ML16243A471

Columbia - Seventh Six-Month Status Update Report for the Implementation of NRC Order EA-12-049, Mitigation Strategies for Beyond Design Basis External Events

ML16243A471
Person / Time
Site:	Columbia
Issue date:	08/30/2016
From:	Javorik A L Energy Northwest
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
EA-12-049, GO2-16-125
Download: ML16243A471 (24)

Text

Alex L. Javorik Columbia Generating Station P.O. Box 968, PE04 Richland, WA 99352-0968 Ph. 509-377-8555 l F. 509-377-4150 aljavorik@energy-northwest.com EA-12-049 10 CFR 50.54(f) August 30, 2016 GO2-16-125

U.S. Nuclear Regulatory Commission ATTN: Document Control Desk

Washington, DC 20555-0001

Subject:

COLUMBIA GENERATING STATION, DOCKET NO. 50-397 ENERGY NORTHWEST'S SEVENTH SIX-MONTH STATUS UPDATE REPORT FOR THE IMPLEMENTATION OF NUCLEAR REGULATORY

COMMISSION (NRC) ORDER EA-12-049 MITIGATION STRATEGIES FOR BEYOND DESIGN BASIS EXTERNAL EVENTS

References:

1. Letter dated March 12, 2012, from E. J. Leeds (NRC) and M. R. Johnson (NRC) to Energy Northwest et.al, "Issuance of Order to Modify Licenses with Regard to Requirements for Mitigation Strategies for Beyond-Design-Basis External Events"

2. Letter dated March 12, 2012, from E. J. Leeds and M. R. Johnson (NRC) to Energy Northwest et.al, "Request for Information Pursuant to Title 10 of the Code of Federal Regulations 50.54(f) Regarding Recommendations 2.1, 2.3, and 9.3, of the Near-Term Task Force Review of Insights from the Fukushima Dai-Ichi Accident"

3. Letter GO2-12-156 dated October 30, 2012, from D. A. Swank (Energy Northwest) to the NRC, "Energy Northwest's Response to the March 12, 2012 Information Request - Communication Assessment"

4. Letter GO2-13-034 dated February 28, 2013, from A. L. Javorik (Energy Northwest) to NRC, "Energy Northwest's Response to NRC Order EA-12-049 - Overall Integrated Plan for Mitigating Strategies"

Dear Sir or Madam,

By Reference 1, the Nuclear Regulatory Commission (NRC) issued Order EA-12-049, which required licensees to develop, implement, and maintain guidance and strategies for mitigation of beyond-design-basis external events. Reference 4 transmitted the Mitigation Strategies Overall Integrated Plan (OIP) for Columbia prepared in response

to Reference 1.

G02-16-125 Page 2 of 2 Reference 1 also required submittal of status reports at six month intervals following initial submittal of the OIP. The enclosure to this letter provides Energy Northwest's seventh six-month status report regarding the implementation of the mitigation strategies.

By Reference 2, the NRC requested that licensees assess the communications systems and equipment that would be used during an emergency.

Energy Northwest submitted the communications assessment for Columbia in Reference 3 and committed to provide the NRC with the status of the implementing actions identified in the assessment as part of the six-month status reports prepared in response to Reference

1. Letter G02-15-124, dated August 25, 2015 reported all open items from the Communications Assessment as complete.

Therefore, Energy Northwest will not provide continued updates on the subject. There are no new or revised regulatory commitments contained in this submittal.

If you have any questions or require additional information, please contact Ms. L. L. Williams at (509) 377-8148.

I declare under penalty of perjury that the foregoing is true and correct.

A"7'*1f ,2016. Respectfully A. L. Javorik Vice President, Engineering

Enclosures:

As stated cc: NRC Region IV Administrator NRC NRA Project Manager NRC Senior Resident lnspector/988C CA Sonoda -BPA/1399 ENCLOSURE TO GO2-16-125 COLUMBIA GENERATING STATION, DOCKET NO. 50-397 ENERGY NORTHWEST'S SEVENTH SIX-MONTH STATUS UPDATE REPORT FOR THE IMPLEMENTATION OF NUCLEAR REGULATORY COMMISSION (NRC)

ORDER EA-12-049 MITIGATION STRATEGIES FOR BEYOND DESIGN BASIS EXTERNAL EVENTS

GO2-16-125 Enclosure Page 1 of 21

1.0 Introduction

This enclosure provides Energy Northwest's seventh six-month status report of the Mitigation Strategies Overall Integrated Plan (OIP). This six-month status report

provides an update of milestone accomplishments and open items since the previous

submittal. 2.0 Milestone Accomplishments All the Milestones required to support restart from Refueling Outage 22 (implementation outage) were reported as complete in letter GO2-16-037 dated February 24, 2016, with

the exception of plant changes directly associated with the reliable hardened

containment vent required by Reference 5. 3.0 Milestone Schedule Status The following table is provided as an update to the milestone schedule documented in the initial submittal of the Mitigation Strategies Overall Integrated Plan. Milestones Target Commence Date Target Completion Date Activity Status Correspondence & Reports:

Submit 60 Day Initial Mitigation

Strategies Status Report Oct. 2012 Oct. 2012 Completed GO2-12-149 Submit Mitigation Strategies Overall

Integrated Plan Feb. 2013 Feb. 2013 Completed GO2-13-034 First Status Update Report for the

Mitigation Strategies Overall

Integrated Plan Aug. 2013 Aug. 2013 Completed GO2-13-123 Second Status Update Report for the

Mitigation Strategies Overall Integrated Plan Feb. 2014 Feb. 2014 Completed GO2-14-031 Third Status Update Report for the

Mitigation Strategies Overall

Integrated Plan Aug. 2014 Aug. 2014 Completed GO2-14-131 Fourth Status Update Report for the

Mitigation Strategies Overall

Integrated Plan Feb. 2015 Feb. 2015 Completed GO2-15-034 Fifth Status Update Report for the

Mitigation Strategies Overall

Integrated Plan Aug. 2015 Aug. 2015 Completed GO2-15-124 Sixth Status Update Report for the

Mitigation Strategies Overall

Integrated Plan Feb. 2016 Feb. 2016 Completed GO2-16-037 Seventh Status Update Report for

the Mitigation Strategies Overall

Integrated Plan Aug. 2016 Aug. 2016 Completed This Letter GO2-16-125 Enclosure Page 2 of 21 Milestones Target Commence Date Target Completion Date Activity Status Eighth Status Update Report for the Mitigation Strategies Overall

Integrated Plan Feb. 2017 Feb. 2017 Not Started Issuance of Energy Northwest letter

of compliance with NRC Order EA-

12-049,Section IV.C.3 Jun. 2017 Aug. 2017 Not Started Evaluations for Mitigation Strategies Phase 1, 2 & 3 Perform Engineering Evaluations Jun. 2013 Apr. 2015 Completed GO2-15-124 Engineering & Modifications for Mitigation Strategies Phase 1, 2 & 3 Develop Engineering Design for

Modifications Jun. 2013 Apr. 2015 Completed GO2-15-124 Plant Modification Installation Apr. 2014 Jun. 2015 Completed GO2-15-124 Diverse and Flexible Coping Strategies (FLEX) Support Guidelines (FSG) Program & Procedures:

Perform FLEX procedure tabletop exercise Dec. 2014 Apr. 2015 Completed GO2-15-124 Develop FSGs Jul. 2013 Apr. 2015 Completed GO2-15-124 Develop testing, calibration, maintenance and surveillance procedures for portable FLEX equipment Jan. 2014 Apr. 2015 Completed GO2-15-124 FLEX Program Procedural Changes

are placed in effect Jun. 2015 Jun. 2015 Completed GO2-15-124 Procurement & Storage Plan:

Complete modification and installation of FLEX buildings Oct. 2013 Jun. 2014 Completed GO2-15-034 Procure and store necessary FLEX

portable equipment Jun. 2013 Apr. 2015 Completed GO2-15-124 Test portable FLEX equipment Mar. 2014 Apr. 2015 Completed GO2-15-124 Establish programmatic controls for

portable FLEX equipment Jan. 2014 Apr. 2015 Completed GO2-15-124 Mitigation Strategies Staffing Analysis:

GO2-16-125 Enclosure Page 3 of 21 Milestones Target Commence Date Target Completion Date Activity Status Perform Mitigation Strategies Staffing Analysis Aug. 2014 Dec. 2014 Completed GO2-15-124 Operations & Training:

Development of Mitigation Strategies

Program training modules Jan. 2015 Mar. 2015 Completed GO2-15-124 Mitigation Strategies Program

training of station personnel Mar. 2015 Jun. 2015 Completed GO2-15-124 Operational/Functional Testing of

Mitigation Strategies Program Structures, Systems, Components (SSC) Mar. 2015 Jun. 2015 Completed GO2-15-124 Final Mitigation Strategies Program

turned over to Operations Jun. 2015 Jun. 2015 Completed GO2-15-124 4.0 Changes to the Compliance Method No additional changes to the method of compliance are being identified. 5.0 Need for Relief/Relaxation and Basis for the Relief/Relaxation The mitigation strategies contained in the initial OIP (Reference 2) were dependent, in part, on the hardened containment wetwell venting capabilities that were to be implemented by NRC Order EA-12-050 (Reference 4) coincident with the implementation of the FLEX strategies. NRC Order EA-13-109 (Reference 5) rescinded

Reference 4 requirements and imposed additional requirements for severe accident

capable hardened containment venting capabilities. Consistent with EA-13-109 Phase 1 requirements, Energy Northwest plans to complete installation of the hardened containment wetwell vent during the spring 2017 refueling outage. However, full compliance with EA-12-049 was required prior to restarting from the spring 2015 Columbia refueling outage. As requested in Reference 7 and approved in Reference 8, full compliance with NRC Order EA-12-049 was relaxed until the completion of the

spring 2017 refueling outage to allow sufficient time to implement a severe accident

capable hardened containment wetwell vent.

No additional relief or relaxation has been identified. Additionally, the need for an amendment request to support pending modifications has not been identified. 6.0 Open Items from Overall Integrated Plan The following table provides a summary and status of the open items documented in the initial submittal of the Mitigation Strategies OIP (Reference 2), Revision 1 of the

Mitigation Strategies OIP contained in the second six-month status update (Reference 9), and responses to NRC Audit Questions regarding the mitigation strategies. This

section shows that the activities required to meet NRC Order EA-12-049 are complete.

The flooding hazard analysis and hardened containment vent items remain open.

GO2-16-125 Enclosure Page 4 of 21 Mitigation Strategies Overall Integrated Plan Open Items List Status Hazards: OI-FLEX FLEX equipment will be stored in structures capable of withstanding the hazards applicable to Columbia

described above. These structures are generally referred to as

"FLEX Buildings." Two FLEX buildings or structures will be utilized to provide diverse storage locations that can maintain an

appropriate environment for the stored equipment and provide

generator backed power as necessary. The construction of the storage facilities is in progress. The list of equipment to be stored therein is being developed, including any vehicles required to

move the equipment. The storage of equipment within buildings

has been specified to limit seismic interactions.

Completed GO2-15-034 OI-FLEX The potential failure of a circulating water (CW) pipe, coincident with the extended loss of alternating current (ac)

power (ELAP), will be considered to ensure that the FLEX storage areas are located such that deployment of at least one

set of portable equipment can be accomplished.

Completed GO2-14-031 OI-FLEX Equipment stored outside will be evaluated for seismic interactions, cold weather operation and ashfall.

Completed GO2-15-034 OI-FLEX The locations and design of equipment connection points are being developed and will ensure at least one

connection point for the FLEX equipment requires access only through seismically robust structures including both the connection point and any areas that plant personnel will have to

access. Completed GO2-15-034 OI-FLEX The procedural interface in NEI 12-06 Section

5.3.3.1 (alternate instrument readouts) will be developed once the

critical monitoring parameters are identified.

Completed GO2-15-034 OI-FLEX Evaluation of FLEX equipment will be completed to

ensure proper functioning under the design basis temperatures and ashfall conditions. This includes manual actions to transport and set up the equipment.

Completed GO2-15-124 OI-FLEX Actions will be developed to ensure the continued

availability of the water inventory sources from the SW ponds in cold weather. In addition, actions will be developed to thaw any frozen service water piping that will be required in Phase 3. The plan to remove ice and snow from equipment deployment routes is under evaluation and actions will be developed as needed.

Completed GO2-15-034 Assumptions: (Some Assumptions may be impacted by the completion of activities developed for Hardened Vents)

OI-FLEX The sequence of events developed to address the

ELAP and loss of the ultimate heatsink (LUHS) will take into

account sources of expected reactor coolant inventory loss. (NRC

Audit Question 15)

Completed GO2-14-131 GO2-16-125 Enclosure Page 5 of 21 Mitigation Strategies Overall Integrated Plan Open Items List Status OI-FLEX Modular Accident Analysis Program (MAAP) analysis will be performed. The resulting time line will establish

the necessary actions that will be taken to protect both the core

and containment.

Completed GO2-14-131 OI-FLEX GOTHIC calculations will evaluate the effects of a loss of heating, venting and air conditioning (HVAC) on the plant

response. An evaluation of the GOTHIC results on equipment qualification will be performed. Areas of the plant requiring access by personnel (including activities identified in the Appendix 1 Timeline) will be evaluated to ensure conditions will

support the actions. (This OI has been changed to explicitly

include activities identified in the Timeline for completeness.)

(NRC Audit Questions 23, 24, 29, 43 and 44)

Completed GO2-14-131 OI-FLEX The design of the permanent structures, systems, and components (SSCs) used to mitigate the ELAP and LUHS

will be verified to be robust with respect to seismic events, floods, and high winds.

Completed GO2-15-034 Sequence of Events:

OI-FLEX The Station Blackout (SBO)/ELAP procedure will

require all load shed actions to be completed in 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />. These load shed actions will be validated to ensure they can be

completed within this time limit. (This OI has been changed because the existing 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> procedural limit will be maintained.)

Completed GO2-14-131 OI-FLEX A plant modification will be performed to address the potential for flooding of the RCIC room from the barometric condenser.

Completed GO2-15-034 OI-FLEX It is estimated to take 15 minutes to complete the

additional load shedding necessary for an ELAP. The 15 minute

duration for shedding the additional loads will be validated. (This

OI has been deleted because the ELAP load shed will be

combined with the SBO load shed and performed at the start of

the event.)

Deleted GO2-14-131 OI-FLEX The maximum time needed for connection of a 480V FLEX generator to power the Division 1 batteries will be

determined.

Completed GO2-15-034 Programmatic:

OI-FLEX Portable FLEX equipment will be initially tested or

otherwise evaluated to ensure acceptable performance.

Completed GO2-15-124 OI-FLEX The maintenance and testing program for FLEX equipment will be documented in the next OIP update following finalization of the program.

Completed GO2-15-124 OI-FLEX Unavailability of equipment and applicable connections that directly perform a FLEX mitigation strategy for

core, containment, and spent fuel pool (SFP) will be managed in accordance with NEI 12-06.

Completed GO2-15-124 GO2-16-125 Enclosure Page 6 of 21 Mitigation Strategies Overall Integrated Plan Open Items List Status OI-FLEX Procedures will ensure that changes to the plant design, physical plant layout, roads, buildings, and structures

used for the storage of portable FLEX equipment will not

adversely impact the approved FLEX strategy.

Completed GO2-15-124 OI-FLEX Changes to FLEX strategies will be assessed using

the change process provided in NEI 12-06 Section 11.8.

Completed GO2-15-124 OI-FLEX Periodic training will be provided to site emergency response leaders on Beyond Design Basis emergency response

strategies and implementing guidelines. (This OI has been

changed to reflect the requirement for periodic training stated in

NEI 12-06 paragraph 11.6.2)

Completed GO2-15-034 OI-FLEX Personnel assigned to direct execution of the mitigation strategies for Beyond Design Basis events will receive

the necessary training to ensure familiarity with the associated

tasks. Completed GO2-15-034 OI-FLEX Establish staging area for the receipt of offsite

resources.

Completed GO2-14-131 OI-FLEX Establish site-specific Strategic Alliance for FLEX

Emergency Response (SAFER) Response Plan for Columbia with the National SAFER Response Center (NSRC) to define and

coordinate NSRC and plant actions in response to events. (This

OI has been changed to use the formal designation of the

"playbook.")

Completed GO2-15-034 OI-FLEX Energy Northwest will perform an evaluation of the acceptability of the Tri-Cities Airport and the Yakima Municipal Airport as SAFER Staging Areas. (This OI has been added to reflect the selection of the Tri Cities and Yakima Airports.) As a

result of the evaluation, the Seattle and Portland airports were

chosen as the SAFER staging areas.

Completed GO2-14-131 Phase 1 Core Cooling: (Some Mitigation Strategies related to Phase 1 Core Cooling may be impacted by the completion of activities developed for Hardened Vents)

OI-FLEX Procedure guidance will be developed to support implementation of Phase 1 Core Cooling strategies as described in the Overall Integrated Plan.

Completed GO2-15-124 OI-FLEX Strategies for maintaining core cooling during an

ELAP and LUHS event during shutdown and refueling will be developed, including the necessary actions and equipment

required during Phases 1, 2, and 3. Energy Northwest will incorporate the supplemental guidance provided in the NEI

position paper entitled "Shutdown / Refueling Modes" to enhance

the shutdown risk process and procedures.

Completed GO2-15-124 GO2-16-125 Enclosure Page 7 of 21 Mitigation Strategies Overall Integrated Plan Open Items List Status OI-FLEX System modifications and evaluations will be completed to support implementation of Phase 1 Core Cooling strategies as described in the Overall Integrated Plan.

See Items a - e below a. A reliable containment hardened vent system will be installed to vent heat from the reactor pressure vessel (RPV)/containment to the atmosphere. Details of this

design will be provided in the Hardened Vent Overall

Integrated Plan required by NRC Order EA-13-109.

Completed GO2-14-107

GO2-14-175 b. Analyses of reactor core isolation cooling (RCIC) operation at elevated temperatures have been undertaken by

General Electric Hitachi (GEH) and Energy Northwest to

identify changes to the RCIC pump or turbine necessary to ensure reliable operation at elevated temperatures.

Energy Northwest will evaluate potential actions including changes to procedures or maintenance practices or implementation of modifications.

Completed GO2-15-124 c. An assessment of RCIC system piping, hangers and supports will be conducted at the elevated temperatures to

ensure satisfactory performance. If needed, modifications

will be performed.

Completed GO2-15-124 d. An evaluation of the feasibility of redesigning or repowering the barometric condenser's level switch will be performed to determine if it can remain functional during an ELAP to provide automatic control of RCIC-P-4.

Completed GO2-14-031 e. MAAP cases using the suppression pool will be re-run using finalized design parameters of the containment hardened vent. The results will be used to define additional actions. (See Open Item OI-FLEX-09). (This OI

has been changed because the suppression pool will be

the credited water source for initial RCIC operation.)

Completed GO2-14-131 OI-FLEX GOTHIC analyses will be confirmed, or revised, to

bound the design of the hardened containment vent after the design is finalized. (This OI has been added to assure that the

subject analyses reflect the design required by EA-13-109.)

Response:

Calculation ME-02-13-03 R1 results show that the hardened containment vent is able to remove the required 1% of 4079 megawatts thermal (MWt) with a 45 psig wetwell pressure. This

would include the currently proposed amendment request for a

power uprate of 1.66%, submitted on June 28, 2016. This amendment request would increase the rated thermal power from the current licensed thermal power of 3486 MWt to 3544 MWt

and remains bounded by this analysis which ensures that the HCVS can remove the amount of energy required by EA-13-109.

Completed.

GO2-16-125 Enclosure Page 8 of 21 Mitigation Strategies Overall Integrated Plan Open Items List Status Phase 1 Containment: (Some Mitigation Strategies Open Items not originally identified in the Overall Integrated Plan related to Phase 1 Containment have been created due to the potential impact of the schedule for activities developed for Phase 1 & 2 Hardened Vents)

OI-FLEX-27 (continued) f. It is anticipated that temporary interim strategies will be developed for venting the containment until the completion of containment hardened vent activities. (This OI has been deleted because an interim venting strategy will not be credited for compliance with EA-12-049.)

Deleted GO2-14-031 g. It is anticipated that revisions to procedures will be developed to implement the temporary interim strategies for venting the containment until the completion of containment hardened vent activities. (This OI has been deleted because an interim venting strategy will not be credited for compliance with EA-12-049.)

Deleted GO2-14-031 Phase 2 Core Cooling:

OI-FLEX Procedure guidance will be developed to support implementation of Phase 2 Core Cooling strategies as described in the Overall Integrated Plan.

Completed GO2-15-124 OI-FLEX System modifications and evaluations will be completed to support implementation of Phase 2 Core Cooling strategies as described in the Overall Integrated Plan.

See items a - d below a. Alternate connection points will be provided to connect FLEX generators to the electrical distribution system.

Completed GO2-15-124 b. An evaluation of running underground cabling from the FLEX Building(s) to the existing electrical connection points outside the Diesel Generator Building will be

performed.

Completed GO2-14-131 c. DG4 or DG5 will have the capability of providing power to Division 1 and Division 2. (This OI has been changed to eliminate duplication of OI-FLEX-29.b and to reflect the

planned capability of the FLEX DGs)

Completed GO2-14-131 d. Provisions will be made to allow the installation of hoses through fence(s). (This OI has been changed to reflect a

change in the strategy for hose routing with respect to

fences.) Completed GO2-14-131 OI-FLEX An evaluation will be completed to ensure a diverse supply of fuel is available, maintained and diverse means are provided for refueling the portable equipment.

Completed GO2-15-034 GO2-16-125 Enclosure Page 9 of 21 Mitigation Strategies Overall Integrated Plan Open Items List Status OI-FLEX Strategies for mitigating an ELAP and LUHS event during cold shutdown and refueling will be developed as described in the Overall Integrated Plan.

Completed GO2-15-124 OI-FLEX An analysis will be performed to confirm that the

Phase 2 configurations described in the OIP for suppression pool make-up can provide adequate flow through the spray header.

(This OI has been deleted as the suppression pool make-up will not use the spray nozzles as part of the make-up flow path.)

Deleted GO2-14-131 OI-FLEX A wind and seismic evaluation in accordance with

the American Society of Civil Engineers (ASCE) 7-10 Building

Risk Category IV will be performed on the above ground alternate

gasoline tank located outside the protected area. (This OI has

been added to track completion of the subject evaluation.)

Completed GO2-15-034 Phase 3 Core Cooling:

OI-FLEX Energy Northwest will establish a site-specific

SAFER Response Plan for Columbia with the NSRC to define

and coordinate NSRC and plant actions in response to events.

Completed GO2-15-034 OI-FLEX Modifications and evaluations will be completed to

support implementation of Phase 3 Core Cooling strategies as described in the Overall Integrated Plan.

See Items a - b below a. Two separate connection points will be installed to provide critical bus power from a 4160-V ac FLEX generator (From

the NSRC).

Completed GO2-15-034 b. A strategy for connecting the large FLEX pump to the service water (SW) system will be developed. SW system

piping will be modified if needed to provide connection

points. Completed GO2-15-034 OI-FLEX The spray pond temperature rise while operating in the shutdown cooling mode without sprays will be determined.

(This OI has been added to determine if cooling tower make-up (TMU) pump operation will be needed.)

Completed GO2-14-131 Phase 1 SFP Cooling:

Procedure guidance will be developed to support implementation

of Phase 1 SFP Cooling strategies. (As discussed in the Overall

Integrated Plan, the SFP does not require any action in Phase 1.

The inventory of water in the pool is generally maintained greater than or equal to 22 feet above the top of irradiated fuel assemblies stored in the fuel pool. The heat up of the pool water

will remove heat from the stored fuel during Phase 1, therefore this open item can be Deleted)

Deleted GO2-14-031 GO2-16-125 Enclosure Page 10 of 21 Mitigation Strategies Overall Integrated Plan Open Items List Status OI-FLEX Modifications will be completed to support implementation of Phase 1 SFP Cooling strategies.

Phase 1 relies on the use of installed plant equipment. As stated

in GO2-14-031, the SFP does not require any action in Phase 1.

The inventory of water in the SFP is generally maintained greater than or equal to 22 feet above the top of irradiated fuel assemblies stored in the fuel pool. The heat up of the pool water

will remove heat from the stored fuel during Phase 1. There are

no modifications required for SFP cooling strategies. The SFPLI

modification required by EA-12-051 has been completed as

reported in letter GO2-15-120.

Completed GO2-15-124 Phase 2 SFP Cooling:

OI-FLEX Procedure guidance will be developed to support implementation of Phase 2 SFP Cooling strategies as described

in the OIP. (This OI has been added to track the procedure

development needed to support Phase 2 SFP Cooling.)

Completed GO2-15-124 OI-FLEX The time that make-up to the SFP must be initiated after an ELAP will be determined for a full core off-load.

Completed GO2-14-131 Phase 3 SFP Cooling:

OI-FLEX Procedure guidance will be developed to support implementation of Phase 3 SFP Cooling strategies.

Completed GO2-15-124 OI-FLEX Evaluations will be completed to support implementation of Phase 3 SFP Cooling strategies. a. An evaluation of the ability of the 4160-V ac FLEX generator (from the NSRC) to repower a Fuel Pool Cooling (FPC) pump

will be completed. An evaluation of the ability of the large-

capacity FLEX pump (from the NSRC) to provide cooling to the FPC heat exchanger will be completed.

Completed GO2-14-131 Phase 1 Safety Support Functions:

OI-FLEX Procedure guidance will be developed to support implementation of Phase 1 Safety Function Support strategies as

described in the Mitigation Strategies Overall Integrated Plan.

Completed GO2-15-034 OI-FLEX System modifications will be completed to support implementation of Phase 1 Safety Function Support strategies as

described in the Mitigation Strategies Overall Integrated Plan. a. GOTHIC modeling is ongoing in support of the ELAP that will identify heat loads in the key locations between the buildings.

This analysis will then define additional actions that may be required using portable equipment, or any modifications to

support operation of installed equipment during Phase 1.

No system modifications were required.

Completed GO2-15-034

GO2-16-125 Enclosure Page 11 of 21 Mitigation Strategies Overall Integrated Plan Open Items List Status Phase 3 Safety Support Functions:

OI-FLEX An evaluation of the conditions of the residual heat removal (RHR) pump rooms under an ELAP event will be

completed to determine if additional actions are needed to remove heat from the rooms prior to and during operation of the

pump. Completed GO2-14-131 Appendix 1 - Sequence of Events Timeline:

OI-FLEX Modification to the sequence of events timeline will be provided in future status update reports as analyses, strategies and evaluations are completed.

Completed GO2-15-034 Appendix 2 - Milestone Schedule:

None - Revisions to the milestone schedule are identified in

Section 2 of this and subsequent future status update reports.

N/A Appendix 3 - Conceptual Sketches:

OI-FLEX Updated sketches will be provided in future status

reports if needed to reflect changes.

Completed GO2-14-131 NRC Audit Question Responses:

OI-FLEX NEI 12-06, Section 5.3.3 Consideration 2:

"Consideration should be given to the impacts from large internal flooding sources that are not seismically robust and do not require ac power (e.g., gravity drainage from lake or cooling

basins for non-safety-related cooling water systems," will be

addressed in future six-month updates. (Response to NRC Audit

Question 02)

Completed GO2-14-131 OI-FLEX The flooding hazards analysis will provide

information about site water level associated with a probable maximum precipitation (PMP) event and a local intense

precipitation (LIP) event. These water levels will be compared to elevations for the FLEX buildings as well as the deployment routes for the equipment. A LiDAR survey of the site was performed and a topographic plan of the site has been generated to assist in this evaluation. The flooding analysis is currently in

progress. The results will be used to provide a response to this question in a future OIP update. (Response to NRC Audit

Question 03) (This OI has been changed because the flooding analysis remains in progress and the OI was not closed in the

February 2014 update.)

Started OI-FLEX A future update to the OIP will address the applicability to Columbia of each of the nine considerations in NEI 12-06 Section 6.2.3.2, Deployment of FLEX Equipment. (Response to NRC Audit Question 04) (This OI has been

changed because the flooding analysis remains in progress and

the OI will be closed in a future update.)

Started GO2-16-125 Enclosure Page 12 of 21 Mitigation Strategies Overall Integrated Plan Open Items List Status OI-FLEX The flooding analysis will be used to determine if any of the external flooding procedures should be changed.

(Response to NRC Audit Question 04)

Not Started OI-FLEX The NRC has endorsed generic resolutions of

concerns regarding use of the MAAP code in mitigation

strategies. Energy Northwest will assess the applicability of the

generic resolutions to Columbia. (Response to NRC Audit

Question 09) Columbia has completed an assessment of the

generic resolution of the issues related to use of MAAP4 for our

ELAP work. The assessment focused on the limitations imposed

by the NRC on their acceptance of the use of MAAP4 for timeline purposes as stated in the NRC letter dated October 3, 2013, from

Jack R. Davis (NRC) to Joseph E. Pollock (NEI). Columbia has used MAAP4 for the determination of wetwell vent timing, fuel

pool cooling/make-up timing, and for RCIC operability

assessments based on calculated suppression pool

temperature. All the limitations in the NRC letter have been

addressed in the assessment which is available for review upon

request. Completed GO2-14-131 OI-FLEX A review of the current fire protection ring header shows that it was designed to Seismic Category II standards

outside Seismic Category I structures. Except for minor portions, it is buried in engineered fill and is largely protected from the effects of high winds and missiles. While use of the fire protection ring header is an operational convenience, its availability is not

credited (Response to NRC Audit Question 13).

Completed GO2-14-031 OI-FLEX The NRC has endorsed a generic resolution of

concerns regarding use of the MAAP code in mitigation

strategies. Energy Northwest will assess the applicability of the generic resolution to Columbia. (Response to NRC Audit

Question 14) See the response in OI-FLEX-46 above.

Completed GO2-14-131 OI-FLEX GOTHIC analyses of the Vital Island will evaluate

hydrogen generation in the battery rooms. The results of those

analyses will determine the need, if any, for measures needed to control hydrogen concentrations in the battery rooms. (Response

to NRC Audit Question 28)

Completed GO2-14-031 OI-FLEX At the point when ELAP mitigation activities

require tie-in of FLEX generators, in addition to existing electrical interlocks, procedural controls, such as inhibiting generator start circuits and breaker rack-outs, will be employed to prevent simultaneous connection of both the FLEX generators and Class

1E generators to the same AC distribution system or component.

FLEX strategies, including the transition from installed sources to

portable sources (and vice versa), will be addressed in the FLEX procedures. (Response to NRC Audit Question 50)

Completed GO2-15-124 GO2-16-125 Enclosure Page 13 of 21 Mitigation Strategies Overall Integrated Plan Open Items List Status OI-FLEX Energy Northwest will address the considerations in NEI 12-06, Section 12.2. (Response to NRC Audit Question

34) Completed GO2-14-131 OI-FLEX Plant specific ELAP analysis results will be

provided in the format and detail equivalent to NEDC-33771P.

Energy Northwest will provide the information in a subsequent

six-month update. (Response to NRC Audit Question 36)

Completed GO2-15-034 OI-FLEX The issue of maintenance and testing of portable

FLEX equipment is being addressed and coordinated on an

industry-wide basis. Energy Northwest will continue to monitor

and participate in these industry activities so that it can develop a maintenance and testing program that meets acceptable standards (including NEI 12-06), and is consistent with those used generically throughout the industry. Energy Northwest will

also utilize existing station procedures coupled with vendor technical information for establishing preventive maintenance activities and schedules. The Columbia maintenance and testing

program for FLEX equipment will be documented in the next OIP update following finalization of the program. (Response to NRC

Audit Question 40)

The maintenance and testing program for portable FLEX

equipment has been added to the FLEX Program Document.

NRC SE Tracker items 33-B and 7-E have been posted to the E-

portal. No additional OIP update will be made.

Completed GO2-15-124 OI-FLEX Finalize the sizing calculation for the FLEX

generators for phase 2 and 3. Completion of this activity is

necessary to provide a comprehensive response to this question (i.e. NRC Audit Question 42 requesting a summary of the sizing calculation for the FLEX generators to show that they can supply

the loads assumed in phases 2 and 3). (Response to NRC Audit

Question 42).

Completed GO2-14-131 OI-FLEX Finalization of the capacity and power

requirements calculation for Phase 3 is not complete.

Completion of this activity is necessary to provide a

comprehensive response to this question (i.e. NRC Audit

Question 45 requesting a description of the electrical power requirements for Phase 3 of the mitigating strategies integrated

plan and the capacity of the power sources). (Response to NRC

Audit Question 45) See OI-FLEX-54 Summary Above.

Completed GO2-14-131 GO2-16-125 Enclosure Page 14 of 21 Mitigation Strategies Overall Integrated Plan Open Items List Status OI-FLEX Energy Northwest will validate the ability to successfully accomplish each bypass under the expected

conditions of a prolonged station blackout as part of the procedure approval process. Based on incorporation of the GEH

recommended trip bypasses, the potential for equipment protection features to interfere with operation of RCIC will be minimized. (Response to NRC Audit Question 56)

Completed GO2-15-034 OI-FLEX Energy Northwest will perform an evaluation to compare (1) the quantity of water required to dissipate, for 72

hours, the decay heat of the reactor core and spent fuel pool during Phases 1 and 2, (2) the volume of water normally in the

spray ponds. (Response to NRC Audit Question 05)

Completed GO2-14-031 OI-FLEX Energy Northwest's periodic OIP updates will identify any planned modifications that it determines may require NRC approval per 10 CFR 50.90. (Response to NRC Audit Question 22) No planned modifications require NRC approval.

Completed GO2-15-034 OI-FLEX The Spent Fuel Pool section of the OIP will be

updated to reflect actions taken in the event of full core off-load to the pool. (Response to NRC Audit Question 24)

Completed GO2-14-131 OI-FLEX This issue (early venting) was identified as a generic concern or question which the nuclear industry will resolve generically through the Nuclear Energy Institute (NEI) and the applicable industry groups (e.g., Boiling Water Reactor Owners Group (BWROG), Electric Power Research Institute (EPRI), etc.). (Response to NRC Audit Question 25)

Completed GO2-14-031 OI-FLEX An updated schedule for the Energy Northwest identified open items will be included in the six-month updates of the Columbia OIP. (Response to NRC Audit Question 46)

Completed GO2-14-131 OI-FLEX Calculations NE-02-12-02, ME-02-12-06, ME 12-07, 2.05.0,1 and CMR-11179 have been uploaded to the Columbia Fukushima portal. (Response to NRC Audit Question

47) Completed GO2-14-131 GO2-15-034 OI-FLEX The timeline in Appendix 1 of the February 28, 2013 Overall Integrated Plan (OIP) for Order EA-12-049 will be revised as necessary to reflect use of the existing ductwork rather

than the hardened containment vent. (Response to NRC Audit

Question 58) (This OI has been deleted because use of

ductwork for containment venting will not be credited for compliance with EA-12-049)

Deleted GO2-14-031 OI-FLEX Energy Northwest will address the conformance to the guidance of NEI 12-06, Section 3.2.2, Guideline (12).

(Response to NRC Audit Question 61)

Completed GO2-14-131 GO2-16-125 Enclosure Page 15 of 21 Mitigation Strategies Overall Integrated Plan Open Items List Status OI-FLEX The NEI position paper includes instructions for licensees to incorporate the following template wording into their

OIPs:

"(Name of licensee) will incorporate the supplemental guidance

provided in the NEI position paper entitled "Shutdown / Refueling Modes" to enhance the shutdown risk process and procedures." (Response to NRC Audit Question 62A)

Completed GO2-14-031 OI-FLEX The NEI white paper includes instructions for licensees to incorporate the following template wording into their

OIPs:

"[Insert Licensee] confirms that the FLEX strategy station battery run-time was calculated in accordance with the Institute of

Electrical and Electronics Engineers (IEEE)-485 methodology using manufacturer discharge test data applicable to the licensee's FLEX strategy as outlined in the NEI white paper on

Extended Battery Duty Cycles. The detailed licensee calculations, supporting vendor discharge test data, FLEX

strategy battery load profile, and other inputs/initial conditions required by IEEE-485 will be available on the licensee's web portal for documents and calculations. The time margin between the calculated station battery run-time for the FLEX strategy and the expected deployment time for FLEX equipment to supply the dc loads is ["8"] hours."

Energy Northwest will incorporate this template wording into a

future OIP update. (Response to NRC Audit Question 62B)(This OI has been changed because the validation of actual time deploying the 480-V ac FLEX generators per OI-FLEX-15 has not

been completed.)

Completed GO2-15-034 OI-FLEX The load shedding procedure is in the process of being developed. The procedure will also direct operators to

depressurize the main generator manually if the main generator

is pressurized with hydrogen before shedding the air side seal oil

backup pump. These actions are expected to preclude a

potential fire and/or explosion from the hydrogen. (Response to

NRC Audit Question 50)

Completed GO2-14-131 7.0 Interim Staff Evaluation Reference 6 transmitted an NRC Interim Staff Evaluation and Audit Report (ISE) which documented the results of a review of the Columbia OIP (Reference 2), six-month

update (Reference 3), and information obtained through the NRC's mitigation strategies

audit process. The ISE documented the staff's conclusion that Energy Northwest has provided sufficient information to determine that there is reasonable assurance that the OIP, when properly implemented, will meet the requirements of Order EA-12-049 at

Columbia. That conclusion was based on the assumption that Energy Northwest would

implement the OIP as described, including the satisfactory resolution of the Open and GO2-16-125 Enclosure Page 16 of 21 Confirmatory Items tabulated in the ISE. In February 2015 the NRC conducted an on-site audit of the implementation of the requirements of Reference 1 (Mitigation) and

NRC Order EA-12-051 on Reliable Spent Fuel Pool Instrumentation. The audit reviewed the Open and Confirmatory items previously identified in this section. The status of the remaining Open, Confirmatory, and New items are now tracked in Section 8.0 below. 8.0 Open Items from the Audit Regarding Implementation Reference 12 transmitted the audit report of the February 2015 audit regarding the implementation of the mitigation strategies and reliable spent fuel pool instrumentation

Orders. The following table was reproduced from Attachment 3 of the audit report and includes the status of Columbia's response to the open items listed. Where indicated, the requested information has been posted on the Columbia e-portal as outlined in the

Columbia Audit Plan dated January 16, 2015.

OPEN ITEMS FROM THE FEBRUARY 2015 MITIGATION/SFPI AUDIT Audit Item Item Description Licensee Input Needed ISE OI 3.1.2.1.A Confirm that FLEX equipment can be adequately protected and deployed in such

an event and whether flooding procedures account for the use of FLEX equipment. Licensee Open Items 43 through 45 remain open as EN is performing a local intense precipitation analysis.

Response: Pending completion of the flooding hazards analysis.

ISE CI 3.2.1.4.A The licensee has not completed calculations supporting the design of the FLEX equipment. Confirm that portable FLEX equipment is adequate to perform its

credited mitigation function(s). Licensee to evaluate head loss to the spent fuel pool while simultaneously filling SFP and RPV level.

Response: Discussion and related calculation were posted to the E-portal on 6/2/15 ISE CI 3.2.2.D Confirm that [Energy Northwest] EN's SFP makeup strategy for Columbia provides for SFP makeup without accessing the refueling floor, as recommended in NEI 12-06, Table C-3, or that an acceptable alternate approach is developed. Licensee to evaluate flow analysis for filling SFP through RHR B loop.

Response: Flow path discussion and drawings were posted to the E-portal on 6/2/15 ISE CI 3.2.3.B The licensee's proposed strategy for

maintaining containment will rely on installation of the hardened containment vent system (HCVS) as required by Order

EA-13-109. When complete, the licensee's calculations supporting the revised containment response and sequence of events timeline should be reviewed to confirm that the timeline is appropriate and that containment functions will be restored

and maintained following an ELAP event. The licensee needs to provide to the NRC staff the final configuration and calculations for the HCVS.

Response: An updated timeline for the HCVS response was provided in letter GO2-15-175, dated December 16, 2015.

GO2-16-125 Enclosure Page 17 of 21 OPEN ITEMS FROM THE FEBRUARY 2015 MITIGATION/SFPI AUDIT Audit Item Item Description Licensee Input Needed AQ 41 The alternate strategy for Phase 2 core cooling involves removal, replacement, and reconfiguration of several flanges and piping

elbows during the ELAP event. The NRC staff requests that the licensee provide a description of the available lighting and habitability around the RHR piping where connections need to be made. The NRC staff asked the licensee to provide further detail of the paths and the locations of the connections points as well as the validation of the ability to perform the actions.

Response: Accessibility and flange installation discussion with maps and photos were posted to the E-portal on 6/9/15. AQ 52 On page 18 of 60 Columbia's OIP states that load shedding will be performed to "prolong battery life to 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br />." On page 22 of 60 Columbia's OIP states, "The 125 VDC batteries are available for 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> without recharging. The 250 VDC batteries are available for 17 hours1.967593e-4 days <br />0.00472 hours <br />2.810847e-5 weeks <br />6.4685e-6 months <br /> without recharging." On page 35 of 60, with reference to power for containment hardened vent valve solenoids and

instrumentation, Columbia's OIP states, "This battery will be designed to support at least 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> of operation without any outside power source." Provide justification for the above discrepancy. The licensee to design the containment hardened vent system battery for a cycle of 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.

Response: The station batteries and the HCV batteries are independent of each other. In letter GO2-15-175, dated December 16, 2015, Applicable EA-12-049 assumptions, Item 049-7 states that the HCVS is independent from the DC power and distribution that can be credited for the duration determined per the EA-12-049, Diverse and Flexible Coping Strategies (FLEX), methodology for battery usage of 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />. The power supply scheme for the HCVS shall be in accordance with EA-13-109 and the applicable guidance. (Reference 10 NEI 12-06, Section 3.2.1.3 item 8) Additionally, in the Columbia Generating Station Plant Specific HCVS Related Assumptions / Characteristics section, Item PLT-2 states that a Class 1E, 24-V battery system dedicated to the HCVS electrical loads consisting of batteries, a battery charger, 24-V DC distribution panels, wiring, cables and raceways will be installed. The battery sizing will sustain operation for a minimum of 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> with no operator action. After 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, supplemental power will be available.

GO2-16-125 Enclosure Page 18 of 21 OPEN ITEMS FROM THE FEBRUARY 2015 MITIGATION/SFPI AUDIT Audit Item Item Description Licensee Input Needed 1-E Please address the following items regarding the use of raw water sources for mitigating an ELAP event:

a. Discuss the quality of the water (e.g.,

suspended solids, dissolved salts) that will be used for primary makeup during ELAP events, accounting for the potential for increased suspended or dissolved material

in some raw water sources during events such as flooding or severe storms.

b. Discuss whether instrumentation available during the ELAP event is capable of providing indication that inadequate core cooling exists for one or more fuel assemblies due to blockage at fuel assemblies' inlets or applicable bypass leakage flowpaths. c. Provide justification that the use of the intended raw water sources will not result in blockage of coolant flow across fuel assemblies' inlets and applicable bypass leakage flowpaths to an extent that would inhibit adequate core cooling. Or, if deleterious blockage at the core inlet cannot be precluded under ELAP conditions, then please discuss alternate means for assuring

the adequacy of adequate core cooling in light of available indications. Licensee to justify the ashfall event would not plug the inlets of the fuel assemblies or that top down cooling would be used to ensure core cooling. Response: Discussion and calculation were posted to the E-portal on 4/13/15 GO2-16-125 Enclosure Page 19 of 21 OPEN ITEMS FROM THE FEBRUARY 2015 MITIGATION/SFPI AUDIT Audit Item Item Description Licensee Input Needed 2-E a. Discuss the design of the suction strainers used with FLEX pumps taking suction from raw water sources, including perforation dimension(s) and approximate surface area. b. Provide reasonable assurance that the strainers will not be clogged with debris (accounting for conditions following, flooding, severe storms, earthquakes or other natural hazards), or else that the strainers can be cleaned of debris at a frequency that is sufficient to provide the required flow. In the response, consider the

following factors:

i. The timing at which FLEX pumps would take suction on raw water relative to the onset and duration of the natural hazard. ii. The timing at which FLEX pumps would take suction on raw water relative to the timing at which augmented staffing would be available onsite.

iii. Whether multiple suction hoses exist for each FLEX pump taking suction on raw water, such that flow interruption would not be required to clean suction strainers. Licensee to analyze the suction strainer design and how far into the water it sits as well as the procedure for ensuring that flow is not interrupted to such a length of time that the fuel would remain covered.

Response: Discussion and strainer vendor information were posted to the E-portal on 4/3/15 10-E Evaluation of FLEX equipment to be completed to ensure proper functioning under the design-basis temperatures and ash fall conditions during both operation and storage. This includes manual actions to transport and set up the equipment as well as storage conditions. Licensee to complete evaluation of operating FLEX equipment under ash fall conditions.

Response: Evaluation was posted to the E-portal on 5/20/15 11-E Please provide an assessment of potential susceptibilities of EMI/RFI in the areas where the SFP instrument is located and how to mitigate those susceptibilities.

A strategy to mitigate EMI/RFI interference in the SFP area.

Response: This response was provided in the EA-12-051 compliance letter GO2-15-120.

GO2-16-125 Enclosure Page 20 of 21 OPEN ITEMS FROM THE FEBRUARY 2015 MITIGATION/SFPI AUDIT Audit Item Item Description Licensee Input Needed 14-E The licensee is requested to provide a summary evaluation to confirm that the temperature and pressures within

containment will not exceed the environmental qualification (EQ) of electrical equipment that is being relied upon as part of their FLEX strategies. The licensee needs to ensure that the EQ profile of the required electrical equipment remains bounding for the entire duration of the event. Provide EQ evaluation Response: Evaluation was posted to the E-portal on 3/11/15

9.0 References

1. Letter dated March 12, 2012, from E. J. Leeds (NRC to Energy Northwest et.

al, "Implementation of Order Modifying Licenses with Regard to Requirements for Mitigation Strategies for Beyond Design Basis External

Events" (EA-12-049) 2. Letter GO2-13-034 dated February 28, 2013, from A. L. Javorik (Energy Northwest) to NRC, "Energy Northwest's Response to NRC Order EA 049 - Overall Integrated Plan for Mitigating Strategies" 3. Letter GO2-13-123 dated August 28, 2013, from D.A. Swank (Energy Northwest) to NRC, "Energy Northwest's First Six Month Status Update

Report for the Implementation of NRC Order EA-12-049 Mitigation Strategies for Beyond Design Basis External Events" 4. Letter dated March 12, 2012, from E. J. Leeds (NRC) to Energy Northwest et. al, "Issuance of Order Modifying Licenses with Regard to Reliable Hardened Containment Vents" (EA-12-050) 5. Letter dated June 6, 2013, from E. J. Leeds (NRC) to Energy Northwest et.

al, "Issuance of Order Modifying Licenses with Regard to Reliable Hardened Containment Vents Capable of Operation Under Severe Accident Conditions" (EA-13-109) 6. NRC letter dated January 29, 2014, from J. S. Bowen (NRC) to M. E. Reddemann (Energy Northwest), "Columbia Generating Station - Interim Staff Evaluation Relating to Overall Integrated Plan in Response to Order

EA-12-049 (Mitigation Strategies)" 7. Letter GO2-14-026 dated February 21, 2014, from D. A. Swank (Energy Northwest) to NRC, "Request for Relaxation from NRC Order EA-12-049,

'Order Modifying Licenses With Regard to Requirements for Mitigation Strategies for Beyond-Design-Basis External Events'" 8. Letter dated April 15, 2014, from E. J. Leeds (NRC) to M. E. Reddemann (Energy Northwest), "Columbia Generating Station - Relaxation of Certain

Schedule Requirements for Order EA-12-049 'Issuance of Order to Modify GO2-16-125 Enclosure Page 21 of 21 Licenses with Regard to Requirements for Mitigation Strategies for Beyond Design Basis External Events'" 9. Letter GO2-14-031, dated February 27, 2014, from D. A. Swank (Energy Northwest) to NRC, "Energy Northwest's Second Six Month Status Update

Report for the Implementation of NRC Order EA-12-049 Mitigation Strategies for Beyond Design Basis External Events" 10. Letter GO2-14-131 dated August 28, 2014, from D. A. Swank (Energy Northwest) to the NRC, "Energy Northwest's Third Six-Month Status Update

Report for the Implementation of NRC Order EA-12-049 Mitigation Strategies for Beyond Design Basis External Events" 11. Letter GO2-15-034 dated March 2, 2015, from D. A. Swank (Energy Northwest) to the NRC, "Energy Northwest's Fourth Six-Month Status Update Report for the Implementation of NRC Order EA-12-049 Mitigation Strategies for Beyond Design Basis External Events" 12. Letter dated June 16, 2015, from S. Monarque (NRC) to M. E. Reddemann (Energy Northwest), "Columbia Generating Station - Report for the Audit

Regarding Implementation of Mitigation Strategies and Reliable Spent Fuel

Pool Instrumentation Related to Orders EA-12-049 and EA-12-051" 13. Letter GO2-14-107 dated June 30, 2014, from D. A. Swank (Energy Northwest) to the NRC, "Energy Northwest's Phase 1 Response to NRC

Order EA-13-109 - Overall Integrated Plan for Reliable Hardened Containment Vents Under Severe Accident Conditions" 14. Letter GO2-14-175 dated December 17, 2014, from D. A. Swank (Energy Northwest) to the NRC, "Energy Northwest's First Six-Month Status Update

Report for the Implementation of NRC Order EA-13-109 - Overall Integrated Plan for Reliable Hardened Containment Vents Under Severe Accident Conditions" 15. Letter GO2-15-124 dated August 25, 2015, from D. A. Swank (Energy Northwest) to the NRC, "Energy Northwest's Fifth Six-Month Status Update

Report for the Implementation of NRC Order EA-12-049 Mitigation Strategies for Beyond Design Basis External Events" 16. Letter GO2-15-175 dated December 16, 2015, from A. L. Javorik (Energy Northwest) to the NRC, "Energy Northwest's Response to NRC Order Ea 109 -Overall Integrated Plan for Reliable Hardened Containment Vents Under Severe Accident Conditions Phases 1 and 2, Revision 1"