MNS-15-093, Response to Request for Additional Information Regarding License Amendment Request Regarding Residual Heat Removal System

Response to Request for Additional Information Regarding License Amendment Request Regarding Residual Heat Removal System

ML15331A039
Person / Time
Site:	McGuire
Issue date:	11/13/2015
From:	Capps S Duke Energy Carolinas
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
CAC MF6666, MNS-15-093
Download: ML15331A039 (17)

Text

DU ESteven D.Cap ENERGY°Vice President ERGYSMcGuire Nuclear Station Duke Energy MGO1VP 1 12700 Hagers Ferry Road Huntersville, NC 28078 o: 980.875.4805 f: 704.875.4809 Steven.Capps@duke-energy.com Serial No: MNS-15-093 10CFR 50.90 November 13, 2015 U.S. Nuclear Regulatory Commission Washington, DC 20555-001 ATTENTION: Document Control Desk

Subject:

Duke Energy Carolinas, LLC (Duke Energy)

McGuire Nuclear Station, Unit 1 Docket No. 50-369 Renewed License No. NPF-9 Response to Request for Additional Information Regarding License Amendment Request Regarding Residual Heat Removal System (CAC No. MF6666)

In a letter dated August 28, 2015, Duke Energy requested a one-time change to TS 3.5.2, "Emergency Core Cooling Systems (ECCS) - Operating." In a letter dated October 26, 2015, the NRC submitted Requests for Additional Information (RAIs). Enclosure 1 of this letter provides Duke Energy's response to those RAIs. to Enclosure 1 contains a table of regulatory commitments that supersedes the commitments made in the August 28, 2015, submittal letter.

Pursuant to 10 CFR 50.91, a copy of this letter has been forwarded to the appropriate North Carolina state officials.

Please direct any questions you may have in this matter to Brian Richards at (980) 875-5171.

I declare under penalty of perjury that the foregoing is true and correct. Executed on November 13, 2015.\\

Sincerely, Steven D. Capps Enclosure

1. Response to Request for Additional Information

)

U.S. Nuclear Regulatory Commission November 13, 2015 Page 2 cc wI/Attachments:

C. Haney Administrator, Region II U.S. Nuclear Regulatory Commission Marquis One Tower 245 Peachtree Center Ave., NE, Suite 1200 Atlanta, GA 30303-1257 J. Zeiler NRC Senior Resident inspector McGuire Nuclear Station G. E. Miller, Project Manager U.S. Nuclear Regulatory Commission 11555 Rockville Pike Mail Stop 0-8 G9A Rockville, MD 20852-2738 W. L. Cox, Ill, Section Chief North Carolina Department of Environment and Natural Resources Division of Environmental Health Radiation Protection Section 1645 Mail Service Center Raleigh, NC 27699-1 645 Response to RAIs

Enclosure I Page 2 of 8 REQUEST FOR ADDITIONAL INFORMATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO A LICENSE AMENDMENT REQUEST REGARDING A TEMPORARY EXTENSION TO RESIDUAL HEAT REMOVAL ALLOWED OUTAGE TIME DUKE ENERGY CAROLINAS. LLC MCGUIRE NUCLEAR STATION. UNIT I DOCKET NO. 50-369 By letter dated August 28, 2015 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML15244B179), Duke Energy Carolinas, LLC (Duke Energy) submitted a license amendment request (LAR) to temporarily change McGuire Nuclear Station, Unit 1, Technical Specifications (TSs) for correction of a degraded condition affecting the 1A Residual Heat Removal pump motor air handling unit.

Based on the NRG staff's review of this amendment request, the NRG staff has determined the following additional information is necessary to support completion of its technical review:

RAIl1

Background:

Duke Energy stated in the amendment that defense-in-depth measures will be installed for the duration of the repairs to the 1 A residual heat removal (RHR) air handling unit (AHU).

Issue:

Engineering change process was used to provide reasonable assurance that the defense-in-depth measures would support continued availability of the 1A RHR system train emergency core cooling system function and that the measure would not adversely impact the safety function of other systems, structures, and components that are not part of the 1A RHR train system train.

Request:

Describe in detail the engineering change that supports this reasonable assurance. This should include (but not limited to):

1. Expected RHR I A room heat load calculations and one hour heat up (for no cooling or fan needed)

2. Available heat removal capacity with the temporary chiller/fan/cooling water supply

3. Required fire protection flow rate and water temperature requirements to support the heat removal capacity

4. Internal missile analysis for this temporary equipment Page 3 of 8

5. Loss of refrigeration evaluation for this temporary AHU

6.

Failure modes and affect analysis of this temporary AHU related to safety-related equipment in the area

7. Available clearance between the temporary AHU (chiller/fan/cooling water supply) and work that will be performed on the RHR 1A fan (provide drawings if available)

McGuire Response:

Site system engineering provided an evaluation to document that, should the IA RHR pump start while repairs to the associated AHU are ongoing, manually starting the temporary cooling equipment within one hour would not cause the room temperature limit of 145°F to be exceeded. This was based on a conservative assumption that the room temperature would rise I15-20° F/hr when the pump is running without forced cooling and that the initial room temperature is 90°F.

This assumption was based on station operating experience when one of McGuire's containment spray pumps (similarly-sized pump in a similarly-sized room) was previously run without its AHU in service. In addition to this operating experience, correlations between heat load and RHR pump room temperature were analyzed for 1A RHR pump runs. By measuring the initial room temperature drop caused by the AHU's heat removal rate exceeding the heat load to the room with both the pump and the AHU running, the temperature increase of 15-20°F/hr resulting from no AHU providing forced cooling was calculated.

The one hour allowance is for starting the temporary chiller and AHU. Forced cooling would be provided within one hour, so the engineering evaluation did not assess the impact on room temperature beyond that period.

The total sensible heat load for the IA RHR pump room is 96,815 BTU/hr. The temporary chiller is rated at 144,000 BTU/hr, and the temporary AHU is rated at 107,170 BTU/hr.

Therefore, the temporary equipment is sized to provide sufficient cooling for the room.

The chiller ratings are based on a cooling water flow rate of 36 gpm at 85°F. The 2 inch fire protection (RF) system drain line being used to supply cooling water to the chiller is capable of providing at least 36 gpm to the chiller, and the impact of this flow diversion has been considered. The oversized chiller ratings compensate for any fluctuations in RF water temperature above 850 F.

The temporary chiller is installed in a hallway on the level above the IA RHR pump room and is not in the vicinity of any other equipment. The design of the chiller is such that missiles would not be generated during a catastrophic equipment failure. Installation testing of the temporary chiller prior to the 1A RHR AHU maintenance work would provide assurance that all connections are tight and that refrigerant levels are correct, which minimizes the potential for a loss of refrigerant. However, if a loss of refrigerant did occur, it would not have an impact on the operability of any permanent plant equipment, including the 1 B RHR pump train.

The potential for the temporary AHU, which is installed inside the 1A RHR pump room, to fail catastrophically has also been evaluated. Based on the design (squirrel-cage fan with multiple attachment points), there is a remote chance of losing any of the fan blades. Although postulated missile damage to the 1A RHR pump would not be expected, it should be noted that

Page 4 of 8 the temporary AHU would only be in operation following an automatic RHR pump start. Since NRC Generic Letter 80-30 states that the specified TS action time represents a temporary relaxation of the single failure criterion, and since the operable 1 B RHR train would not be affected (located in a separate room), the potential for missiles from the temporary AHU would not adversely impact the ECCS function provided by the RHR pumps.

The temporary AHU is installed in the 1A RHR pump room and is located approximately 15 feet away from the permanent AHU. The distances and orientations are such that work on the permanent fan would not damage the temporary AHU. The general layout of the temporary equipment is shown on the sketches in Attachment 2 of this enclosure.

RAI 2

B~ackground:

Duke Energy stated in the amendment that the requested allowed outage time (AOT) required is 240 hours0.00278 days <br />0.0667 hours <br />3.968254e-4 weeks <br />9.132e-5 months <br />.

Issue:

Of the 240 hours0.00278 days <br />0.0667 hours <br />3.968254e-4 weeks <br />9.132e-5 months <br /> requested for the AOT, sixty-five (65) hours are allocated during the repairs for unanticipated repairs; for example, fan wheel cracking, significant shaft damage.

R~equest:

1. Describe all the spare parts that will be on site related to the unanticipated repairs so that if needed, repairs will be performed within the new proposed AOT of 240 hours0.00278 days <br />0.0667 hours <br />3.968254e-4 weeks <br />9.132e-5 months <br />.

2. Describe if new cooling coils are part of this contingent, in case of damage during disassemble or reassembly.

3. For item 2, describe the addition testing that would be required for these new parts, if replaced, and has this time added to the time line to be completed in this new AOT of 240 hours0.00278 days <br />0.0667 hours <br />3.968254e-4 weeks <br />9.132e-5 months <br />.

McGuire Response:

1. The LAR allocated 65 hours7.523148e-4 days <br />0.0181 hours <br />1.074735e-4 weeks <br />2.47325e-5 months <br /> for unanticipated repairs that might occur during the maintenance evolution. Part of this allocation is intended to cover scheduled repairs that simply take longer than projected, but it would also be used if other, unexpected damage is found during the repair evolution. Beyond the bearings whose replacements are already in the scope of work, a fan shaft, a fan wheel, and a fan belt are also in stock and on-site.

2. There are no spare cooling coils on site. However, although it is possible for them to be damaged during removal or reinstallation, any damage could likely be weld-repaired.

Such repairs, if necessary, are factored into the 65 hours7.523148e-4 days <br />0.0181 hours <br />1.074735e-4 weeks <br />2.47325e-5 months <br /> for unanticipated work.

3. Any testing associated with potential repairs to the cooling coils would fall into the normal post-maintenance testing on the AHU that will be performed after the already-planned repairs.

Page 5 of 8

Background:

Duke Energy stated in the amendment that compensatory measures and commitments will be in place for the requested AOT time required of 240 hours0.00278 days <br />0.0667 hours <br />3.968254e-4 weeks <br />9.132e-5 months <br />.

Issue:

Several commitments are performed 'prior to exceeding' the 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> AOT. That is:

1. Testing of the chiller and AHU

2. Sump pump availability

3. Protected equipment

4. Monitor the National Weather Service

5. Contact Transmission Control Center

6. Establish roving fire watches in 6 areas

7. Procedure will have been developed to start alternate cooling Request:

Justify why the above noted commitments are not performed before exceeding the normal 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> ACT. Based on the proposed time line, after AHU inspections (i.e., at the end of 53 hours6.134259e-4 days <br />0.0147 hours <br />8.763227e-5 weeks <br />2.01665e-5 months <br />), if the AHU bearing needs to be replaced, it would seem that the commitments should have been established before entering the initial work.

Describe why performing these 7 commitments at this point of the work has a benefit for defense-in depth function.

Describe why training is not part of these commitments as it relates to procedures for operating the temporary AHU equipment.

McGuire Response:

All commitments that were previously to be performed prior to exceeding the normal 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> ACT have been conservatively reworded to ensure that they are performed prior to entering the repair evolution for the AHU. See Attachment 3 for revised wording, which supersedes the commitments established in the August 28, 2015, letter.

No training is warranted for the procedure used to start the temporary cooling equipment. This is because the steps are simple and straightforward and because normal maintenance practices include pre-job briefings, which drive review of procedure steps prior to work evolutions.

Page 6 of 8

Background:

Duke Energy stated in the amendment that the potential break in the two inch cooling water supply hose could cause fire protection (RE) to start flooding on elevations 716' or 695' of the Auxiliary Building. Existing flooding analysis calculations have already reviewed the impact of a failure of six inch and eight inch RF piping, so failure of a two inch hose is bounded. Due to the low volume in the closed loop, a break in the 1.5 inch chilled water loop is not a flooding concern.

Issue:

The amendment lacks justification of the 2 inch rubber hose capability to withstand RE pressure.

Negative effects to the RHR room and RHR pump/motors have not been evaluated for water spray in the event of RE hose breakage.

Request:

Describe if water spray into the RHR 1A room has been evaluated for negative effects in the event of hose breakage.

McGuire Response:

The 2 inch rubber hosing used to supply RE water to the temporary chiller is rated for 200 psi.

The RE supply pressure is less than 150 psi, so the system pressure is within the design limits of the hose. When connected to the chiller, the hose is not routed near any equipment that would be harmed by water spray in the event that the hose does break.

The 1.5 inch hose used to connect the chiller to the AHU inside the lA RHR pump room is rated for 250 psi, which bounds the 45 psi pressure that would be seen in this closed loop. In the event of hose failure, water could spray into the pump room until the limited volume of water in the loop (approximately 60 gallons) fully drained. However, due to the fully-enclosed nature of the lA RHR pump motor, this brief period of spray would not adversely affect the equipment.

Furthermore, floor drains inside the pump room would ensure that excessive volumes of water do not remain on the floor.

Page 7 of 8

Background:

Duke Energy stated in the amendment that the proposed LAR involves a one-time extension to TS 3.5.2 to facilitate repairs to the 1 A RHR AHU. During the AHU repair evolution, important equipment (opposite train) will be protected and compensatory measures will be in place.

These activities are controlled by Duke Energy's normal risk management program.

Issue:

TS 3.5.2 Mode of applicability is Modes 1, 2, or 3. The repair work is assumed to have started with Unit 1 in Modes 1, 2 and 3. While in Mode 1, in the event of a Unit 1 reactor trip with the IA RHR AHU ongoing maintenance, it is not clear the course of action during an unexpected shutdown. That is, the LAR does not specifically address, for example, TS 3.0.3 is entered during the extended repairs for Unit 1 RHR 1 A AHU.

Request:

If Unit 1 must comply with TS and enters Mode 4 and Mode 5 with only one Operable RHR (since the AHU is being repaired), describe the necessary steps that would take place and include any additional compensatory measures and commitments that have not been previously addressed (while in Mode 1, 2 or 3). Specifically, address Mode 4 and Mode 5 actions with only one RHR pump Operable.

McGuire Response:

If McGuire Unit 1 fails to meet TS 3.5.2, it must be in Mode 4 within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />. This situation could occur if the lA RHR AHU repair work takes longer than anticipated such that the proposed AOT extension runs out. In such a scenario, operators would take action to bring the unit into the required mode per TS 3.5.2.

Once in Mode 4, TS 3.5.3, "ECCS - Shutdown," only requires one RHR pump to be operable.

As long as the unit remains in Mode 4 (or in Mode 5 with the RCS loops filled), a single operable RHR pump is sufficient to meet the requirements of TS 3.5.3, TS 3.4.6, "ROS Loops - Mode 4,"

and TS 3.4.7, "RCS Loops - Mode 5, Loops Filled." TS 3.4.8, "ROS Loops - Mode 5, Loops Not Filled," does require two operable RHR trains, but since one train can fulfill the function, the second train is required only for redundancy. Under normal circumstances, the decision to enter reduced inventory operations is under operator control, but a loss of coolant accident could result in the loops not being filled. If this occurred while maintenance on the IA RHR AHU was underway, the temporary cooling equipment would allow the lA RHR train to remain available. The 1 B RHR pump would be unaffected and would remain operable. Completion of repair work to the IA RHR AHU to restore train operability would occur as allowed by plant conditions.

With only one operable RHR train, McGuire Unit 1 can be brought down to Mode 5 and still meet its TS requirements as long as the RCS loops remain filled, so no additional compensatory measures or commitments are necessary. Previously existing plant procedures are sufficient to ensure the safety of the public.

Page 8 of 8

RAI 6

The amendment proposes to add a temporary footnote to the Completion Time in TS 3.5.2 Condition A. The language in the note is not consistent with the recommended style of Standard TSs. The footnote is not succinct and has potential for misinterpretation by Operators and Inspectors. Also, when a compensatory measure is a condition of a TS, it should not be referred to as a commitment in the TS wording. Please revise the Footnote to have an appropriate amount of detail and clarity.

McGuire Response: of this enclosure contains an updated version of the TS red-marks, including a revised footnote. This footnote is more succinct and no longer refers to the compensatory measures as '"commitments."

ATTACHMENT 1 McGuire Technical Specifications Page Markups

ECCS -- Operating 3.5.2 3.5 EMERGENCY CORE COOLING SYSTEMS (ECCS) 3.5.2 ECCS -- Operating LCO 3.5.2 APPLICABILITY:

Two ECCS trains shall be OPERABLE.

MODES 1, 2, and 3.

I.I.rI I~JL1I I------------------------------------------

In MODE 3, both safety injection (SI) pump or RHR pump flow paths may be isolated by closing the isolation valves for up to 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> to perform pressure isolation valve testing per SR 3.4.14.1.

ACTIONS CONDITION REQUIRED ACTION COMPLETION TIME A.

One or more trains A.1 Restore train(s) to 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />

• inoperable.

OPERABLE status.

AND At least 100% of the ECCS flow equivalent to a single OPERABLE ECCS train available.

B.

Required Action and B.1 Be in MODE 3.

6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> associated Completion Time not met.

AND B.2 Be in MODE 4.

12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />

• For Unit 1 only, the Completion Time for Required Action A.1 may be extended one-time to 10 days during the 1A RHR AHU repair evolution and is contingent on meeting the compensatory measures described in MNS correspondence letter MNS-15-093. Upon completion of the repair evolution, this footnote is no longer applicable and will expire on March 31, 2016.

3.5.2-1 Mc~ir Uits1 nd2 35.-1Amendment Nos. I-+,

4t"",,6--

ATTACHMENT 2 Sketches of Temporary Equipment Layout

ll v'. Ii I Ik7ti SE,ION, i-PL*AN AT EL. 695"-0" SCALE :,:o MC-I!

0 7

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11 12

V ATTACHMENT 3 Regulatory Commitments

The following table identifies the regulatory commitments made by Duke Energy in support of the requested license amendment. Any other statements made in this licensing submittal are provided for informational purposes only and are not considered to be regulatory commitments.

This table supersedes the commitments made in the August 28, 2015, submittal. Please direct any questions related to this matter to Brian Richards at (980) 875-5171.

Commitment Description 1

The alternate forced cooling equipment (chiller and AHU) will be installed and tested in accordance with the EC process prior to the 1A RHR AHU repair evolution.

2 At least one WZ C sump pump will be available prior to the 1A RHR AHU repair evolution.

3 The following SSCs will be protected prior to the 1A RHR AHU repair evolution, and elective maintenance to them will be deferred during the repairs to the 1A RHR pump motor AHU:

• 1B RHR train

• lB Nuclear Service Water System (NSWS) train

• 1 B Component Cooling Water System (CCWS) train

• 1 B Emergency Diesel Generator (EDG)

• Power supply to the alternate cooling equipment

• One WZ C sump pump 4

Prior to the lA RHR AHU repair evolution, McGuire will monitor the National Weather Service for potential severe weather conditions. To the extent practical, severe weather conditions will be avoided.

5 Prior to the 1A RHR AHU repair evolution, and daily thereafter, McGuire will contact the Transmission Control Center (TCC) regarding system grid stability. To the extent practical, system grid instability will be avoided.

6 Prior to the IA RHR AHU repair evolution, roving fire watches will be established in the following areas to minimize the chance of fire-induced LOCAs:

Unit 1 4.16kV Switchgear Rooms Unit 1 Auxiliary Feedwater Pump Room 1 B Diesel Generator Room Fire Area 14 - vicinity of I/2EMXB1 Fire Area 19 - vicinity of 1/2EMXG Fire Area 25 - vicinity of 11C02 7

Prior to the 1A RHR AHU repair evolution, procedures will have been developed to start the alternate cooling when required, and personnel will be designated to ensure that the equipment is started before room temperatures exceed the limits.