ML19183A475

NRR E-mail Capture - Formal Release of RAIs Ref: Columbia HVAC LAR L-2019-LLA-0034

ML19183A475
Person / Time
Site:	Columbia
Issue date:	07/02/2019
From:	John Klos Plant Licensing Branch IV
To:	Ronnie Garcia Energy Northwest
References
L-2019-LLA-0034
Download: ML19183A475 (6)

Text

NRR-DRMAPEm Resource From: Klos, John Sent: Tuesday, July 2, 2019 9:56 AM To: Garcia, Richard M.; Wolfgramm, Desiree M.

Cc: Klos, John

Subject:

Formal release of RAIs Ref: Columbia HVAC LAR L-2019-LLA-0034

Rick, By application dated February 25, 2019 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML19057A549), Energy Northwest, (the licensee), requested the NRC staff review and approve a proposed license amendment request (LAR) to their licensing basis for the Columbia Generating Station. The proposed amendment would allow use of the control room chilled water (CCH) system or the emergency service water (SW) system as acceptable cooling sources in support of the control room air conditioning (AC) system.

Specifically, the CCH would be utilized for the safety related function of maintaining the main control room (MCR) less than or equal to the 104 °F equipment qualification temperature limit during and following design basis events (DBEs), and maintaining the long term, steady state MCR design condition temperature less than or equal to 85 °F that supports 30 days continuous MCR occupancy. In addition, the proposed change would utilize the CCH system as the preferred cooling source in support of the control room AC system due to SW heat removal capability limitations.

The requested information is necessary for the NRC staff to complete the safety evaluation, including determination related to adequate protection of public health and safety.

Each question has a NRC Regulation bases, as noted below. A clarification call was held with your staff on June 27, 2019 to further define the questions below and these Requests for Additional Information (RAI)s are now released formally with a 30 day calendar response time from today; thereby, these RAIs are due Friday August 2, 2019 by the close of business.

RAI-1

Previous License Condition 2.C(21) stated, [T]the licensee shall have operable before May 31, 1984, redundant, seismic Category I environmentally qualified water chillers for control room HVAC. By letter dated May 31, 1984 (ADAMS Legacy Accession No. 8406130150), the licensee confirmed that this license condition has been satisfied. NRC Inspection Report 50-397-90-05 dated August 1, 1989 (ADAMS Legacy Accession No. 9008270010), documented that the chillers had been installed as required. Therefore, this license condition has been satisfied, Reference ADAMS Accession No. ML120800078.

The LAR Enclosure 1, page 12 and 13 states:

The CCH system is a safety-related system designed and qualified to perform its design basis functions under normal plant operations or design basis events. The system includes two redundant 50 ton capacity chillers that each have more than adequate capacity to remove the heat load in the MCR Station analyses conclude a single CCH system train can maintain 115 kW electrical heat load plus one division of MCR lighting with a SW temperature of 90 F and 100 GPM CCH flow through the AHU emergency cooling coil and maintain the MCR at 85F. In contrast, the SW system is capable of removing 34 kW electrical heat load plus one division of emergency lighting with an analyzed SW temperature of 89.6 F and 110 GPM SW flow directly to the AHU emergency cooling coil to maintain the MCR at 104 F, the MCR equipment qualification temperature limit.

1

The LAR Enclosure 1, page 14 and 15 states:

The manual actions associated with MCR cooling initiation are not defined by Columbia as time critical actions as two hours are available to initiate cooling and maintain the MCR 96 oF transient temperature and nine hours are available to initiate cooling before the 104 °F equipment calculation limit is reached.

NUREG-0800, Standard Review Plan (SRP) 9.4.1, Control Room Area Ventilation System (CRAVS), states that control room heating and cooling subsystems should have the ability to maintain a suitable ambient temperature for control room personnel and equipment.

RAI-1 Question:

Please describe the analyses performed to support the proposed manner in which the CCH and SW systems will be utilized, such that the new configuration will be able to meet MCR bounding design limits. Also, describe the analyses performed to address transient MCR temperature conditions. Please focus on the following:

• Bounding design basis MCR heat load and available heat load removal margins using either the CCH or SW as heat removal systems, relative to summer months limiting conditions associated with MCR continuous occupation (ambient conditions, and UHS temperatures)?

• Any differences between heat load removal capacity between Division 1 and Division 2 for the CCH trains.

• Calculation performed in support of the heat up rates of the MCR before the initiation of the manual actions.

• Identify which of the calculations are based on steady state conditions and which are based on transient conditions.

RAI-2

The LAR Enclosure 1, page 9 states:

The CCH chiller divisional units does have one common component which is a vent header that is tied to both CCH chiller units. The vent header removes discharged refrigerant in the event the chiller refrigerant overpressure rupture disk is actuated. The vent header availability is not required for the chiller to startup nor for the refrigerant to transfer heat from the evaporator to the condenser. Therefore, loss of the common vent header would not impact the ability of the CCH chillers to fulfill their safety-related function.

NUREG-0800, SRP 9.2.7, Chilled Water System, system safety function can be accomplished, assuming a single failure of a component to perform its intended safety function.

RAI-2 Question:

Describe the direct causes for a rupture disk to actuate and when it can occur (chillers in standby, in operation, or both). Describe the relationship of the overpressure rupture disk(s) and the vent header such that the loss of the common vent header would not impact the safety-related function of both CCH divisions. Describe the relationship of the overpressure rupture disk(s) and explain the impact of the rupture of a disk on one division chiller could have on the opposite CCH division chiller related to common cause failure.

RAI-3

The LAR Enclosure 1, pages 6 and 7 contain the following statements:

No changes are specified to TS 3.7.4, Control Room Air Conditioning (AC) System, as a result of this LAR, and there is no need for any new specification. The Control Room AC system is included in Columbias TS as a system satisfying Criterion 3 of 10 CFR 50.36. CCH and SW are support systems 2

for the Control Room AC system providing cooling water necessary for the Control Room AC system to perform the safety function of cooling the main control room. This consideration of CCH and SW as support systems to the Control Room AC system is consistent with the definition of OPERABLE-OPERABILITY in TS 1.1, Definitions. Consequently, no dedicated TS requirement is required for CCH since its performance in support of the Control Room AC system is embedded in TS 3.7.4 operability requirements. SW operability when supporting the Control Room AC system is also addressed by TS 3.7.1, Standby Service Water (SW) System and Ultimate Heat Sink (UHS), as SW provides cooling to remove heat from various station equipment to result in and maintain safe shutdown of the reactor.

There are two trains of CCH and two trains of Emergency SW that can provide cooling to the Control Room AC system AHU emergency cooling coils credited in TS 3.7.4. Therefore, up to four cooling supply options are available when both CCH trains are available, and SW is available to the CCH chiller condensers, and when the two trains of SW are evaluated as capable of the required heat removal to provide direct cooling flow to the AHU. TS 3.7.4 states that two Control Room AC cooling subsystems shall be OPERABLE in MODES 1, 2, and 3, which will include cooling provided by either CCH or SW, or a combination of those cooling sources. Upon approval of this LAR, the Bases for TS 3.7.4 will be revised to document the use of either CCH or SW, when capable of the required heat removal, as acceptable cooling sources to meet the long term, steady state 85F control room habitability temperature which bound the 104 °F equipment qualification temperature limit. Consequently, TS 3.7.4 LCO would only be entered, with regard to cooling sources available, when no cooling source is available to supply the respective Control Room AC subsystem for DBE response, or neither cooling source (CCH, SW) is capable of providing the required cooling. Additionally, in the event that future heat load additions surpass the ability of SW to support Control Room AC system operability, SW will be available to provide limited cooling to the control room as defense in depth. The reason for the proposed change is to provide maximum flexibility with regard to allowable Control Room AC system cooling sources which will also address SW capability limitations.

The SW system is currently capable of maintaining the MCR within the equipment qualification temperature limit of 104°F, however, the capability of SW to maintain the MCR within the long term, steady state 85°F habitability design condition temperature is limited during the warmer months. Future MCR equipment additions have the potential to exhaust the margin available when using SW for meeting the equipment qualification temperature limit. Additional MCR emergency cooling capacity is available by utilizing the CCH system as the preferred cooling source. The CCH system has more than adequate capacity for the MCR heat load to ensure the steady state MCR habitability temperature is met, which bounds the equipment qualification temperature limit (refer to Section 3.2.1). This LAR is not tied to implementation of any specific station heat load addition modification. Future MCR heat load additions will be evaluated by the station modification process and only allowed after evaluation with acceptable results and in accordance with the appropriate regulatory reviews.

NUREG-0800, Standard Review Plan (SRP) 9.4.1, Control Room Area Ventilation System (CRAVS), states that control room heating and cooling subsystems should have the ability to maintain a suitable ambient temperature for control room personnel and equipment. 10CFR 50.36 (b) requires TSs to be derived from the analyses and evaluation included in the safety analysis report, and amendments thereto.

RAI Question 3:

Based on the above statements, and the proposed licensing basis change for TS 3.7.4, with two CCH systems inoperable but with two sources of cooling water available from SW, it appears the plant would not have to enter into an action statement of the TS on cooler days/months. In addition, with two CCH systems inoperable and only one source of cooling water available from SW, it appears the plant would enter Condition A in TS 3.7.4, with a completion time of 30 days.

Please explain how, once the plant enters Condition A with both CCH systems unavailable, transitional situations such as potential changes in SW and outside ambient temperatures beyond the systems capability to maintain sustained 30-day 85 oF temperature in the control room will be addressed during post-accident conditions.

3

In addition, please explain the relationship between the SW temperature, outside ambient temperature and the control room temperature used to determine that a single control room AC division with only SW available to its cooling coil can maintain sustained 85 oF temperature in the control room.

RAI 4

Title 10 of the Code of Federal Regulations (10 CFR) Part 50.48, Fire Protection requires each operating nuclear power plant to provide the means to limit fire damage to structures, systems, and components (SSCs) important to safety to ensure the ability to safely shut down the reactor.

Regulatory position 5, Safe-Shutdown Capability, in Regulator Guide (RG) 1.189, Fire Protection for Nuclear Power Plants, Revision 3, ADAMS Accession no. ML17340A875, provides for a mean to meet the above requirement. This regulatory position, states, in part, that [t]he safe-shutdown analysis should demonstrate that the success path SSCs, including electrical circuits, remain free of fire damage in the event of postulated fires.

Section 2.4 of the proposed license amendment request (LAR) states that the proposed change requires the emergency cooling function, when supplied by the CCH, to rely on additional equipment (the CCH system loop, including CCH chiller and pump) for the purpose of equipment cooling and results in crediting additional active components that are required to perform the designed functions of maintaining the [main control room] MCR equipment qualification temperature.

It is unclear whether the additional systems and components are credited to achieve and maintain safe shutdown following accident events, including fire events, and whether evaluation is performed to ensure that one train of safe shutdown equipment will remain free from damage.

If credited for post-fire safe shutdown, confirm that the CCH system loop, including the CCH chiller and pump and their associated power, control, and instrumentation cables, have been included in the plants safe shutdown equipment list, and they have been evaluated as part of the safe shutdown fire area analysis to ensure that one train of safe shutdown equipment will remain free from damage for a postulated fire in any area of the plant in accordance with RG 1.189, Revision 3.

RAI 5

10 CFR 50.48 also requires each operating nuclear power plant to provide the means to limit fire damage to SSCs important to safety to ensure the ability to safely shut down the reactor. Regulatory position 5.3 in RG 1.189 provides for a mean to meet the above requirement. This regulatory position states, in part, that [t]he post-fire safe-shutdown analysis should ensure that one success path remains free of fire damage for a single fire in any single plant fire area.

Section 3.2.2 of the LAR states that manual actions, which included actions for fires impacting a single division of MCR cooling or a fire affecting both CCH trains, can be successfully performed and would not impact the Post-Fire Safe Shutdown strategy for Columbia.

This statement implies redundant CCH trains can be damaged by a single fire.

Describe the credited backup equipment line-up when both CCH trains are affected by a single fire. Confirm that the backup equipment has been evaluated to be free from damage and can be manually operated for this particular fire scenario.

RAI 6

4

10 CFR Part 50, Appendix A, General Design Criteria (GDC) 3, Fire Protection, requires SSCs important to safety to be designed and located to minimize the probability and effects of fires and explosions.

Although the proposed LAR does not impact any active or passive fire protection systems, the post-fire safe shutdown equipment and strategy, which is part of the Fire Protection Program is impacted.

The LAR does not appear to include a regulatory evaluation for GDC 3 and how that criteria is accounted for in the LAR. The licensee is requested to respond to this concern.

John Klos DORL Callaway, Columbia Project Manager U.S. NRC, Office of Nuclear Reactor Regulation, Division of Operating Reactor Licensing, O9D22 NRC/NRR/DORL/LPL4, MS O9E3 Washington, DC 20555-0001 301.415.5136, John.Klos@NRC.gov 5

Hearing Identifier: NRR_DRMA Email Number: 78 Mail Envelope Properties (SN6PR09MB3661F834C9BB547A35F16D30E3F80)

Subject:

Formal release of RAIs Ref: Columbia HVAC LAR L-2019-LLA-0034 Sent Date: 7/2/2019 9:55:30 AM Received Date: 7/2/2019 9:55:32 AM From: Klos, John Created By: John.Klos@nrc.gov Recipients:

"Klos, John" <John.Klos@nrc.gov>

Tracking Status: None "Garcia, Richard M." <rmgarcia@energy-northwest.com>

Tracking Status: None "Wolfgramm, Desiree M." <dmwolfgramm@energy-northwest.com>

Tracking Status: None Post Office: SN6PR09MB3661.namprd09.prod.outlook.com Files Size Date & Time MESSAGE 15433 7/2/2019 9:55:32 AM Options Priority: Standard Return Notification: No Reply Requested: No Sensitivity: Normal Expiration Date:

Recipients Received: