View source for CNL-21-015, Expedited Application to Modify Watts Bar Nuclear Plant, Unit 1 Technical Specification 3.7.12, Auxiliary Building Gas Treatment System, for One-Time Exception to Permit Opening of the Auxiliary Building Secondary Containment Enclosure as

{{Adams
| number = ML21062A267
| issue date = 03/03/2021
| title = Expedited Application to Modify Watts Bar Nuclear Plant, Unit 1 Technical Specification 3.7.12, Auxiliary Building Gas Treatment System, for One-Time Exception to Permit Opening of the Auxiliary Building Secondary Containment Enclosure as N
| author name = Polickoski J
| author affiliation = Tennessee Valley Authority
| addressee name = 
| addressee affiliation = NRC/Document Control Desk, NRC/NRR
| docket = 05000390
| license number = NPF-090
| contact person = 
| case reference number = CNL-21-015, WBN-TS-20-023
| document type = Letter type:CNL, License-Application for Facility Operating License (Amend/Renewal) DKT 50
| page count = 18
| project = 
| stage = Request
}}

=Text=
{{#Wiki_filter:1101 Market Street, Chattanooga, Tennessee 37402 CNL-21-015 March 3, 2021 10 CFR 50.90 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.C. 20555-0001 Watts Bar Nuclear Plant Unit 1 Facility Operating License No. NPF-90 NRC Docket No. 50-390

==Subject:==
Expedited Application to Modify Watts Bar Nuclear Plant, Unit 1 Technical Specification 3.7.12, Auxiliary Building Gas Treatment System, for One-Time Exception to Permit Opening of the Auxiliary Building Secondary Containment Enclosure As Needed to Support the Watts Bar Nuclear Plant, Unit 2 Replacement Steam Generator Outage (WBN-TS-20-023)
In accordance with the provisions of Title 10 of the Code of Federal Regulations (10 CFR) 50.90, Application for amendment of license, construction permit, or early site permit, Tennessee Valley Authority (TVA) is submitting a request for an amendment to Facility Operating License No. NPF-90 for the Watts Bar Nuclear Plant (WBN) Unit 1.
The proposed change modifies the existing Note in the Limiting Condition for Operation (LCO) for WBN Unit 1 Technical Specification (TS) 3.7.12, "Auxiliary Building Gas Treatment System (ABGTS)," to allow the Auxiliary Building Secondary Containment Enclosure (ABSCE) boundary to be opened, at specific controlled access points, on a continuous basis during the WBN Unit 2 Cycle 4 refueling outage (U2R4) when the WBN Unit 2 replacement steam generators (RSGs) are scheduled to be installed. The proposed change to the Note in the LCO in WBN Unit 1 TS 3.7.12 is needed because the ABSCE boundary is shared between WBN Units 1 and 2, and because WBN Unit 1 will be operating during U2R4. Consistent with the current Note to the WBN Unit 1 TS 3.7.12 LCO, administrative controls will be established for the continuous openings during U2R4 to ensure the ABSCE can be closed consistent with the safety analysis. provides a description of the proposed changes, technical evaluation of the proposed changes, regulatory evaluation, and a discussion of environmental considerations. to the enclosure provides the existing Unit 1 TS page marked-up to show the proposed changes. Attachment 2 provides the Unit 1 TS page retyped to show the proposed changes. Attachment 3 provides the existing Unit 1 TS Bases page marked-up to show the proposed changes. Changes to the existing TS Bases are provided for information only and will be implemented under the Technical Specification Bases Control Program.

U.S. Nuclear Regulatory Commission CNL-21-015 Page 2 March 3, 2021 TVA has determined that there are no significant hazard considerations associated with the proposed change and that the change qualifies for a categorical exclusion from environmental review pursuant to the provisions of 10 CFR 51.22(c)(9). In accordance with 10 CFR 50.91, Notice for Public Comment; State Consultation, TVA is sending a copy of this letter and the enclosure to the Tennessee Department of Environment and Conservation.
As previously noted, the WBN Unit 2 RSGs are scheduled to be installed during U2R4 scheduled for February 2022. To support the schedule for the RSG project and the openings of the ABSCE boundary needed for the RSG project, TVA requests NRC approval of the proposed license amendment on an expedited basis by February 1, 2022, with implementation upon commencement of U2R4. The basis for the expedited review is that TVA initially planned to replace the WBN Unit 2 SGs during U2R5 (fall 2023). However, because of indications discovered during the WBN Unit 2 SG inspection in U2R3 (fall 2020), TVA decided in late December 2020 to move the WBN Unit 2 SG replacement to U2R4.
There are no new regulatory commitments associated with this submittal. If you have any questions about this proposed change, please contact Kimberly D. Hulvey, Senior Manager, Fleet Licensing, at (423) 751-3275.
I declare under penalty of perjury that the foregoing is true and correct. Executed on this 3rd day of March 2021.
Respectfully, James T. Polickoski Director, Nuclear Regulatory Affairs

==Enclosure:==

Evaluation of Proposed Change cc (Enclosure):
NRC Regional Administrator - Region II NRC Project Manager - Watts Bar Nuclear Plant NRC Senior Resident Inspector - Watts Bar Nuclear Plant Director, Division of Radiological Health - Tennessee State Department of Environment and Conservation

Enclosure Evaluation of Proposed Change

==Subject:==
Expedited Application to Modify Watts Bar Nuclear Plant, Unit 1 Technical Specification 3.7.12, Auxiliary Building Gas Treatment System, for One-time Exception to Permit Opening of the Auxiliary Building Secondary Containment Enclosure As Needed to Support the Watts Bar Nuclear Plant, Unit 2 Replacement Steam Generator Outage (WBN-TS-20-023)
TABLE OF CONTENTS 1.0     

==SUMMARY==
DESCRIPTION ............................................................................................. 2 2.0     DETAILED DESCRIPTION.............................................................................................. 2 2.1    Background.................................................................................................................. 2 2.2    Proposed Changes ...................................................................................................... 2 2.3    Condition Intended to Resolve ..................................................................................... 3

==3.0     TECHNICAL EVALUATION==
............................................................................................. 3 3.1    System Description ...................................................................................................... 3 3.1.1   Primary Containment ............................................................................................. 3 3.1.2   Auxiliary Building Secondary Containment Enclosure ............................................ 3 3.1.3   Auxiliary Building Gas Treatment System .............................................................. 4 3.2    Technical Analysis ....................................................................................................... 4 3.2.1   ABSCE Operability to Support Unit 1 Operation during the RSG Outage ............... 4 3.2.2   Unit 2 RSG Outage Activities ................................................................................. 5 3.2.3   Conclusion ............................................................................................................. 6

==4.0     REGULATORY EVALUATION==
 ........................................................................................ 6 4.1    Applicable Regulatory Requirements and Criteria ........................................................ 6 4.2    Precedent .................................................................................................................... 8 4.3    Significant Hazards Consideration ............................................................................... 8 4.4    Conclusion ..................................................................................................................10

==5.0     ENVIRONMENTAL CONSIDERATION==
 ..........................................................................10

==6.0     REFERENCES==
 ...............................................................................................................10 ATTACHMENTS
: 1. Proposed TS Changes (Mark-Ups) for WBN Unit 1
: 2. Proposed TS Changes (Final Typed) for WBN Unit 1
: 3. Proposed TS Bases Changes (Mark-Ups) for WBN Unit 1 (For Information Only)
CNL-21-015                                                E1 of 10

Enclosure 1.0   

==SUMMARY==
DESCRIPTION In accordance with the provisions of Title 10 of the Code of Federal Regulations (10 CFR) 50.90, Application for amendment of license, construction permit, or early site permit, Tennessee Valley Authority (TVA) is requesting a license amendment to Facility Operating License No. NPF-90 for the Watts Bar Nuclear Plant (WBN), Unit 1.
The proposed change modifies the existing Note in the Limiting Condition for Operation (LCO) for WBN Unit 1 Technical Specification (TS) 3.7.12, "Auxiliary Building Gas Treatment System (ABGTS)," to allow the Auxiliary Building Secondary Containment Enclosure (ABSCE) boundary to be opened, at specific controlled access points, on a continuous basis during the WBN Unit 2 Cycle 4 refueling outage (U2R4) when the WBN Unit 2 replacement steam generators (RSGs) are scheduled to be installed (the RSG Outage). The proposed change to the Note in the LCO in WBN Unit 1 TS 3.7.12 is needed because the ABSCE boundary is shared between WBN Units 1 and 2, and because WBN Unit 1 will be operating during U2R4. Consistent with the current Note to the WBN Unit 1 TS 3.7.12 LCO, administrative controls will be established for the continuous openings during U2R4 to ensure the ABSCE can be closed consistent with the safety analysis.
2.0   DETAILED DESCRIPTION

==2.1   BACKGROUND==

In Reference 1, the Nuclear Regulatory Commission (NRC) issued WBN Unit 1 License Amendment No. 116 and WBN Unit 2 License Amendment No. 16, which, in part, added the Note in the LCO to WBN Units 1 and 2 TS 3.7.12 to allow the ABSCE boundary to be opened intermittently under administrative controls that ensure the ABSCE can be closed consistent with the safety analysis. As noted in Section 3.0 to Reference 1, and described in further detail in Reference 2, TVA clarified that the current Note in the LCO to WBN Units 1 and 2 TS 3.7.12 is intended for short duration events only and that TVA planned to submit a separate license amendment request (LAR) to modify the proposed Note to the TS 3.7.12 LCO to allow a one-time exception for the ABSCE breaches to be opened continuously to support the RSG project. In Reference 1, NRC stated, The staff concurs that the new note as proposed in the current amendments is intended for short duration events only.

==2.2   PROPOSED CHANGE==
S The proposed TS change adds the following information to the Note in LCO 3.7.12 of the Unit 1 TS:
As a one-time exception for the Watts Bar Unit 2 Cycle 4 Refueling Outage, scheduled to commence in spring 2022, during which the Unit 2 Replacement Steam Generators (RSGs) will be installed, the breaches of the ABSCE boundary needed to support the Unit 2 RSG project activities (Unit 2 Upper Containment Personnel Air Lock Access, Unit 2 Lower Containment Personnel Air Lock Access, Unit 2 Containment Equipment Hatch, and Auxiliary Building General Supply Fan 737 Elevation Room A12 Access and Backup) may be opened on a continuous basis, under administrative controls that ensure the ABSCE can be closed consistent with the safety analysis.
CNL-21-015                                  E2 of 10

Enclosure Attachment 1 to this enclosure provides the existing Unit 1 TS page marked-up to show the proposed changes. Attachment 2 provides the Unit 1 TS page retyped to show the proposed changes. Attachment 3 provides the existing Unit 1 TS Bases pages marked-up to show the proposed changes. Changes to the existing TS Bases are provided for information only and will be implemented under the TS Bases Control Program.
2.3   CONDITION INTENDED TO RESOLVE The proposed change is needed to support continuous openings of the ABSCE boundary during the WBN Unit 2 RSG project. The ABSCE boundary is shared between Unit 1 and Unit 2. WBN Units 1 and 2 TS 3.7.12 is applicable during Modes 1-4. While WBN Unit 2 will be shutdown during the RSG project in U2R4, WBN Unit 1 will still be operating. Therefore, continuous opening of the ABSCE boundary to support the WBN Unit 2 RSG project would require WBN Unit 1 to enter the LCO for WBN Unit 1 TS 3.7.12. As noted in Section 2.1 to this enclosure, the current Note to the LCO to WBN Unit 1 TS 3.7.12, allowing the ABSCE boundary to be opened intermittently under administrative controls that ensure the ABSCE can be closed consistent with the safety analysis, was intended for short duration events only. Therefore, as noted in References 1 and 2, a separate LAR is needed to provided a temporary change to the Note to the LCO to WBN Unit 1 TS 3.7.12 to permit a limited number of continuous openings of the ABSCE boundary, as described in Section 3.2 to this enclosure, subject to maintaining the ability to close the ABSCE boundary consistent with the safety analysis.

==3.0   TECHNICAL EVALUATION==

Section 3.1 contains a description of the affected systems. Section 3.2 contains a technical analysis of the proposed TS changes.
3.1   SYSTEM DESCRIPTION A description of the relevant portions of the WBN containment system is presented below as background for evaluation of the proposed changes.
3.1.1 Primary Containment The primary containment systems for both Unit 1 and Unit 2 consist of steel containment vessels (SCVs) and separate Shield Buildings. The SCVs are low-leakage, freestanding steel structures consisting of a cylindrical wall, a hemispherical dome, and a bottom liner plate encased in concrete. The Shield Buildings are reinforced concrete structures enclosing an annulus and the SCV.
The primary containment personnel hatch passes from the SCV through the Shield Building and opens directly to the Auxiliary Building.
3.1.2 Auxiliary Building Secondary Containment Enclosure The ABSCE is that portion of the Auxiliary Building and Condensate Demineralizer Waste Evaporator Building (and for certain configurations, the annulus and primary containment) which serves to maintain an effective barrier for airborne radioactive contaminants released in the Auxiliary Building during abnormal events.
CNL-21-015                                   E3 of 10

Enclosure 3.1.3 Auxiliary Building Gas Treatment System The ABGTS is a fully redundant air cleanup system provided to reduce radioactive releases from the ABSCE to the environment during an accident to levels sufficiently low to keep the site boundary dose rates below the requirements of 10 CFR 100. This is accomplished by exhausting air from the ABSCE to maintain a negative pressure within the ABSCE boundary. Exhaust air leaving the ABSCE is processed by the ABGTS filter train before it is discharged to the outside.
The ABGTS, and the ABSCE that provides the ventilation envelope supporting ABGTS operability, are shared between Unit 1 and Unit 2. Together, they provide a secondary containment barrier maintained under negative pressure during certain postulated accidents involving airborne radioactivity, and provide contaminant removal sufficient to keep radioactivity levels in the air released to the environment low enough to assure compliance with the requirements of 10 CFR 100.

==3.2   TECHNICAL ANALYSIS==

3.2.1 ABSCE Operability to Support Unit 1 Operation during the RSG Outage Passages (breaches) through the shared ABSCE boundary are limited to intermittent openings per the current wording of the Note in Unit 1 TS 3.7.12, which states:
The Auxiliary Building Secondary Containment Enclosure (ABSCE) boundary may be opened intermittently under administrative controls that ensure the ABSCE can be closed consistent with the safety analysis.
In response to an NRC Request for Additional Information (RAI), TVA informed NRC in Reference 3 that the administrative controls to ensure the ABSCE can be closed consistent with the safety analysis are described in a TVA procedure. As noted in Section 3.1 of Reference 1:
The licensee stated that the proposed Note in TS 3.7.12 would apply to any breach of the ABSCE that exceeds the total allowable breach area for the ABSCE. The total allowable breach area for operability of the ABSCE boundary is approximately 150 square inch. The total allowable breach area is derived from AB pressure testing and assures the required pressure criteria of -0.25 in.
water gauge (WG) can be maintained. The maximum allowable breach area is updated continuously based on the most recent surveillance testing results.
Section 3.1 of Reference 1 and the TVA response to NRC ARCB-RAI-2 in Reference 3, described in detail the proceduralized controls to ensure the ABSCE can be closed consistent with the safety analysis. These proceduralized controls ensure that the breach opening can be closed within two minutes of notification from the main control room (MCR), which allows sufficient time to be able to drawdown the ABSCE to
      -0.25 inch water gauge (in. w.g.) within four minutes consistent with the safety analysis in Section 15.5.3 of the WBN dual-unit Updated Final Safety Analysis Report (UFSAR).
CNL-21-015                                    E4 of 10

Enclosure As further noted in Section 3.1 of Reference 1:
The NRC staff has reviewed the proposed change to add a note to TS LCO 3.7.12 provided in the licensee's application and supplements, and has determined that it is consistent with the NRC-approved design basis as reflected in Watts Bar UFSAR Section 15.5.3. Because the proposed change is consistent with the NRC-approved design basis, there is reasonable assurance that in the event of a LOCA, the radioactive release will be mitigated as assumed in the licensing basis and therefore, the regulatory limits stated in 10 CFR 100.11 will be met. The proposed note is consistent with similar notes for ventilation system boundaries in NUREG-1431, with additional clarity provided regarding compliance with the accident analyses during the application of the note. The licensee has demonstrated that adequate procedures exist at Watts Bar to comply with the note.
For the continuous openings of the ABSCE boundary to support the WBN Unit 2 RSG project, the same proceduralized controls reviewed by NRC in Reference 1 will remain in effect. Therefore, the ability to ensure the ABSCE can be closed consistent with the safety analysis during the RSG Outage is assured.
3.2.2 Unit 2 RSG Outage Activities In a typical outage, the Unit 2 containment is considered part of the ABSCE when the Unit 2 Upper and Lower Containment Personnel Air Locks and the Unit 2 Equipment Hatch are open, and therefore these openings are not considered breaches of the ABSCE. However, during the RSG Outage, temporary openings in the Unit 2 shield building concrete dome and steel containment vessel will be created in order to remove the existing SGs and install the RSGs. These temporary openings cannot be closed within the required time frame to remain consistent with the safety analysis. Thus, once these openings are created, the ABSCE boundary will be moved to exclude the Unit 2 containment. Therefore, these two Air Locks and the Equipment Hatch will be considered breaches of the ABSCE when the temporary openings in the shield building dome are created.
Breaches of this shared ABSCE boundary are controlled in accordance with Unit 1 TS 3.7.12 to maintain operability of the ABSCE in support of Unit 1 operation.
The following breaches of the ABSCE boundary are planned to be opened on a continuous basis during the Unit 2 RSG Outage. The locations of these breaches are shown on WBN dual-unit UFSAR Figures 6.2.3-5, 6.2.3-6, and 6.2.3-7.
* Unit 2 Upper Containment Personnel Air Lock Access (Plant Door A157). This access is intended to be used principally by workers accessing upper containment areas. Equipment may also transit through this access. (UFSAR Figure 6.2.3-5 coordinates W-A11)
* Unit 2 Lower Containment Personnel Air Lock Access (Plant Door A77). This access is intended to be used principally by workers accessing lower containment areas.
Equipment may also transit through this access. (UFSAR Figure 6.2.3-7 coordinates V-A16)
CNL-21-015                                   E5 of 10

Enclosure
* Unit 2 Containment Equipment Hatch (Room 757.0-A15, also known as the shield building equipment hatch sleeve). This access is intended to be used principally by workers and equipment for access to primary containment areas. During the RSG Outage, this hatch will be secured as needed by a temporary ABSCE door (WBN-0-DOOR-410-R003) capable of being closed within two minutes.
(UFSAR Figure 6.2.3-5 coordinates V-A11)
* Auxiliary Building General Supply Fan 737 Elevation Room A12 Access and Backup (Plant Doors A132/A133). During the RSG Outage, personnel will pass through this access to enter the Auxiliary Building from outside areas. In addition to personnel, equipment may also transit through this access. (UFSAR Figure 6.2.3-6 coordinates U-A13)
The administrative controls used to implement the existing Note in Unit 1 TS 3.7.12 regarding openings of the ABSCE boundary have been identified for impact under this LAR to ensure that these four continuous breaches will be properly controlled during U2R4. Thus, all of these openings will have the capability to be closed in the event of an Auxiliary Building Isolation (ABI) in order to reestablish the integrity of the ABSCE within two minutes of notification from the MCR. Based on similar continuous breach experience with other TVA nuclear projects, there is confidence that the above breaches can be closed and the ABSCE boundary restored consistent with the safety analysis.
Due to the fact that these openings of the ABSCE boundary can be closed as required under the existing requirements, no new safety analysis was necessary.
3.2.3 Conclusion ABSCE boundary integrity ensures that the release of through-the-line leakage of radioactive materials from the primary containment would be restricted to those leakage paths and associated leakage rates assumed in the safety analyses. This restriction, in conjunction with operation of the ABGTS, limits the site boundary radiation doses to within the regulatory limits of 10 CFR 100 during accident conditions. The proposed change does not affect the ability of an operable ABGTS to perform its intended function.
During times when the ABSCE boundary is open, administrative controls will ensure that the U2R4 continuous breaches will be quickly sealed to maintain the validity of the licensing basis analyses of accident consequences.
Therefore, TVA concludes that the proposed change is acceptable and complies with applicable regulatory requirements.

==4.0   REGULATORY EVALUATION==

4.1   APPLICABLE REGULATORY REQUIREMENTS AND CRITERIA Regulations 10 CFR 50.67, Accident Source Term, establishes limits on the accident source term used in design basis radiological consequence analyses with regard to radiation exposure to individuals and to control room occupants.
CNL-21-015                                   E6 of 10

Enclosure General Design Criteria WBN Unit 1 was designed to meet the intent of the "Proposed General Design Criteria for Nuclear Power Plant Construction Permits" published in July 1967. The WBN construction permit was issued in January 1973. The UFSAR, however, addresses the General Design Criteria (GDC) published as Appendix A to 10 CFR 50 in July 1971.
Conformance with the GDCs is described in Section 3.1.2 of the UFSAR.
Each criterion listed below is followed by a discussion of the design features and procedures that meet the intent of the criteria. Any exception to the 1971 GDC resulting from earlier commitments is identified in the discussion of the corresponding criterion.
Criterion 16 - Containment design. Reactor containment and associated systems shall be provided to establish an essentially leak-tight barrier against the uncontrolled release of radioactivity to the environment and to assure that the containment design conditions important to safety are not exceeded for as long as postulated accident conditions require.
Compliance with GDC 16 is described in Section 3.1.2.2 of the WBN UFSAR.
Criterion 19 - Control room. A control room shall be provided from which actions can be taken to operate the nuclear power unit safely under normal conditions and to maintain it in a safe condition under accident conditions, including loss-of-coolant accidents. Adequate radiation protection shall be provided to permit access and occupancy of the control room under accident conditions without personnel receiving radiation exposures in excess of 5 rem whole body, or its equivalent to any part of the body, for the duration of the accident. Equipment at appropriate locations outside the control room shall be provided (1) with a design capability for prompt hot shutdown of the reactor, including necessary instrumentation and controls to maintain the unit in a safe condition during hot shutdown, and (2) with a potential capability for subsequent cold shutdown of the reactor through the use of suitable procedures.
Compliance with GDC 19 is described in Section 3.1.2.2 of the WBN UFSAR.
Criterion 60 - Control of releases of radioactive materials to the environment. The nuclear power unit design shall include means to control suitably the release of radioactive materials in gaseous and liquid effluents and to handle radioactive solid wastes produced during normal reactor operation, including anticipated operational occurrences. Sufficient holdup capacity shall be provided for retention of gaseous and liquid effluents containing radioactive materials, particularly where unfavorable site environmental conditions can be expected to impose unusual operational limitations upon the release of such effluents to the environment.
Compliance with GDC 60 is described in Section 3.1.2.6 of the WBN UFSAR.
Criterion 64 - Monitoring radioactivity release. Means shall be provided for monitoring the reactor containment atmosphere, spaces containing components for recirculation of loss-of-coolant accident fluids, effluent discharge paths, and the plant environs for radioactivity that may be released from normal operations, including anticipated operational occurrences, and from postulated accidents.
Compliance with GDC 64 is described in Section 3.1.2.6 of the WBN UFSAR.
CNL-21-015                                   E7 of 10

Enclosure 4.2   PRECEDENT The change proposed in this LAR to allow continuous opening of the ABSCE boundary under administrative controls that ensure the ABSCE can be closed consistent with the safety analysis is similar to the one for intermittent opening of the ABSCE boundary approved by the NRC in Reference 1.
4.3   SIGNIFICANT HAZARDS CONSIDERATION Tennessee Valley Authority (TVA) is requesting an amendment to Facility Operating License NPF-90 for the Watts Bar Nuclear Plant (WBN) Unit 1. The proposed change modifies the existing Note in the Limiting Condition for Operation (LCO) for WBN Unit 1 Technical Specification (TS) 3.7.12, "Auxiliary Building Gas Treatment System (ABGTS)," to allow the Auxiliary Building Secondary Containment Enclosure (ABSCE) boundary to be opened, at specific controlled access points, on a continuous basis during the WBN Unit 2 Cycle 4 refueling outage (U2R4) when the WBN Unit 2 replacement steam generators (RSGs) are scheduled to be installed. The proposed change to the Note in the LCO in WBN Unit 1 TS 3.7.12 is needed because the ABSCE boundary is shared between WBN Units 1 and 2, and because WBN Unit 1 will be operating during the U2R4 outage. Consistent with the current Note to the WBN Unit 1 TS 3.7.12 LCO, administrative controls will be established for the continuous openings during the RSG project to ensure the ABSCE can be closed consistent with the safety analysis.
TVA has evaluated whether or not a significant hazards consideration is involved with the proposed amendment(s) by focusing on the three standards set forth in 10 CFR 50.92, Issuance of amendment, as discussed below:
: 1. Does the proposed amendment involve a significant increase in the probability or consequence of an accident previously evaluated?
Response: No Administrative controls, as reviewed and approved by the Nuclear Regulatory Commission, exist to ensure that the U2R4 continuous openings of the ABSCE boundary needed to support the RSG project can be rapidly closed and that the ABSCE boundary can be restored closed consistent with the safety analysis.
For cases where the ABSCE boundary is opened under administrative controls, appropriate compensatory measures are required by the proposed TS to ensure the ABSCE boundary can be rapidly restored and the dose analysis assumptions can be supported. The administrative controls for restoring the ABSCE boundary have been reviewed and remain effective for restoring the U2R4 continuous breaches of this boundary.
Based on these administrative controls, the accident consequences do not cause an increase in dose above the applicable General Design Criteria, Standard Review Plan, or 10 CFR 100 limits. The plant operators will continue to maintain the ability to mitigate a design basis event.
The proposed changes do not require physical changes to plant systems, structures, or components. The ABGTS is an accident-mitigating feature, and its operability is CNL-21-015                                   E8 of 10

Enclosure unaffected by this change. As such, ABGTS is not associated with a potential accident-initiating mechanism. Therefore, the changes do not affect accident or transient initiation or consequences.
Therefore, the proposed change does not involve a significant increase in the probability or consequences of an accident previously evaluated.
: 2. Does the proposed amendment create the possibility of a new or different kind of accident from any accident previously evaluated?
Response: No.
The proposed changes would not require nor create any new or different accidents to be postulated and subsequently evaluated, since no changes are being made to the plant or accident mitigating measures that would introduce any new accident causal mechanisms. This license amendment request does not impact any plant systems that are potential accident initiators; nor does it have any significantly adverse impact on any accident mitigating systems.
Therefore, the proposed change does not create the possibility of a new or different kind of accident from any accident previously evaluated.
: 3. Does the proposed amendment involve a significant reduction in a margin of safety?
Response: No.
The proposed changes do not alter the plant design, including instrument setpoints, nor does it change the assumptions or accident mitigating system response contained in the safety analyses.
The safety margin with respect to this change is established in the licensing basis for WBN in response to 10 CFR 50 Appendix A General Design Criterion 16 Containment Design and is described in Section 3.1.2.2 of the WBN dual-unit Updated Final Safety Analysis Report (UFSAR). This change does not exceed or alter a design basis and thus it does not significantly reduce the margin of safety.
The proposed changes to permit a one-time exception during the WBN Unit 2 spring 2022 outage in support of the RSG project to allow the ABSCE boundary to be opened, at specific controlled access points, on a continuous basis with administrative controls in place are consistent with the current Note in WBN Unit 1 TS 3.7.12 and its supporting analysis that allows intermittent opening of the ABSCE boundary under administrative controls and the associated requirements for closure of the ABSCE boundary. Therefore, it is expected that the plant and the operators would maintain the ability to mitigate design basis events and none of the fission product barriers would be affected by this change. Therefore, the proposed change does not involve a significant reduction in a margin of safety.
Based on the above, TVA concludes that the proposed amendment does not involve a significant hazards consideration under the standards set forth in 10 CFR 50.92 (c), and, accordingly, a finding of no significant hazards consideration is justified.
CNL-21-015                                    E9 of 10

Enclosure 4.4   Conclusion The proposed one-time exception permitting opening of the ABSCE boundary on a continuous basis under administrative controls in support of Unit 2 RSG Project activities during the RSG outage is consistent with the current Note in Unit 1 TS 3.7.12 that allows intermittent opening of the ABSCE boundary under administrative controls and its associated requirements for closure of the ABSCE boundary. Based on experience with the current administrative controls, TVA concludes that this one-time change to WBN Unit 1 TS 3.7.12 is acceptable.
In conclusion, based on the considerations discussed above, (1) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, (2) such activities will be conducted in compliance with the Commissions regulations, and (3) the issuance of the amendment will not be inimical to the common defense and security or to the health and safety of the public.

==5.0   ENVIRONMENTAL CONSIDERATION==

A review has determined that the proposed amendment would change a requirement with respect to installation or use of a facility component located within the restricted area, as defined in 10 CFR 20, or would change an inspection or surveillance requirement. However, the proposed amendment does not involve (i) a significant hazards consideration, (ii) a significant change in the types or significant increase in the amounts of any effluents that may be released offsite, or (iii) a significant increase in individual or cumulative occupational radiation exposure. Accordingly, the proposed amendment meets the eligibility criterion for categorical exclusion set forth in 10 CFR 51.22(c)(9). Therefore, pursuant to 10 CFR 51.22(b), no environmental impact statement or environmental assessment need be prepared in connection with the proposed amendment.

==6.0   REFERENCES==
: 1. NRC letter to TVA, Watts Bar Nuclear Plant, Units 1 and 2 - Issuance of Amendments Regarding Auxiliary Building Gas Treatment System (CAC Nos. MF8526 and MF8527), dated October 17, 2017 (ML17236A057)
: 2. TVA letter to NRC, CNL-17-093, Revised Response to Request for Additional Information Related to License Amendment Request to Revise Technical Specification 3.7.12, Auxiliary Building Gas Treatment System (ABGTS), for Watts Bar Nuclear Plant, Units 1 and 2 (CAC Nos. MF8526 and MF8527), dated July 21, 2017 (ML17205A322)
: 3. TVA letter to NRC, CNL-17-044, Response to Request for Additional Information Related to License Amendment Request to Revise Technical Specification 3.7.12, Auxiliary Building Gas Treatment System (ABGTS), for Watts Bar Nuclear Plant, Units 1 and 2 (CAC Nos. MF8526 and MF8527), dated May 5, 2017 (ML17125A244)
CNL-21-015                                   E10 of 10

ATTACHMENT 1 Proposed TS Changes (Mark-Ups) for WBN Unit 1 CNL-21-015

ABGTS 3.7.12 3.7 PLANT SYSTEMS 3.7.12 Auxiliary Building Gas Treatment System (ABGTS)
LCO 3.7.12               Two ABGTS trains shall be OPERABLE.
                         -------------------------------------------NOTE-------------------------------------------------------
The Auxiliary Building Secondary Containment Enclosure (ABSCE) boundary may be opened intermittently under administrative controls that ensure the ABSCE can be closed consistent with the safety analysis.
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APPLICABILITY:
MODES 1, 2, 3, and 4.
ACTIONS CONDITION                                     REQUIRED ACTION                             COMPLETION TIME A.      One ABGTS train                      A.1        Restore ABGTS train to                       7 days inoperable.                                      OPERABLE status.
B.      Two ABGTS trains                     B.1        Initiate actions to implement                Immediately Inoperable due to                                mitigating actions.
inoperable ABSCE boundary.                           AND B.2        Verify mitigating actions ensure             24 hours main control room occupants do not exceed 10 CFR 50 Appendix A GDC 19 limits.
AND B.3         Restore ABSCE boundary to                   7 days OPERABLE status.
(continued)
Watts Bar-Unit 1                                           3.7-27                    Amendment No. 92, 112, 116

ATTACHMENT 2 Proposed TS Changes (Final Typed) for WBN Unit 1 CNL-21-015

ABGTS 3.7.12 3.7 PLANT SYSTEMS 3.7.12 Auxiliary Building Gas Treatment System (ABGTS)
LCO 3.7.12               Two ABGTS trains shall be OPERABLE.
                         -------------------------------------------NOTE-------------------------------------------------------
The Auxiliary Building Secondary Containment Enclosure (ABSCE) boundary may be opened intermittently under administrative controls that ensure the ABSCE can be closed consistent with the safety analysis.
As a one-time exception for the Watts Bar Unit 2 Cycle 4 Refueling Outage, scheduled to commence in spring 2022, during which the Unit 2 Replacement Steam Generators (RSGs) will be installed, the breaches of the ABSCE boundary needed to support the Unit 2 RSG project activities (Unit 2 Upper Containment Personnel Air Lock Access, Unit 2 Lower Containment Personnel Air Lock Access, Unit 2 Containment Equipment Hatch, and Auxiliary Building General Supply Fan 737 Elevation Room A12 Access and Backup) may be opened on a continuous basis, under administrative controls that ensure the ABSCE can be closed consistent with the safety analysis.
APPLICABILITY:           MODES 1, 2, 3, and 4.
ACTIONS CONDITION                                     REQUIRED ACTION                             COMPLETION TIME A.      One ABGTS train                      A.1        Restore ABGTS train to                       7 days inoperable.                                      OPERABLE status.
B.      Two ABGTS trains                     B.1        Initiate actions to implement                Immediately Inoperable due to                                mitigating actions.
inoperable ABSCE boundary.                           AND B.2        Verify mitigating actions ensure             24 hours main control room occupants do not exceed 10 CFR 50 Appendix A GDC 19 limits.
AND B.3         Restore ABSCE boundary to                   7 days OPERABLE status.
Watts Bar-Unit 1                                           3.7-27                       Amendment No. 92, 112, 116,

ATTACHMENT 3 Proposed TS Bases Changes (Mark-Ups) for WBN Unit 1 (For Information Only)
CNL-21-015

ABGTS B 3.7.12 BASES (continued)
LCO                 Two independent and redundant trains of the ABGTS are required to be OPERABLE to ensure that at least one train is available, assuming a single failure that disables the other train, coincident with a loss of offsite power. Total system failure, such as from a loss of both ventilation trains or from an inoperable ABSCE boundary, could result in exceeding a dose of 5 rem whole body or its equivalent to any part of the body to the main control room occupants in the event of a large radioactive release.
The ABGTS is considered OPERABLE when the individual components necessary to control exposure in the fuel handling building are OPERABLE in both trains. An ABGTS train is considered OPERABLE when its associated:
: a.        Fan is OPERABLE;
: b.        HEPA filter and charcoal adsorber are not excessively restricting flow, and are capable of performing their filtration function; and
: c.        Heater, moisture separator, ductwork, valves, and dampers are OPERABLE, and air circulation can be maintained.
The LCO is modified by a Note allowing the ABSCE boundary to be opened intermittently under administrative controls that ensure the ABSCE can be closed consistent with the safety analysis. For entry and exit through doors the administrative control of the opening is performed by the person(s) entering or exiting the area. For other openings, these controls are proceduralized and consist of stationing a dedicated individual at the opening who is in continuous communication with the control room. This individual will have a method to rapidly close the opening when a need for auxiliary building isolation is indicated. The ABSCE boundary must be able to be restored within four minutes (including the time for restoration of the ABSCE boundary and drawdown) in accordance with UFSAR Section 15.5.3.
As a one-time exception for the Watts Bar Unit 2 Cycle 4 Refueling Outage, scheduled to commence in sSULQJ 2022, during which the Unit 2 Replacement Steam Generators (RSGs) will be installed, the breaches of the ABSCE boundary needed to support the Unit 2 RSG project activities (Unit 2 Upper Containment Personnel Air Lock Access, Unit 2 Lower Containment Personnel Air Lock Access, Unit 2 Containment Equipment Hatch, and Auxiliary Building General Supply Fan 737 Elevation Room A12 Access and Backup) may be opened on a continuous basis, under administrative controls that ensure the ABSCE can be closed consistent with the safety analysis.
These controls are the same as for the existing Note as described above.
APPLICABILITY       In MODE 1, 2, 3, or 4, the ABGTS is required to be OPERABLE to provide fission product removal associated with ECCS leaks due to a LOCA and leakage from containment and annulus.
In MODE 5 or 6, the ABGTS is not required to be OPERABLE since the ECCS is not required to be OPERABLE.
(continued)
Watts Bar-Unit 1                              B 3.7-56                     Revision 55, 87, 119, 139, Amendment 92, 116}}