PLA-7528, Supplemental Information for License Amendment Request to Address Secondary Containment Access Openings
| ML16257A598 | |
| Person / Time | |
|---|---|
| Site: | Susquehanna  |
| Issue date: | 09/13/2016 |
| From: | Franke J Susquehanna, Talen Energy |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| PLA-7528 | |
| Download: ML16257A598 (10) | |
Text
SEP 1 3 2016 Jon A. Franke Susquehanna Nuclear, LLC Site Vice President 769 Salem Boulevard Berwick, PA 18603 Tel. 570.542.2904 Fax 570.542.1504 Jon.Franke@TalenEnergy.com U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555-0001 SUSQUEHANNA STEAM ELECTRIC STATION SUPPLEMENTAL INFORMATION FOR LICENSE AMENDMENT REQUEST TO ADDRESS SECONDARY CONTAINMENT ACCESS OPENINGS PLA-7528 TALEN ~
ENERGY Docket No. 50-387 50-388
References:
I.
Letter PLA-7486, "Susquehanna Steam Electric Station Proposed License Amendment Request to Address SecondWJI Containment Access Openings, "dated July 27, 2016, (Accession ML162IOAOOI).
- 2.
NRC letter, "Supplemental Information Needed for Acceptance of Requested Licensing Action Re: Request to Address Secondwy Containment Access Openings, " dated August 25, 2016 (Accession ML16237Al44).
Susquehanna Nuclear, LLC is providing requested supplemental information for a License Amendment Request (LAR) affecting Susquehanna Steam Electric Station (SSES) Unit 1 and 2 Technical Specifications (TS). The proposal affects TS 3.6.4.1 "Secondary Containment," Surveillance Requirement (SR) 3.6.4.1.3 to provide an allowance for brief, inadvertent, simultaneous opening of redundant Secondary Containment access doors during nmmal entry and exit conditions.
Reference 2 requests supplemental information from Susquehanna Nuclear, LLC to support the NRC in reviewing the LAR subject of reference 1, with an opportunity to provide the requested information by September 14, 2016. Attachment 1 provides responses to these requests.
Susquehanna Nuclear, LLC has reviewed the infmmation supporting a finding of no significant hazards consideration and the environmental consideration provided to the NRC in Reference 1. The additional infmmation provided by this submittal does not affect the bases for concluding that the proposed license amendment does not involve a significant hazards consideration. Furthermore, the additional information does not affect the bases for concluding that neither an environmental impact statement nor an environmental assessment need to be prepared in connection with the proposed amendment.
There are no new regulatory commitments associated with this response.
Document Control Desk PLA-7528 If you have any questions or require additional information, please contact Mr. Jason Jennings, Manager of Nuclear Regulatory Affairs, at (570) 542-3155.
I declare under penalty of peljury that the foregoing is true and correct.
Executed on:
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Sincerely, J. A. Franke :
Response to Opportunity to Supplement Copy:
NRC Region I Mr. J. E. Greives, NRC Sr. Resident Inspector Ms. T. E. Hood, NRC Project Manager Mr. M. Shields, PA DEP/BRP to PLA-7528 Susquehanna Nuclear, LLC Supplemental Information Needed for Acceptance of Requested Licensing Action Re:
Amendment Request to Address Secondary Containment Access Openings Response to Opportunity to Supplement
Opportunity to Supplement License Amendment Request, Susquehmma response Questions to be addressed From Reference 2:
"In order for the NRC staff to complete its detailed technical review, one of the following is needed:
- 1. Account for a ground level release in your fuel handling accident analysis, and any other impacted analysis, and provide atmospheric dispersion factors (x/Q's) for the analysis, or
- 2. Provide a bounding analysis that addresses the ground level release including x/Q' s even for the short time proposed in the amendment request, or
- 3. Provide an analysis that shows that the standby gas treatment system has enough capacity to maintain the Secondary Containment at a negative pressure with both doors open and that no radioactivity will release through the open doors at ground level (to be bounded by the current analysis of record).
During the clarification call, the NRC staff indicated that the response would need to address:
- 1. The analysis compared to RG 1.183
- 2. The release point(s)
- 3. The safety evaluation where the NRC approved the x/Q's for the release point(s)
(provide ADAMS accession number if known).
- 4. Why the previously approved x/Q' s are valid for this application" Susquehanna Response The only two accidents that credit Secondary Containment from a dose consequence perspective are the Loss of Coolant Accident (LOCA) and Fuel/Equipment Handling Accident.
Station personnel passing through a Secondary Containment personnel access door is considered a normal plant activity. However, the simultaneous opening of both an inner and outer door in an access opening does not satisfy TS SR 3.6.4.1.3. Once one door is closed, the SR is met. The time that both inner and outer doors are simultaneously open is typically less than 10 seconds for personnel access. The importance of promptly closing Secondary Containment boundary doors is communicated in generic plant access training. Airlock doors have indicating lights to provide a status of the airlock and whether entry is permitted. An audible ala1m sounds if both airlock doors are open. This alarm provides indication to plant personnel to close the airlock doors. These features provide adequate assurance that the airlock doors will be closed within 1 0 seconds.
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Oppmiunity to Supplement License Amendment Request, Susquehanna response The Susquehanna secondary containment consists of three distinct zones. Zones I and II are the portions of the Unit 1 and 2 reactor buildings below elevation 779' surrounding the Unit 1 and 2 primary containment, respectively. Zone III consists of the pmiion of the Unit 1 and 2 reactor building above elevation 779' with the exception of Heating, Ventilation, and Air Conditioning (HV AC) equipment rooms. During a postulated LOCA without a concurrent Loss of Offsite Power (LOOP), the ventilation zone associated with the unit experiencing the LOCA and Zone III will isolate (e.g., Zone I and III for a Unit 1 LOCA or Zone II and III for a Unit 2 LOCA). If a LOOP occurs concurrent with a LOCA, then all three zones will isolate assuming all three zones are operable or required to be operable. Note that SSES has a railroad bay area that can be aligned as Zone I, III, or as No-Zone. For a fuel handling accident, only Zone III isolates assuming a LOOP has not occurred.
The Secondary Containment drawdown analysis assumes that the vacuum within the affected Secondary Containment zones at time 0 seconds of a Loss of Coolant Accident (LOCA) is 0.0 inches water gauge (in. w.g.) and has an allowable Standby Gas Treatment System (SGTS) exhaust flow rate equal to 140% of the Secondary Containment free air volume/day. This analysis demonstrates that SGTS can drawdown the secondary containment (assuming worst case 3 zone drawdown) within 5 minutes.
The LOCA dose consequence analysis uses the allowable SGTS exhaust flow rate and conservatively doubles the drawdown time (10 minute drawdown) to compute the on-site and off-site doses. The post-LOCA dose analysis conservatively assumes that for the entire 10 minute draw down time the release from Secondary Containment is a ground level unfiltered release. The modeled unfiltered releases from the Secondary Containment during the drawdown period are the design SGTS flow rate (11,110 cfm) and the building is assumed to have an out-leakage equivalent to 140% of the Secondary Containment free air volume per day.
After the 10 minute (600 second) time is reached, a vacuum of0.25 in w.g. is established. All exhaust from Secondary Containment is now filtered through the SGTS prior to release to the environment.
The most recent drawdown times obtained during testing are shown in Table 1. Note that the test which includes all Zones in the drawdown volume is the most limiting.
Table 1 - Historical drawdown times Test type SGTS Time (sec)
Time (sec)
Division 101 Bay aligned to Zone 3 101 Bay excluded Zone 1 and 3 isolation Div 1 77 80 Zone 1 and 3 isolation Div2 81 77 Zone 2 and 3 isolation Div 1 80 69 Page 2 of 7
Opportunity to Supplement License Amendment Request, Susquehanna response Zone 2 and 3 isolation Div2 Zone 1, 2, and 3 isolation Div 1 Zone 1, 2, and 3 isolation Div 2 58 75 60 62 78 84 Because the margin for drawdown time is relatively large, the brief, inadvertent, simultaneous opening of both an inner and outer personnel access door during nmmal entry and exit conditions followed by prompt closure does not challenge the design basis drawdown time of 10 minutes or the ability to maintain a 0.25 in vacuum water gauge and does not result in an increase in any on-site or offsite dose for the LOCA dose analysis. This change does not require a change to the secondary containment drawdown testing since testing multiple zones bounds the case of Zone III only. Additionally, the assumed SGTS exhaust flow rate for this event is not mechanistic and therefore the system performance will also be within the assumptions of the analysis.
The LOCA dose consequence analysis uses dispersion factors (xJQ values) based on a ground level release, since all postulated release locations are less than 2.5 times the height of adjacent structures. Dispersion factors used in the LOCA dose consequence analysis include those for the Exclusion Area Boundary (EAB), Low Population Zone (LPZ), and Control Room.
The dispersion factors for the Exclusion Area Boundary (EAB) and Low Population Zone (LPZ) were calculated using plant meteorological data from 1999 -2003, Regulatory Guide 1.145 "Atmospheric Dispersion Models for Postulated Accident Consequence Assessments at Nuclear Power Plants," and the WINDOWS computer program which is similar to the P A VAN code. 5 The dispersion factors for the control room were calculated using plant meteorological data from 1999 -2003 and used Regulatory Guide 1.194 "Atmospheric Relative Concentrations for Control Room Radiological Habitability Assessments at Nuclear Power Plants" and the ARCON96 computer code.6'7 All3 aforementioned dispersion factors were reviewed by the NRC as part of the SSES adoption of an alternative source te1m (AST) in accordance with 10 CFR 50.67, "Accident Source Te1m." The NRC review and acceptance of the dispersion factors are documented in the NRC Safety Evaluation for implementation of alternative radiological source term. 3'4 The dispersion factors are not invalidated by airlock door events since the event occurs for a brief period of time at the onset of the accident. Section 3.3 of Regulatory Guide 1.183 "Alternative Radiological Source Terms for Evaluating Design Basis Accidents at Nuclear Power Reactors," states that there is a 2 minute time delay until the onset of the gap release (release of all fission products in the gap between the fuel pellet and fuel Page 3 of 7
Oppmiunity to Supplement License Amendment Request, Susquehanna response cladding). The door will be closed by the time the gap release phase is assumed to occur.
Therefore, during a LOCA there is no radiological release caused by fuel damage during simultaneous opening of the 2 doors in the access opening.
The method of calculating the dispersion factors is not dependent on the doors in an access opening being briefly opened or closed since the release due to fuel damage does not begin until two minutes into the accident. The same dispersion factors are used during the drawdown of Secondary Containment and post drawdown, when Secondary Containment is isolated and vacuum is established.
The current dose consequence analysis for a fuel handling accident does not include any drawdown time for Secondary Containment. The dose consequence analysis assumes that there is no hold-up in Secondary Containment and that all activity is released to the environment over a two hour period. This is a conservative assumption since an exhaust flow rate beyond the current flow capacity of the SGTS would be required to meet a release period of 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />. If the actual SGTS flow rate was used, substantially more time would be needed to release all the radioactive material within Secondary Containment which would allow for radioactive decay, thereby lowering the dose consequences.
During normal operation, the refuel floor is maintained at a vacuum of 0.25 in. w.g. by normal operating ventilation systems. This is required by Unit 1 and Unit 2 Technical Specification SR 3.6.4.1.1. The exhaust ductwork on the refuel floor is equipped with radiation monitors to detect a fuel handling accident. When a radiological release is sensed by the radiation monitors, a Zone 3 Secondary Containment isolation signal is generated. This initiates the SGTS and the normal Zone 3 ventilation system trips.
The radiation monitor is positioned such that it will detect the release and send a closure signal to the Secondary Containment isolation dampers. The distance between the isolation dampers and the radiation detectors is such that the transit time for air from the radiation detector to the Secondary Containment isolation damper is greater than the isolation damper closure time. This prevents any release from bypassing filtration via the SGTS. The NRC acceptance of this modeling is documented in the NRC safety evaluation for implementation of an alternative radiological source term?*4 With both airlock doors briefly open, the refuel floor vacuum will decrease due to air in-leakage onto the refuel floor due to the pressure differential. It is reasonable to expect that the refuel floor will remain under a vacuum since the nmmal in-leakage onto the refuel floor is well below the capacity of SGTS. When the door is opened, the refuel floor vacuum will decrease to the point that the flow through the open door is equivalent to the excess SGTS flow capacity but the refuel floor will remain under vacuum. An equilibrium condition will be reached when the flow through the refuel floor in-leakage and the flow through the open airlock door is equivalent to the SGTS exhaust flow rate.
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Opportunity to Supplement License Amendment Request, Susquehmma response To conservatively bound the decrease in refuel floor vacuum, the dose consequence analysis for the fuel handling accident is being revised as part of this submittal to include a 10 minute drawdown. This approach consistently models the performance of Secondary Containment for the LOCA and fuel handling accident dose consequence analysis and will conservatively envelope both airlock doors being opened inadvertently for a brief period of time.
The current fuel handling accident dose consequence analysis was submitted to the NRC during the application for use of an Alternative Source Term. These submittals are documented in ADAMS under the original license amendment requested by Susquehanna, as supplemented by additional docketed correspondence.8'9' lO, 11' 12' 13, 14' 15, 16 The only deviation from the previously submitted refuel handling accident dose consequence analysis is with respect to SGTS filtration. Specifically, SGTS filtration in the analysis used to support this request is revised to be 0% for the first 10 minutes. Note that this is a ground level release; since the refuel floor pressure will be at a slight vacuum the assumed SGTS release point does not change.
As previously stated, the atmospheric dispersion factors used in the fuel handling accident are the values approved by the NRC for implementation of an Alternative Radiological Source Term. The resultant dose consequences for the worst case fuel/equipment handling accident in which 460.8 fuel rods are failed are listed in Table
- 2.
Table 2-Dose consequences for worst case fuel/equipment handling accident Dispersion Factor Calculated Dose Regulatory Limit (Rem TEDE)
EAB 2.33 6.3 LPZ 0.137 6.3 Control Room 0.178 5.0 All dose consequences are well within the regulatory limits established for the fuel handling accident and bound the case in which airlock doors are briefly, inadvertently opened. Using the detailed discussion in the above paragraphs, a response to all 3 questions has been provided in a manner which indicates how the analysis aligns with Regulatory Guide 1.183, applicable release points, the NRC Safety Evaluation for x/Q values utilized, and how the NRC approved x/Q values are valid for this application.
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Opportunity to Supplement License Amendment Request, Susquehatma response References
- 1.
Letter PLA-7486, "Susquehanna Steam Electric Station Proposed License Amendment Request to Address Secondmy Containment Access Openings," dated July 27, 2016, (Accession ML16210AOOJ).
- 2.
NRC letter, "Supplemental Information Needed for Acceptance of Requested Licensing Action Re: Request to Address Seconda!JI Containment Access Openings," dated August 25, 2016 (Accession MLJ6237 Al44).
- 3.
NRC letter to Susquehanna, "Susquehanna Steam Electric Station, Units 1 and 2-Issuance of Amendment Re: Implementation of Alternative Radiological Source Term (TAC Nos. MC8730 and MC8731), "dated Janumy 31, 2007 (Accession ML070080301).
- 4.
NRC letter to Susquehanna, "Susquehanna Steam Electric Station, Units 1 and 2 - Correction to Amendment Nos. 239 and 216 (TAC Nos. MC8730 and MC8731), "dated May 10, 2007 (Accession ML071270053).
- 5.
Regulatory Guide 1.145, Revision 1, "Atmospheric Dispersion Models for Postulated Accident Consequence Assessments at Nuclear Power Plants," dated Februmy, 1983.
- 6.
Regulat01y Guide 1.194, Revision "Atmospheric Relative Concentrations for Control Room Radiological Habitability Assessments at Nuclear Power Plants, "dated June, 2003.
- 7.
J. V Ramsdell, Jr., and C.A. Simonen, "Atmospheric Relative Concentrations in Building Wakes," NUREG/CR-6331, Revision], USNRC, May 1997.
- 8.
Letter PLA-5963, "Susquehanna Steam Electric Station Proposed Amendment No. 281 to License NPF-14 and Proposed Amendment No. 251 to License NPF-22: Application for License Amendment and Related Technical Specification Changes to Implement Full-Scope Alternative Source Term in Accordance with 10 CFR 50. 67, "Dated October 13, 2005 (Accession ML060120353).
- 9.
Letter PLA-6055, "Susquehanna Steam Electric Station Proposed Amendment No. 281 to License NPF-14 and Proposed Amendment No. 251 to License NPF-22: Application for License Amendment and Related Technical Specification Changes to Implement Full-Scope Alternative Source Term in Accordance with 10 CFR 50. 67, "Dated May 18, 2006 (Accession ML061520457).
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Opportunity to Supplement License Amendment Request, Susquehanna response I 0.
Letter PLA-6114, "Susquehanna Steam Electric Station Proposed Amendment No. 281 to License NPF-14 and Proposed Amendment No. 251 to License NPF-22: "Application for License Amendment and Related Technical Specification Changes to Implement Full-Scope Alternative Source Term in Accordance with I 0 CFR 50.67 - Response to Request for Additional Information, ""Dated September 15, 2006 (Accession ML062710318).
II.
Letter PLA-6112, "Susquehanna Steam Electric Station Proposed Amendment No. 281 to License NP F-14 and Proposed Amendment No. 2 51 to License NPF-22: Application for License Amendment and Related Technical Specification Changes to Implement Full-Scope Alternative Source Term in Accordance with I 0 CFR 50. 67, "Dated September 15, 2006 (Accession ML062710360).
- 12.
Letter PLA-6114, "Susquehanna Steam Electric Station Proposed Amendment No. 281 to License NPF-14 and Proposed Amendment No. 251 to License NPF-22: "Application for License Amendment and Related Technical Specification Changes to Implement Full-Scope Alternative Source Term in Accordance with I 0 CFR 50.67-Follow up to Request for Additional Information (RAJ),"" Dated September 29, 2006 (Accession ML062850276)
- 13.
Letter PLA-6120, "Susquehanna Steam Electric Station Proposed Amendment No. 281 to License NPF-14 and Proposed Amendment No. 251 to License NPF-22: "Application for License Amendment and Related Technical Specification Changes to Implement Full-Scope Alternative Source Term in Accordance with I 0 CFR 50. 67, ""Dated October 20, 2006 (Accession ML063040598).
- 14.
Letter PLA-6124, "Susquehanna Steam Electric Station Proposed Amendment No. 281 to License NP F-14 and Proposed Amendment No. 251 to License NP F-22: "Application for License Amendment and Related Technical Specification Changes to Implement Full-Scope Alternative Source Term in Accordance with I 0 CFR 50.67-Response to Request for Additional Information,"" Dated November 14,2006 (AccessionML063310433).
- 15.
Letter PLA-6139, "Susquehanna Steam Electric Station Proposed Amendment No. 281 to License NPF-14 and Proposed Amendment No. 251 to License NPF-22: "Application for License Amendment and Related Technical Specification Changes to Implement Full-Scope Alternative Source Term in Accordance with I 0 CFR 50. 67, ""Dated December 13, 2006 (Accession ML063540439).
- 16.
Letter PLA-6145, "Susquehanna Steam Electric Station Proposed Amendment No. 281 to License NPF-14 and Proposed Amendment No. 251 to License NPF-22: "Application for License Amendment and Related Technical Specification Changes to Implement Full-Scope Alternative Source Term in Accordance with I 0 CFR 50.67 - Response to Request for Additional Information,"" Dated December 14, 2006 (Accession ML063610311).
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