Text

Request for Enforcement Discretion for Technical Specification (TS) 3.1.7, Standby Liquid Control (SLC) System.
	ML17261B164
Person / Time
Site:	Dresden
Issue date:	09/14/2017
From:	Karaba P; Exelon Generation Co
To:	; Document Control Desk, Office of Nuclear Reactor Regulation
References
	17-0041
	Download: ML17261B164 (20)
	v • d • e

Exelon Generation Dresden Nuclear Power Station 6500 North Dresden Road Morris, IL 60450 September 14, 2017 SVPLTR: #17-0041 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Dresden Nuclear Power Station, Unit 3 Renewed Facility Operating License No. DPR-25 NRG Docket No. 50-249

Subject:

Request for Enforcement Discretion for Technical Specification {TS) 3.1. 7, "Standby Liquid Control (SLC) System" On September 12, 2017, Exelon Generation Company, LLC (EGG) verbally requested a Notice of Enforcement Discretion (NOED) associated with Technical Specification {TS) 3.1.7, "Standby Liquid Control (SLC) System," for Dresden Nuclear Power Station (DNPS), Unit 3.

The following information was discussed with representatives of the NRG on September 12, 2017, at 1615 hours0.0187 days 0.449 hours 0.00267 weeks 6.145075e-4 months , with subsequent approval being verbally granted by the NRG at 1746 hours0.0202 days 0.485 hours 0.00289 weeks 6.64353e-4 months .

The need for the NOED arose when on September 12, 2017, at 1131 hours0.0131 days 0.314 hours 0.00187 weeks 4.303455e-4 months a flaw in a pipe fitting was identified on the Unit 3 SLC discharge pipe that rendered both SLC subsystems inoperable. The requested NOED was to grant enforcement discretion from compliance with the Completion Time of TS 3.1.7, Required Action B.1 for an additional 35 hours4.050926e-4 days 0.00972 hours 5.787037e-5 weeks 1.33175e-5 months . The NOED was designed to avoid a plant shutdown because of compliance with TS 3.1.7, Required Action C.1, which required Unit 3 to be placed in Mode 3 (i.e., Hot Shutdown) at 0731 hours0.00846 days 0.203 hours 0.00121 weeks 2.781455e-4 months on September 13, 2017. As discussed during the NOED conference call, if the SLC System could not be made operable during the requested enforcement discretion period, DNPS, Unit 3 would be required to be placed in Mode 3 at or before 1831 hours0.0212 days 0.509 hours 0.00303 weeks 6.966955e-4 months on September 14, 2017.

During the maintenance activity, station Operators received a shift briefing covering the expected operator response to a postulated Anticipated Transient Without Scram (ATWS) event with SLC unavailable. In addition, Operators received Just In Time Training on procedure DEOP 0500-01, "Alternate Standby Liquid Injection," in preparation for the maintenance activity.

As discussed during the NOED teleconference, the decision was made to repair the Unit 3 SLC flaw by replacing the pipe fitting. Following pipe fitting replacement, the system was restored to operable status at 2035 hours0.0236 days 0.565 hours 0.00336 weeks 7.743175e-4 months on September 12, 2017. The repairs were completed in advance of the suggested time frame based on weld quality being met with no contamination issues.

This is within the Completion Time of the allowed enforcement discretion.

September 14, 2017 U.S. Nuclear Regulatory Commission Page 2 The enclosure provides the information necessary for approval of the requested enforcement discretion. The enclosure has been reviewed and approved by the DNPS Plant Operations Review Committee in accordance with the requirements of the EGC Quality Assurance Topical Report. There are no regulatory commitments contained within this letter.

Should you have any questions or comments regarding this matter, please contact DNPS Regulatory Assurance Manager, Bruce Franzen, at 815-416-2800.

Respectfully, Peter J. Karaba Site Vice President Dresden Nuclear Power Station Exelon Generation Company, LLC

Enclosure:

Request for Enforcement Discretion for Technical Specification 3.1. 7, "Standby Liquid Control (SLC) System" cc: Regional Administrator - NRC Region Ill NRC Senior Resident Inspector - Dresden Nuclear Power Station NRC Project Manager - NRR - Dresden Nuclear Power Station

bee: Illinois Emergency Management Agency - Division of Nuclear Safety Vice President - Licensing and Regulatory Affairs Regulatory Assurance Manager - Dresden Nuclear Power Station Director - Licensing and Regulatory Affairs Manager - Licensing - Clinton, Dresden, and Quad Cities Stations Dresden Nuclear Power Station Licensing Administrator Site Vice President - Dresden Nuclear Power Station Dresden Regulatory Assurance, SVP File Commitment Tracking Coordinator - Midwest Exelon Document Control Desk Licensing (Hard Copy)

Exelon Document Control Desk Licensing (Electronic Copy)

ENCLOSURE Dresden Nuclear Power Station, Unit 3 Docket No. STN 50-249 Renewed Facility Operating License No. DPR-25 Request for Enforcement Discretion for Technical Specification 3.1.7, "Standby Liquid Control (SLC) System"

ENCLOSURE Request for Enforcement Discretion for Technical Specification 3.1.7, "Standby Liquid Control (SLC) System" 1 Specifically address what type of NOED is being requested (regular or natural event), which of the NOED criteria for appropriate plant conditions specified in IMC 0410, subsection 03.03 is satisfied, and how those criteria are satisfied. (Also reference subsection 06.02 of IMC 0410).

Exelon Generation Company, LLC (EGG) requests enforcement discretion for Dresden Nuclear Power Station (DNPS), Unit 3 from Technical Specification (TS) 3.1.7, "Standby Liquid Control (SLC) System," Condition B, which requires restoration of one Unit 3 SLC subsystem to an Operable status at 1931 hours0.0223 days 0.536 hours 0.00319 weeks 7.347455e-4 months on September 12, 2017.

Without enforcement discretion, at 1931 hours0.0223 days 0.536 hours 0.00319 weeks 7.347455e-4 months on September 12, 2017, DNPS, Unit 3 will be required to be in Mode 3 (i.e., Hot Shutdown) within 12 hours1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months in accordance with TS 3.1.7, Condition C.

A regular Notice of Enforcement Discretion (NOED) is being requested in accordance with NOED Criterion 03.03(b) of NRG Inspection Manual, Chapter 0410, "Notices of Enforcement Discretion." Criterion 03.03(b) involves the following condition: "an unnecessary down-power or the shutdown of a reactor without a corresponding health and safety benefit." The determination of this criterion's applicability is based on the avoidance of an unnecessary operational transient caused by the shutdown of the reactor to comply with the TS and, thus, minimizes potential safety consequences and operational risks associated with a plant shutdown.

2 Provide a description of the TS or other license conditions that will be violated.

DNPS, Unit 3 requests enforcement discretion from certain requirements of TS 3.1.7, "Standby Liquid Control (SLC) System," Condition C, by granting temporary enforcement discretion for the Completion Time (CT) of TS 3.1.7, Required Action (RA) 8.1 for an additional 35 hours4.050926e-4 days 0.00972 hours 5.787037e-5 weeks 1.33175e-5 months .

At 1131 hours0.0131 days 0.314 hours 0.00187 weeks 4.303455e-4 months on September 12, 2017, a flaw in a pipe fitting was identified on the Unit 3 SLC discharge pipe that rendered both Unit 3 SLC subsystems inoperable. This placed Unit 3 in TS 3.1.7, Condition B, "Two SLC subsystems inoperable." The eight-hour CT of TS 3.1.7, RA 8.1 expires at 1931 hours0.0223 days 0.536 hours 0.00319 weeks 7.347455e-4 months on September 12, 2017.

TS 3.1.7, Condition C requires that, when in Modes 1, 2, and 3, if one inoperable SLC subsystem is not restored to operable status, the unit be placed in Mode 3 (i.e., Hot Shutdown) within 12 hours1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months and Mode 4 within 36 hours4.166667e-4 days 0.01 hours 5.952381e-5 weeks 1.3698e-5 months (i.e., 0731 hours0.00846 days 0.203 hours 0.00121 weeks 2.781455e-4 months on September 13 and 14, 2017, respectively). This request for enforcement discretion is being made to avoid an unnecessary operational transient caused by the shutdown of a reactor without a corresponding health and safety benefit as the result of compliance with TS 3.1. 7.

The SLC System is designed to provide the capability of bringing the reactor, at any time in a fuel cycle, from full power and minimum control rod inventory, which is at the peak of the xenon transient, to a subcritical condition with the reactor in the most reactive, xenon free state without taking credit for control rod movement. The SLC System satisfies the requirements of 10 CFR 50.62 on anticipated transient without scram (ATWS).

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ENCLOSURE Request for Enforcement Discretion for Technical Specification 3.1.7, "Standby Liquid Control (SLC) System" The SLC System is also used to maintain suppression pool pH at or above 7 following a Loss of Coolant Accident (LOCA) involving significant fission product releases.

Maintaining suppression pool pH levels at or above 7 following an accident ensures that iodine will be retained in the suppression pool water.

The SLC System consists of a boron solution storage tank, two positive displacement pumps, two explosive valves that are provided in parallel for redundancy, and associated piping and valves used to transfer borated water from the storage tank to the reactor pressure vessel. The borated solution is discharged near the bottom of the core shroud, where it then mixes with the cooling water rising through the core.

3 Provide a description of the circumstances, including as a minimum: likely causes; the need for prompt action; the action taken to avoid the need for a NOED; and any relevant historical events.

DNPS, Unit 2 is operating at 95% power due to being in coastdown for its upcoming outage in November 2017. DNPS, Unit 3 is operating at 100% power. During an Equipment Operator round at 0130 hours0.0015 days 0.0361 hours 2.149471e-4 weeks 4.9465e-5 months on September 10, 2017, sodium pentaborate crystallization build-up under piping insulation on SLC discharge piping was identified with no active leak. The boron crystals appeared dry and residual. There are no mechanical joints in the vicinity and no active leak present, and Unit 3 SLC was determined to be operable.

During subsequent inspection and examination of the SLC pipe at 1131 hours0.0131 days 0.314 hours 0.00187 weeks 4.303455e-4 months on September 12, 2017, a flaw in a pipe fitting was identified on the 304 stainless steel SLC common discharge pipe and a weep-type leak was identified with the pump in operation.

As a result of this discovery, it was determined that the Code Class 2 pressure boundary was not intact. Technical Requirements Manual Section 3.4.a, Condition B, "Structural Integrity," was entered and required the system to be isolated. Both SLC subsystems were declared inoperable in accordance with TS 3.1.7. At 1131 hours0.0131 days 0.314 hours 0.00187 weeks 4.303455e-4 months on September 12, 2017, Unit 3 entered an eight-hour CT clock in accordance with TS 3.1.7, Condition B, RA B.1. Without enforcement discretion, at 1931 hours0.0223 days 0.536 hours 0.00319 weeks 7.347455e-4 months on September 12, 2017, Unit 3 will be required to shutdown in accordance with TS 3.1. 7, Condition C.

Enforcement discretion is being sought to suspend the required shutdown and allow continued operation of Unit 3. A repair plan has been developed that will satisfy American Society of Mechanical Engineers (ASME),Section XI, 2007 Edition, including Addenda through 2008 requirements. The required time to implement this repair is estimated to be an additional 35 hours4.050926e-4 days 0.00972 hours 5.787037e-5 weeks 1.33175e-5 months (i.e., the total time to complete this repair is estimated to be 43 hours4.976852e-4 days 0.0119 hours 7.109788e-5 weeks 1.63615e-5 months ).

Repair options were reviewed to identify any options that could be completed within the time clocks listed in TS 3.1.7. Based on the ASME code class repair options, the construction of an Engineered Clamp was explored since it may be able to be installed within the RA times of TS 3.1. 7. However, the construction of the box and the specified supports have shown that this option cannot be fully implemented to support the current situation and there is little operating experience for the use of a temporary leak repair on Code Class 2 piping.

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ENCLOSURE Request for Enforcement Discretion for Technical Specification 3.1.7, "Standby Liquid Control (SLC) System" Enforcement discretion is requested to defer the required shutdown and allow continued operation of DNPS, Unit 3 until repairs can be completed. If the SLC System cannot be made operable during the requested enforcement discretion period, Unit 3 will be placed in Mode 3 operation on or before 1831 hours0.0212 days 0.509 hours 0.00303 weeks 6.966955e-4 months on September 14, 2017. If unexpected conditions are discovered during the SLC repairs that would exceed the requested discretionary time, EGG will terminate the discretionary period and Unit 3 will be shutdown in a deliberate and controlled manner.

Based on materials of construction, operational history, and a visual inspection, the most-likely cause of the through-wall leak is a manufacturing defect.

A similar NOED was requested and approved for DNPS, Unit 2 on January 19, 2007.

EGG requested a NOED for DNPS, Unit 2 for TS 3.1.7 for a leak on the SLC tank temperature alarm sensor that rendered both SLC subsystems inoperable. The requested NOED was to temporarily allow for an additional 72 hours8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months of plant operation to effect repairs to the SLC tank.

4 Provide information that shows the Station fully understands the cause of the situation that has led to the NOED request.

The cause that led to the NOED request is system leakage on Code Class 2 piping.

Based on the emergent discovery of crystallized boron deposits on the SLC System piping, an investigation was performed to determine the source of the deposits. The investigation involved cleaning and removing the boron deposits, and then pressurizing the affected piping segment to normal operating pressure to determine if the deposits were due to a leak. Upon running the SLC System, a through-wall leak in the tee fitting was identified as the cause of the boron deposits. The leak was characterized as minor seepage. EGG has determined that full replacement of the degraded tee is needed to .

restore full qualification. Based on materials of construction and operational history, the most-likely cause of the through-wall leak is a manufacturing defect. A causal evaluation, including a failure analysis, will be performed in accordance with EGC's Corrective Action Program to confirm the cause. Corrective actions including any required additional monitoring will be developed as part of the causal analysis. In addition, a walkdown of the SLC System identified no other concerns with piping integrity. No additional troubleshooting is needed to complete the planned repair.

5 Detail the proposed course of action to resolve the situation, so enforcement discretion is no longer required.

The option to replace the degraded fitting involves removing the degraded tee-fitting, preparing the associated welding sites, and welding replacement piping and fitting in accordance with applicable ASME Code requirements. This option requires a period of an additional 35 hours4.050926e-4 days 0.00972 hours 5.787037e-5 weeks 1.33175e-5 months to complete the repair and associated post-maintenance tests. See Attachment 1 for a detailed timeline.

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ENCLOSURE Request for Enforcement Discretion for Technical Specification 3.1.7, "Standby Liquid Control (SLC) System" 6 Explain that the resolution itself will not result in a different, unnecessary transient.

The proposed NOED provides an additional 35 hours4.050926e-4 days 0.00972 hours 5.787037e-5 weeks 1.33175e-5 months of plant operation to implement repairs to the Unit 3 SLC discharge piping. While the SLC System will be unavailable during the repair period, this action will not result in a different unnecessary transient that would affect radiological health and safety of the public for the following reasons:

SLC is a backup reactivity control system; the primary means of shutting down the reactor with Reactor Protection System (RPS) remain Operable. Other backup features are also operable including the Alternate Rod Insertion (ARI) and the ATWS Recirculation Pump Trip systems. DEOP 0500-01, "Alternate Standby Liquid Injection," would be used to inject sodium pentaborate through alternate injection path while the normal injection source is unavailable.

The SLC System is not an initiator of any analyzed design basis accident.

Therefore, the NOED request does not increase the probability of a plant transient (i.e., does not increase the likelihood of an ATWS precursor).

Compensatory actions have been implemented to further minimize risk including protection of key systems and deferring operational and elevated risk activities.

A risk assessment has determined there is a negligible increase in radiological risk to the public.

If the SLC System cannot be made operable during the requested enforcement discretion period, Unit 3 will be placed in Mode 3 operation on or before 1831 hours0.0212 days 0.509 hours 0.00303 weeks 6.966955e-4 months on September 14, 2017. If unexpected conditions are discovered during the SLC discharge piping inspections that cannot be addressed within the enforcement discretion period, EGG will terminate the discretionary period and Unit 3 will be shutdown in a deliberate and controlled manner.

7 Explain that there was insufficient time to process an emergency license amendment, or that a license amendment is not needed.

The event resulting in entry into TS 3.1.7, Condition B occurred at 1131 on September 12, 2017. The eight-hour Completion Time to restore one SLC subsystem to operable status does not provide adequate time to prepare and submit an emergency license amendment request.

EGC has concluded a license amendment request (LAR) is not warranted for the following reasons:

The NOED will be in effect for a relatively short duration (i.e., current Completion Time of eight-hours with an additional 35 hours4.050926e-4 days 0.00972 hours 5.787037e-5 weeks 1.33175e-5 months ).

This action represents a one-time deferral. A permanent change to the Technical Specifications is not required.

The conditions requiring the NOED are not typical and had not occurred in the last 1O years at DNPS.

Additionally, in letters from M. A. Satorius (NRG) to C. M. Crane (EGC) dated October 18, 2006 (i.e., Accession No. ML062920184), and January 24, 2007 (i.e., Accession No.

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ENCLOSURE Request for Enforcement Discretion for Technical Specification 3.1.7, "Standby Liquid Control (SLC) System" ML070240595}, the NRC exercised discretion to not enforce compliance with the actions required in TS 3.1.7, Condition B for Quad Cities Nuclear Power Station (QCNPS), Unit 1 and DNPS, Unit 2 respectively. These notices of enforcement discretion (NOEDs) provided a 72-hour extension to the eight-hour CT specified in TS 3.1.7, RA B.1. This extension enabled each site to avoid a TS-required shutdown while implementing repair and restoration activities for the SLC System.

Subsequent to the NRC granting enforcement discretion, EGC submitted an LAR that proposed a revision to TS 3.1.7 that extended the Completion Time (CT} for Required Action B.1 from eight hours to 72 hours8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months . This LAR was submitted to the NRC in a letter dated November 10, 2009 (i.e., Accession No. ML093140516). In developing the technical basis for this LAR, EGC utilized the guidance in Regulatory Guide 1.174, "An Approach for Using Probabilistic Risk Assessment In Risk-Informed Decisions on Plant-Specific Changes to the Licensing Basis." The analysis attempted to demonstrate, with reasonable assurance, that the proposed license amendment satisfied the risk acceptance guidelines in Regulatory Guide 1.174 and Regulatory Guide 1.177, "An Approach tor Plant-Specific, Risk-Informed Decision-making: Technical Specifications."

In a letter dated September 23, 201 O (i.e., Accession No. ML102660195}, the NRC forwarded a request for additional information (RAI) concerning the November 10, 2009, LAR. EGC provided the requested information in a letter dated October 12, 201 O (i.e., Accession No. ML102861911}.

On November 10, 2010, a teleconference was held between NRC Division of Operating Reactor Licensing personnel and EGC. During this teleconference, the NRC indicated that the LAR could not be approved based on the information provided by EGC. Based on this feedback, EGC withdrew the LAR, and requested that the NRC formally document the unresolved issues associated with the LAR. This request was submitted to the NRC in a letter dated November 16, 2010 (i.e., Accession No. ML103200394). The requested information was provided by the NRC in a letter dated January 6, 2011 (i.e., Accession No. ML103420021 ). The NRC's concerns regarding the approval of an extension to the CT for TS 3.1. 7, RA 8.1 were related to defense-in-depth actions associated the inoperability of all TS-required SLC subsystems.

While analyses can clearly support a temporary allowance to deviate from TS 3.1. 7 in accordance with the NOED process, the circumstances that led to the withdrawal of the LAR that requested a permanent extension of TS 3.1. 7, RA 8.1 as discussed above have not changed. In light of this information, EGC concludes that it would not be feasible to modify the Completion Time for TS 3.1.7, Required Action 8.1; therefore, EGC does not currently intend to submit an LAR to modify TS 3.1.7.

In the near future, EGC intends to pursue the implementation of a TS Program for Risk-Informed Completion Times (RICTs} in accordance with Technical Specifications Task Force (TSTF} Traveler TSTF-505, "Provide Risk-Informed Extended Completion Times -

RITSTF Initiative 4b." The RICT is the time interval from discovery of a condition requiring entry into a TS action with the provision to utilize a RICT until the 10-5 incremental core damage probability (ICDP) or 1o-s incremental large early release probability (ILERP)

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ENCLOSURE Request for Enforcement Discretion for Technical Specification 3.1.7, "Standby Liquid Control (SLC) System" threshold is reached, or 30 days, whichever is shorter. The maximum RICT of 30 days is referred to as the "back-stop CT."

For example, a sample calculation was performed for ICDP and ILERP to obtain the RICT and Risk Management Action Times (RMATs) for DNPS, Unit 3 TS 3.1.7, RA B.1. The results of these calculations are given in Table 1 below.

Table 1: Resulting RICT and RMAT for DNPS TS 3.1.7 RA B.1 Risk Metric RICT (days) RMAT (days)

ICDP 594 59 ILERP 206 21 The analysis calculated the RICT and RMAT times for a postulated DNPS RICT program.

The results indicate exceeding the RICT threshold after 206 days. According to the guidance in NEI 06-09, "Risk-Informed Technical Specifications Initiative 4b, Risk-Managed Technical Specifications (RMTS} Guidelines," the maximum allowable RICT (i.e., back-stop CT) is 30 days. Therefore, the postulated RICT for the inoperability of all TS-required SLC subsystems for DNPS, Unit 3 would be 30 days. Implementation of the RICT Program at DNPS would significantly reduce the likelihood of future requests to deviate from TS 3.1.7 to perform corrective maintenance on the SLC System.

EGG supports the establishment of an acceptable approach for licensees to address the inoperability of all trains of TS-required systems through the development of a companion TSTF Traveler to TSTF-505. This course of action will ensure that NOEDs for situations of such low risk are unnecessary.

8 Describe the condition and operational status of the plant, including safety-related equipment out of service or otherwise inoperable and nonsafety-related equipment that is degraded or out of service that may have risk significance and that may increase the probability of a plant transient or may complicate the recovery from a transient or may be used to mitigate the condition.

Unit 2 is operating at 95% power due to being in coastdown for its upcoming outage in November 2017. Unit 3 is operating at 100% power. On-line risk is currently green on Unit 2. On-line risk for Unit 3 is yellow due to the unavailability of Unit 3 SLC. There are no additional inoperable safety-related components other than the Unit 3 SLC System. As a result of this temporary situation, no maintenance activities will be performed on the RPS, ATWS Recirculation Pump Trip, and ARI systems or their support systems. All Unit 3 operational and elevated risk activities will be prohibited. Attachment 2 provides a list of activities that are deferred until the U3 SLC System is restored to an operable status.

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ENCLOSURE Request for Enforcement Discretion for Technical Specification 3.1.7, "Standby Liquid Control (SLC) System" 9 Request a specific time period for the NOED, including a justification for the duration of the noncompliance.

EGC has determined that there is a minimal safety consequence of continuing operation an additional 35 hours4.050926e-4 days 0.00972 hours 5.787037e-5 weeks 1.33175e-5 months . This determination is based on the low probability of the combination of events that would lead to an undesirable transient. Given the low risk significance for the additional 35 hours4.050926e-4 days 0.00972 hours 5.787037e-5 weeks 1.33175e-5 months and the inherent risk introduced by imposing the operational transient of unnecessarily shutting down the unit, the short duration of the requested enforcement discretion is justified.

The decision was made to cut out and replace the designated flawed fitting in support of a Code repair/replacement plan. The details of the significant work activities are included in Attachment 1.

These activities are estimated to be completed within the additional 35 hour4.050926e-4 days 0.00972 hours 5.787037e-5 weeks 1.33175e-5 months enforcement discretion period.

1O Detail and explain compensatory measures the plant has both taken and will take to reduce the risk associated with the specified configuration.

Compensatory actions will include protecting the RPS and its primary support systems, and limiting trips and transients by not performing any other elective maintenance, operational, or elevated risk activities during the NOED period. Operator training was reviewed to ensure licensed operators have been trained on the required ATWS actions when SLC is not available. All actions are summarized below.

1. SLC is restored to available status within the bounding 72 hour8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months time period assumed in the PAA analysis. This action will ensure online risk is maintained within the PAA assessment assumptions.

2. Protection of both ATWS Recirculation Pump Trip Systems, which includes ARI. This action will mitigate the need for SLC.

3. The Unit 3 RPS system is protected. This action will mitigate the need for SLC.

4. Operational or elevated risk activities are prohibited during the discretionary enforcement period. This action will minimize the likelihood of initiation events*

(i.e., plant transients) and thus minimize the need for SLC. See Attachment 2 for a list of deferred work that was scheduled to be performed.

5. Designate Unit 2 and Unit 3 offsite power sources as protected pathways.

6. Designate Unit 2 and Unit 3 onsite AC power sources as protected pathways.

7. All operating crews received Just In Time Training on the Alternate Standby Liquid injection procedure (i.e., DEOP 0500-01, "Alternate Standby Liquid Injection").

8. A compensatory action is included in the NOED to brief operator actions and response in the event of a loss of offsite power during the time the NOED is in effect.

9. An Operations Supervisor will verify protected pathway postings are accurate on a shiftly basis.

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ENCLOSURE Request for Enforcement Discretion for Technical Specification 3.1.7, "Standby Liquid Control (SLC) System" 11 Discuss the status and potential challenges to offsite and onsite power sources, including any current or planned maintenance in the distribution system and any current or planned maintenance to the emergency diesel generators.

All offsite power sources are fully operational, with no maintenance planned on these systems during the enforcement discretion period. No adverse weather is in the forecast, with temperatures between 52 and 82 degrees Fahrenheit. In addition, EGG has verified grid/offsite power status for DNPS, Unit 3 with the transmission system operator.

All onsite power sources are fully operational, including up-to-date surveillances and the required fuel reserves. No maintenance related to on-site power is planned during the enforcement discretion period.

Any scheduled work involving onsite or offsite power is deferred until after the repairs to the Unit 3 SLC System are completed. Offsite power (i.e., the 345 KV switchyard) is

. posted as a protected pathway.

12 Include the safety basis for the request and an evaluation of the safety significance and potential consequences of the proposed course of action.

a. Use the zero maintenance PRA model to establish the plant's baseline risk and the estimated risk increase associated with the period of enforcement discretion.

Baseline NOED (Zero Maintenance) Configuration CDFo LERFo CDF1 LERF1 3.01 E-06 7.03E-07 5.03E-06 1.88E-06

b. Discuss the dominant risk contributors (cut sets or sequences or both) and summarize the risk insights for the plant-specific configuration the plant intends to operate in during the period of enforcement discretion.

A review of the top cutsets for both Core Damage Frequency (GDF) and Large Early Release Frequency (LERF) was performed. With both trains of SLC out of service, RPS failures are the primary driver of the risk increase over the baseline model. Additionally, the primary increase in initiating events contribution is concentrated on general transients (turbine trips) paired with mechanical RPS failures (ATWS). This is expected as SLC is used for mitigation of ATWS events.

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ENCLOSURE Request for Enforcement Discretion for Technical Specification 3.1.7, "Standby Liquid Control (SLC) System"

c. Discuss how the compensatory measures are accounted for in the PRA.

The PRA inherently assumes no additional maintenance unavailability, as the assessment is performed using the zero maintenance model. No other compensatory measures were explicitly credited in the quantitative analysis performed using the PRA.

d. Discuss the extent of condition of the failed or unavailable component(s) to other trains/divisions of equipment and what adjustments, if any, to the related PRA common cause factors have been made to account for potential increases in their failure probabilities.

No adjustments to common cause factors were made as there are only two trains of SLC on Unit 3, and both trains are considered unavailable for this assessment.

e. Discuss external event risks for the specified plant configuration.

' DNPS does not have a Fire PRA model for Unit 3. The Unit 2 Fire PRA model (DR213F1) is considered an interim model. Due to the similarities between the two units, it was determined that the Unit 2 Fire PRA model could be utilized to glean fire risk insights. The Unit 2 model was evaluated for unavailability of the Unit 2 SLC trains, and the resulting risk increase was small. Specifically, F-CDF increased by 1.7%, and F-LERF increased by 3.4%.

Aggregating the resulting F-ICCDP and F-ICLERP values with the Full-Power Internal Events PRA results would not alter the conclusion of this assessment. There are no additional insights from the fire PRA.

DNPS does not have a seismic PRA model. A review of the Individual Plant Examination of External Events (IPEEE) was performed to determine if the unavailability of SLC introduces a unique change in station risk. The IPEEE screened the seismic impact to the Control Rod Drive (CRD) system and did not identify any unique impacts to rod insertion or RPS. As such, seismic initiating events are judged not significant to this NOED request.

This determination approach is consistent with NRC SOP guidance provided in NRC

. Inspection Manual IMC- 0609, "Significance Determination Process," Appendix A, "Determining the Significance of Reactor Inspection Findings for At-Power Situations,"

Attachment 3, "User Guidance for Screening of External Events Risk Contributions."

External flooding risk is also discussed in the IPEEE. There were no unique impacts of SLC unavailability identified for external flooding. There is no expected increase in risk from external flooding for the NOED condition.

Severe weather and high winds risk is addressed through the use of high risk evolutions in the online risk management program. These are qualitative assessments that utilize the plant transient decision trees.

There is not a significant increase in external event risk expected for the duration of this NOED period.

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ENCLOSURE Request for Enforcement Discretion for Technical Specification 3.1.7, "Standby Liquid Control (SLC) System" 13 Demonstrate that the NOED condition, along with any compensatory measures, will not result in more than a minimal increase in radiological risk, either in a quantitative assessment that risk will be within the normal work control levels (ICCDP less than or equal to 5E-7 and/or ICLERP less than or equal to 5E-8) or in a defensible qualitative manner.

Following a LOCA, SLC maintains suppression pool pH levels at or above 7 following an accident and ensures that iodine will be retained in the suppression pool water. Torus pH is not included in the risk analyses and is not considered a risk significant function.

The NOED condition was evaluated for Unit 3 with the Dresden Full-Power Internal Events model DR313A. Assumptions made in this analysis are as follows:

Both trains of SLC are unavailable

No additional maintenance will be performed for the NOED period

No additional compensatory measures are quantitatively credited in the assessment

An extension of 72 hours8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months is used for calculation of ICCDP and ICLERP CDF and LERF Results As defined in Manual Chapter (MC) 0410, the risk metrics associated with NOEDs are Incremental Conditional Core Damage Probability (ICCDP) and Incremental Conditional Large Early Release Probability (ICLERP). These are defined as:

ICCDP = (CDF1 - CDFo) x T1 I To (Acceptance Criteria 5. 5.0E-07)

ICLERP = (LERF1 - LERFo) x T1 I To (Acceptance Criteria 5. 5.0E-08)

Where:

CDF1 : Zero maintenance conditional CDF, taking into account the equipment that is out of service for the NOED request (CDF with the NOED condition)

CDFo: Zero maintenance baseline CDF LERF1: Zero maintenance conditional LERF, taking into account equipment that is out of service for the NOED request (LERF with the NOED condition)

LERFo : Zero Maintenance LERF T1: Duration of the NOED

[Extended OOS time beyond the Completion Time (CT)]

= 72 hours8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months (3 days)

Page 10

ENCLOSURE Request for Enforcement Discretion for Technical Specification 3.1.7, "Standby Liquid Control (SLC) System" To : One year = 8, 760 hours0.0088 days 0.211 hours 0.00126 weeks 2.8918e-4 months These metrics are calculated as shown using the above equations.

ICCDP = (CDF1 - CDFo) x T1 I To CDF1 = 5.03E-06 (From Table under Item 12.a)

CDFo = 3.01 E-06 (From Table under Item 12.a)

T1 = 72 hours8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months To = 8,760 hours0.0088 days 0.211 hours 0.00126 weeks 2.8918e-4 months (one year)

ICCDP = {5.03E 3.01 E-06) x (72 I 8760)

= 1.7E-08 Similarly:

ICLERP = (LERF1 - LERFo) x T1 I To LERF1 = 1.88E-06 (From Table under Item 12.a)

LERFo = 7.03E-07 (From Table under Item 12.a)

T1 = 72 hours8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months To = 8,760 hours0.0088 days 0.211 hours 0.00126 weeks 2.8918e-4 months (one year)

ICLERP = {1.88E 7.03E-07) x (72 I 8,760)

= 9.7E-09 Page 11

ENCLOSURE Request for Enforcement Discretion for Technical Specification 3.1.7, "Standby Liquid Control (SLC) System" The values calculated above meet the acceptance criteria as shown on the following table.

R'IS kAssessment Resu Its S ummarv Risk Metric Result Acceptance Criteria ICCDP 1.7E-08 ==> SE-07 ICLERP 9.7E-09 ==> SE-08 The above results are acceptable with respect to the risk thresholds established for NOED acceptability. This analysis will need to be re-performed if the plant configuration changes.

14 Discuss forecasted weather and pandemic conditions for the requested NOED period and any plant vulnerabilities related to weather or pandemic conditions.

Forecasted weather conditions for the NOED are favorable. A compensatory action is included in the NOED to brief operator actions and response in the event of a loss of offsite power during the time the NOED is in effect. The current forecast shows:

Tuesday (9/12/17) - Mostly sunny, with a high near 78°F.

Tuesday Night - A 20 percent chance of showers after 1am. Partly cloudy, with a low around 57°F.

Wednesday (9/13/17) - A 20 percent chance of showers, mainly before 1pm. Mostly cloudy, with a high near 72°F.

Wednesday Night - Mostly cloudy, with a low around 57°F.

15 Include the basis for the conclusion the noncompliance will not create undue risk to public health and safety.

EGC has evaluated the risk and determined that it is sufficiently low. A summary of the evaluation is provided as part of Item 13 above. To further protect the health and safety of the public, a number of risk management actions have been taken to increase operator awareness of critical equipment, to provide assurance that assumptions in the risk model are maintained, and to minimize the likelihood of a transient for the duration of the noncompliance.

Page 12

ENCLOSURE Request for Enforcement Discretion for Technical Specification 3.1.7, "Standby Liquid Control (SLC) System" The proposed NOED provides an additional 35 hours4.050926e-4 days 0.00972 hours 5.787037e-5 weeks 1.33175e-5 months of plant operation to implement repairs to the Unit 3 SLC pump discharge piping. While the SLC System will be unavailable during the repair period, this action is not detrimental to public health and safety for the following reasons.

SLC is a backup reactivity control system; the primary RPS is operable. Other backup features are also operable including the ARI and the ATWS Recirculation Pump Trip systems. DEOP 0500-01, Alternate Standby Liquid Injection, provides guidance to inject Sodium Pentaborate into the reactor when SLC is not functional.

The SLC System is not an initiator of any analyzed design basis accident.

Therefore, the NOED request does not increase the probability of a plant transient (i.e., does not increase the likelihood of an ATWS precursor).

Compensatory actions have been implemented to further minimize risk including the protection of key systems and deferring operational risk activities.

The AST function to maintain suppres~ion pool pH is not a risk-significant function.

A risk assessment has determined there is a negligible increase in radiological risk to the public.

16 Include the basis for the conclusion the noncompliance will not involve adverse

. consequences to the environment.

The proposed NOED does not involve any adverse consequences to the environment. As noted above, the proposed action does not represent a potential detriment to the public health and safety. A bounding risk assessment determined that the calculated risk is consistent with the site's normal work control levels and therefore there is a negligible increase in radiological risk to the public. In addition, there is no significant change in the types or significant increase in the amounts of any effluent that may be released offsite, since the proposed actions do not affect the generation of any radioactive effluent nor do they affect any of the permitted release paths. Finally, there is no significant increase in individual or cumulative occupational radiation exposure. The actions proposed in this request for enforcement discretion will not significantly affect plant radiation levels, and therefore do not significantly affect dose rates and occupational exposure.

17 Did the facility organization that normally reviews safety issues approve the request?

The request for enforcement discretion has been approved by the DNPS Plant Operations Review Committee (PORC) in accordance with the EGC Quality Assurance Program.

Page 13

ENCLOSURE Request for Enforcement Discretion for Technical Specification 3.1.7, "Standby Liquid Control (SLC) System" 18 Did the station commit that it will submit a written NOED request within two working days and a follow-up license amendment request following the NRC's verbal granting of the NOED?

EGG will submit a formal NOED request within two working days following NRG verbal approval as required per NRG IMC 0410.

EGC's decision regarding the submittal of a follow-up license amendment was discussed in a call with the NRG on September 12, 2017. EGG has concluded a license amendment request is not warranted for the following reasons:

The NOED will be in effect for a relatively short duration (i.e., additional 35 hours4.050926e-4 days 0.00972 hours 5.787037e-5 weeks 1.33175e-5 months ).

This action represents a one-time allowance. A permanent change to the Technical Specifications is not required.

The conditions requiring the NOED are not typical and had not occurred in the last 1O years at Dresden Station.

As discusseid in Item 7 above, EGC concluded that the circumstances leading the decision to withdraw the November 10, 2009, LAR have not changed.

EGC is pursuing an initiative to implement RICTs that, once implemented, will reduce the likelihood of the need to seek enforcement discretion for deviating from TS 3.1.7 for the performance of corrective maintenance on the DNPS SLC Systems in the future. Additionally, EGG supports the development and approval of a companion TSTF Traveler that will address NRC concerns related to the application of the RICT Program for the inoperability of all trains of TS-required systems.

19 Additional information for Natural Event NOEDs:

This request for Enforcement Discretion does not involve severe weather or other natural phenomena-related events; therefore, the associated Natural Event NOED questions do not apply.

Page 14

ATTACHMENT 1 Timeline of Significant Work Activities Clearance Order Tag-Out Hang 1 hour1.157407e-5 days 2.777778e-4 hours 1.653439e-6 weeks 3.805e-7 months Remove Heat Trace 1 hour1.157407e-5 days 2.777778e-4 hours 1.653439e-6 weeks 3.805e-7 months Remove Tee-Piping 1 hour1.157407e-5 days 2.777778e-4 hours 1.653439e-6 weeks 3.805e-7 months Clean and prep pipe 5 hours5.787037e-5 days 0.00139 hours 8.267196e-6 weeks 1.9025e-6 months Fit up and weld out socket #1 8 hours9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months Fit up and weld out socket #2 8 hours9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months Fit up and weld out socket #3 8 hours9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months Grind out welds to remove defects 3 hours3.472222e-5 days 8.333333e-4 hours 4.960317e-6 weeks 1.1415e-6 months Weld Exam and Quality Inspect 3 hours3.472222e-5 days 8.333333e-4 hours 4.960317e-6 weeks 1.1415e-6 months Install Heat Trace 1 hour1.157407e-5 days 2.777778e-4 hours 1.653439e-6 weeks 3.805e-7 months Clear Clearance Order Tag-Out 2 hours2.314815e-5 days 5.555556e-4 hours 3.306878e-6 weeks 7.61e-7 months Subtotal Duration 41 hours4.74537e-4 days 0.0114 hours 6.779101e-5 weeks 1.56005e-5 months Operability Post Maintenance Run 2 hours2.314815e-5 days 5.555556e-4 hours 3.306878e-6 weeks 7.61e-7 months Total Duration 43 hours4.976852e-4 days 0.0119 hours 7.109788e-5 weeks 1.63615e-5 months Page 1

ATTACHMENT 2 List of Activities That Will Be Deferred Until the Repairs to U3 SLC Have Been Completed Unit 2

9/11 0700-1500 OP QTR TS DG Cooling Water Pump Test 7D (PM Grit 10/08/17)

9/11 2300 - 9/13 0500 OP 24M DG Test/Endurance Run and Full Load Reject/ECCS/Hot Restart 7D (Endurance PM Grit 10/19/17, Monthly PM Grit 09/21/17, Semi-annual PM Grit 10/25/17, fuel oil sample PM Grit 09/20/17, fuel oil transfer pump PM Grit 10/05/17)

Unit3

IM QTR TS Reactor Water Low Level Scram/Isolation ATS Functional (DIS 0500-

02) SDTC (PM Grit 09/18/17)

D3 QTR TS VALVE TIMING (IST) lso condenser valve stroke (DOS 1600-05) 14D VC (PM Grit 09/21/17)

IM QTR TS Containment Spray Interlock, Containment High Pressure Switches Calibration (DIS 1500-04) SDTC (PM Grit 10/06/17)

IM QTR TS Electromatic/Target Rock RVS PC/PS Calibrate/Functional (DIS 0250-

03) RM EV 14D (PM Grit 09/17/17)

. IM QTR TS CST Level Switches and Torus Level Switches Functional Test (DIS 2300-14) 14D (PM Grit 10/05/17)

IM QTR TS HPCI Steam Line High Flow Isolation MTU Functional (DIS 2300-01)

SDTC (PM Grit 10/05/17)

OP QTR TS HPCI MOV Operability 14D (PM Grit 10/07/17)

IM QTR TS HPCI Reactor Low Pressure Isolation MTU Functional (DIS 2300-03)

SDTC (PM Grit 10/05/17)

OP QTR TS LPCI Valve Operability and ISTfor 1501-3A/B (PM Grit 10/07/17)

OP QTR TS CCSW Pump Operability Test and IST (PM Grit 10/08/17)

OP 2Y TS LPCI Pump Comprehensive Operability Test and IST Surveillance (quarterly PM Grit 10/08/17, comprehensive PM Grit 01/05/18)

OP QTR TS HPCI Pump Operability Test and IST Surveillance 14D HL (PM Grit 10/09/17)

OP/EP 1Y HX Thermal Performance Test 38 LPCI Heat Exchanger (PM Grit 09/15/18)

IM QTR Reactor Low Pressure (350 psig) ECCS Permissive (DIS 1500-36) EV SDTC (PM Grit 09/18/17)

OP 1M TS Air Sparge SLC Tanks For Sampling (PM Grit 09/22/17)

OP Control Rod Drive Exercising RM (PM Grit 09/26/17)

D31M TS CS DISCH PIPING WATER SOLID VERIFICATION (PM Grit 09/20/17)

D31M TS LPCI DISCH PIPING WATER SOLID VERIFICATION (PM Grit 09/21/17)

D3 1MTS HPCI DISCH PIPING WATER SOLID VERIFICATION (PM Grit 09/18/17)

CH D3 1M TS SLC TANK BORON CONCENTRATION (PM Grit 09/22/17)

Page 1

ML17261B164

Text

Subject:

Enclosure:

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