION LEVEL SCHEME CHANGE DIABLO CANYON POWER PLANT, UNITS 1 AND 2 DOCKET NUMBERS 50-275 AND 50-323 By letter dated October 25, 2016 (Agencywide Documents Access and Management System (ADAMS) Accession Number ML16315A184), Pacific Gas and Electric Company requested approval for an emergency action level (EAL) scheme change for Diablo Canyon Power Plant, Units 1 and 2, (DCPP).
The requirements of Section 50.47(b)(4) to Title 10 of the Code of Federal Regulations (10 CFR) state, in part, that:
A standard emergency classification and action level scheme, the bases of which include facility system and effluent parameters, is in use by the nuclear facility licensee, and State and local response plans call for reliance on information provided by facility licensees for determinations of minimum initial offsite response measures.
The most recent industry EAL scheme development guidance is provided in the Nuclear Energy Institute (NEI) document NEI 99-01, Development of Emergency Action Levels for Non-Passive Reactors (ADAMS Accession Number ML12326A805). By letter dated March 28, 2013, the U.S. Nuclear Regulatory Commission (NRC) endorsed NEI 99-01, Revision 6, as acceptable generic (i.e., non-plant-specific) EAL scheme development guidance (ADAMS Accession No. ML12346A463).
DCPP proposes to revise their current EAL scheme to one based upon NEI 99-01, Revision 6 (hereafter referred to as endorsed guidance).
The requests for additional information (RAI) listed below are necessary to facilitate the continued technical review being conducted by the NRC staff. A timely and thorough response to these RAIs is requested in order to meet the proposed deadline requested by the licensee.
RAI-DCPP-1 The Basis discussions for the proposed DCPP EAL scheme include an ERO [Emergency Response Organization] Decision Making Information section and a Background section. This is not consistent with the endorsed guidance, nor is it consistent with the current approved DCPP EAL scheme. There may be a potential that a decision maker could either limit their review to the ERO Decision Making Information section or treat information in the background section as less important. This could result in overlooking information, such as the following: If the RCS [reactor coolant system] is not INTACT and CONTAINMENT CLOSURE is not established during the event, the SM/SEC/ED should also refer to CA3, which is located in the Background discussion for DCPP CU3.1.
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Please explain why two sections are required for the basis discussion, as the two sections in the proposed license amendment request (LAR) could impact the timeliness or accuracy of event classifications, or revise accordingly consistent with the endorsed guidance.
RAI-DCPP-2 Section 4.3 (Instrumentation Used for EALs) of the endorsed guidance states: Scheme developers should ensure that specific values used as EAL setpoints are within the calibrated range of the referenced instrumentation.
Please confirm that all setpoints and indications used in the proposed DCPP EAL scheme are within the calibrated range(s) of the stated instrumentation and that the resolution of the instrumentation is appropriate for the setpoint/indication.
RAI-DCPP-3 Section 4.7 (EAL/Threshold References to AOP [Abnormal Operating Procedure] and EOP
[Emergency Operating Procedure] Setpoints/Criteria) of the endorsed guidance states: As reflected in the generic guidance, the criteria/values used in several EALs and fission product barrier thresholds may be drawn from a plants AOPs and EOPs. The NRC staff expects that changes to AOPs and EOPs will be evaluated in accordance with the provisions of 10 CFR 50.54(q).
Please explain what controls are in place at DCPP to ensure that a subsequent change to an AOP or EOP is screened to determine if an evaluation pursuant to 10 CFR 50.54(q) is required.
RAI-DCPP-4 The definitions contained in endorsed guidance for the General Emergency, Site Area Emergency, Alert and Notification of Unusual Event [Unusual Event] classification levels begin with Events are in progress... The DCPP definitions in Section 5.0 for a General Emergency, Site Area Emergency, Alert and Unusual Event begin with Events are in process. [Emphasis added.]
Please revise these definitions to reflect the definitions in the endorsed guidance or provide a justification for the difference.
RAI-DCPP-5 The current DCPP Table R-1 (Effluent Monitor Classification Thresholds) has monitors 1(2)-RM-24/24R, 1(2)-RM-28/28R, 1(2)-RM-71/72/73/74 and 0-RM-3 with associated threshold values.
The proposed DCPP Table R-1 does not include these monitors, nor are they identified as a change in the LAR.
Please explain why these monitors are not included in the proposed DCPP EAL scheme, or revised accordingly.
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RAI-DCPP-6 The proposed DCPP Table R-1 has threshold values that are different than the current DCPP Table R-1 threshold values and uses different monitors for the Site Area Emergency classification. These changes are not identified in the LAR.
Please explain the basis for the change in these threshold values and the change in radiation monitors for the Site Area Emergency classification.
RAI-DCPP-7 The proposed DCPP EAL RU2.1 threshold value states, in part: UNPLANNED rise to low alarm setpoint in corresponding radiation levels as indicated by. The NRC staff could not determine what is meant by this condition based on the information provided in the submittal.
Please explain what conditions will meet this threshold value and provide a justification that decision makers can make a timely and accurate assessment using the existing wording, or revise the statement as necessary to clarify consistent with endorsed guidance.
RAI-DCPP-8 The proposed DCPP EAL RA2.1 shows a classification level of Unusual Event instead of an Alert, which could result in an inaccurate event declaration.
Please revise as necessary to ensure the EAL identifier and classification level are aligned as the proposed EAL RA2.1.
RAI-DCPP-9 The proposed DCPP Basis for EAL EU1.1 states:
The values in Table E-1 are derived from ISFSI [independent spent fuel storage installation] FSAR Tables (ref 1, 2). Since the UFSAR Table 7.3-1A are the maximum calculated dose rate values, and are not expected to ever be exceeded, a conservative approach of exceeding the highest possible fuel value dose rates, plus 5 mrem/hour, was used as an indication of damage to an Overpack. Note: These values are approximately 2 times the maximum expected dose rate for low burn-up fuel (ref 2).
E-HU1 in the endorsed guidance states:
The technical specification multiple of 2 times, which is also used in Recognition Category A of IC AU1 [RU1.1 for DCPP], is used here to distinguish between non-emergency and emergency conditions. The emphasis for this classification is the degradation in the level of safety of the spent fuel cask and not the magnitude of the associated dose or dose rate.
- a. The provided values are significantly below the expected threshold values provided in the endorsed guidance, which could result in an Unusual Event declaration for a dose that is only slightly above the maximum calculated dose rate values. Please explain, why the Page 3 of 14
endorsed guidance of 2 times the technical specification values was not used or revise accordingly.
- b. Concerning the above note relating to low burn-up fuel. The NRC staff could not determine the purpose of this note based on the information provided. Please explain if this note is intended to indicate that all current and future spent fuel casks will be only loaded with low burn-up fuel or revise accordingly.
RAI-DCPP-10 The proposed DCPP EALs CA1.2, CS1.3, and CG1.2 threshold values include a reference to Table C-1 (Sumps/Tanks), which includes several sumps that typically may not provide a level indication that could be used to quantify RCS leakage or typically may contain a sump pump that operates automatically.
Please explain how these sumps can be used to quantify RCS leakage as needed to provide an indication of core uncovery or revise accordingly. This explanation should address automatic sump pumps, if used, that could limit the effectiveness of the sump as a method to quantify RCS leakage as needed to support a timely and accurate assessment.
RAI-DCPP-11 The final paragraph in the ERO Decision Making Information Basis for the proposed DCPP EAL CG1.1 contains a discussion relative to the inability to monitor RCS level. However, the threshold value for EAL CG1.1 is based on indicated reactor vessel level and is not based on a loss of indication.
Please justify the inclusion of a discussion related to a loss of indication for an EAL that is not based on a loss of level, or revise consistent with endorsed guidance to prevent an inaccurate or delayed assessment.
RAI-DCPP-12 The proposed DCPP Basis for EALs CU2.1, SU1.1 and SA1.1 state:
For emergency classification purposes, capability means that, whether or not the buses are actually powered from it, an AC [alternating current] power source(s) can be aligned to the vital buses within 15 minutes:
- By a clear procedure path, And
- Breakers and equipment are readily available to power up the bus within the allotted time frame.
The endorsed guidance recognizes that vital alternating current (AC) buses are typically energized from a single power supply with the capability to align the vital AC bus to an alternate power supply. DCPP has included the above basis discussion to clarify the term capability.
However, this clarification could imply that the licensee has 15 minutes to attempt to energize at least one vital bus at which time the licensee could have an additional 15 minutes to classify the event. Considering that the de-energization of vital AC buses would require an Alert declaration pursuant to EAL CA2.1 or a Site Area Emergency pursuant to SS1.1 within 15 minutes, the Page 4 of 14
additional time potentially implied by the DCPP discussion relative to capability could delay an accurate and timely assessment of EAL CU2.1 or SA1.1.
The clarification for the term capability is not consistent with endorsed guidance; nor is it identified as a difference in Attachment 1, EAL Comparison Matrix.
Please remove or revise the clarification for the meaning of capability in the respective bases discussions, or explain how the addition of this condition could not potentially delay or prevent classification of a loss of vital AC power to emergency buses.
RAI-DCPP-13 DCPP EALs CA2.1, SS1.1, SG1.1 and SG2.1 state:
Loss of all offsite and all onsite AC power capability. [Emphasis added]
Additionally, the DCPP Basis for EALs CA2.1, SS1.1, SG1.1 and SG2.1 state:
For emergency classification purposes, "capability" means that, whether or not the buses are actually powered from it, an AC power source(s) can be aligned to the vital buses within 15 minutes:
- By a clear procedure path, And
- Breakers and equipment are readily available to power up the bus within the allotted time frame.
The intent of these EALs is to ensure that an EAL is declared upon a total loss of AC power that compromises the performance of all systems requiring electric power for emergency core cooling, containment heat removal/pressure control, spent fuel heat removal, and the ultimate heat sink. This additional criteria could prevent the EAL from being declared in a condition where the AC power sources are available, but not connected to the emergency buses. The NRC staff considers the addition of this criteria to the EALs, and the definition in the basis, to be a deviation from endorsed guidance.
Please explain how the addition of this condition could not potentially delay or prevent classification of a loss of AC power to emergency buses, or revise accordingly to remove the term capability in the EALs listed above and the clarification for the meaning of capability in the respective bases.
RAI-DCPP-14 The threshold values for proposed DCPP EALs CA2.1, SS1.1, SG1.1 and SG2.1 include a reference to a table of power supplies. The intent of these EALs is to ensure that an EAL is declared upon a total loss of AC power that compromises the performance of all systems requiring electric power for emergency core cooling, containment heat removal/pressure control, spent fuel heat removal, and the ultimate heat sink. A list of readily available power sources may lead to event declarations when mitigative strategies are effective in reestablishing emergency power to these buses. In other words, if a list of power sources is provided for these EALs, and those sources are unavailable, then an EAL decision-maker would be compelled to declare events even if mitigative strategies using other power sources are effective. It is not Page 5 of 14
necessary to document these power sources for these EALs, as the EAL is not concerned with the power source as much as the power loss to the emergency bus. (Ref: EPFAQ 2015-015.)
Please remove the tables from these EALs, or provide a justification for the difference from endorsed guidance.
RAI-DCPP-15
- a. In proposed DCPP EALs CU5.1 and SU7.1, the Table C-5 or S-4 (Communication Methods) for onsite communications include an extensive list of communication methods. The intent of onsite communications is to support normal operations and all Table S-4 onsite communication methods have to be lost to satisfy declaration criteria. The NRC staff could not determine how either the Unit 1, Unit 2 and Technical Support Center (TSC) radio consoles, or the Hot Shutdown Panel radio consoles, by themselves, could support onsite communications. For example, how would onsite communications occur if the only method of onsite communication available was the Hot Shutdown Panel radio console?
Additionally, onsite notification methods include portable radio equipment, the operations radio system, the security radio system, mobile radios, and satellite phones. The NRC staff could not determine if these were redundant systems or, if they were redundant systems, how these various systems could be used as necessary to support routine plant operations.
For example, how would various members of the plant staff obtain radios and/or satellite phones as needed to conduct plant operations?
Please explain how the proposed communication methods for onsite communication can be completed with any single method provided by Table C-5 or S-4 for onsite communications.
This explanation should include the accessibility to redundant equipment and how communications would be completed without requiring the relaying of information.
- b. In proposed DCPP EAL CU5.1 and SU7.1, the Table C-5 or S-4 (Communication Methods) for offsite communications include the Central Alarm Station (CAS) and the Secondary Alarm Station (SAS) consoles, and the Hot Shutdown Panel radio consoles.
Please explain how the proposed communication methods for offsite communication can be completed with any single method provided by Table C-5 or S-4 for offsite communications.
This explanation should include how communications would be completed without requiring the relaying of information.
RAI-DCPP-16 The ERO Decision Making Information section of the basis discussion for proposed DCPP EALs CA6.1 and SA9.1 states:
With respect to event damage caused by an equipment failure resulting in a FIRE or EXPLOSION, no emergency classification is required in response to a FIRE or EXPLOSION resulting from an equipment failure if the only safety system equipment affected by the event is that upon which the failure occurred. An emergency classification is required if a FIRE or EXPLOSION caused by an equipment failure damages safety system equipment that was otherwise functional or operable (i.e., equipment that was not the source/location of the failure). For example, if a FIRE or EXPLOSION resulting from the failure of a Page 6 of 14
piece of safety system equipment causes damage to the other train of the affected safety system or another safety system, then an emergency declaration is required in accordance with this IC [initiating condition] and EAL.
The statement above would indicate that an EAL declaration pursuant to EAL CA6.1 or SA9.1 would not be required if a FIRE or EXPLOSION damages safety system equipment that was not the source of the fire and that equipment was in service at the time of the event. This statement is consistent with the proposed NRC response to EPFAQ 2016-002, which is currently available for public comment. However, the example provided in the above statement could imply that an EAL declaration pursuant to EAL CA6.1 or SA9.1 would only be required if two safety trains are affected. The first being the on the system that is the source of the FIRE or EXPLOSION, and the second being the second train of equipment that is damaged by the FIRE or EXPLOSION.
The provided example appears to be more in alignment with the EPFAQ 2016-002 response to a second, but related, question relative to the impact of FIRE or EXPLOSION damage to a safety system (or component) that was out of service at the time of the event.
- a. Please remove or revise the example provided in the statement quoted above as necessary to avoid a potential misclassification under EALs CA6.1 or SA9.1.
- b. The basis discussion for the statement quoted above provides information that could modify declarations based on a FIRE or EXPLOSION. Please add a note to the threshold values for EALs CA6.1 and SA9.1 that clearly indicates that an emergency classification is required if a FIRE or EXPLOSION caused by an equipment failure damages safety system equipment that was otherwise functional or operable, or explain how decision makers will be able to perform timely and accurate assessments of EALs CA6.1 or SA9.1.
RAI-DCPP-17 The ERO Decision Making Information sections of the basis discussions for the proposed DCPP EALs HU1.1, HA1.1 and HS1.1 include security event categories. However, it appears the specific categories are not required by the EAL threshold values. Additionally, this information could potentially delay or prevent a security classification if a decision maker were to assume that only events identified by these codes would require an EAL declaration.
Please consider removing the reference to security event categories, or explain how this information would not potentially delay or prevent the declaration of a security related event.
RAI-DCPP-18 The proposed DCPP EAL HU2.1 includes the following note:
Note 11: If the Earthquake Force Monitor (EFM) is out of service, refer to CP M-4 Earthquake for alternative methods to assess earthquakes.
Sufficient information relative to CP M-4 was not provided for NRC staff review. As such, the NRC staff could not determine if a decision maker could make a timely and accurate assessment of a seismic event using CP M-4.
Please provide addition information or explain how a decision maker can perform a timely and accurate assessment of a seismic condition using CP M-4.
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RAI-DCPP-19 The areas listed in Table H-1 (Fire Areas) in proposed DCPP EALs HU4.1 and HU4.2 seem to be vague or too all-encompassing. The endorsed guidance states: the site-specific list of plant room should specify these rooms or areas that contain SAFETY SYSTEM equipment.
Please explain if the listed areas are restricted to only the areas that contain equipment needed for safe operation, safe shutdown and safe cool-down, or revise accordingly consistent with endorsed guidance.
RAI-DCPP-20 The ERO Decision Making Information section of the basis discussion for the proposed DCPP EAL HU4.2 states:
An Incipient Alarm meets the intent of a single fire alarm. A pre-alarm does not meet the intent of a "single fire alarm."
The key difference in the fire alarms associated with DCPP EALs HU4.1 and HU4.2 is that a single fire alarm provides a verification time of 30 minutes. No distinction is made relative to the type of fire alarm. DCPP EAL HU4.2 includes two additional types of alarms that are not addressed in DCPP EAL HU4.1. The NRC staff could not determine if the incipient alarm is an indication of a fire or if an incipient alarm represented a fire that may occur in hours or days following the alarm.
Please provide additional information for the NRC staff to determine whether or not an incipient alarm is equivalent to an actual fire alarm. If an incipient alarm is equivalent to a fire alarm, please include a note in HU4.1 and HU4.2 to provide the decision maker with sufficient information to make a timely and accurate assessment.
RAI-DCPP-21 The ERO Decision Making Information section of the basis discussion for the proposed DCPP EAL HS6.1 states:
The determination of whether or not "control" is established at the remote safe shutdown location(s) is based on SM/SEC/ED judgment. The SM/SEC/ED is expected to make a reasonable, informed judgment within 15 minutes whether or not the operating staff has control of key safety functions from the remote safe shutdown location(s). The 15 minute clock starts once plant control has been transferred to the Hot Shutdown Area (OP AP-8A Attachment 4 480V Bus Alignment and Appendix F Electrical System Actions).
The explanation provided above implies that completion of the identified step is the start time of the 15 minute declaration clock rather than transferring control from the control room to the hot shutdown area. This could delay the declaration of HS6.1 in a timely manner. A licensee can typically transfer control to their site-specific remote control stations and implement their site-specific procedures within 15 minutes. If, in the judgement of the decision maker, control of the applicable HS6.1 safety functions will not be able to establish, then a declaration of HS6.1 is expected within 15 minutes.
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Please remove the discussion that could add an extended or indeterminate amount of time to the EAL declaration start time, or explain how the requiring the completion of the identified steps will not delay a timely EAL declaration.
RAI-DCPP-22 The 3rd bullet in Table S-3 (Significant Transients) for the proposed DCPP EAL SA3.1 states:
Electrical load rejection 25% electrical load. This is inconsistent with the endorsed guidance that states: Electrical load rejection 25% full electrical load. [Emphasis added]
Additionally, the DCPP basis for this EAL lists load rejections of greater than 25% full electrical load as a significant transient.
Please revise the EAL in alignment with the endorsed guidance, or provide a justification for this difference.
RAI-DCPP-23 The ERO Decision Making Information section of the basis discussion for the proposed DCPP EAL SU4.1 states:
This EAL would be met if TS 3.4.16 Required Action C.1 (place plant in Mode 3 in 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />) or C.2 (place plant in Mode 5 in 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />) were not met.
This statement indicates that a declaration would not be required if the plant were shut down in the designated amount of time. This is not consistent with endorsed guidance which states:
This IC addresses a reactor coolant activity value that exceeds an allowable limit specified in Technical Specifications. [Emphasis added]
Please revise the EAL in alignment with the endorsed guidance, or provide a justification for this difference.
RAI-DCPP-24 For the proposed DCPP EALs SU6.1, SU6.2, SA6.1 and SS6.1, a power level (greater than or equal to 5%) was added to the EALs. The intent of the endorsed guidance is to align the EAL classifications with site-specific EOP criteria for a successful reactor shutdown, which would benefit the decision makers by providing consistent criteria. The power level provided in the developer notes in the endorsed guidance is an example that represents one typical EOP indication for a generic power plant and was not intended to be a complete list of EOP indications for any specific power plant. The Reactor Trip or Safety Injection Action/Expected Response for Typical Westinghouse plants, such as DCPP, include reactor power decreasing and rod insertion indications to determine if the anticipated transient without a scram (ATWS) response procedure should be initiated. Additionally, the subcriticality critical safety function status trees (CSFSTs) for typical Westinghouse plants include both power and startup rate to determine whether or not an ATWS has occurred. The proposed ATWS EALs for DCPP appear to rely solely on a reactor power of 5% as an indication of a reactor trip.
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Please revise to reflect the EOP reactor shutdown criteria in the EOPs, or use wording similar to endorsed guidance as necessary to support timely and accurate assessment of DCPP EALs SU6.1, SU6.2, SA6.1 and SS6.1.
RAI-DCPP-25 For the proposed DCPP EALs SA6.1 and SS6.1, the basis discussions include discussions that imply that if power were below a system design heat removal capacity, then an immediate response is not required for a reactor that has not been shutdown following a either the initiation of an automatic or manual trip. This is not consistent with endorsed guidance. Note: The basis discussions for SA6.1 and SS6.1 are similar enough to allow using only the below discussion for SA6.1 The Background discussion of the Basis for the proposed DCPP EAL SA6.1 (Alert) states:
This IC addresses a failure of the RTS [reactor trip system] to initiate or complete an automatic or manual reactor trip that results in a reactor shutdown, and subsequent operator manual actions taken at the reactor control consoles to shut down the reactor are also unsuccessful. This condition represents an actual or potential substantial degradation of the level of safety of the plant. An emergency declaration is required even if the reactor is subsequently shutdown by an action taken away from the reactor control consoles since this event entails a significant failure of the RTS.
This discussion is consistent with both the basis discussion for an automatic or manual trip that failed to shut down the reactor and the definition of an Alert that is included in endorsed guidance. However, Background discussion of the Basis for the proposed DCPP EAL SA6.1 also states:
This EAL addresses any automatic or manual reactor trip signal that fails to shut down the reactor (reactor power< 5%) followed by a subsequent manual trip that fails to shut down the reactor to an extent the reactor is producing energy in excess of the heat load for which the SAFETY SYSTEMS were designed (ref. 1).
On the power range scale 5% rated power is a minimum reading on the power range scale that indicates continued power production. It also approximates the decay heat which the shutdown systems were designed to remove and is indicative of a condition requiring immediate response to prevent subsequent core damage. Below 5%, plant response will be similar to that observed during a normal shutdown. Nuclear instrumentation can be used to determine if reactor power is greater than 5% power (ref. 3, 4).
The above paragraphs could imply that as long as you are less than 5% power, than no actual or potential degradation of the level of safety of the plant exists. Considering that a failure of the RTS would most likely become apparent during transient conditions that either initiated an automatic reactor trip signal or were of sufficient magnitude for the operators to attempt a manual reactor trip, a failure of the RTS to shut down the reactor would represent an actual or potential substantial degradation of the level of safety of the plant. As such, an Alert should be declared if the reactor was not subcritical following an event involving a failure of the RTS to shut down the reactor whether or not reactor power was currently above 5% at the time of EAL assessment.
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Additionally, the above paragraphs could imply that the actual or potential substantial degradation of the level of safety of the plant is based in system design rather than the reactor producing energy in excess of the existing heat load capability.
Please revise the basis discussion to clearly indicate that an Alert or Site Area Emergency, as appropriate, should be declared when an automatic or manual trip failed to shut down the reactor and manual trip actions at the control room panels were not successful in shutting down the reactor, or explain how the proposed wording will not cause delays or misclassifications for DCPP EAL SA6.1 and SS6.1 as appropriate.
RAI-DCPP-26 For DCPP EAL SS6.1, the licensee is proposing to add RCS bleed and feed criteria to the CSFST heat sink red path condition being met. In addition to being a deviation from endorsed guidance, the addition of RCS bleed and feed criteria does not appear to be consistent with the endorsed guidance. [Note: The RCS bleed and feed criteria was also added to the fission product barrier matrix. This is discussed in a separate RAI that is specific to the fission product barriers.]
The proposed DCPP EAL SS6.1 adds the condition AND bleed and feed criteria met to the CSFST Heat Sink RED path conditions met threshold value. The licensee has provided Attachment A of Attachment 1 to the DCPP LAR as justification. The proposed DCPP EAL SS6.1 basis discussion states:
This IC addresses a failure of the RTS to initiate or complete an automatic or manual reactor trip that results in a reactor shutdown, all subsequent operator actions to manually shut down the reactor are unsuccessful, and continued power generation is challenging the capability to adequately remove heat from the core and/or the RCS. This condition will lead to fuel damage if additional mitigation actions are unsuccessful and thus warrants the declaration of a Site Area Emergency.
The above discussion is consistent with both the basis discussion for an automatic or manual trip that failed to shut down the reactor and all manual actions to shut down the reactor are not successful and the definition of a Site Area Emergency that is included in endorsed guidance.
The endorsed guidance developer notes for EAL SS5, which corresponds to DCPP SS6.1, states:
Insert site-specific parameters associated with inadequate RCS heat removal via the steam generators. These parameters should be identical to those used for the Inadequate Heat Removal threshold Fuel Clad Barrier Potential Loss 2.B and threshold RCS Barrier Potential Loss 2.A in the PWR EAL Fission Product Barrier Table.
Although both DCPP SS6.1 and the and the fission product barrier use the same criteria as described above, the basis discussion for DCPP SS6.1 does not typically provide a discussion that contains the same level of detail that is found in the fission product barrier basis discussion.
As such, the following fission product table discussions are included to provide details relative to the heat sink red path conditions that are used as assessment criteria for DCPP SS6.1.
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Enter the site-specific parameters and values that define an extreme challenge to the ability to remove heat from the RCS via the steam generators. These will typically be parameters and values that would require operators to take prompt action to address this condition.
For plants that have implemented Westinghouse Owners Group Emergency Response Guidelines, enter the parameters and values used in the Heat Sink Red path.
Additionally, the CSFST Rules of Usage for typical Westinghouse plants, such as DCPP, identify that under an extreme challenge condition, typically identified as red path, that the operator shall immediately stop the procedure in effect and initiate functional restoration of the safety function under extreme challenge.
Based on the above, CSFST Heat Sink Red path conditions represent an extreme challenge to the ability to remove RCS heat via the steam generators (SGs). As such, the addition of the condition AND bleed and feed criteria met to Heat Sink Red path conditions is not consistent with endorsed guidance.
Please remove the AND bleed and feed criteria met from the proposed SS6.1 or provide justification, in addition to that provided in Attachment A of Attachment 1 of the LAR, that supports this deviation from endorsed guidance.
RAI-DCPP-27 The proposed Potential Loss Threshold 1, for RCS or Steam Generator (SG) Tube Leakage, in the DCPP Fuel Clad Fission Barrier, states: CSFST Integrity-Red Path conditions met, under the DCPP RCS Barrier. This is not consistent with the DCPP bases, which states: CSFST RCS Integrity-Red Path. [Emphasis added]
Please revise accordingly to address inconsistency, or explain how a decision maker can make a timely and accurate assessment without providing the same title that is used in the CSFST title for RCS Integrity.
RAI-DCPP-28 The proposed DCPP fission product barriers: B.2 for Fuel Cladding, and B.1 for the RCS, add the condition AND bleed and feed criteria met to the CSFST Heat Sink RED path conditions met threshold value. The licensee has provided Attachment A of Attachment 1 of the DCPP LAR as justification for this difference. Note: DCPP considers the proposed change to be a difference. (However, the NRC staff considers the proposed change as a deviation from endorsed guidance.)
The endorsed guidance for fission product barriers: B.2 for Fuel Cladding, and B.1 for the RCS, state:
Enter the site-specific parameters and values that define an extreme challenge to the ability to remove heat from the RCS via the steam generators. These will typically be parameters and values that would require operators to take prompt action to address this condition.
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For plants that have implemented Westinghouse Owners Group Emergency Response Guidelines, enter the parameters and values used in the Heat Sink Red path.
Additionally, the CSFST Rules of Usage for typical Westinghouse plants, such as DCPP, identify that under an extreme challenge condition, typically identified as red path, that the operator shall immediately stop the procedure in effect and initiate functional restoration of the safety function under extreme challenge. As such, CSFST heat sink red path represents an extreme challenge to the ability to remove RCS heat via the SGs.
Please remove the AND bleed and feed criteria met from the proposed fission product barriers or provide justification, in addition to that provided in Attachment A of Attachment 1 of the LAR, that supports this deviation from endorsed guidance. Note: The NRC staff does not consider the proposed wording to be consistent with a standard EAL scheme.
RAI-DCPP-29 For the proposed fuel clad and RCS fission product barriers, RED entry conditions for the heat sink CSFST are used as a threshold for a potential loss of either of these barriers. However, the endorsed guidance states:
In accordance with EOPs, there may be unusual accident conditions during which operators intentionally reduce the heat removal capability of the steam generators; during these conditions, classification using threshold is not warranted.
This guidance is included in the barrier threshold basis discussions; however, it is not included in the relevant barrier thresholds.
Please explain why the endorsed guidance concerning making classifications for heat sink conditions when operators intentionally reduce heat removal capability, in accordance with EOPs, is not included in the fission product barrier thresholds as this could result in an inaccurate EAL declaration, or revise accordingly.
RAI-DCPP-30 All of the proposed DCPP Fission Product Barriers Loss bases for Emergency Director Judgement include the following bulleted statement:
Barrier monitoring capability is decreased if there is a loss or lack of reliable indicators.
This assessment should include instrumentation operability concerns, readings from portable instrumentation and consideration of offsite monitoring results.
The Fission Product Barrier Potential Loss bases for Emergency Director Judgement in the endorsed guidance states:
The Emergency Director should also consider whether or not to declare the barrier potentially lost in the event that barrier status cannot be monitored.
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The statement in the DCPP Fission Product Barriers Loss bases may cause a delay in classification due to confusion as to application of the loss or potential loss of the barrier in question. In addition, the three bulleted items appearing in the DCPP bases for the loss or potential loss are identical and may confuse the decision maker in differentiating between a loss and a potential loss.
Please revise the proposed Fission Product Barrier Emergency Director Judgement, Loss and/or Potential Loss bases to remove any wording that could either bound and/or modify the judgement of the Emergency Director concerning a loss, or potential loss, of a fission product barrier, or explain how this wording will not potentially inhibit the judgement of the Emergency Director.
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