Text

License Amendment Request to Incorporate Revised Alternative Source Term Dose Calculation
	ML16029A418
Person / Time
Site:	Clinton
Issue date:	01/29/2016
From:	Simpson P; Exelon Generation Co
To:	; Document Control Desk, Office of Nuclear Material Safety and Safeguards, Office of Nuclear Reactor Regulation
References
	RS-16-019
	Download: ML16029A418 (42)
	v • d • e

100W 1111 Id~ d Vv.11 rr* IV llP IL l'OS5'i Exelon Generation v J/ 00001 Cl RS-16-019 10 CFR 50.90 January 29, 2016 U.S. Nuclear Regulatory Commission A TIN: Document Control Desk Washington, DC 20555-001 Clinton Power Station, Unit 1 Facility Operating License No. NPF-62 NRC Docket Nos. 50-461 and 72-1046

Subject:

License Amendment Request to Incorporate Revised Alternative Source Term Dose Calculation In accordance with 10 CFR 50.90, "Application for amendment of license, construction permit, or early site permit," Exelon Generation Company, LLC (EGG) requests an amendment to Facility Operating License No. NPF-62 for Clinton Power Station (CPS), Unit 1. The proposed change would revise an input parameter for the Loss-of-Coolant Accident (LOCA) dose calculation in the CPS Updated Safety Analysis Report (USAR) and the CPS Technical Specification (TS) Bases. The current LOCA dose calculation methodology was submitted and approved by the NRC in Amendment 167 to NPF-62, which implemented an alternative source term (AST) methodology in accordance with 10 CFR 50.67, "Accident source term."

This proposed change is necessary to implement dry cask storage (DCS) activities at CPS in August 2016. Due to the added heat from a loaded spent fuel cask in Secondary Containment, the post-LOCA drawdown time for Secondary Containment will increase from the current licensing basis (CLB) value of 12 minutes to 19 minutes. This increased drawdown time results in an increase in the post-LOCA dose for the Control Room. Although the resultant Control Room dose is within the 10 CFR 50.67 requirement, the increase in consequences is more than minimal, and as such requires prior NRG approval, in accordance with 10 CFR 50.59(c)(1)(iii).

The attachment and associated enclosures provide an evaluation of the proposed change, and includes marked-up USAR and Technical Specification Bases pages, for information only.

The proposed amendment has been approved by the CPS Plant Operations Review Committee and approved by the Nuclear Safety Review Board in accordance with the requirements of the EGG Quality Assurance Program.

EGG requests approval of the proposed license amendment by August 1, 2016. Once approved, the amendment will be implemented within 30 days.

January 29, 2016 U.S. Nuclear Regulatory Commission Page2 In accordance with 10 CFR 50.91, "Notice for public comment; State consultation," paragraph (b), EGC is notifying the State of Illinois of this application for license amendment by transmitting a copy of this letter and its attachments to the designated State Official.

There are no regulatory commitments contained in this letter. Should you have any questions concerning this letter, please contact Mr. John L. Schrage at (630) 657-2821.

I declare under penalty of perjury that the foregoing is true and correct. Executed on the 29th day of January 2016.

Patrick R. Simpson Manager - Licensing Exelon Generation Company, LLC

Attachment:

Evaluation of Proposed Change cc: NRC Regional Administrator, Region Ill NRC Senior Resident Inspector - Clinton Power Station Illinois Emergency Management Agency - Division of Nuclear Safety

ATTACHMENT Clinton Power Station, Unit 1 License Amendment Request Revision of USAR to Incorporate Revised Alternative Source Term Dose Calculation Page 1 of 10

Subject:

Revision of USAR to Incorporate Revised Alternative Source Term Dose Calculation 1.0

SUMMARY

DESCRIPTION 2.0 DETAILED DESCRIPTION

3.0 TECHNICAL EVALUATION

3.1 System Description 3.2 Evaluation of Proposed Change

4.0 REGULATORY EVALUATION

4.1 Applicable Regulatory Requirements/Criteria 4.2 No Significant Hazards Consideration 4.3 Conclusions

5.0 ENVIRONMENTAL CONSIDERATION

6.0 REFERENCES

Marked-up USAR and TS Bases Pages Physical Input Parameters and Assumptions, Post-LOCA Dose Calculations Conservatisms in Post-LOCA Dose Calculations Impact of Increased Drawdown Time on Chapter 15 Accident Analyses Environmental Qualification Evaluation Due to Increased Heat Load

ATTACHMENT Clinton Power Station, Unit 1 License Amendment Request Revision of USAR to Incorporate Revised Alternative Source Term Dose Calculation Page 2 of 10 1.0

SUMMARY

DESCRIPTION In accordance with 10 CFR 50.90, Exelon Generation Company, LLC (EGC) requests an amendment to Facility Operating License No. NPF- 62 for Clinton Power Station (CPS), Unit 1 to revise the Current Licensing Basis described in the CPS Updated Safety Analysis Report (USAR), Section 6.2.3, "Secondary Containment Functional Design," Section 6.5.1,"

Engineered Safety Feature (ESF) Filter Systems," and Section 15.6.5, "Loss-of-Coolant Accidents (Resulting from Spectrum of Postulated Piping Break Within the Reactor Coolant Pressure Boundary) - Inside Containment." In addition, the proposed amendment will revise CPS Technical Specification (TS) Bases section B 3.6.4.1, "Secondary Containment."

The proposed change will revise an input parameter for the Loss-of-Coolant Accident (LOCA) dose calculation and the subsequent calculation results. The current LOCA dose calculation methodology was submitted and approved by the NRC in Amendment 167 to NPF-62, which implemented an alternative source term (AST) methodology in accordance with 10 CFR 50.67, "Accident source term."

This proposed change is necessary to implement dry cask storage (DCS) activities at CPS in August 2016. Due to the added heat from a loaded spent fuel cask in Secondary Containment, the post-LOCA drawdown time for Secondary Containment will increase from the current licensing basis (CLB) value of 12 minutes to 19 minutes. This increased drawdown time results in an increase in the post-LOCA dose for the Control Room. Although the resultant Control Room dose is within the 10 CFR 50.67 requirement, the increase in consequences is more than minimal, and as such requires prior NRC approval, in accordance with 10 CFR 50.59(c)(1)(iii).

EGC has conducted evaluations to validate that the proposed configuration complies with the applicable 10 CFR 50, Appendix A, General Design Criteria (GDC), as well as the requirements of 10 CFR 50.49, "Environmental qualification of electric equipment important to safety for nuclear power plants," 10 CFR 50.67, and Regulatory Guide 1.183, "Alternative Radiological Source Terms for Evaluating Design Basis Accidents at Nuclear Power Reactors."

2.0 DETAILED DESCRIPTION EGC is currently preparing to implement initial DCS activities at CPS in accordance with 10 CFR 72.210, "General license issued." These activities are scheduled to commence in August 2016, and will be necessary to achieve full core offload capability.

During the cask loading process, a fully-loaded cask will be present in the Fuel Building (FB).

EGC has determined that the added heat from a fully-loaded design basis cask will impact the post-LOCA temperature in various areas of Secondary Containment. As a result, the time period necessary for the Standby Gas Treatment System (SGTS) to achieve and maintain the required negative pressure in Secondary Containment will increase from the CLB value of 12 minutes to 19 minutes. This drawdown time value is documented in USAR Sub-section 6.2.3.3.2.1, "Short-Term Pressure History," USAR Subsection 6.5.1.1.1, "Standby Gas Treatment System," USAR Subsection 15.6.5.5.1.2, "Fission Product Transport to the

ATTACHMENT Clinton Power Station, Unit 1 License Amendment Request Revision of USAR to Incorporate Revised Alternative Source Term Dose Calculation Page 3 of 10 Environment," USAR Figure 15.6-1, "Schematic of LOCA Transport Pathways," and TS Bases Section B 3.6.4.1.

Since the Secondary Containment drawdown time is an input value into the post-LOCA dose calculations described in USAR Section 15.6.5, EGC has re-evaluated the impact of the increased drawdown time on post-accident radiological consequences for the Exclusion Area Boundary (EAB), the Low Population Zone (LPZ) Boundary, and the Control Room. The revised post-LOCA dose calculation was performed in accordance with the guidance in Regulatory Guide 1.183 and NUREG-0800, "Standard Review Plan for the Review of Safety Analysis Reports for Nuclear Power Plants: LWR Edition," (SRP) Section 15.0.1, "Radiological Consequences Analyses Using Alternative Source Terms."

This radiological consequence evaluation identified that the post-accident doses for LPZ and Control Room locations increased, while the value for the EAB post-accident dose remained constant. The increase in the post-accident dose for the LPZ, which is documented in USAR Table 15.6.5-6, "Loss-of-Coolant Accident (Design Basis Analysis) Radiological Effects," was not more than minimal, and therefore could be changed in accordance with 10 CFR 50.59.

However, the increase in post-accident Control Room dose, which is documented in USAR Subsection 15.6.5.5.2, "Control Room," while within the 10 CFR 50.67 limit, was more than minimal, and as such requires prior NRC approval. Specifically, the postulated post-LOCA Control Room dose will increase from the current value of 4.73 Rem to 4.84 Rem, relative to the 10 CFR 50.67 and GDC-19, "Control Room," limit of 5 Rem. Enclosure 1 provides a marked-up version of the affected USAR and TS Bases pages, for information only.

3.0 TECHNICAL EVALUATION

3.1 System Description The Secondary Containment is a structure that completely encloses the primary containment except for the upper personnel hatch, and consists of the Containment Gas Control Boundary (CGCB), the CGCB extension (i.e., siding within the auxiliary building), the FB, the emergency core cooling system (ECCS) Residual Heat Removal (RHR) heat exchanger rooms, the RHR pump rooms, the Reactor Water Cleanup (RWCU) pump room, and the main steam pipe tunnel.

The Secondary Containment boundary is described in CPS USAR Sections 6.2.3.1, 6.2.3.2, 6.2.3.3, and USAR Figure 6.2-132, sheets 1 to 6.

The Secondary Containment, in conjunction with the operation of SGTS is designed to limit the total effective dose equivalent (TEDE) within the guidelines of 10 CFR 50.67 at the EAB and LPZ. Also, the design limits the TEDE dose for the Control Room occupants to within the guidelines of 10 CFR 50.67 and GDC 19. Both the Secondary Containment and the SGTS are designed to permit periodic inspection and testing of principal systems and components such as fans, dampers, and filters, as required by GDC 43.

The performance objective of the Secondary Containment is to provide a volume that completely surrounds the primary containment which will capture fission products that might

ATTACHMENT Clinton Power Station, Unit 1 License Amendment Request Revision of USAR to Incorporate Revised Alternative Source Term Dose Calculation Page 4 of 10 otherwise leak to the environment following a design basis accident. The Secondary Containment boundary is sufficiently leak tight such that the SGTS will maintain the Secondary Containment at a negative pressure equivalent to 1/4 inch of water within a specified time frame.

By letter dated April 3, 2003, (Reference 6.1), as supplemented by letters dated December 23, 2003, December 9, 2004, December 17, 2004, March 30, 2005, and August 19, 2005 (References 6.2 through 6.6, respectively), AmerGen Energy Company, LLC (i.e., the CPS licensee prior to EGC), requested a license amendment to support AST methodology for design basis accidents, in accordance with 10 CFR 50.67, with the exception that Technical Information Document (TID) 14844, "Calculation of Distance Factors for Power and Test Reactor Sites,"

would continue to be used as the radiation dose basis for equipment environmental qualification.

The LOCA analysis supporting the Reference 6.1 license amendment request assumed an unfiltered release from secondary containment for 12 minutes following accident initiation. By letter and Safety Evaluation dated September 19, 2005 (Reference 6.7), the NRC approved Amendment 167 to NPF-62. This included explicit approval for the 12-minute unfiltered release time frame.

In May 2015, EGC implemented a design change for CPS that revised the operating cycle to the current value of 12 months. This design change revised an input parameter to the original AST post-LOCA dose calculation. As a result, EGC reanalyzed the original AST dose calculations with a 12-month operating cycle. The resultant change to the EAB, LPZ, and Control Room post-LOCA dose values remained below the 10 CFR 50.67 limits, and were implemented in accordance with the requirements of 10 CFR 50.59 (i.e., the resultant change to the values was not more than minimal).

3.2 Evaluation of Proposed Change The implementation of DCS activities at CPS will result in the introduction of additional heat to secondary containment due to the decay heat of spent fuel in a loaded cask. EGC has evaluated the post-LOCA pressure response of Secondary Containment assuming the higher heat load, utilizing the design basis short-term pressure history response analysis. The results of this analysis validated that SGTS will achieve and maintain the required negative pressure in secondary containment within 19 minutes. This represents a seven minute increase from the current value.

In addition, actual SGTS train performance history during TS 3.6.4.1.4 Secondary Containment drawdown surveillances indicates that the required negative pressure equivalent to 1/4 inch of water is achieved in approximately one half of the procedural acceptance criteria of 78 seconds.

This acceptance criteria is based on the required drawdown time, without the post-LOCA heat loads. Although this surveillance is conducted with normal operating conditions (i.e., as opposed to LOCA conditions), the margin from the acceptance criteria of 78 seconds to the analytical drawdown time provides additional assurance that SGTS will achieve the required negative pressure within 19 minutes following a LOCA, assuming a fully loaded design basis cask in the FB.

ATTACHMENT Clinton Power Station, Unit 1 License Amendment Request Revision of USAR to Incorporate Revised Alternative Source Term Dose Calculation Page 5 of 10 EGC has evaluated the impact of this increased Secondary Containment drawdown time (i.e.,

from 12 minutes to 19 minutes) on post-LOCA radiation doses (i.e., Total Effective Dose Equivalent - TEDE) at the EAB, the boundary of the LPZ, and the Control Room. This evaluation utilized the same calculational methodology that was used to support application of an AST methodology, as described in References 6.1 through 6.6, and approved by the NRC in Reference 6.7.

The results of the evaluations for the 12-month operating cycle with increased drawdown time are provided in the table below, relative to both the original AST dose calculation values and the 12-month operating cycle values, both of which used a 12-minute drawdown time. Enclosure 2 provides the physical input parameters and assumptions that were used for the revised post-LOCA dose calculations, as well as the corresponding parameters used in the original calculations (i.e., in support of Amendment 167) and the 12-month operating cycle calculations. provides a discussion of both quantitative and qualitative uncertainties in the post-LOCA dose calculations, relative to the 10 CFR 50.67 limits.

Increased Secondary Containment Drawdown Time Post-LOCA Radiation Doses (TEDE) (Rem) 12-Month Fuel Original AST Proposed Cycle with 12- 10 CFR 50.67 drawdown time drawdown time minute AST Limits (12 minutes) (19 minutes) drawdown time EAB 17.11 17.31 17.31 25 LPZ Boundary 7.28 7.37 7.42 25 Control Room 4.70 4.73 4.84 5 In addition to evaluating the impact of the increased drawdown time on the radiological consequences of a LOCA (i.e., as described in USAR Section 15.6.5), EGC has validated that the increased drawdown time does not impact any other AST-affected accident described in USAR Chapter 15, "Accident Analyses." Enclosure 4 provides this validation.

Finally, in that a fully-loaded cask will add heat into Secondary Containment, EGC has evaluated the impact of the added heat on the environmental qualification (EQ) of affected equipment in Secondary Containment. This evaluation, which is described in Enclosure 5, indicates that for the affected EQ equipment in Secondary Containment, the increased temperatures are either enveloped by the original EQ evaluation or EGC has verified that the increased temperature will not impact the qualification.

ATTACHMENT Clinton Power Station, Unit 1 License Amendment Request Revision of USAR to Incorporate Revised Alternative Source Term Dose Calculation Page 6 of 10

4.0 REGULATORY EVALUATION

4.1 Applicable Regulatory Requirements/Criteria The proposed change will revise an input parameter for the post-LOCA dose calculation and the subsequent calculation results. The following NRC requirements and guidance documents are applicable to the review of the proposed change:

10 CFR 50.49, "Environmental qualification of electric equipment important to safety for nuclear power plants," requires licensees to establish a program for qualifying the safety-related electric equipment that is relied upon to remain functional during and following design basis events to ensure:

(i) The integrity of the reactor coolant pressure boundary; (ii) The capability to shut down the reactor and maintain it in a safe shutdown condition; or (iii) The capability to prevent or mitigate the consequences of accidents that could result in potential offsite exposures comparable to the guidelines in 10 CFR 50.67.

10 CFR 50.67, "Accident source term," requires those licensees with an approved alternative source term to ensure, with reasonable assurance, that:

(i) An individual located at any point on the boundary of the exclusion area for any 2-hour period following the onset of the postulated fission product release, would not receive a radiation dose in excess of 0.25 Sv (25 rem) total effective dose equivalent (TEDE).

(ii) An individual located at any point on the outer boundary of the low population zone, who is exposed to the radioactive cloud resulting from the postulated fission product release (during the entire period of its passage), would not receive a radiation dose in excess of 0.25 Sv (25 rem) total effective dose equivalent (TEDE).

(iii) Adequate radiation protection is provided to permit access to and occupancy of the control room under accident conditions without personnel receiving radiation exposures in excess of 0.05 Sv (5 rem) total effective dose equivalent (TEDE) for the duration of the accident.

10 CFR 50, Appendix A, General Design Criterion (GDC) 19, "Control Room" requires licensees to provide adequate radiation protection 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.

ATTACHMENT Clinton Power Station, Unit 1 License Amendment Request Revision of USAR to Incorporate Revised Alternative Source Term Dose Calculation Page 7 of 10 Regulatory Guide (RG) 1.183, "Alternative Radiological Source Terms for Evaluating Design Basis Accidents at Nuclear Power Reactors," provides guidance to licensees of operating power reactors on acceptable applications of alternative source terms (ASTs); the scope, nature, and documentation of associated analyses and evaluations; consideration of impacts on analyzed risk; acceptable radiological analysis assumptions for use in conjunction with the accepted AST, and content of submittals.

EGC has validated that the proposed change complies with the applicable regulations, requirements, and guidance.

4.2 No Significant Hazards Consideration Exelon Generation Company, LLC (EGC) will implement initial dry cask storage (DCS) activities at Clinton Power Station Unit 1 (CPS) in accordance with 10 CFR 72.210, "General license issued." These activities are scheduled to commence in August 2016, and will be necessary to achieve full core offload capability.

EGC has determined that the added heat from a fully-loaded design basis cask will impact the post-LOCA temperature in various areas of Secondary Containment. As a result, the time period necessary for the Standby Gas Treatment System (SGTS) to achieve and maintain the required negative pressure in Secondary Containment, following a design basis loss-of-coolant accident (LOCA) will increase. Since this drawdown time is an input value into the post-LOCA dose calculations described in USAR Section 15.6.5, EGC has evaluated the impact of the increased drawdown time on post-accident radiological consequences, utilizing the NRC-approved alternative source term (AST) methodology. This radiological consequence evaluation resulted in a projected increase in the post-accident Control Room dose. Although the increased value for post-LOCA Control Room dose remains within the 10 CFR 50.67 regulatory limit, the increase is more than minimal, and as such requires prior NRC approval.

The revised post-LOCA Control Room dose calculation was performed in accordance with the guidance in Regulatory Guide 1.183, "Alternative Radiological Source Terms for Evaluating Design Basis Accidents at Nuclear Power Reactors" and NUREG-0800, "Standard Review Plan for the Review of Safety Analysis Reports for Nuclear Power Plants: LWR Edition," (SRP)

Section 15.0.1, "Radiological Consequences Analyses Using Alternative Source Terms."

EGC 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:

ATTACHMENT Clinton Power Station, Unit 1 License Amendment Request Revision of USAR to Incorporate Revised Alternative Source Term Dose Calculation Page 8 of 10

1. Does the proposed amendment involve a significant increase in the probability or consequences of an accident previously evaluated?

Response: No The proposed change results in additional heat added to Secondary Containment and the resultant increase in the time to achieve and maintain the required negative pressure in Secondary Containment following a LOCA. Neither the additional heat load from DCS activities, nor the resultant increase in the time to achieve and maintain the required negative pressure in Secondary Containment affect any initiator or precursor of any accident previously evaluated. Therefore, the proposed change does not involve a significant increase in the probability of an accident previously evaluated.

The proposed change results in an increase in the post-LOCA radiological dose to a Control Room occupant. However, the resultant post-LOCA Control Room dose remains within the regulatory limits of 10 CFR 50.67 and GDC 19. Therefore, the proposed change does not involve a significant increase in the consequences of an accident previously evaluated.

In summary, 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 change does not alter the design function or operation of Secondary Containment or the Standby Gas Treatment system, or the ability of each to perform its design function. EGC has evaluated the post-LOCA pressure response of Secondary Containment assuming the higher heat load, utilizing the design basis short-term pressure response analysis. The results of this analysis validated that SGTS will achieve and maintain the required negative pressure in Secondary Containment within the specified timeframe. The proposed change does not alter the safety limits, or safety analysis associated with the operation of the plant. Accordingly, the change does not introduce any new accident initiators. Rather, this proposed change is the result of an evaluation of the Control Room doses following the most limiting LOCA that can occur at CPS. The proposed change does not introduce any new modes of plant operation. As a result, no new failure modes are introduced.

Therefore, the proposed change does not create the possibility of a new or different kind of accident from any previously evaluated.

ATTACHMENT Clinton Power Station, Unit 1 License Amendment Request Revision of USAR to Incorporate Revised Alternative Source Term Dose Calculation Page 9 of 10

3. Does the proposed amendment involve a significant reduction in a margin of safety?

Response: No The revised post-LOCA dose consequences to a Control Room occupant were calculated in accordance with the requirements of 10 CFR 50.67, Regulatory Guide 1.183, and SRP 15.0.1 and are consistent with the post-LOCA dose calculations approved by the NRC in Amendment No. 167 to the CPS Facility Operating License NPF-62.

The margin of safety is considered to be that provided by meeting the applicable regulatory limits. The additional heat load that is added to Secondary Containment during DCS activities, leading to an increase in Secondary Containment drawdown time results in an increase in Control Room dose following the LOCA design basis accident. However, since the Control Room dose following the design basis accident remains within the regulatory limits, there is not a significant reduction in a margin of safety.

Therefore, operation of CPS in accordance with the proposed change will not involve a significant reduction in a margin of safety.

Based on the above, EGC 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.

4.3 Conclusions 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 Commission's 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

EGC has evaluated the proposed amendment for environmental considerations. The review has resulted in the determination 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 effluent 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.

ATTACHMENT Clinton Power Station, Unit 1 License Amendment Request Revision of USAR to Incorporate Revised Alternative Source Term Dose Calculation Page 10 of 10

6.0 REFERENCES

6.1 M.J. Pacilio (AmerGen Energy Company, LLC) to U.S. NRC letter, "Request for License Amendment Related to Application of Alternative Source Term," dated April 3, 2003 6.2 K.R. Jury (AmerGen Energy Company, LLC) to U.S. NRC letter, "Additional Information Supporting the Request for License Amendment Related to Application of Alternative Source Term," dated December 23, 2003 6.3 K.R. Jury to U.S. NRC letter, "Additional Information Supporting the Request for License Amendment Related to Application of Alternative Source Term," dated December 9, 2004 6.4 K.R. Jury to U.S. NRC letter, "Additional Information Supporting the Request for License Amendment Related to Application of Alternative Source Term," dated December 17, 2004 6.5 K.R. Jury to U.S. NRC letter, "Additional Information Supporting the Request for License Amendment Related to Application of Alternative Source Term," dated March 30, 2005 6.6 K.R. Jury to U.S. NRC letter, "Additional Information Supporting the Request for License Amendment Related to Application of Alternative Source Term, dated August 19, 2005" 6.7 K.N. Jabbour (U.S. NRC) to C.M. Crane (AmerGen Energy Company, LLC) letter, "Clinton Power Station, Unit 1 - Issuance of an Amendment - re: Application of an Alternative Source Term Methodology (TAC No. MB8365)," dated September 19, 2005

ENCLOSURE 1 Clinton Power Station, Unit 1 License Amendment Request Marked-up USAR and TS Bases Pages USAR Page 6.2-51 USAR Page 6.2-54 USAR Page 6.5-2 USAR Page 6.5-3 USAR Page 15.6-10 USAR Page 15.6-12 USAR Page 15.6-13 USAR Page 15.6-34 USAR Figure 15.6-1, Page 2 of 2 TS Bases Page B 3.6-88a

CPS/USAR 6.2.2.4 Tests and Inspections Preoperational tests were performed to verify individual component operation, individual logic element operation, and system operation up to the containment spray nozzles. A sample of the sparger nozzles were bench tested for flow rate versus pressure drop to evaluate the original hydraulic calculations. Refer to Subsection 5.4. 7.4 for further discussion of preoperational testing.

The containment spray nozzles may be operationally tested by connecting an air line to a test connection on the spray header, and blowing air out the nozzles. Unobstructed (free) air flow will be verified for each nozzle by either thermography (infrared camera) or physical inspection, which may include the addition of streamers to the nozzles or actual inspection of each nozzle for air flow.

6.2.2.5 Instrumentation Requirements The details of the instrumentation are provided in Subsection 7.3.1.1.4. The suppression pool cooling mode of the RHR system is manually initiated from the control room.

6.2.3 Secondarv Containment Functional Design The secondary containment completely encloses the primary containment, except for the upper personnel hatch, and consists of the containment gas control boundary, the containment gas control boundary extension (siding within the auxiliary building), the fuel building, the ECCS RHR heat exchanger rooms, the pump rooms, the RWCU pump room, and the main steam pipe tunnel. During normal operation, the fuel building ventilation system maintains the secondary containment at a slightly negative pressure. Following a design basis accident, the standby gas treatment system (SGTS) achieves and maintains a negative pressure in the areas that comprise the secondary containment.

In addition, the SGTS provides the capability to remove potential contamination released to the secondary containment volume after an accident in primary containment. The design and operation of the fuel building ventilation system and the SGTS are discussed in Subsections 9.4.2 and 6.5.1 respectively. Chapter 15 discusses the operation of these systems under accident conditions.

6.2.3.1 Design Basis The functional requirements for the secondary containment arise from the Code of Federal Regulation limits for the release of radioactive materials within the plant and at the plant boundary during normal operation and following postulated accidents within the primary containment. The specific design criteria implemented to meet these functional requirement are set forth below.

a. The secondary containment structures is of Seismic Category I design and is sufficiently leak tight that the SGTS can maintain the required negative pressure within the secondary containment volume for wind speeds up to approximately 30 mph. The secondary containment, in conjunction with the operation of the SGTS, is designed to achieve and maintain an 0.25-inch water gauge negative pressure in the boundary region within 12 minutes of the initiation of SGTS.

19 minutes CHAPTER06 6.2-51 REV. 15, JANUARY 2013

CPS/USAR The leakage is determined by evaluation flow characteristics through small cracks based on manufacturer's certified leak test results on building siding; air leakage test results contained in "Conventional Building for Reactor Containment," NAA-SR-10100; and specified leak rates on valves, dampers, and penetrations. Wind effect are considered as described in Subsection 6.5.1.1.

b. Calculations indicate that the SGTS fan has been adequately sized to achieve an 0.25-inch water gauge negative pressure in less than 12 19 minutes after the LOCA event.

6.2.3.3.2 Secondarv Containment System The secondary containment system was analyzed to determine the effects of a OBA in primary containment on the pressure and temperature histories for subcompartments within the system.

This analysis was carried out using a modified version of COMPARE/MOD1 computer code.

Two separate analyses were performed. These were:

a. a short-term analysis for the pressure histories, and,

b. a long-term analysis for the temperature histories.

6.2.3.3.2.1 Short-Term Pressure Historv The short-term analysis was performed using three interconnected nodes within the secondary containment and one node representing the outside environment. The transient was calculated by performing a balance of mass and energy addition, removal, and accumulation within each of the nodes. Mass flow between the nodes was prescribed in a conservative manner (i.e.,

minimum flow for a given pressure differential). Mass addition to nodes was due to infiltration of outside air, evaporation from the spent fuel pool, and junction flow. Mass removal from nodes was due to operation of the SGTS as well as junction flow. Energy addition to nodes was due to the presence of various heat sources while energy removal was due to heat transfer to heat sinks and the operation of fan coolers. 19 minutes It should be noted that the SGTS has the ability to draw down the secondary containment to below -0.25 inch water gauge well within the first 12 minutes following a LOCA. Furthermore, the secondary containment pressure would remain below this value as long as the SGTS continues to operate, since the secondary containment heat loads will be balanced by the temperature dependent heat sinks and fan coolers as the transient proceeds. Specifically, design pressure in the secondary containment (-0.25" water gauge) is reached in less than 12 minutes. 19 CHAPTER06 6.2-54 REV. 15, JANUARY 2013

CPS/USAR

c. The standby gas treatment system (SGTS) equipment train air handling capability is based on the total inleakages to the secondary containment while all of the areas in the secondary containment are maintained at 0.25 inch water gauge negative pressure with respect to outside ambient pressure to preclude ground level leakage of untreated air to the environment. The secondary containment air pressure begins to decrease exponentially after the standby gas treatment system is started. For low wind speeds, a design pressure of 0.25 inch water gauge is reached within 12 minutes after this design basis LOCA. The 19 minutes time period until the secondary containment reaches a negative pressure of 0.25 inch water gauge should not be considered as a period of direct outleakage for the following reasons:

1. The pressure gradient forcing leakage from the primary containment is less than 4 psig during this time period. The containment design and construction, and testing requirements provide leakage integrity and such a small pressure difference provides little driving force for leakage across small leak paths.

2. The most predominant potential containment leak paths are piping penetrations and door seals which penetrate the containment at elevations enclosed by the secondary containment which consists of the ECCS pump rooms, steam tunnel, RWCU pump rooms, and fuel building.

Due to the large volume of these areas, the small amount of radioactive gases leaking through would require some interval of time to diffuse through the secondary containment to the outside.

3. Fuel cladding is not postulated to fail prior to containment isolation.

4. The entire secondary containment, including the containment gas control boundary (CGCB), is maintained at approximately 0.25 inch water gauge negative pressure during normal operations.

d. Primary containment leakage, except for bypass leakage through the upper personnel air lock, will be contained within the secondary containment and will be processed through the SGTS. The secondary containment inleakage is determined by utilizing published leakage data for applicable building construction and incorporating known leakage values for piping, electrical, and duct penetrations at pressure control boundaries. The expected SGTS flow rate is approximately equal to the total free air volume of the fuel building, ECCS pump rooms, RWCU pump rooms, steam pipe tunnel, and the containment gas control boundary evacuated at a rate of one per day. The design flow rate through the SGTS also accounts for volumetric expansion of building air volumes due to temperature rises as equipment residual heat is released after the non-safety-related ventilation and process system shutdown.

CHAPTER06 6.5-2 REV. 15, JANUARY 2013

CPS/USAR

e. The secondary containment leakage is calculated based laminar flow characteristic through small cracks.

The portion of secondary containment most affected by wind effects is the containment gas control boundary (CGCB) based on its construction, air change rate, and percentage of total secondary containment surface area exposed to direct winds. The SGTS fans are adequately sized to pull secondary containment negative for low to moderate wind speed.

The analysis shows that no secondary containment outleakage (bypass of SGTS) results for low to moderate wind speeds up to approximately 30 mph.

Above this wind speed, the secondary containment outleakage increases gradually without increasing offsite dose rates due to more favorable atmospheric dispersion conditions.

Additional analyses indicate that for low wind speeds the secondary containment pressures of -0.25 inch water gauge is reached in less than 12 minutes after LOCA. 19 minutes

f. Two single unit capacity standby gas treatment system equipment trains (SGTSEn and associated dampers, piping, instruments, and controls are provided. The system is in compliance with the intent of Regulatory Guide 1.52 as described in Table 6.5-3.

g. Each SGTSET is sized and specified for the worst conditions, treating incoming air-steam mixtures saturated at 150°F containing fission products and particulates at a rate equivalent to the containment and main steam isolation valve design leakage. Fission products available in the containment atmosphere for release were determined in accordance with Regulatory Guide 1.3 and for Alternative Source Term analyses, Regulatory Guide 1.183.

h. Each equipment train contains the amount of charcoal required to adsorb the total amount of halogen fission products which leak from primary containment into secondary containment.

i. Each train is provided with a demister, air heater, and prefilter to assure the optimum gas conditions entering the high-efficiency particulate air (HEPA) and charcoal filters. The air heater is sized to reduce air entering at 150°F, 100% relative humidity to a maximum 70% relative humidity. The demister is specified to remove any entrained moisture in the airstream.

j. A standby cooling air fan is provided for each SGTSET to remove heat generated by fission product decay on the HEPA filters and charcoal adsorbers after shutdown of the train.

Charcoal desorption temperature is given in ERDA 76-21. No credit is taken for equipment or environment heat sink. Control building cooling air is routed through the shutdown train and exhausted to the atmosphere.

CHAPTER06 6.5-3 REV. 15, JANUARY 2013

CPS/USAR 15.6.5.5.1.1 Fission Product Release from Fuel It is assumed that 100% of the noble gases, 30% of the iodines and other halogens, and smaller fractions of other core isotopes as specified in Table 1 of RG 1.183 are released from an equilibrium core operating at a power level of 3543 MWt prior to the accident. While not specifically stated in RG 1.183, this assumed release implies fuel damage applicable to melt conditions. Even though this condition is inconsistent with operation of the ECCS (see Section 6.3), it is conservatively assumed applicable for the evaluation of this accident. Of this release, 100% of the noble gases become airborne. Due in part to mixing into the suppression pool of the Standby Liquid Control System solution injected into the core, the suppression pool pH is controlled at values above 7 following the core release period. Therefore as per RG 1.183 the chemical form of the iodine released to the containment is assumed to be 95% particulate (aerosol), 4.85% elemental, and 0.15% organic. Before leaving containment, natural deposition of aerosols is assumed, reducing the aerosol availability for airborne release to the environment.

15.6.5.5.1.2 Fission Product Transport to the Environment The transport pathway consists of leakage from the containment to the secondary containment*-

like structures by several different mechanisms and discharge to the environment through the Standby Gas Treatment System (SGTS)

The secondary containment herein after referred to as "the gas control boundary".

(1) Containment leakage.

The design basis leak rate of the primary containment and its penetrations (excluding the main steam lines feedwater lines, and purge penetrations) is 0.65% per day for the first 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months and 0.413% per day for the duration of the accident. Of this leakage, 92% is to the secondary containment and from there to the environment via a 99% SGTS.

(2) Leakage from the Main Steam Isolation Valves (MSIVs) to the SGTS. It is assumed the MSIVs leak 100 SCFH per valve, 200 SCFH total for the first 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months , and 63.6 SCFH for the duration of the accident. The airborne fission products are assumed to be instantaneously uniformly mixed in the drywell and containment net free volume.

19 minutes (3) 100% of the containment leakage during the first 12 minutes and 8% of the containment leakage after this time bypasses containment.

(4) Containment atmosphere leakage from the feedwater penetrations is released to the environment at a leak rate equivalent to 10.98 cfm for the first (1) hour. After 1 hour1.157407e-5 days 2.777778e-4 hours 1.653439e-6 weeks 3.805e-7 months , suppression pool water supplied by the RHR to the feedwater leakage control system (FWLC) leaks at 2.0 gpm outside of secondary containment and iodine is released to the environment for the duration of the accident period.

(5) Containment atmosphere leakage from the purge penetrations is released to the environment at a rate of 0.3386 cfm for the first 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months , and 0.2153 cfm for the duration of the accident.

Figure 15.6.5-1 provides schematic of LOCA transport pathways.

CHAPTER 15 15.6-10 REV. 15, JANUARY 2013

CPS/USAR 15.6.5.5.2 Control Room A radiological analysis has been performed (Reference 1) to determine if the ventilation system satisfies the radiation protection guidelines of the NRC Standard Review Plan 6.4 (Reference 4) and, for AST, 10 CFR 50.67 and Regulatory Guide 1.183. The results of the analysis shown below are within these guidelines. A schematic of the control room intake vents is shown in Drawing M01-1115.

The dose received during the 30-day period after a Loss-of-Coolant Accident is:

DOSE (REM) NRC LIMIT (REM)

TEDE 4.73 4.84 5

Includes the contribution of direct radiation from external sources .

A list of assumptions and input data follow: The assumptions and inputs listed are nominal base values. Different levels of conservatism may be used in radiological analysis performed to support plant operation provided that USAR dose values are not exceeded.

(1) Source Terms The source terms used in this analysis are consistent with the guidance found in R.G,1.183.

CHAPTER 15 15.6-12 REV. 17, OCTOBER 2015

CPS/USAR (2) Leakage parameters Primary containment leak rate (%/day) 0.65 Feedwater Penetration Leak Rate (gpm) 2.00 Bypass leak rate (% of containment 8 leak rate) (Exfiltration assumed for first 12 min.) 19 min.)

MSIV leak rate (SCFH/line, Total) 100, 200 0-24 hours 63.6, 127 24-720 hours (3)* Ventilation parameters Intake flow rate (cfm) (filtered) 3,000+/-10%

Intake filter efficiency for iodines (%) 99 Recirculation flow rate (cfm) (filtered) 61,000+/- 10%

Total in-leakage (cfm) 1100 Recirculation filter efficiency for 70 iodines(%)

Control room free volume (ft3) includes 324,000 old Technical Support Center)

The calculated post-LOCA control room doses account for the most conseNative single failure of the ventilation system.

(4) Meteorological Data Clinton site data from 2000 through 2002 and methodology of Reference 4 were employed for the dose calculations. The following x/Q values were calculated and used in the control room dose assessment:

INTERVAL (hrs.) x/Q VALUES (sec/m 3) Unfiltered x/Q Nalues (sec/m 3) 2 2.36 x 10"" 1.54 x 10"3 6 1.77x10"" 1.09 x 10-3 16 7.33 x 10-* 4.67 x 10""

72 5.33 x 10-* 3.21x10""

624 4.48 x 10-* 2.64 x 10""

xlQ values include credit of a factor of 4 reduction for the effects of Dual Separated Air Intakes, in accordance with Reference 4.

CHAPTER 15 15.6-13 REV. 13, JANUARY 2009

CPS/USAR TABLE 15.6.5-6 LOSS-OF-COOLANT ACCIDENT (DESIGN BASIS ANALYSIS)

RADIOLOGICAL EFFECTS*

TEDE EXCLUSION AREA BOUNDARY 17.31 (975 Meters)

LOW POPULATION ZONE 7.37 7.42 (4018 Meters)

Included doses from Bypass leakage, Feedwater Penetration leakage, MSIV leakage and Purge Penetration leakage.

CHAPTER 15 15.6-34 REV. 17, OCTOBER 2015

CPS/USAR Leakage Rates and Secondary Containment Mixing Parameters Path Description Parameters & Values L1 Primary Containment Leak Rate:

Leakage Bypassing 0.08*La = 0.052%/day from 0 to 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months Secondary Containment to = 0.033%/day from 1 to 30 days the Environment L2 Primary Containment Leak Rate: 19 Leakage to Secondary 0.92*La = 0.598%/day from 0 to 10 min Containment Unfiltered during drawdown period and includes the two

= 0.598%/day from 10 min to 24 hrs minute gap SGTS filtered 19 release time

= 0.380%/day from 1 to 30 days SGTS filtered L3 MSIV Leakage to Leak Rate:

Environment 200 scfh for all main steam lines, 100 scfh for maximum for any one MS line; reduced to 63.6% of these rates after 1 day L4 FWIV Containment Air Leak Rate:

Leakage to Environment 10.98 cfm total, for the one hour before FWIV LCS fills the lines L5 ECCS Leakage to Leak Rate:

Secondary Containment 5 gpm from 0 to 30 days L6 FWIV LCS Leakage of Leak Rate:

ECCS Liquid to the 2 gpm from 0 to 1 days Environment 1 gpm from 1 to 30 days

[Conservatively includes fill time]

L7 Purge Penetrations 101 Leak Rate (for each of two penetrations):

and 102 Leakage to the 0.02*La = 0.013%/day from 0 to 1 day Environment = 0.0083%/day from 1 to 30 days L8 Release of Secondary No Secondary Containment mixing credit Containment Atmosphere Modeled as:

through SGTS to the Volume = 1 cu.ft.

Environment Outflow = 1000 cfm CLINTON POWER STATION UPDATED SAFETY ANALYSIS REPORT FIGURE 15.6.5-1 Page 2 of 2 Schematic of LOCA Transport Pathways REV. 13, JANUARY 2009

Secondary Containment B 3.6.4.1 BASES SURVEILLANCE SR 3.6.4.1.4 and SR 3.6.4.1.5 REQUIREMENTS (continued) The SGT System exhausts the secondary containment atmosphere to the environment through appropriate treatment equipment.

Each SGT subsystem is designed to draw down pressure in the secondary containment to > 0.25 inches vacuum water gauge within the time required and maintain pressure in the secondary containment at > 0.25 inches of vacuum water gauge for 1 hour1.157407e-5 days 2.777778e-4 hours 1.653439e-6 weeks 3.805e-7 months at a flow rate of < 4400 cfm. To ensure that all fission products released to the secondary containment are treated, SR 3.6.4.1.4 and SR 3.6.4.1.5 verify that a pressure in the secondary containment that is less than the lowest postulated pressure external to the secondary containment boundary can rapidly be established and maintained. When the SGT System is operating as designed, the establishment and maintenance of secondary containment pressure cannot be accomplished if the secondary containment boundary is not intact. Establishment of this pressure is confirmed by SR 3.6.4.1.4, which demonstrates that secondary containment can be drawn down to > 0.25 inches of vacuum water gauge in the required time using one SGT subsystem.

Specifically, the required drawdown time limit is based on ensuring that the SGT system will draw down the secondary 19 containment pressure to 0.25 inches of vacuum water gauge within 12 minutes (i.e., 10 minutes from start of gap release which occurs 2 minutes after LOCA initiation) under LOCA conditions. Typically, however, the conditions under 17 which drawdown testing is performed pursuant to SR 3.6.4.1.4 are different than those assumed for LOCA conditions. For this reason, and because test results are dependent on or influenced by certain plant and/or atmospheric conditions that may be in effect at the time testing is performed, it is necessary to adjust the test acceptance criteria (i.e.,

the required drawdown time) to account for such test conditions. Conditions or factors that may impact the test results include wind speed, whether the turbine building ventilation system is running, and whether the containment equipment hatch is open (when the test is performed during plant shutdown/outage conditions). The acceptance criteria for the drawdown test are thus based on a computer model (Ref. 7), verified by actual performance of drawdown tests, in which the drawdown time determined for accident conditions is adjusted to account for performance of the test during normal but certain plant conditions. The test acceptance criteria are specified in the applicable plant test procedure(s). Since the drawdown time is dependent upon secondary containment integrity, the drawdown requirement cannot be met if the secondary containment boundary is not intact.

SR 3.6.4.1.5 demonstrates that the pressure in the secondary containment can be maintained > 0.25 inches of vacuum water gauge for 1 hour1.157407e-5 days 2.777778e-4 hours 1.653439e-6 weeks 3.805e-7 months using one SGT subsystem at a flow rate of

< 4400 cfm. The 1 hour1.157407e-5 days 2.777778e-4 hours 1.653439e-6 weeks 3.805e-7 months test period allows secondary containment to be in thermal equilibrium at steady state (continued)

CLINTON B 3.6-88a Revision No. 13-2

ENCLOSURE 2 Clinton Power Station, Unit 1 License Amendment Request Physical Input Parameters and Assumptions Post-LOCA Dose Calculations Page 1 of 14 The following information provides the physical input parameters and assumptions that were used for the revised post-LOCA dose calculations (i.e., 12-month operating cycle with 19-minute drawdown time), as well as the corresponding parameters used in both the original calculations (i.e., in support of Amendment 167) and the 12-month operating cycle calculations.

Table 1 provides the core source terms used in the original 2005 post LOCA dose calculation analysis and the source terms used for the current 12-month operating cycle post-LOCA dose calculation. The core source terms for the 12-month operating cycle calculations were also used in the revised post-LOCA dose calculations supporting this license amendment request.

Table 2 provides the general parameters that are applicable to post-accident AST dose calculations for multiple accidents, and Table 3 provides the parameters and data that are applicable to the post-LOCA dose calculation.

Table 1 Core Source Term The core source terms used in the 2005 and the current 12-month cycle post-LOCA dose calculation are provided below. All source terms were based on the extended power uprate (EPU) power level of 3,473 MWt. The differences in the core source term are due mainly to differences in bundle enrichments and burnup.

Rated Thermal Power: 3,473 MWt, CPS License, TS Definition Analysis: 3,543 MWt (= 102% of 3,473 MWt), Accident Power per RG 1.49 Ci/MWt Ci/MWt 12-Month Fuel Cycle 2005 EPU AST 18-Isotope 34.3 GWD/MTU core month Fuel Cycle average 1170 EFPD 1095.75 EFPD Burnup Burnup CO-58 1.529E+02 2.59E+02 CO-60 1.830E+02 4.45E+02 KR-85 3.170E+02 3.32E+02 KR-85M 6.870E+03 6.80E+03 KR-87 1.310E+04 1.30E+04 KR-88 1.850E+04 1.82E+04 RB-86 6.420E+01 6.66E+01 SR-89 2.490E+04 2.44E+04 SR-90 2.490E+03 2.62E+03 SR-91 3.130E+04 3.09E+04 SR-92 3.400E+04 3.37E+04 Y-90 2.580E+03 2.81E+03 Y-91 3.230E+04 3.17E+04 Y-92 3.420E+04 3.39E+04 Y-93 3.980E+04 3.95E+04 ZR-95 4.940E+04 4.74E+04 ZR-97 4.500E+04 4.97E+04 NB-95 4.510E+04 4.76E+04

ENCLOSURE 2 Clinton Power Station, Unit 1 License Amendment Request Physical Input Parameters and Assumptions Post-LOCA Dose Calculations Page 2 of 14 Ci/MWt Ci/MWt 2005 EPU AST 18- 12-Month Fuel Cycle Isotope month Fuel Cycle 34.3 GWD/MTU core 1095.75 EFPD Burnup average EFPD Burnup MO-99 5.080E+04 5.13E+04 TC-99M 4.450E+04 4.47E+04 RU-103 4.250E+04 4.30E+04 RU-105 2.950E+04 3.01E+04 RU-106 1.590E+04 1.68E+04 RH-105 2.760E+04 2.82E+04 SB-127 2.980E+03 3.02E+03 SB-129 8.800E+03 8.89E+03 TE-127 2.950E+03 3.00E+03 TE-127M 3.950E+02 4.06E+02 TE-129 8.660E+03 8.75E+03 TE-129M 1.290E+03 1.31E+03 TE-131M 3.930E+03 3.95E+03 TE-132 3.840E+04 3.85E+04 I-131 2.700E+04 2.71E+04 I-132 3.910E+04 3.91E+04 I-133 5.490E+04 5.50E+04 I-134 6.020E+04 6.03E+04 I-135 5.140E+04 5.15E+04 XE-133 5.360E+04 5.30E+04 XE-135 1.750E+04 1.77E+04 CS-134 5.590E+03 6.07E+03 CS-136 1.900E+03 2.01E+03 CS-137 3.440E+03 3.66E+03 BA-139 4.880E+04 4.88E+04 BA-140 4.720E+04 4.72E+04 LA-140 4.920E+04 5.01E+04 LA-141 4.450E+04 4.45E+04 LA-142 4.290E+04 4.29E+04 CE-141 4.480E+04 4.47E+04 CE-143 4.110E+04 4.10E+04 CE-144 3.590E+04 3.61E+04 PR-143 4.000E+04 3.97E+04 ND-147 1.790E+04 1.80E+04 NP-239 5.680E+05 5.91E+05 PU-238 9.710E+01 1.09E+02 PU-239 1.120E+01 1.19E+01 PU-240 1.480E+01 1.60E+01 PU-241 4.680E+03 5.05E+03 AM-241 5.100E+00 5.87E+00 CM-242 1.330E+03 1.53E+03 CM-244 7.800E+01 9.55E+01

ENCLOSURE 2 Clinton Power Station, Unit 1 License Amendment Request Physical Input Parameters and Assumptions Post-LOCA Dose Calculations Page 3 of 14 Table 2 Parameters and Data Applicable to All AST Post-accident Dose Calculations 12-Month Operating Cycle with General AST Analysis 2005 EPU AST 12-Month Operating Cycle Increased Secondary Containment Design lnput 18-month Operating Cycle Positive Pressure Period Core Power Level 3543 MWth (current) 3543 MWth (current) 3543 MWth (current)

Dose Conversion Factors Federal Guidance Report (FGR) 11 and FGR 11 and 12 as built into the FGR 11 and 12 as built into the Inhalation 12 for Inhalation CEDE and cloud RADTRAD code RADTRAD code Whole Body Dose submersion EDE. Values are built into RADTRAD for a total of 60 isotopes.

Personnel Dose Inputs Onsite (CR) Breathing Rate 3.47E-04 3.47E-04 3.47E-04 3

(m /sec) 3 Offsite Breathing Rate (m /sec) 3.5E-04 3.5E-04 3.5E-04 0 - 8 hour9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months s: 1.8E-04 1.8E-04 1.8E-04 8 - 24 hour2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months s: 2.3E-04 2.3E-04 2.3E-04 1 - 30 days:

CR Occupancy Factors 1.0 1.0 1.0 0 - 1 day: 0.6 0.6 0.6 1 - 4 days: 0.4 0.4 0.4 4 - 30 days:

ENCLOSURE 2 Clinton Power Station, Unit 1 License Amendment Request Physical Input Parameters and Assumptions Post-LOCA Dose Calculations Page 4 of 14 Table 2 Parameters and Data Applicable to All AST Post-accident Dose Calculations 12-Month Operating Cycle with General AST Analysis 2005 EPU AST 12-Month Operating Cycle Increased Secondary Containment Design lnput 18-month Operating Cycle Positive Pressure Period EAB - X/Q's Distance to EAB 975 meters 975 meters 975 meters Atmospheric Dispersion Factors 2.46E-04 2.46E-04 2.46E-04 (sec/m3)

(2000-2003 Meteorological data) 0-2 hr LPZ - X/Q's Distance to LPZ 4018 meters 4018 meters 4018 meters Atmospheric Dispersion Factors (sec/m3) 2.48E-05 2.48E-05 2.48E-05 0-8 hr 1.65E-05 1.65E-05 1.65E-05 8-24 hr 6.81E-06 6.81E-06 6.81E-06 1-4 days 1.91E-06 1.91E-06 1.91E-06 4-30 days

ENCLOSURE 2 Clinton Power Station, Unit 1 License Amendment Request Physical Input Parameters and Assumptions Post-LOCA Dose Calculations Page 5 of 14 Table 2 Parameters and Data Applicable to All AST Post-accident Dose Calculations 12-Month Operating Cycle with General AST Analysis 2005 EPU AST 12-Month Operating Cycle Increased Secondary Containment Design lnput 18-month Operating Cycle Positive Pressure Period CR - X/Q's Filtered CR Intake:

Atmospheric Dispersion Factors (sec/m3) 0-2 hr 2.36E-04 2.36E-04 2.36E-04 2-8 hr 1.77E-04 1.77E-04 1.77E-04 8-24 hr 7.33E-05 7.33E-05 7.33E-05 1-4 days 5.33E-05 5.33E-05 5.33E-05 4-30 days 4.48E-05 4.48E-05 4.48E-05 Unfiltered CR Intake:

Atmospheric Dispersion Factors (sec/m3) 0-2 hr 1.54E-03 1.54E-03 1.54E-03 2-8 hr 1.09E-03 1.09E-03 1.09E-03 8-24 hr 4.67E-04 4.67E-04 4.67E-04 1-4 days 3.21E-04 3.21E-04 3.21E-04 4-30 days 2.64E-04 2.64E-04 2.64E-04

ENCLOSURE 2 Clinton Power Station, Unit 1 License Amendment Request Physical Input Parameters and Assumptions Post-LOCA Dose Calculations Page 6 of 14 Table 2 Parameters and Data Applicable to All AST Post-accident Dose Calculations 12-Month Operating Cycle with General AST Analysis 2005 EPU AST 12-Month Operating Cycle Increased Secondary Containment Design lnput 18-month Operating Cycle Positive Pressure Period Control Room Volume (cu. ft.) 324,000 324,000 324,000 (includes TSC)

Control Room Filtered Intake Rate - 3000 - 10% = 2700 3000 - 10% = 2700 3000 - 10% = 2700 CREF Mode (cfm)

Control Room Filtered Inleakage (cfm)

Filtered Recirculation Rate (cfm) 61,000 - 10% = 54,900 61,000 - 10% = 54,900 61,000 - 10% = 54,900 Intake Filter Efficiency 99.0% for Aerosols 99.0% for Aerosols 99.0% for Aerosols 99.0% for Elemental and Organic Iodine 99.0% for Elemental and Organic Iodine 99.0% for Elemental and Organic Iodine Effective Intake Filter Penetration 1.0% for Aerosols 1.0% for Aerosols 1.0% for Aerosols 1.0% for Elemental and Organic Iodine 1.0% for Elemental and Organic Iodine 1.0% for Elemental and Organic Iodine Intake Filter Bypass Allowance 0.05% for all iodines 0.05% for all iodines 0.05% for all iodines

ENCLOSURE 2 Clinton Power Station, Unit 1 License Amendment Request Physical Input Parameters and Assumptions Post-LOCA Dose Calculations Page 7 of 14 Table 2 Parameters and Data Applicable to All AST Post-accident Dose Calculations 12-Month Operating Cycle with General AST Analysis 2005 EPU AST 12-Month Operating Cycle Increased Secondary Containment Design lnput 18-month Operating Cycle Positive Pressure Period Recirc Filter Efficiency 70% for all Iodines For input to the 70% for all Iodines For input to the 70% for all Iodines For input to the RADTRAD code, 68% is used for the RADTRAD code, 68% is used for the RADTRAD code, 68% is used for the Recirculation Filter efficiency. This is to Recirculation Filter efficiency. This is Recirculation Filter efficiency. This is to account for the bypass of 2% of the to account for the bypass of 2% of the account for the bypass of 2% of the filter efficiency. filter efficiency. filter efficiency.

Effective Recirc Filter 30.0% for all Iodines 30.0% for all Iodines 30.0% for all Iodines Penetration Recirc Filter Bypass Allowance 2.0% for all Iodines 2.0% for all Iodines 2.0% for all Iodines Combined CR Filter Efficiency 99.664% for Aerosols 99.664% for Aerosols 99.664% for Aerosols 99.664% for Elemental and Organic 99.664% for Elemental and Organic 99.664% for Elemental and Organic Iodine Iodine Iodine Total Filtered Inleakage 1,100 cfm 1,100 cfm 1,100 cfm Control Room Filtered Intake and 20 minutes 20 minutes 20 minutes Recirculation Air Filtration Initiation During this period of no filtration and During this period of no filtration and During this period of no filtration and Time (manual) no CR pressurization, an inleakage of no CR pressurization, an inleakage no CR pressurization, an inleakage of 1650 cfm is assumed, which is 1/2 of of 1650 cfm is assumed, which is 1650 cfm is assumed, which is 1/2 of assumed filter makeup value used for 1/2 of assumed filter makeup value assumed filter makeup value used for CR pressurization. used for CR pressurization. CR pressurization.

ENCLOSURE 2 Clinton Power Station, Unit 1 License Amendment Request Physical Input Parameters and Assumptions Post-LOCA Dose Calculations Page 8 of 14 Table 3 Parameters and Data Applicable to Post-LOCA Dose Calculation LOCA AST Analysis 2005 EPU AST 12-Month Operating Cycle with Design lnput 18-month Operating Cycle 12-Month Operating Cycle Increased Secondary Containment Positive Pressure Period Primary Containment Mixing A drywell bypass leakage rate of A drywell bypass leakage rate of A drywell bypass leakage rate of 3,000 cfm for the first two hours is 3,000 cfm for the first two hours is 3,000 cfm for the first two hours is used, followed by an assumption of used, followed by an assumption of used, followed by an assumption of well-mixed drywell-containment well-mixed drywell-containment well-mixed drywell-containment conditions thereafter. conditions thereafter. conditions thereafter.

Leak Rate: Leak Rate: Leak Rate:

Primary Containment Leakage 0.92*La = 0.598%/day from 0 to 12 0.92*La = 0.598%/day from 0 to 12 0.92*La = 0.598%/day from 0 to 19 to Secondary Containment min (Unfiltered during drawdown min (Unfiltered during drawdown min (Unfiltered during drawdown period and includes two minute gap period and includes two minute gap period and includes two minute gap release time) release time) release time) 0.92*La = 0.598%/day from 12 0.92*La = 0.598%/day from 12 0.92*La = 0.598%/day from 19 min to 24 hrs (SGTS filtered) min to 24 hrs (SGTS filtered) min to 24 hrs (SGTS filtered)

= 0.380%/day from 1 to 30 days = 0.380%/day from 1 to 30 days = 0.380%/day from 1 to 30 days (SGTS filtered) (SGTS filtered) (SGTS filtered)

ENCLOSURE 2 Clinton Power Station, Unit 1 License Amendment Request Physical Input Parameters and Assumptions Post-LOCA Dose Calculations Page 9 of 14 Table 3 Parameters and Data Applicable to Post-LOCA Dose Calculation LOCA AST Analysis 2005 EPU AST 12-Month Operating Cycle with Design lnput 18-month Operating Cycle 12-Month Operating Cycle Increased Secondary Containment Positive Pressure Period ECCS Leakage into Secondary Containment Leak Rate 5 gpm (2 times the maximum 5 gpm plus 2 gpm RCIC 5 gpm plus 2 gpm RCIC 1 1 allowable admin limit) backleakage backleakage Fraction Flashed 10% 10% 10%

Filtered by SGTS Yes - after drawdown Yes - after drawdown Yes - after drawdown Purge Penetrations 101 and Leak Rate (for each of two Leak Rate (for each of two Leak Rate (for each of two 102 Leakage to the penetrations): penetrations): penetrations):

Environment 0.02*La = 0.013%/day from 0 to 1 0.02*La = 0.013%/day from 0 to 1 0.02*La = 0.013%/day from 0 to 1 day day day

= 0.0083%/day from 1 to 30 days = 0.0083%/day from 1 to 30 days = 0.0083%/day from 1 to 30 days Primary Containment Leak 0.65% per day for first 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months (La); 0.65% per day for first 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months (La); 0.65% per day for first 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months (La);

Rate (SGTS Filtered and 0.413% per day thereafter 0.413% per day thereafter 0.413% per day thereafter Secondary Containment Bypass) 1 In 2007, EGC identified that the original AST dose calculations did not include potential releases from the RCIC and HPCS full flow test lines to the RCIC storage tank. EGC implemented a minor revision to add the release pathway associated with an assumed two gallons per minute backleakage into the RCIC storage tank and subsequent release to the environment through the tank vent. The only change in the dose values was an increase in the LPZ dose of less than 0.5% of the USAR values.

ENCLOSURE 2 Clinton Power Station, Unit 1 License Amendment Request Physical Input Parameters and Assumptions Post-LOCA Dose Calculations Page 10 of 14 Table 3 Parameters and Data Applicable to Post-LOCA Dose Calculation LOCA AST Analysis 2005 EPU AST 12-Month Operating Cycle with Design lnput 18-month Operating Cycle 12-Month Operating Cycle Increased Secondary Containment Positive Pressure Period Total MSIV Leak Rate Limits 200 scfh total for four lines 100 200 scfh total for four lines 100 200 scfh total for four lines 100 scfh for any one line scfh for any one line scfh for any one line Post-24 hours analytical values 127 scfh total, 63.6 scfh for any one 127 scfh total, 63.6 scfh for any one 127 scfh total, 63.6 scfh for any one line line line

ENCLOSURE 2 Clinton Power Station, Unit 1 License Amendment Request Physical Input Parameters and Assumptions Post-LOCA Dose Calculations Page 11 of 14 Table 3 Parameters and Data Applicable to Post-LOCA Dose Calculation LOCA AST Analysis 2005 EPU AST 12-Month Operating Cycle with Design lnput 18-month Operating Cycle 12-Month Operating Cycle Increased Secondary Containment Positive Pressure Period FWIV leak rate: Total for two penetrations Total for two penetrations Total for two penetrations Air (Containment atmosphere): 10.98 cfm for 1 hour1.157407e-5 days 2.777778e-4 hours 1.653439e-6 weeks 3.805e-7 months (before FWIV LCS 10.98 cfm for 1 hour1.157407e-5 days 2.777778e-4 hours 1.653439e-6 weeks 3.805e-7 months (before FWIV LCS 10.98 cfm for 1 hour1.157407e-5 days 2.777778e-4 hours 1.653439e-6 weeks 3.805e-7 months (before FWIV LCS fill the lines) fill the lines) fill the lines)

Water (ECCS): 2 gpm (constant) from 0 to 30 days 2 gpm (constant) from 0 to 30 days 2 gpm (constant) from 0 to 30 days FWIV Leakage Flashing 10% 10% 10%

Fraction:

Primary Containment 8.0% La for first day 8.0% La for first day 8.0% La for first day Bypassing Secondary 5.09% La after first day 5.09% La after first day 5.09% La after first day Containment Aerosol Natural Deposition Power's model built into RADTRAD Power's model built into RADTRAD Power's model built into RADTRAD Coefficients Used in the as natural deposition time dependent as natural deposition time dependent as natural deposition time dependent Containment deposition lambdas. deposition lambdas. deposition lambdas.

Suppression pool scrubbing Not credited Not credited Not credited

ENCLOSURE 2 Clinton Power Station, Unit 1 License Amendment Request Physical Input Parameters and Assumptions Post-LOCA Dose Calculations Page 12 of 14 Table 3 Parameters and Data Applicable to Post-LOCA Dose Calculation LOCA AST Analysis 2005 EPU AST 12-Month Operating Cycle with Design lnput 18-month Operating Cycle 12-Month Operating Cycle Increased Secondary Containment Positive Pressure Period Mainsteam Line AEB 98-03 well-mixed flow is No Change No Change Deposition/Plate-out (where assumed. Aerosol settling in credited) horizontal lines only; elemental deposition in all credited lines.

Aerosol Settling and Elemental Iodine Deposition in Piping are based on:

Pipe parameters such as volume, aerosol settling area, and elemental iodine deposition areas containment leak rates as a function of leak acceptance criteria; inboard and outboard flow rates Main Steam Line and No credit is taken for holdup and No credit is taken for holdup and No credit is taken for holdup and Condenser Holdup Credit for plate-out downstream of seismically plate-out downstream of seismically plate-out downstream of seismically MSIV Leakage qualified main steam piping or in the qualified main steam piping or in the qualified main steam piping or in the condenser since these components condenser since these components condenser since these components have not been evaluated for seismic have not been evaluated for seismic have not been evaluated for seismic ruggedness. ruggedness. ruggedness.

ENCLOSURE 2 Clinton Power Station, Unit 1 License Amendment Request Physical Input Parameters and Assumptions Post-LOCA Dose Calculations Page 13 of 14 Table 3 Parameters and Data Applicable to Post-LOCA Dose Calculation LOCA AST Analysis 2005 EPU AST 12-Month Operating Cycle with Design lnput 18-month Operating Cycle 12-Month Operating Cycle Increased Secondary Containment Positive Pressure Period Containment Spray Removal Not credited Not credited Not credited Mechanism Minimum Suppression Pool 146,400 146,400 146,400 volume (ft3)

Releases to Containment No Core Activity Release for first 120 No Core Activity Release for first 120 No Core Activity Release for first 120 seconds. seconds. seconds.

(Release Fractions and Timing per RG (Release Fractions and Timing per RG (Release Fractions and Timing per RG 1.183) 1.183) 1.183)

SGTS Flow Rate (cfm) 4000 + 10% = 4400 4000 + 10% = 4400 4000 + 10% = 4400 Because credit is not taken for mixing in Because credit is not taken for mixing in Because credit is not taken for mixing in secondary containment, an artificially secondary containment, an artificially secondary containment, an artificially low secondary containment volume low secondary containment volume low secondary containment volume 3

(1 ft and an artificially high SGTS flow (1 ft3 and an artificially high SGTS flow (1 ft3 and an artificially high SGTS flow 3 3 3 rate (10 cfm) are used for RADTRAD rate (10 cfm) are used for RADTRAD rate (10 cfm) are used for RADTRAD analyses analyses analyses SGTS Iodine Filter Efficiency 99% for Aerosols 99% for Aerosols 99% for Aerosols 99% for Elemental and Organic Iodine 99% for Elemental and Organic Iodine 99% for Elemental and Organic Iodine

ENCLOSURE 2 Clinton Power Station, Unit 1 License Amendment Request Physical Input Parameters and Assumptions Post-LOCA Dose Calculations Page 14 of 14 Table 3 Parameters and Data Applicable to Post-LOCA Dose Calculation LOCA AST Analysis 2005 EPU AST 12-Month Operating Cycle with Design lnput 18-month Operating Cycle 12-Month Operating Cycle Increased Secondary Containment Positive Pressure Period Containment Volume 3

Drywell (ft ) 241,699 241,699 241,699 Containment (outside Drywell) 1,512,341 1,512,341 1,512,341 (ft3)

Primary Containment Total 1.754E+06 where applicable (ft3) 1.754E+06 1.754E+06 MSIV Leakage Rate 100 scfh for two shortest lines, totaling 100 scfh for two shortest lines, totaling 100 scfh for two shortest lines, totaling 200 scfh total allowable leakage 200 scfh total allowable leakage 200 scfh total allowable leakage Fraction of Containment 100% first 12 minutes, 8% after first 12 100% first 12 minutes, 8% after first 12 100% first 19 minutes, 8% after first 19 Leakage that Bypasses SGTS minutes minutes minutes Secondary Containment 12 minutes (includes two minutes gap 12 minutes (includes two minutes gap 19 minutes (includes two minutes gap Drawdown Time release time) release time) release time)

ENCLOSURE 3 Clinton Power Station, Unit 1 License Amendment Request Conservatisms in Post-LOCA Dose Calculations Page 1 of 2 Exelon Generation Company, LLC (EGC) performed the Clinton Power Station, Unit 1 (CPS) post-LOCA dose calculations, for the proposed change, in accordance with Regulatory Guide (RG) 1.183, "Alternative Radiological Source Terms for Evaluating Design Basis Accidents at Nuclear Power Reactors." RG 1.183 requires a number of assumptions that result in conservative onsite and offsite dose values.

In order to provide reasonable assurance of adequate margin to minimize the impact of potential uncertainties in both the dose calculations and the input parameters, EGC evaluated the impact of additional conservative assumptions that are related to actual operating conditions or testing requirements.

The information below provides a sensitivity study of these additional conservatisms, which provides a qualitative estimate for the margin available in the current LOCA dose calculation, relative to the 10 CFR 50.67 limit. That is, the conservatisms were relaxed, on an individual basis, and the calculation results were compared with the results obtained with the conservatism. All calculations were performed using the RADTRAD computer code, version 3.03.

Leak-Before-Break Credit As stated in RG 1.183 (i.e., in Section 3.3, "Timing of Release Phases"), for facilities licensed with leak-before-break (LBB) methodology, the onset of gap release may be assumed to be 10 minutes. This assumption has been used by other licensees in alternative source term (AST) calculations; However, since CPS is not licensed with an LBB methodology, EGC assumed that gap release started at two minutes, in accordance with RG 1.183.

In order to quantify the margin that this would provide, EGC revised the current LOCA analysis to start the gap release at 10 minutes post-accident. In the reanalysis, decay during this 10-minute interval was ignored and the secondary containment bypass was terminated at nine minutes in the model. This is equivalent to a total positive pressure period of 19 minutes.

The results of this reanalysis indicate that, with credit for LBB, there would be approximately a 2.5% reduction in the postulated Control Room dose.

Containment Spray Credit RG 1.183 allows licensees to take credit for aerosol removal by containment sprays. EGC did not credit spray removal in the CPS LOCA analysis, nor has it been modeled in the CPS LOCA analysis. As an alternative, EGC utilized a surrogate LOCA model, based on the simplified spray model provided in NUREG/CR-5966, "A Simplified Model of Aerosol Removal by Containment Sprays," to quantify the potential dose impact of containment sprays. In a Safety Evaluation dated March 30, 2015 (i.e., ADAMS Accession No. ML15075A139), the NRC approved the use of this model in a full AST license amendment for the Perry Nuclear Power Plant.

ENCLOSURE 3 Clinton Power Station, Unit 1 License Amendment Request Conservatisms in Post-LOCA Dose Calculations Page 2 of 2 The results of the reanalysis using the surrogate LOCA model, with credit for Containment Spray, indicates that there would be approximately a 20% reduction in the postulated Control Room dose. Although the margin from this surrogate LOCA model is not directly applicable to the CPS dose calculations, it does provide additional qualitative margin to the post-LOCA Control Room dose value for CPS.

ESF Leakage Credit For ESF leakage pathways, the design basis seven gallon per minute (gpm) leak rate used in the CPS post-LOCA dose calculations for the sum of the simultaneous leakage from all components in the ESF recirculation systems is more than twice the administrative limit of 2.5 gpm, which implements the requirements of CPS Technical Specification 5.5.2, "Primary Coolant Sources Outside Containment." To evaluate the impact of this conservative assumption, EGC revised the current analysis using the administrative ESF leakage value.

The results of the reanalysis indicated that, with the lower ESF leakage assumption, there would be approximately a 1.5% reduction in the postulated Control Room dose.

Secondary Containment Mixing Credit In that EGC does not credit mixing in secondary containment, an artificially low secondary containment volume and an artificially high SGTS flow rate were used for the current CPS post-LOCA RADTRAD analyses. To quantify the effect of using a more realistic mixing credit, EGC reanalyzed the CPS post-LOCA dose calculations assuming a conservative secondary containment volume of 1.4E+06 ft3 (i.e., relative to the actual volume of 1.71E+06 ft3 ), a mixing credit for half of this volume, and the design SBGT system flow rate, plus 10%.

The results of the reanalysis indicated that, with the Secondary Containment mixing credit described above, there would be approximately a 10.4% reduction in the postulated Control Room dose.

ENCLOSURE 4 Clinton Power Station, Unit 1 License Amendment Request Impact of Increased Drawdown Time on Chapter 15 Accident Analyses The Chapter 15 Accident Scenarios that were part of the full AST submittal are listed in the table below. All of the non-LOCA AST analyses take no credit for operation of the Standby Gas Treatment System, secondary containment isolation, or control room air intake or recirculation filtration for the full duration of the accident event.

AST Accident Scenario Longer Justification Drawdown Time Applicable Fuel Handling Accident (FHA) No The FHA inside containment is limiting and assumes that containment integrity and SGTS are not available or necessary.

Because no credit is taken for secondary containment, the drawdown time is irrelevant.

Control Rod Drop Accident (CRDA) No No credit for SGTS or secondary containment is taken. All activity released from the fuel is transported to the turbine/condenser prior to release to the atmosphere.

Main Steam Line Break (MSLB) accident No No credit for SGTS or secondary outside containment containment is taken. All activity released from the fuel is transported outside the primary and secondary containment to the environment.

The remaining accidents presented in the FSAR (listed below) are bounded by the LOCA analysis dose consequences or do not involve a release into the secondary containment. None of these analyses are impacted by the increased secondary containment drawdown time.

15.3.3 Seizure of One Recirculation Pump 15.3.4 Recirculation Pump Shaft Break 15.6.2 Instrument Line Break 15.6.6 Feedwater Line Break 15.7.1.1 Main Condenser Gas Treatment System Failure 15.7.3 Liquid Radwaste Tank Failure 15.7.5 Cask Drop Accident 15.8 ATWS

ENCLOSURE 5 Clinton Power Station, Unit 1 License Amendment Request Environmental Qualification Evaluation Due to Increased Heat Load Page 1 of 2 In preparation for the implementation of initial dry cask storage activities at Clinton Power Station, Unit 1 (CPS), Exelon Generation Company, LLC (EGC) evaluated the impact of a fully-loaded design basis spent fuel cask on post-LOCA temperatures in the CPS Secondary Containment. This evaluation identified temperature increases in various areas within 15 of 20 Secondary Containment environmental zones. As a result, EGC conducted a two-phase evaluation to ensure the environmental qualification (EQ) of all equipment important to safety within these zones, thus ensuring compliance with the requirements of 10 CFR 50.49, "Environmental qualification of electric equipment important to safety for nuclear power plants."

The evaluation also included the affected mechanical equipment qualified in the EQ program.

The initial phase of the EGC EQ evaluation examined the environmental qualification of applicable equipment within the CPS Fuel Building (FB) (i.e., 11 of the 15 affected environmental zones). Currently, the CPS FB is designed to an upper temperature limit of 147°F, plus 15°F margin (162°F) for a post-accident duration of 110 days, which includes a 10%

margin to the 100 day post-accident duration. This design temperature of 147°F is reached at 2.5E6 seconds post-accident, and remains at this value up to day 100. The additional heat added by a fully loaded design basis spent fuel cask results in a post-accident temperature of 148°F at approximately day 30 and a peak temperature of approximately 152°F at day 100.

Using CPS zone maps, EGC conducted detailed walkdowns of the impacted areas in the FB, and reviewed EQ binders to identify affected zones and equipment. This resulted in identification of 60 EQ binders (i.e., out of 106 binders) having an affected zone, and therefore a component that could be potentially impacted.

Given the postulated temperature increase with the addition of a fully-loaded design basis spent fuel cask, EGC utilized the Arrhenius methodology via System 1000 Version 17.0.c for all calculations, and independently verified the results.

As a conservative approach, EGC evaluated the ability of EQ equipment in the affected FB zones to withstand a constant 170°F (i.e., 152°F plus 15°F margin, plus an additional 3°F margin) from LOCA initiation up to day 110.

If however, the existing test program equivalent aging hours for a specific EQ binder or area did not envelop the aging hours resulting from a constant 170°F (i.e., from LOCA initiation up to day 110), EGC utilized an alternate approach (i.e., 170°F for the first 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months following LOCA initiation, and 155°F for the next 109 days). This alternate approach was also conservative to the postulated FB temperature with a fully loaded design basis spent fuel cask (i.e., 148°F at approximately day 30 and a peak temperature of approximately 152°F at day 100).

For each of the 60 EQ binders with an affected zone, using either the initial conservative approach, or the alternate approach, the equivalent aging hours for a postulated LOCA event with a fully loaded spent fuel cask are bounded by the equivalent aging performed during the simulated accident testing (i.e., as documented in the EQ binder), unless otherwise justified.

ENCLOSURE 5 Clinton Power Station, Unit 1 License Amendment Request Environmental Qualification Evaluation Due to Increased Heat Load Page 2 of 2 Subsequent to completion of the initial phase of the EQ evaluation, EGC identified four additional environmental zones within secondary containment with increases in post-LOCA temperature due to the design basis fuel cask. Consistent with the initial phase of the EQ evaluation, EGC reviewed all EQ binders to identify those binders applicable to the four additional impacted zones. This review identified six additional EQ binders applicable to the four zones that were not evaluated during the initial phase. For five of the six EQ binders, the postulated post-accident temperature, assuming a fully-loaded spent fuel cask in the FB, is bounded by the existing qualification.

The equipment evaluated in the sixth EQ binder is qualified for several environmental harsh zones. Amongst the impacted zones where the temperature increased, the maximum temperature would be 155°F. The existing evaluation in the EQ binder evaluated the equipment to the most severe environment of all zones the binder considers. The required temperature profile for first 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months is 330°F (i.e., with a short-term peak temperature of 339.97°F for 0.5 seconds) for the first 3 hours3.472222e-5 days 8.333333e-4 hours 4.960317e-6 weeks 1.1415e-6 months , 310°F for the next 3 hours3.472222e-5 days 8.333333e-4 hours 4.960317e-6 weeks 1.1415e-6 months , then 250°F for 18 hours2.083333e-4 days 0.005 hours 2.97619e-5 weeks 6.849e-6 months . After that, the existing evaluation assumes temperature decreasing at a steady rate from 250°F to 100°F for the next 109 days (2616 hours0.0303 days 0.727 hours 0.00433 weeks 9.95388e-4 months ). This results in an equivalent time of 151 hours0.00175 days 0.0419 hours 2.496693e-4 weeks 5.74555e-5 months (i.e., using the reference temperature of 250°F).

Considering the new increased temperature of 155°F, the required temperature profile remains the same for the first 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months , then decreases at a steady rate from 250°F to 155°F for 109 days (2616 hours0.0303 days 0.727 hours 0.00433 weeks 9.95388e-4 months ). The new equivalent time, using the reference temperature of 250°F, is less than 300 hours0.00347 days 0.0833 hours 4.960317e-4 weeks 1.1415e-4 months , which is still significantly less than the equivalent test time of 144.6 days (3472 hours0.0402 days 0.964 hours 0.00574 weeks 0.00132 months ) that is documented in the EQ binder. Therefore, since the new equivalent time is less than the equivalent test time, there is no impact on the qualification of equipment in the sixth binder.

In addition to the potential impact of increased temperature on the environmental qualification of affected equipment, EGC evaluated any potential EQ impact from a postulated increase in post-accident radiation levels in secondary containment (i.e., due to the increased drawdown time).

Post-LOCA secondary containment airborne radionuclide activities and associated doses are determined based on the modeling assumptions that: 1) there is a primary containment leak rate of 0.65% per day into the secondary containment for the first 20 minutes following LOCA initiation; 2) the airborne radioactivity leaked into the secondary containment is immediately homogenized within the secondary containment free air volume; and 3) the airborne activity in the secondary containment is removed at a constant SGTS exhaust flow rate of 4000 cfm. The drawdown time of 19 minutes represents the time it takes to reach and maintain -1/4 inch water gauge which is required in order to credit SGTS filtration of the exhaust. The analysis to determine the dose in the secondary containment is not dependent on whether the 4000 cfm exhaust is filtered by the SGTS and thus the drawdown time does not impact the calculation.

As such, the time to draw down the secondary containment atmosphere has no effect on calculated post-LOCA radiation dose rates and doses within the secondary containment.