Text

Nine-Month Response to NRC Generic Letter 2008-01, Managing Gas Accumulation in Emergency Core Cooling, Decay Heat Removal, and Containment Spray Systems
	ML082970220
Person / Time
Site:	Fermi
Issue date:	10/14/2008
From:	Plona J; Detroit Edison
To:	; Document Control Desk, Office of Nuclear Reactor Regulation
References
	GL-08-001, NRC-08-0064
	Download: ML082970220 (30)
	v • d • e

Joseph H. Plona Site Vice President 6400 N. Dixie Highway, Newport, MI 48166 Tel: 734.586.5910 Fax: 734.586.4172 DTE Energy-GL 2008-01 October 14, 2008 NRC-08-0064 U. S. Nuclear Regulatory Commission Attention: Document Control Desk Washington D C 20555-0001

References:

1. Fermi 2 NRC Docket No. 50-341 NRC License No. NPF-43

2. NRC Generic Letter 2008-01, "Managing Gas Accumulation in Emergency Core Cooling, Decay Heat Removal, and Containment Spray Systems," dated January 11, 2008

3. Detroit Edison Letter to NRC, "Three-Month Response to NRC Generic Letter 2008-01," NRC-08-0032, dated April 11, 2008

4. NRC Letter to Detroit Edison, "Fermi 2-Re: Generic Letter 2008-01, Managing Gas Accumulation in Emergency Core Cooling, Decay Heat Removal, and Containment Spray Systems, Proposed Alternative Course of Action (TAC No. MD7827)" dated September 19, 2008

Subject:

Fermi 2 Nine-Month Response to NRC Generic Letter 2008-01, "Managing Gas Accumulation in Emergency Core Cooling, Decay Heat Removal, and Containment Spray Systems" The Nuclear Regulatory Commission (NRC) issued Generic Letter (GL) 2008-01 (Reference 2) to request that each licensee evaluate the licensing basis, design, testing, and corrective action programs for the Emergency Core Cooling Systems (ECCS), Decay Heat Removal (DHR) systems, and Containment Spray systems, to

USNRC NRC-08-0064 Page 2 ensure that gas accumulation is maintained less than the amount that challenges operability of these systems, and that appropriate action is taken when conditions adverse to quality are identified.

GL 2008-01 requested each licensee to submit a written response in accordance with 10 CFR 50.54(f) within nine months of the date of the GL to provide the information summarized below:

(a) A description of the results of evaluations that were performed pursuant to the requested actions. The description should provide sufficient information to demonstrate present or future compliance with the quality assurance criteria in Sections III, V, XI, XVI, and XVII of Appendix B to 10 CFR Part 50 and the licensing basis and operating license as those requirements apply to the subject systems.

(b) A description of all corrective actions, including plant, programmatic, procedure, and licensing basis modifications that were determined to be necessary to assure compliance with these regulations; and, (c) A statement regarding which corrective actions were completed, the schedule for completing the remaining corrective actions, and the basis for that schedule.

Detroit Edison submitted a 3-month response (Reference 3) to GL 2008-01 with a proposed alternative course of action for Fermi 2. The response stated that Fermi 2 could not meet the requested 9-month schedule for submitting the requested information because walkdowns of certain sections of the subject system piping cannot be completed during power operation. These sections of piping are inaccessible for the following reasons: (1) location inside the primary containment; (2) location in high radiation areas; (3) need to remove insulation from piping; or (4) the need to erect scaffolding. In Reference 4, NRC determined that the proposed alternative course of action was acceptable. The Enclosure to this letter contains Detroit Edison's nine-month response to GL 2008-01 in accordance with References 3 and 4.

Based on the evaluation provided herein, Detroit Edison has concluded that the subject systems or functions at Fermi 2 are in compliance with the Technical Specifications (TS) definition of Operability, i.e., capable of performing their intended safety function and that these systems or functions are in compliance with 10 CFR 50, Appendix B, Criteria III, V, XI, XVI and XVII, with respect to the concerns outlined in GL 2008-01 regarding gas accumulation. As committed in Reference 3, and requested in Reference 4, Detroit Edison will complete its assessment of those inaccessible portions of these systems or functions during the next Refuel Outage and provide a supplement to this response with those results

USNRC NRC-08-0064 Page 3 within 90 days from startup of the upcoming Refuel Outage but no later than July 31, 2009. Reference 3 provided a basis for acceptability of the proposed alternative course of action for Fermi 2 based on operating experience, testing, evaluation programs, and previous system walkdowns. In Reference 4, NRC found the proposed Fermi 2 course of action acceptable.

The following commitment which was originally made in Reference 3 is hereby revised based on the request in Reference 4.

Detroit Edison will complete its assessment of those inaccessible portions of the systems or functions during the next Fermi 2 Refuel Outage and provide a supplement to this report with those results within 90 days from startup of the upcoming Refuel Outage but no later than July 31, 2009.

Technical Specifications (TS) improvements are being addressed by the TS Task Force (TSTF) to provide an approved TSTF Traveler for making changes to standard TS related to the potential for unacceptable gas accumulation. The development of the TSTF Traveler relies on the results of the evaluations being performed to address the various plant designs. Detroit Edison is continuing to support the industry and NEI Gas Accumulation Management Team activities in the development of potential generic TS changes via the TSTF Traveler process and subsequent NRC review and approval in accordance with the Consolidated Line Item Improvement Process (CLIIP).

The following additional commitment is also made in this letter:

Detroit Edison will evaluate the applicability and the need to submit a license amendment request for adopting the pertinent CLIIP at Fermi 2 within 60 days of the issuance of the Notice of Availability in the Federal Register.

Should you have any questions regarding this submittal, please contact Mr. Ronald W. Gaston, Manager, Nuclear Licensing at (734) 586-5197.

Sincerely, Joe Pe lo. -

Enclosure

USNRC NRC-08-0064 Page 4 cc: NRC Project Manager NRC Resident Office Reactor Projects Chief, Branch 4, Region III Regional Administrator, Region III Supervisor, Electric Operators, Michigan Public Service Commission

USNRC NRC-08-0064 Page 5 I, Kevin J. Hlavaty, do hereby affirm that the foregoing statements are based on facts and circumstances which are true and accurate to the best of my knowledge and belief.

KEVIN J. AVATY Director, Nuclear Production and Plant Manager On this 1+ day of 6 -*OC+e ,2008 before me personally appeared Kevin J. Hlavaty, being first duly sworn and says that he executed the foregoing as his free act and deed.

Notary Public SHARON 8. 1AMRW~jq OTARYPUBUC, STATE.OFAT.

S # CO POFol 14 -J.

Enclosure to NRC-08-0064 Fermi 2 Nine-Month Response to NRC Generic Letter 2008-01

Enclosure to NRC 08-0064 Page 1 Table of Contents DESCRIPTION Page A. INTRODUCTION 2 B. EVALUATION RESULTS 3 I. Licensing Basis Evaluation 3

1. Review Summary 3

2. Changes to Licensing Basis Documents 4

3. Conclusion 5 II. Design Evaluation 5

1. Review of the Design Basis Documents 5

2. Gas Volume Acceptance Criteria 6

3. Drawing Review 8

4. System Confirmation Walkdowns 10

5. Procedure Review 11

6. Potential Gas Intrusion Mechanisms 14

7. Changes to the Design Basis Documents 18 III. Testing Evaluation 18

1. Surveillance Procedure Review 18

2. Surveillance Procedure Revision 18 IV. Corrective Action Program Evaluation 19 V. Conclusion of All Evaluations 19 C.

SUMMARY

OF CORRECTIVE ACTIONS AND SCHEDULE 20 Table 1: Refueling Outage Walkdown Items 22 Table 2: List of Regulatory Commitments 24

Enclosure to NRC 08-0064 Page 2 A. INTRODUCTION This Enclosure contains the Detroit Edison's nine-month response for Fermi 2 to NRC Generic Letter (GL) 2008-01 "Managing Gas Accumulation in Emergency Core Cooling, Decay Heat Removal, and Containment Spray Systems," dated January 11, 2008. In GL 2008-01, the NRC requested "that each addressee evaluate its ECCS, DHR, and Containment Spray systems licensing basis, design, testing, and corrective actions to ensure that gas accumulation is maintained less than the amount that challenges operability of these systems, and that appropriate action is taken when conditions adverse to quality are identified."

The following information is provided in this response:

(a) A description of the results of evaluations that were performed pursuant to the requested actions. The description provides sufficient information to demonstrate present or future compliance with the quality assurance criteria in Sections III, V, XI, XVI, and XVII of Appendix B to 10 CFR Part 50 and the licensing basis and operating license as those requirements apply to the subject systems; (b) A description of all corrective actions, including plant, programmatic, procedure, and licensing basis modifications that were determined to be necessary to assure compliance with these regulations; and, (c) A statement regarding which corrective actions were completed, the schedule for completing the remaining corrective actions, and the basis for that schedule.

The following systems or functions were determined to be included in the scope of GL 2008-01 for Fermi 2:

Emergency Core Cooling Systems (ECCS) o High Pressure Coolant Injection (HPCI) o Residual Heat Removal (RHR) Low Pressure Coolant Injection (LPCI) o Core Spray (CS)

Decay Heat Removal Systems (DHR) o RHR Shutdown Cooling (SDC) o RHR Suppression Pool Cooling

Containment Spray o RHR Containment Cooling (Drywell and Suppression Pool Sprays)

Enclosure to NRC 08-0064 Page 3 B. EVALUATION RESULTS I. Licensing Basis Evaluation The Fermi 2 licensing basis was reviewed with respect to gas accumulation in the ECCS, DHR, and Containment Spray Systems. This review included the Technical Specifications (TS), TS Bases, Updated Final Safety Analysis Report (UFSAR),

Technical Requirements Manual (TRM), TRM Bases, responses to NRC generic communications, Regulatory Commitments, and License Conditions.

1. Review Summary:

1.1 Technical Specifications (TS): The current Fermi 2 TS use the Standardized Technical Specifications format (NUREG-1433, Revision 1).

ECCS Systems:

Technical Specification Surveillance Requirement (SR) 3.5.1.3 states: "Verify, for each ECCS injection/spray subsystem, the piping is filled with water from the pump discharge valve to the injection valve." (Frequency 31 days) 1.2 TS Bases:

ECCS Systems:

TS Bases B 3.5.1 "ECCS - Operating" provides a description of the ECCS systems and the discharge charging water systems. TS Bases for SR 3.5.1.3 provides a justification for the 31 day frequency of the surveillance to ensure discharge lines are full of water.

No changes are identified to the TS and TS Bases as a result of the review. Refer to Section 2, "Changes to Licensing Basis Documents," for a discussion on industry efforts in the potential development of a standard TS improvement item.

1.3 Updated Final Safety Analysis Report (UFSAR)

UFSAR Section 3.9.1.2 "Dynamic Testing Procedures" includes a discussion of keep fill systems, system vents, and potential for introducing air in the systems.

The description for RHR and HPCI keep fill systems does not reflect current system configuration. A Condition Assessment Resolution Document (CARD) was written to revise UFSAR Section 3.9.1.2.b.3. Refer to Section 2, "Changes to Licensing Basis Documents," CARD 08-26690.

UFSAR Section 5.5.7.3.3 "Containment Cooling Subsystem" includes a discussion of the containment spray keep fill system and the operation of the system. The UFSAR Section states that lines are filled solid up to the outermost

Enclosure to NRC 08-0064 Page 4 containment isolation valve. A CARD was written to evaluate the term "filled solid" and revise the UFSAR, as necessary. Refer to Section 2, "Changes to Licensing Basis Documents," CARD 08-26381.

UFSAR Section 6.3.2.2.5 "ECCS Discharge Line Fill System," includes a discussion of the keep fill systems for ECCS systems. No potential changes were identified to this section.

1.4 Technical requirements Manual and Bases No relevant information was found in the TRM and TRM Bases.

1.5 Responses to Generic Communications GL 88-17, "Loss of Decay Heat Removal," was only applicable to Pressurized Water Reactors (PWRs). No actions were taken in response to this GL.

GL 97-04, "Assurance of Sufficient Net Positive Suction Head for Emergency Core Cooling and Containment Heat Removal Pumps," requested a review of the design bases analyses used to determine the available Net Positive Suction Head (NPSH) for ECCS (including CS and RHR) and Containment Heat Removal pumps. Adequate NPSH was shown to be available for the subject systems.

There were no operability concerns identified. No commitments were made in the response to the NRC.

1.6 Review of Regulatory Commitments Licensee Event Report (LER)85-060 included the following Regulatory Commitment: "All system procedures for systems having primary containment penetrations were revised to ensure that test, vent, and drain valves were specified to be in the closed position with the line capped."

1.7 License Conditions There are no relevant License Conditions for ECCS, RHR SDC or Containment Spray suction and discharge piping gas intrusion.

2. Changes to Licensing Basis Documents CARD 08-26380 was written to track the industry initiatives in the evaluation and development of a generic TS change based on the results of plant evaluations of GL 2008-01.

TS improvements are being addressed by the TS Task Force (TSTF) to provide an approved TSTF Traveler for making changes to standard TS related to the potential for unacceptable gas accumulation. The development of the TSTF

Enclosure to NRC 08-0064 Page 5 Traveler relies on the results of the evaluations being performed to address the various plant designs. Detroit Edison is continuing to support the industry and NEI Gas Accumulation Management Team activities in the development of potential generic TS changes via the TSTF Traveler process and subsequent NRC review and approval in accordance with the Consolidated Line Item Improvement Process (CLIIP).

UFSAR Section 5.5.7.3.3 states: "The RHR system is serviced by an automatic fill system that maintains the containment spray lines filled solid up to the outermost containment isolation valves." The industry, owner's groups, and the NRC have recognized that "filled solid" is not an accurate description. CARD 08-26381 was written to evaluate the UFSAR statement and revise as necessary.

UFSAR Section 3.9.1.2.b.3 states: "Air and steam voids that may develop in a stagnant system due to leakage are prevented in the RHR and Core Spray Systems by providing pump discharge check valves and automatic demineralized water charging on the pump discharge piping. The HPCI (and RCIC) pump lines do not need a charging system because the condensate storage tank provides the same function. The pump suction piping of these systems is pressurized by the condensate storage tank. These systems discharge to the Feedwater line from the pump. Thus, the water in the discharge piping cannot leak into the higher pressure Feedwater line." The UFSAR description does not reflect current configuration in that the RHR charging system is supplied by condensate water and HPCI discharge piping is provided with a charging system. CARD 08-26690 was written to revise the UFSAR statement regarding the keep fill systems for RHR and HPCI.

3. Conclusion Based on the licensing basis evaluation, Detroit Edison has determined that the current Licensing Basis for Fermi 2 adequately addresses the requirements of 10CFR50, Appendix A General Design Criteria, 10CFR50, Appendix B Quality Assurance Criteria, and IOCFR50.36, Technical Specifications.

II. Design Evaluation

1. Review of the Design Basis Documents The Design Basis Documents for RHR, CS and HPCI were reviewed. Below is a summary of the review.

1.1 Description of Keep Fill Systems RHR pump discharge lines are charged with condensate water and CS pump discharge lines are charged with demineralized water. Alarms are provided for RHR and CS fill line low pressure. During the initial fill, the discharge lines are

Enclosure to NRC 08-0064 Page 6 filled by manually venting the high point vents to avoid any trapped air pockets in the discharge lines. The piping is kept full to prevent water hammer when the pumps start and to minimize delay of LPCI and CS flow to the reactor.

The HPCI suction and discharge piping (up to the normally closed injection valve) is kept full by the static head from the Condensate Storage Tank. The HPCI discharge piping between the injection valve and pump discharge check valve is charged with condensate water to eliminate the possibility of forming a steam void near the injection valve. In addition to keep-fill, there is a cooling fin assembly mounted on the HPCI injection line in the steam tunnel. This helps to prevent a steam void from forming upstream of the HPCI injection valve.

1.2 Current Gas Accumulation Acceptability Currently there are no gas volume acceptance criteria for the piping on the suction side of the ECCS pumps. Both the piping and the pumps are at a lower elevation than the lowest level of the suction sources. In addition, calculations have set submergence levels high enough to prevent vortexing or air intrusion from the suction sources. The possible sources of air pockets are vertical valve bonnets, unvented piping locations, and the possibility of improperly sloped piping. The valve bonnet volumes are insignificant, the piping slope has been confirmed for all accessible piping and the potential for improperly sloped pipe or unvented

-piping locations in inaccessible areas will be identified in walkdowns during the refueling outage.

For pump discharge lines, the current acceptance criteria for the vented flow stream at the high point vent locations are not quantitatively monitored. The vented flow stream is monitored for symptoms that there may be a void. A void in the piping could be indicated by: lack of initial flow when the vent valve is cracked open, an interruption in the flow stream, or chugging of the flow stream.

Surveillance procedures require that any indication of voids be reported to the Shift Manager, and a CARD written to investigate the condition and take appropriate corrective action.

2. Gas Volume Acceptance Criteria The following describe industry.efforts performed to address GL 2008-01 and Detroit Edison's evaluation and utilization of these efforts.

2.1 Pump Suction Piping In order to address the need for a common acceptance criteria, the Boiling Water Reactor Owners Group (BWROG) established a program to define an acceptable gas void size that would not adversely affect the pump. Based on an evaluation of available gas intrusion data, it was determined that a 2% continuous suction gas void fraction is acceptable. In the unlikely event a void fraction existed of this

Enclosure to NRC 08-0064 Page 7 magnitude, system operability would still need to be assessed by comparing the effects of air intrusion on the Net Positive Suction Head (NPSH) required to the available NPSH. However, this criterion was not used in the evaluation performed for GL 2008-01.

For Boiling Water Reactor (BWR) ECCS systems, suction gas voids are not expected to occur. However if a gas void was found in a suction line, it would be expected to be a fixed finite volume. Industry guidance recommends that an average void fraction less than 10% can be tolerated for a period no greater than 5 seconds. This criterion was used in the evaluation performed for GL 2008-01.

2.2 Pump Discharge Piping A Joint Owner's Group program evaluated pump discharge piping gas accumulation. Gas accumulation in the piping downstream of the pump to the first closed isolation valve or the Reactor Coolant System (RCS) pressure boundary isolation valves will result in amplified pressure pulsations after a pump start. The subsequent pressure pulsation may cause relief valves in the subject systems to lift, or result in unacceptable pipe loads. The Joint Owner's Group program established a method to determine the limit for discharge line gas accumulation to be utilized by the member utilities.

The method uses plant specific information for piping restraints and relief valve set points in the subject systems to determine the acceptable gas volume accumulation.

Detroit Edison used this methodology for Fermi 2 and established the applicable limits for gas accumulation in the discharge piping of the HPCI, CS and RHR systems. The applicable limits were used to evaluate potential areas where gas may be trapped as identified from drawing reviews and system walkdowns.

Additional details are provided under the Drawing Review and System Confirmation Walkdowns sections below.

2.3 Downstream ECCS Piping Analysis In order to provide guidance to address voiding in the ECCS system piping from the first closed isolation valve to the vessel, a BWROG study was performed.

The analysis of ECCS piping downstream of the injection valves has shown that, except for HPCI, the existence of air voids in this piping will have no adverse consequences related to accident conditions. Even if small voids did exist the pressure transient would not be greater than an actual injection during an accident.

Due to the wide variety in plant piping configurations for HPCI the report did not make any definitive statements concerning HPCI. A drawing review for the Fermi 2 HPCI to Feedwater piping layout shows that it is a short run that ties into the bottom of the Feedwater line. This section of piping is filled from the

Enclosure to NRC 08-0064 Page 8 Feedwater line initially and should remain full. Small air pockets due to minor slope issues would be similar to the other ECCS systems. Even if a small void exists, the pressure transient would not be greater than an actual injection during an accident.

2.4 Effects of RCS Gas Ingestion The BWROG prepared a report to determine the Potential Effects of Gas Intrusion on ECCS Analysis.

A conservative "worst case" scenario evaluation determined a limiting Loss of Coolant Accident (LOCA) Peak Cladding Temperature (PCT) heatup rate of 12 degrees Fahrenheit per second for the U.S. BWR fleet. Using this heatup rate, 48°F of PCT impact is assessed with a maximum of 4-second delay in the ECCS actuation.

An assessment justified that gas voids passing through the core do not pose an additional safety concern mainly because of the unlikely path for air to get into the core and high void conditions already present in the core during a LOCA.

Assessments on the Loss of Feedwater (LOFW) and Anticipated Transient Without Scram (ATWS) events concluded that a 5 second delay in ECCS flow would not significantly affect the analysis results and have no impact on meeting the acceptance criteria. The evaluation of station blackout events indicated that a 10 second delay would not impact the ability of the water makeup system to maintain the vessel water level above the top of active fuel. Similarly, it is concluded that a 10 second delay would have an insignificant impact on meeting the acceptance criteria in Appendix R fire safe shutdown analysis.

3. Drawing Review 3.1 General Local high points in the piping systems were identified from isometric and Piping and Instrumentation (P&ID) drawings. These drawings were selected because they represent the entire piping system; whereas, walkdown inspections are limited by floors, walls, obstructions and limited accessibility. The piping systems in the GL 2008-01 scope were previously addressed within the scope of NRC Bulletin 79-14, "Seismic Analyses for As-Built Safety-Related System."

As-built walkdowns of the affected piping were completed and pertinent drawing revisions made. The piping dimensions shown on the isometric drawings are accurate within + 2 inches.

Enclosure to NRC 08-0064 Page 9 3.2 Scope The extent of drawing review included all main runs and all branch piping that is pressurized during each mode of operation. However, instrument lines were examined separately and are not included in this drawing review scope. Refer to the discussion under "Fill and Vent Procedure Review" below.

3.3 Identification of the High Points Isometric and P&ID drawings were reviewed along with the one line elevation profile drawings. All areas vulnerable to gas accumulation were highlighted on the isometric drawings and recorded for further evaluation. The review included the following items for consideration as areas potentially vulnerable to gas accumulation:

" High points in pipe runs, including elevation variation in nominally horizontal pipes

" High points created by closed valves in vertical piping runs

" Heat exchanger U-tubes and other equipment high points

" Horizontal pipe diameter transitions that introduce traps at the top of the larger piping or piping upstream of components (orifice plates or reducers)

" Tees where gas contained in flowing water can pass into a stagnant pipe where it accumulates

" Valve bonnets

" Pump casings 3.4 Results Analytical assessments were performed for each of the vulnerable locations to determine if the quantity of potentially trapped gas could adversely impact system function. To perform these assessments, credit was taken for the fact that major portions of these systems are dynamically vented during surveillance runs or following maintenance and post modification testing. Therefore, these assessments concentrated on those portions of piping that contain stagnant fluid sections.

An analytical assessment was performed assuming any one of the subject systems were to initiate with an air void size equal to the maximum possible size as determined from the drawing review. The assessment concluded that the resulting pressure disturbance may be large enough to lift the system's suction or discharge relief valves; however, it would not cause a peak pressure or support loading that exceed operating limits associated with the transient. Lifting a relief valve would not prevent the system from performing its design function. The relief valve would close shortly after the initial pressure disturbance because the system operating pressure is lower than the relief valve reseat pressure.

Enclosure to NRC 08-0064 Page 10 Furthermore, the maximum postulated suction air void size is less than industry guidance limits and will not adversely affect pump operability. Therefore, the quantity of potentially unvented gas that was identified during the drawing review will not adversely impact the function of any of the systems within the scope of the GL.

3.5 New or Modified Vent Valve Locations from Drawing Review The drawing review identified that a vent on a 22 ft horizontal pipe section of the Div. 1 Core Spray injection piping is not located at the pipe high point. This segment of piping is located in a high radiation area and therefore, this condition has not been validated by walkdown. An engineering evaluation was performed to estimate the dynamic effects on the CS system, assuming that an air bubble exists in this section of piping upon system initiation. It was concluded that the estimated peak pressure and unbalanced forces will not adversely impact the CS system function. CARD 08-20407 includes an action item to evaluate the need to relocate this vent.

4. System Confirmation Walkdowns 4.1 Description of Walkdowns Walkdowns of the accessible HPCI, CS, and RHR Systems were performed to confirm drawing configuration and identify piping sections which would be susceptible to gas intrusion/accumulation.

A walkdown checklist was developed to gather pertinent data for accessible piping, including the following:

Pipe slope

" Location of high point vents

Location of pump casing vents Since the potential for the volume of trapped gas in short horizontal piping segments is negligible, walkdown teams were instructed to obtain slope measurements on accessible horizontal piping with lengths of 8 feet or greater.

Insulation is installed on all RHR, CS and HPCI piping outside the HPCI pump room. HPCI piping in the [PCI pump room is not insulated. Digital levels with an accuracy of +/- 0.1 degrees were used to determine the slope of horizontal runs.

The levels were placed on top of uniform sections of metal jacket insulated piping to determine the slope. Slopes of piping with blanket insulation will be measured during the upcoming refueling outage, as necessary. -

Enclosure to NRC 08-0064 Page 11 High point vent and pump casing vent locations were evaluated against the design drawings to verify proper installation.

4.2 Summary of Results As a result of the walkdown effort, no discrepancies were identified between the design drawings and the field location of high point or pump casing vents.

Review of the slope measurement results concluded that the volume of air associated with any pipe slope is small. Based on the air void acceptance criteria developed for Fermi 2, there is adequate margin available to account for slope measurements with slight variations from the slope shown on design drawings.

4.3 Refueling Outage Walkdowns Table 1 provides a list of piping sections that have not been walked down and the reason the walkdown was not performed. The Table consists of piping sections that are not flushed and filled by the surveillance runs. As stated in Section 3.4 above, credit was taken for dynamic venting during surveillance runs.

4.4 New or Modified Vent Valve Locations from Walkdowns There are no new or modified vents needed as a result of the walkdown effort.

Additional actions may be taken following the walkdowns that will occur during the next Refueling Outage.

5. Procedure Review 5.1 Fill and Vent Procedure Review The following general fill and vent process is used for all the subject systems:

Perform/verify pre-fill/standby valve lineup.

Align a source of makeup water. For RHR and Core Spray, the keep fill/makeup source is located high in system. For HPCI, the CST on the suction side of the pump is the source and uses gravity to fill the system.

Allow makeup system to fill and pressurize the system.

Vent the system and major components in the standby configuration and cycle and vent test lines/alternate configurations.

Continue venting until air free water is observed flowing from the vent.

Following outages and significant maintenance activities, operating procedures are used to refill the subject systems. These procedures coupled with surveillance test procedures provide the means to fill and vent the subject systems as well as purge air and other non condensable gases from associated piping and

Enclosure to NRC 08-0064 Page 12 components. No new procedures are required to control venting of the subject systems.

The fill and vent procedures were evaluated to determine if the sequence of steps was effective and whether or not adequate acceptance criteria were provided. In each case, the sequence of steps was found to be effective. Acceptance criteria for venting activities, and generic guidance for terminating the venting process requires venting to continue until air free water is observed flowing from the vent hose.

Generic direction is given in the instrument lineup to ensure that the instrument is ready for service, this includes local instrument rack lineup, power available to the instrument and any necessary venting or backfilling is accomplished.

The application of fill and vent procedures to system restoration following maintenance during plant operation in Modes 1 thru 4 was also evaluated. The procedures include modified instructions for venting sections of systems following normal routine maintenance activities. Return to service fill and vent instructions verify the system is filled with water and vents within the maintenance boundary are utilized to vent the system. The operability surveillance is run for Post Maintenance Testing (PMT). Any of these runs would dynamically vent the test flow path. Calculations performed show that, at normal system flow rates, potential air pockets in the suction and discharge lines will be swept downstream of downward sloping pipes.

5.2 Revisions to Fill and Vent Procedures No procedure revisions were identified to maintain compliance.

Several procedure enhancements were identified as a result of the review as stated below. The schedule for corrective action completion is provided in the summary under Section C of this Enclosure.

A recommendation was made to revise the core spray procedure 23.203 (section 5.1 & 5.2) to add a step to vent the drywell penetration at valves F013/F014 before the inboard isolation valve F005 is closed. CARD 08-26406 has been generated to track the evaluation of this recommendation.

A recommendation was made to revise HPCI procedure, 23.202 (section 5.1), to vent at the suction high point at valves F037/F038. Also, additional venting was recommended at test line inboard vent valves F156/F157. Another recommendation was made to add a step to perform a high point vent when swapping the suction back to the CST from the suppression pool if the system was in standby without the keep fill system in operation for more than an hour.

CARD 08-26407 has been generated to track the evaluation of this recommendation.

Enclosure to NRC 08-0064 Page 13 A recommendation was made to revise RHR procedure 23.205 to direct operator actions in the event that the SDC supply piping is inaccessible for fill and venting.

CARD 08-26410 has been generated to track the evaluation of this recommendation.

A recommendation was made to revise RHR procedure 23.205 (section 5.1, 5.2, 5.3, 5.4, & 5.7) to open the RHR LPCI bypass valve F61 1.during venting of the LPCI injection piping. Also, another recommendation was made to open the RHR SDC inboard suction bypass valve F608 during the venting of the SDC supply piping. CARD 08-26413 has been generated to track the evaluation of this recommendation.

A recommendation was made to revise CS, HPCI, and RHR procedures to require high point venting upon restoration after loss of keep fill pressure to avoid void formation at high points. CARD 08-2641.7 has been generated to track the evaluation of this recommendation.

5.3 Review of RHR Manual Operation Procedure Shutdown Cooling is a mode of operation of the RHR system. This mode is a non-safety related mode (reference UFSAR 5.5.7) used to transfer reactor core decay heat and reactor primary system sensible heat to the RHR Service Water in order to permit cooldown and to maintain the reactor in a cold shutdown condition for refueling and servicing. This mode is activated after the reactor pressure has been reduced by the discharge of steam from the reactor to the main condenser or suppression pool to a pressure that will not result in over pressurization of the RHR low design pressure piping. This mode is activated manually by operator action.

The RHR System Operating Procedure directs the placement of RHR in the Shutdown Cooling mode. These steps are summarized below (one Division is placed in service):

RHR Pumps placed in OFF/Reset

Suppression Pool Suction Valves closed

RHR Shutdown Down Cooling Suction Isolation valves opened

Minimum Flow valve closed

LPCI discharge piping, up to LPCI Inboard Isolation Valve, is vented

RHR Heat Exchanger is vented

" Shutdown Cooling suction line is vented (using Keep Fill)

Keep Fill is isolated

Injection piping is flushed and warmed to 200 degrees Fahrenheit by allowing reactor water to flow backwards through the RHR discharge line to the suppression pool via the warmup line

Enclosure to NRC 08-0064 Page 14

RHR system suction is flushed and warmed to 200 degrees Fahrenheit by allowing reactor water to flow from the RHR suction connection to the Reactor Recirculation system through the RHR pumps and heat exchanger bypass line to the suppression pool via the warmup line

" RHR system is vented at high point vents

RHR Pump is placed in Shutdown Cooling mode of operation

" Keep Fill is restored Pump operation is monitored locally by the Reactor Building Rounds Operator at least once per shift. The Operator in the Control Room can monitor pump operation by observing pump discharge pressure (indicator), pump current (indicator), loop flow (recorder and indicator), heat exchanger inlet and outlet temperature (recorder), and by reactor coolant high temperature alarms.

The safety related decay heat removal function of the RHR system is the suppression pool cooling mode (Emergency Operation). This mode of operation is designed to remove reactor core decay heat and sensible heat from the suppression pool following a LOCA. This manually controlled mode is required to be initiated following a LOCA to limit containment pressure and temperature to acceptable values.

The suppression pool cooling line is also known as the test line. This test line is used during the quarterly Pump and Valve Operability surveillance and is also used to support testing of systems that add heat to the Suppression pool.

Therefore, this line is dynamically vented at a minimum frequency of once per quarter.

6. Potential Gas Intrusion Mechanisms The following potential gas intrusion mechanisms were reviewed:

6.1 Accumulators or Other High-Pressure Sources Of the systems in the scope of GL 2008-01, only RHR uses an accumulator with a gas blanket for maintaining pressurized conditions in the system during standby or operation. A keep fill system is used to maintain the RHR pump discharge piping system filled to prevent water hammer during startups. This keep fill system maintains pressure with a compressed air tank. The tank is used to provide a constant supply pressure to the distribution header. The pressure conditions in the keep fill system are the same as in the RHR discharge piping. A loss of keep fill pressure in the RHR system could allow gas to come out of solution, creating voids. A malfunction of the keep fill system is detected by a pressure indicator and alarm located on the RHR pump discharge piping. This pressure indicator and alarm will alert operators to abnormal keep fill conditions.

Enclosure to NRC 08-0064 Page 15 Proper steps will be taken to restore keep fill and ensure the system is properly vented.

6.2 RCS Leakage It is possible that the RCS or Feedwater system could leak into an ECCS system, where the pressure is lower. This water is reactor water and generally will have low levels of dissolved gas present. However, leakages of significant amounts of RCS inventory would increase the ambient pressure and temperature, likely causing some flashing, and the possible opening of the relief valve. Leakage is unlikely in these systems because there are two containment valves which are tested for seat leakage on aperiodic basis. If leakage does occur, there are sufficient controls in place to detect leakage.

6.3 Pressure Reduction The suctions of the ECCS systems are either from the suppression pool or CST.

There are no control valves or elevation changes in the suction piping to create pressure reductions which would cause gas to come out of solution.

During testing, HPCI draws suction from the CST and returns water to the CST.

After testing, a fill and vent is performed prior to placing HPCI back in standby mode.

The RHR system contains flow restricting orifices, which are located in the warm-up/flush line, the RHR test lines, the RHR injection valve bypass lines, and the RHR minimum flow lines. Multiple flow orifices in the injection valve bypass lines and the test lines are arranged in series to minimize the pressure drop across a single orifice while still controlling flow to required rates. The warm-up/flush line orifice and the minimum flow line orifices are used in modes of operation where the flow rates are 500 gpm or less. These orifices have significant pressure drops that could cause dissolved gases to come out of solution downstream. However, the flow path for these gas voids is to the suppression pool. Gas bubbles would be swept to the RHR test line and would not adversely affect system functions.

6.4 Incorrect Maintenance and Testing The HPCI pump surveillance procedure operating alignment in test mode ensures that the alignment does not generate or introduce voids in the system. After the pumps are run, a fill and vent of HPCI is required prior to returning the system to Standby. This removes high temperature water in the discharge piping in addition to venting any voids.

Enclosure to NRC 08-0064 Page 16 The alignment of the keep fill system is done while aligning the HPCI system into Standby Mode. After opening the keep fill isolation valve, a HPCI discharge line high point venting is performed to remove any air/gas pockets in the line.

The HPCI system operating procedure addresses loss of keep fill pressure while suction is aligned to the suppression pool in the precautions and limitations section. It states that should HPCI suction be aligned to the suppression pool (in standby) for more than twelve consecutive hours without keep fill in service that the system be considered inoperable. It also recommends a discharge line high point vent upon realignment to the CST as addressed above.

Filling and venting of the RHR system will occur subsequent to maintenance activities on the system. Filling of the RHR system is made from the Condensate Storage System. Provisions are included in the system operating procedure to prevent certain events such as voiding of the RHR piping due to failure of injection check valve to open during pre-warming of the RHR piping.

6.5 Level Instruments Potential Failure The CST and Suppression pool levels are checked every 12 hours1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months (Tech Spec SR 3.5.2.1 and SR 3.5.2.2). The levels for the suppression pool and CST are each monitored by redundant level indicators; therefore no submergence issues or vortexing concerns were identified that could affect the ECCS systems.

6.6 Isolation Valve or Check Valve Leakage The only location where two ECCS systems are connected is at the HPCI minimum flow line where it ties into the Core Spray test line en route to the suppression pool. Any air / gas pockets would be carried into the suppression pool.

The interface between the RHR system to the Reactor Recirculation System (RRS) presents the opportunity for leakage through isolation valves and check valves. There are two containment isolation valves located between these systems. They are required to be leak rate tested per Technical Specifications.

The isolation valves will effectively isolate these systems, thereby eliminating gas intrusion concerns from the Reactor Coolant System.

6.7 Higher Temperature Effects The only location in the HPCI system where heat conduction is a possibility is at the HPCI discharge injection valve. This valve is connected at the Feedwater discharge header. As a result of past fluid transients, approximately five feet of pipe fins were added to dissipate heat transfer as a result of any postulated heat conduction and injection valve in-leakage from the Feedwater side. In addition, a

Enclosure to NRC 08-0064 Page 17 keep fill system was also added to enhance elimination of vapor voids at the injection valve.

The HPCI test procedures instruct the operator to startup the system with the discharge valve closed, and then throttle open the test line isolation valve to maintain pressure in the injection piping and prevent voiding. Based on the discussion herein, there is no concern regarding vapor voiding at the HPCI discharge injection valve.

There are two containment isolation valves between the RRS and the RHR system. These valves are leak rate tested periodically and can be reasonably assumed to isolate. Heat conduction due to the higher RCS fluid temperature as compared to the RHR system fluid temperature through the piping and isolation valves has the potential to introduce voiding in the RHR system piping if the fluid is heated to its saturation temperature. However, the fluid in the piping between the RCS and the RHR system is stagnant and acts as a heat sink. The keep fill pressure on the RHR system provides adequate fluid sub-cooling margin to bound the postulated heat conduction effect. Also, pressure indicators/alarms can indicate voiding in the RHR piping due to excessive temperature increases.

Therefore, it is unlikely that the RCS would conduct enough heat to the RHR system to cause gas voids to form. Additionally, any significant RCS leakage into the RHR system would be detected.

The only location in the CS system where heat conduction is a possibility is at the CS discharge injection valve. This is unlikely to present a problem since the CS system is separated from the RCS by two isolation valves and has the keep fill system to maintain the system at an elevated pressure thus raising the saturation temperature.

6.8 Vortices and Suction Swap The HPCI system suction line is designed to prevent vortex formation and air ingestion during operation. HPCI suction is transferred from the CST to the suppression pool on low level to preclude vortex formation in the suction line.

The CS and RHR systems take their suction from the suppression pool. In accordance with Technical Specification Surveillance Requirement 3.5.2.1 and 3.5.2.2, the suppression pool level is verified every 12 hours1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months to be within two inches of the normal water level. This provides adequate NPSH and prevents potential vortex formation or gas entrainment in the suction side of these systems.

The CST level is also verified every 12 hours1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months to be above the level required for adequate NPSH.

Enclosure to NRC 08-0064 Page 18

7. Changes to the Design Basis Documents No changes to Design Basis Documents have been identified.

III. Testing Evaluation

1. Surveillance Procedure Review Periodic fill verification is required for each ECCS injection/spray subsystem from the pump discharge valve to the injection valve in accordance with Fermi Technical Specification Surveillance Requirement SR 3.5.1.3.

Fill verification is performed until an air free stream of water is observed flowing from the vent hose. The vented flow stream is monitored for indications that there may be a void in the piping being vented. Indications that there may be a void in the piping would be: no initial flow when the vent valve is cracked open, an interruption in the flow stream, or chugging of the flow stream.

Periodic fill verification procedures specify vent points that are used to ensure the subject piping is sufficiently full of water for each subsystem. Systems are not preconditioned by other surveillance tests prior to performing the periodic fill verification procedures.

Surveillance procedures require that if any venting operation indicates that the system is not filled with water, a CARD be generated to investigate and correct the cause of the void, and the condition is reported to the Shift Manager.

2. Surveillance Procedure Revision Fill verification procedures require initiating a CARD if air is detected during the performance of the procedure. They also require venting for at least two minutes at locations where the piping to be vented is up in the overhead and the vent line is routed down to where the vent valves can be operated from the floor. The two minutes requirement accounts for venting the dead leg of the vent line piping.

Based on the surveillance procedure performed, it is concluded that the procedures are adequate.

One enhancement was identified to revise the CS, HPCI, and RHR surveillance procedures to include venting and post-venting actions such as recording observations and/or gas volumes. CARD 08-26419 has been generated to track the evaluation of this recommendation.

Enclosure to NRC 08-0064 Page 19 IV. Corrective Action Program Evaluation Detroit Edison's Corrective Action Program is used to document gas intrusion/accumulation issues as potential nonconforming conditions. Existing procedures for the ECCS, RHR and Containment Spray require a CARD to be initiated, and the Shift Manager notified if the accumulated gas volume acceptance criteria specified in the procedures are exceeded. As part of Detroit Edison's Corrective Action Program, CARDs related to plant equipment are evaluated for potential impact on operability and reportability. Therefore, Detroit Edison's review concluded that issues involving gas intrusion/accumulation are properly prioritized and evaluated under the Corrective Action Program.

V. Conclusion of All Evaluations Based on the evaluations described above, Detroit Edison has concluded that the subject systems or functions at Fermi 2 are in compliance with the TS definition of Operability, i.e., capable of performing their intended safety function and that these systems or functions are in compliance with 10 CFR 50, Appendix B, Criteria III, V, XI, XVI and XVII, with respect to the concerns outlined in GL 2008-01 regarding gas accumulation. As committed in Reference 3, and requested in Reference 4, Detroit Edison will complete its assessment of those inaccessible portions of these systems or functions during the next Refuel Outage and provide a supplement to this response with those results within 90 days from startup of the upcoming Refuel Outage but no later than July 31, 2009. Reference 3 provided a basis for acceptability of the proposed alternative course of action for Fermi 2 based on operating experience, testing, evaluation programs, and previous system walkdowns. In Reference 4, NRC found the proposed Fermi 2 course of action acceptable.

Enclosure to NRC 08-0064 Page 20 C.

SUMMARY

OF CORRECTIVE ACTIONS AND SCHEDULE The table below provides a summary of corrective action documents generated as a result of the evaluation performed for GL 2008-01. No corrective actions were identified as necessary to address the GL; however, many enhancements to procedures and processes have been identified as described below in addition to the status or schedule for action completion and the basis for the schedule.

CARD Description Status / Schedule Basis Licensing Document Review 08-26380 Evaluate need for TS change based on Within 60 days from Industry industry TSTF being developed and issuance of CLIIP schedule NRC approval of a CLIIP Notice of Availability 08-26381 Evaluate statement in UFSAR Section Change will be Enhancement to 5.5.7.3.3 regarding containment spray processed with the UFSAR lines being filled solid up to the next 10 CFR 50.71e description outermost containment isolation required update, valves. expected in October 2009 08-26690 Revise UFSAR Section 3.9.1.2.b.3 to Change will be Correction to reflect current configuration for RHR processed with the UFSAR and HPCI systems. next 10 CFR 50.71e description required update, expected in October 2009 Design (Drawing) Review 08-20407 Evaluate the need to relocate a vent Walkdown next Engineering Action near a 22 ft horizontal pipe section of refueling outage and evaluation of Item 42 Div 1 Core Spray injection piping. relocate vent, as condition necessary Procedures Review 08-26406 Evaluate recommendation to revise Complete procedure Enhancement to core spray procedure 23.203 to add a revision, as procedure step to vent the drywell penetration at necessary, by July 15, valves F013/F014 before valve F005 2009 is closed.

Enclosure to NRC 08-0064 Page 21 CARD Description Status / Schedule Basis 08-26407 Evaluate recommendation to revise Complete procedure Enhancement to HPCI procedure 23.202 to vent the revision, as procedure suction high point at valves necessary, by July 15, F037/F038. Also, the last pump 2009 discharge header vent should consider including another vent at valves F156/F157.

Evaluate recommendation to add a step to perform a high point vent when swapping the suction back to CST from the suppression pool if the system was in standby without the keepfill system in operation for more than an hour.

08-26410 Evaluate recommendation to revise Complete procedure Enhancement to RHR procedure 23.205 to direct revision, as procedure operator actions in the event that SDC necessary, by July 15, supply piping is inaccessible for filling 2009 and venting.

08-26413 Evaluate recommendation to revise Complete procedure Enhancement to RHR procedure 23.205 to open F611 revision, as procedure during venting of the LPCI injection necessary, by July 15, piping. Also, consider opening valve 2009 F608 during venting of the SDC supply piping.

08-26417 Evaluate recommendation to revise Complete procedure Enhancement to Core Spray, HPCI, and RHR revision, as procedure procedures to require high point necessary, by July 15, venting upon restoration after loss of 2009 keep fill pressure to avoid void formation at high points.

08-26419 Evaluate recommendation to revise Complete procedure Enhancement to Core Spray, HPCI, and RHR revision, as procedure surveillance procedures to include necessary, by July 15, venting and post-venting actions such 2009 as recording observations and/or gas volumes.

Walkdown 08-20407 Complete walkdowns of inaccessible Complete walkdowns Basis provided Action portions of the systems during the next by April 25, 2009. in 3-month Items 23 Refuel Outage. Submit results to letter dated and 24 NRC 90 days after April 11, 2008 I refueling outage

Enclosure to NRC 08-0064 Page 22 Table 1 Refueling Outage Walkdown Items System Isometric Piping Section Reason Not Performed Number CS Div 1 M-3052-2 All horizontal piping Location in primary containment.

in the Drywell M-3144-2 Wall penetration at Locked high radiation area. RWCU elevation 628-0 1/16" Heat Exchanger Room.

to Drywell Note: Dose levels will not significantly penetration X-16B change when the Plant is shutdown.

CS Div 2 M-3053-2 All horizontal piping Location in primary containment.

in the Drywell HPCI M-3167-2 From elbow at Needs Scaffold.

elevation 555'-6 1/8" to wall penetration From elbow at Needs scaffold (Torus Room).

elevation 575'-0 1/2" (south of column 11) to elbow going up to floor penetration From elbow at High radiation area (Steam Tunnel).

elevation 587'-5 9/16" to E4100GO01 (Fins)

M-3163-2 From elbow south of Insulation needs to be removed.

hanger G13 to MOV E4150F042 (Torus Room)

RHR M-3152-2 From hanger G15 to Needs scaffold (Outside of Torus). May hanger G04 at also require insulation to be removed.

elevation 572'-6" (Torus Room)

SDC suction line Needs scaffold (outside of Torus and from elbow at crosses over Torus). May also require elevation 578'-5 1/4" insulation to be removed.

to relief valve (El 100F029) and vents at elevation 591'

Enclosure to NRC 08-0064 Page 23 Table 1 (continued)

Refueling Outage Walkdown Items System Isometric Piping Section Reason Not Performed

_ Number I RHR M-3146-2 RHR pump discharge Needs scaffold (outside of Torus and

& piping from division 1 crosses over Torus). May also require M-3151-2 Test line to division 2 insulation to be removed.

test line and vents at elevation 594' M-3146-2 SDC bypass around Insulation requires removal.

F017A M-3151-2 24" header to F017B Insulation requires removal. May require scaffold.

SDC bypass around Insulation requires removal. May F017B require scaffold.

M-3159-2 Division 1 Drywell Needs scaffold. May also require spray line at elevation insulation to be removed.

578-6" from elbow at N369'-3 7/8" /E399'-

10 5/16" to elbow at N365'-10 5/8"/E410'-

8 1/4" (Torus Room)

M-3164-1 Division 2 Drywell Needs scaffold. May also require spray line at elevation insulation to be removed.

578'-0 1/8" (Torus Room)

Division 2 Drywell No access to top of pipe. Measuring spray line at elevation slope will require blue spray guard and 630'-9"(RB2 outside metal insulation removed. Slope will of south RWCU have to be taken from bottom of pipe.

pump room)

M-2298-2 All horizontal piping Location in primary containment.

in the Drywell.

division 1 LPCI injection line M-2299-2 All horizontal piping Location in primary containment.

in the Drywell. SDC suction line.

M-2327-1 All horizontal piping Location in primary containment.

in the Drywell.

division 2 LPCI injection line

Enclosure to NRC 08-0064 Page 24 Table 2 List of Regulatory Commitments The following table identifies those actions committed to by Detroit Edison in this document. Any other statements in this submittal are provided for information purposes and are not considered to be regulatory commitments. Please direct questions regarding these commitments to Mr. Ronald W. Gaston, Manager, Nuclear Licensing at (734) 586-5197.

REGULATORY COMMITMENTS DUE DATE / EVENT

1. Detroit Edison will complete its Within 90 days from startup of the assessment of those inaccessible upcoming Refuel Outage but no later portions of the systems or than July 31, 2009 functions during the next Fermi 2 Refuel Outage and provide a supplement to this report with those results

2. Detroit Edison will evaluate the Within 60 days of the issuance of the applicability and the need to Notice of Availability in the Federal submit a license amendment Register request for adopting the pertinent CLIIP at Fermi 2