ML11137A112
| ML11137A112 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 05/12/2011 |
| From: | Gillespie T Duke Energy Carolinas |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| LAR 10-03, Supp 2 | |
| Download: ML11137A112 (13) | |
Text
Duke T. PRESTON GILLESPIE, JR.
Vice President ergy.
Oconee Nuclear Station Duke Energy ON01 VP / 7800 Rochester Hwy.
Seneca, SC 29672 May 12, 2011 864-873-4478 864-873-4208 fax T. Gillespie@duke-energy. com U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, D. C. 20555-0001
Subject:
Duke Energy Carolinas, LLC Oconee Nuclear Station, Units 1, 2, and 3 Docket Numbers 50-269, 50-270, and 50-287 "License Amendment Request for Approval to Operate a Reverse Osmosis System to Remove Silica from the Borated Water Storage Tanks and Spent Fuel Pools during Unit Operation" License Amendment Request (LAR) No. 2010-03, Supplement 2 On November 15, 2010, Duke Energy Carolinas, LLC (Duke Energy) submitted a License Amendment Request (LAR) to request approval to operate a Reverse Osmosis System to remove silica from the Borated Water Storage Tanks and Spent Fuel Pools during Unit Operation. Duke Energy supplemented the LAR by letter dated February 18, 2011, in response to a request for additional information transmitted electronically on December 20, 2010. By electronic mail dated March 16, 2011, and April 24, 2011, NRC requested Duke Energy to supplement the LAR with further information. Enclosures 1 and 2 provide the additional information. Enclosure 3 provides a list of Regulatory Commitments being made as a result of this LAR.
Inquiries on this proposed amendment request should be directed to Boyd Shingleton of the ONS Regulatory Compliance Group at (864) 873-4716.
I declare under penalty of perjury that the foregoing is true and correct. Executed on May 12, 2011.
Sincerely, T. Preston Gillespie, Jr., Vice President Oconee Nuclear Station
Enclosure:
- 1. Duke Energy Response to NRC Request for Additional Information transmitted March 16, 2011
- 2. Duke Energy Response to NRC Request for Additional Information transmitted April 24, 2011
- 3. List of Regulatory Commitments www. duke-energy corn m I.
Nuclear Regulatory Commission May 12, 2011 Page 2 bc w/enclosure:
Mr. Victor McCree, Regional Administrator U. S. Nuclear Regulatory Commission - Region II Marquis One Tower 245 Peachtree Center Ave., NE, Suite 1200 Atlanta, Georgia 30303-1257 Mr. John Stang, Project Manager Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission Mail Stop 0-8 G9A Washington, D. C. 20555 Mr. Andy Sabisch Senior Resident Inspector Oconee Nuclear Site Ms. Susan E. Jenkins, Manager Radioactive & Infectious Waste Management Division of Waste Management South Carolina Department of Health and Environmental Control 2600 Bull St.
Columbia, SC 29201
ENCLOSURE 1 DUKE ENERGY RESPONSE TO NRC REQUEST FOR ADDITIONAL INFORMATION RECEIVED MARCH 16, 2011
LAR No. 2010-03, Supplement 2 - Duke Energy Response to NRC RAI Received March 16, 2011 May 12, 2011 Page 1 NRC RAI I Per Regulatory Guide (RG) 1.183, "Alternative Radiological Source Terms for Evaluating Design Basis Accidents at Nuclear Power Plants," dated July 2000 (ADAMS Accession No. ML003716792), Regulatory Position C.1.3.2, "Reanalysis Guideline:"
The NRC staff does not expect a complete recalculation of all facility radiological analyses, but does expect licensees to evaluate all impacts of the proposed changes and to update the affected analyses and the design bases appropriately. An analysis is considered to be affected if the proposed modification changes one or more assumptions or inputs used in that analysis such that the results, or the conclusions drawn on those results, are no longer valid.
Also, RG 1.183, Section B, "Discussion," states:
Although the LOCA is typically the maximum credible accident, NRC staff experience in reviewing license applications has indicated the need to consider other accident sequences of lesser consequence but higher probability of occurrence to evaluate the response of a facility's engineered safety features.
Standard Review Plan (SRP) 15.0, "Introduction - Transient and Accident Analysis," Revision 3, dated March 2007 (ADAMS Accession No. ML070710376) states:
The reviewer considers the possible case variations of AQOs [anticipated operational occurrences] and postulated accidents presented to verify that the licensee has identified the limiting cases.
Please provide an evaluation of the impact of the proposed change on all accidents and AOO's in the design bases or include a justification supporting why an evaluation of the impact is not needed. If an evaluation of other design bases accidents is provided, please provide the regulatory bases for the acceptance criteria (i.e. Title 10 of the Code of Federal Regulations (10 CFR), Part 50, Appendix A, "General Design Criteria for Nuclear Power Plants," General Design Criterion (GDC) 19, 10 CFR, Section 50.67, "Accident source term" (10 CFR 50.67) or 10 CFR Part 100, "Reactor Site Criteria") and any regulatory guidance used to make this determination.
Duke Energy Response to RAI I The November 15, 2010, License Amendment Request provides an evaluation of the impact of Reverse Osmosis (RO) System operation on the safety related function of the BWST and SFP.
The Borated Water Storage Tank (BWST) supports the Emergency Core Cooling System (ECCS) and the Reactor Building Spray (RBS) System by providing a source of borated water for ECCS and RBS pump operation. The Spent Fuel Pools (SFPs) provide for the safe storage of spent fuel as well as act as a source of borated water for use by the Standby Shutdown Facility Reactor Coolant Makeup system.
LAR No. 2010-03, Supplement 2 - Duke Energy Response to NRC RAI Received March 16, 2011 May 12, 2011 Page 2 Duke Energy also evaluated the impact of the proposed change on any inputs and assumptions in the Chapter 15 design basis accident dose analyses. The Chapter 15 LBLOCA dose analysis assumes ECCS and RBS actuation, which eventually leads to sump recirculation. Upon initiation of sump recirculation, sump back-leakage to the BWST is assumed. Duke Energy will add a time critical operator action (TCOA) to the Emergency Operating Procedure (EOP) to isolate the RO System from the BWST at the safety related Class C seismic boundary valve (see response to RAI 2a for more details on the TCOA). Therefore, the RO System does not impact the assumptions in the design basis LBLOCA dose analysis. No other Chapter 15 design basis accident dose analysis models the BWST, or post accident back-leakage to the BWST. Since Duke Energy is adding the TCOA to isolate the RO System from the BWST at the safety related Class C seismic boundary valve, there is no longer a need to install a non QA-1 switch at an alternate accessible location to allow remote shutdown, therefore, this feature will be removed from the overall design of the RO System.
The SFP is credited for maintaining the Technical Specification (T.S.) 3.7.11 minimum water level over the fuel in the case of a Fuel Handling Accident (FHA) (single assembly accident or cask drop accident). The RO System will not result in a T.S. 3.7.11 change, so it has no impact on the FHA dose analysis assumptions. In addition, Duke Energy will prohibit fuel movement and cask handling activities during operation of the RO System, so a FHA will not occur while the RO System is in operation. This restriction will remain in place until such time Duke Energy completes calculations that demonstrate the transport of SFP water with radioactivity concentrations resulting from the FHA do not prevent the access required to shutdown the RO system when required.
Since only the LBLOCA and FHA Chapter 15 dose analyses include credit for the BWST or SFP, and since the RO system will not impact any inputs or assumptions in those analyses, no changes to the Chapter 15 design basis accident dose analyses are necessary to implement this proposed change.
NRC RAI 2 The November 15, 2010, amendment request (ADAMS Accession No. ML1032201011) analyzes several scenarios involving some design basis accidents. An example, taken from page 13 is given below:
For the design basis LBLOCA [large break loss of coolant accident], the BWST [borated water storage tank] will be expended in a short time period; not long enough for RO
[reverse osmosis] System operation to significantly reduce BWST boron concentration or volume (i.e., TS [technical specification] limits for boron and temperature maintained).
Therefore, there is no need to isolate the RO unit post LBLOCA (BWST has already performed its safety function) when the RO unit is aligned to the BWST for the ONS
[Oconee Nuclear Station] unit with the LBLOCA. However, should the RO unit be aligned to the Unit 1 BWST or Unit 3 BWST and a LBLOCA occurs on Unit 2, the RO unit will eventually need to be shut down to avoid going below the TS limits for volume or boron concentration for the unaffected Oconee Unit. No access will be available to shutdown the RO unit or close the supply valve to isolate the Unit I BWST due to higher radiation levels at the RO unit location (Room 349). The modification installs a non QA-1 switch [emphasis added] in an alternate accessible location to allow remote shutdown of the RO unit prior to
LAR No. 2010-03, Supplement 2 - Duke Energy Response to NRC RAI Received March 16, 2011 May 12, 2011 Page 3 degrading the Unit 1 BWST. If aligned to the Unit 3 BWST, the RO unit may be shutdown using this switch or by closing a supply valve in the Unit 3 SFP [spent fuel pool] area since it will remain accessible.
Section 15.15.4, "Effects of Engineered Safeguards Systems Leakage," of the ONS Updated Final Safety Analysis Report states:
An additional source of fission product leakage during the maximum hypothetical accident can occur from leakage of engineered safeguards systems extemal to the Reactor Building during the recirculation phase for long-term cooling. A detailed analysis of the potential leakage from these systems is presented in Section 6.1.3. A value of 25 gallons per hour (gph) leakage from LPI [low pressure injection], HPI [high pressure injection] and BS
[reactor building spray] systems was assumed in the MHA dose analysis. The MHA dose analysis also assumes back-leakage to the Borated Water Storage Tank (BWST) at a rate of 5 gallons per minute (gpm).
Regulatory Position C. 1. 12, "Defense in Depth," of RG 1.183 states:
Modifications proposed for the facility generally should not create a need for compensatory programmatic activities, such as reliance on manual operator actions.
Regulatory Position C.5.1.2, "Credit for Engineered Safeguard Features," of RG 1.183 states:
Credit may be taken for accident mitigation features that are classified as safety-related, are required to be operable by technical specifications, are powered by emergency power sources, and are either automatically actuated or, in limited cases, have actuation requirements explicitly addressed in emergency operating procedures. The single active component failure that results in the most limiting radiological consequences should be assumed. Assumptions regarding the occurrence and timing of a loss of offsite power should be selected with the objective of maximizing the postulated radiological consequences.
Appendix A, "Seismic and Geological Siting Criteria for Nuclear Power Plants," to 10 CFR Part 100, requires that nuclear power plants must be designed so that certain structures, systems and components remain functional if the safe-shutdown earthquake ground motion (SSE) occurs. These plant features are those necessary to ensure (1) the integrity of the reactor coolant pressure boundary, (2) the capability to shut down the reactor and maintain it in a safe shutdown condition, or (3) the capability to prevent or mitigate the consequences of accidents that could result in potential offsite exposures comparable to the guideline exposures of 10 CFR 100.11 or 10 CFR 50.67, as applicable.
2a.
The November 15, 2010, amendment request states that "Therefore, there is no need to isolate the RO unit post LBLOCA (BWST has already performed its safety function) when the RO unit is aligned to the BWST for the ONS unit with the LBLOCA." The current design analysis assumes back-leakage of reactor coolant system fission product leakage to the BWST after a loss of coolant accident (LOCA). The proposed RO system while operating and aligned to the BWST takes suction from the BWST and could transport this reactor coolant system back-leakage to the RO system. Since the RO system is not
LAR No. 2010-03, Supplement 2 - Duke Energy Response to NRC RAI Received March 16, 2011 May 12, 2011 Page 4 classified as a safety related component and not automatically isolated, per Regulatory Position C.5.1.2 credit is not taken for accident mitigation for the RO system or for its isolation. Those parts of the RO system not SSE qualified would also not be typically credited. Please provide a justification supporting why this release pathway should not be considered in the design basis LOCA dose analysis or consider it in the design basis LOCA dose analysis.
2b.
For any other design basis accidents or scenarios impacted by the proposed change, please justify any credit for accident mitigation features that are not consistent with Regulatory Position C5.1.2 or are not SSE qualified or justify why this is not necessary.
2c.
For any proposed compensatory actions that involve human actions, please justify how these actions can be assured to be completed with the potential for harsh environments (radiation, temperature, pressure, humidity, or failure of high energy pipes) which could impede or prevent human actions. Please specify and justify the methods used to make these determinations (i.e. RG 1.183, Standard Review Plan Section 18.0, "Human Factors Engineering" (Adams Accession No. ML070670253 etc.)).
2d.
The analyses provided for items 2a and 2b should justify how the licensing basis dose consequences required by 10 CFR 50.67, 10 CFR 100 or General Design Criterion 19, as applicable, are met. Please provide a justification for each change of inputs, methods, acceptance criterion, and assumptions (including any reliance on human actions). It would be helpful to provide a table of the current design basis, the proposed design basis and a justification for each change. Providing the actual calculations is also very helpful because it has been found to increase the efficiency of the review.
Duke Energy Response to RAI 2a Duke Energy's evaluation addressed the impact of RO system operation on the safety related function of the BWST or the SFP. However, the evaluation did not address the potential for sump back-leakage to the BWST being transported to the Auxiliary Building by the continued operation of the RO System when aligned to that BWST. Rather than evaluate the impact of the RO System circulating post LOCA fluids in the Auxiliary Building, Duke Energy will add a TCOA to isolate the RO System to preclude intake of post LOCA fluids into the RO system.
LAR No. 2010-03, Supplement 2 - Duke Energy Response to NRC RAI Received March 16, 2011 May 12, 2011 Page 5 The safety related Class C seismic boundary valve located in the spent fuel cooler room will be used to isolate the system. Therefore, this release pathway does not need to be considered in the design basis LOCA dose analysis. Duke Energy has determined that at least 33 minutes is available to close the valve (based on time to switch over to the sump for ECCS pump suction).
The TCOA will be based on this time until additional calculations are completed that support a longer time. This longer time will be considered acceptable provided it ensures access to the valve.
Duke Energy is performing calculations to determine how long access to the safety related Class C seismic boundary valve is available after switchover to the recirculation phase. Any additional time allotted for the TCOA will be based on results of these calculations.
Since Duke Energy will isolate the RO System prior to any transport of back-leakage to the RO system, this release pathway does not need to be considered in the design basis LBLOCA dose analysis.
Duke Energy Response to RAI 2b As detailed in response to RAI 1, other than the LBLOCA, no other design basis accidents are impacted by the proposed change.
Duke Energy Response to RAI 2c The location of the seismic boundary valve is accessible (i.e., within normal reach with no climbing or tools required) during normal operations and will remain accessible for at least 33 minutes post LOCA. Refer to the response to RAI 2a for more detail. The manual seismic boundary valve is a two inch manual ball valve (1/4 turn) that can be closed in less than a minute.
Duke Energy has evaluated the environment in the spent fuel cooler room (location of the seismic boundary valve) and pathways to the spent fuel cooler room post LOCA (the 33 minutes prior to switch over to the sump for ECCS pump suction) and determined that the resulting radiation, temperature, pressure, and humidity will not impede or prevent operator access.
Additional calculations are being performed in conjunction with justifying any additional time for the TCOA beyond the 33 minutes.
Duke Energy Response to RAI 2d The operation of the RO system, as described above, does not affect the licensing basis dose consequences since the system will be isolated to preclude intake of post LOCA fluids into the RO System. Therefore, no radioactive liquid can be transported from the RO System to the Auxiliary Building. No changes to the inputs, methods, acceptance criterion, or assumptions in the Chapter 15 design basis accident dose analyses are required to implement this proposed change.
ENCLOSURE 2 DUKE ENERGY RESPONSE TO NRC REQUEST FOR ADDITIONAL INFORMATION RECEIVED APRIL 24, 2011
LAR No. 2010-03, Supplement 2 - Duke Energy Response to NRC RAI Received April 24, 2011 May 12, 2011 Page 1 RAI Section 3.5 of the enclosure to the license amendment request described the evaluation of impacts due to auxiliary building flooding. The existing licensing basis is that flooding from un-isolated portions of non-seismic systems would be flow-limited such that operators have time to identify and isolate the source. Operators would detect this flooding either through procedural response to a seismic event or through a high level alarm produced by sensors in the auxiliary building sump. Section 3.5 described that similar analyses of breaks in the reverse osmosis system confirmed that operators could isolate any failed portion of the piping prior to adversely affecting structures, systems, and components important to safety, which were identified as LPI and HPI pumps. NRC Branch Technical Position 3-3, "Protection Against Postulated Piping Failures in Fluid Systems Outside Containment," describes that separation between fluid system piping and essential components should be achieved by plant physical layouts that provide sufficient distances between essential components and fluid system piping such that the environmental effects of any postulated piping failure cannot impair the integrity or operability of essential components. Recent industry operating experience demonstrates the sensitivity of electrical switchgear to water leakage or spray.
Since the addition of the reverse osmosis system would introduce a new design function and constraints on the routing of the new piping are minimal, additional consideration of environmental effects from failure of the new piping relative to the current licensing basis is appropriate. Describe the criteria applied to the routing of the reverse osmosis system piping in the auxiliary building, particularly with regard to separation from essential components (e.g., switchgear) and measures to ensure leakage would be routed to the auxiliary building sump to support prompt detection.
Duke Energy Response to RAI The RO System piping was routed in the Auxiliary Building to provide the most efficient configuration. As noted in the November 15, 2010, LAR, Duke Energy installed a seismically qualified barrier to protect a safety-related cable tray from potential damage by potentially falling non-seismic RO System piping. No other criteria besides seismic interaction were applied to prevent interactions with safety-related equipment that might be nearby since the current Oconee licensing basis does not require the postulation of other interactions with safety-related equipment near non-seismic moderate energy piping. None of the RO System piping is high energy piping except that in Room 349. This high energy piping has been evaluated against applicable high energy line break criteria. The Oconee licensing basis does not require moderate energy pipe routing to consider the effect of spray on safety-related electrical equipment. The effects of an RO System pipe break on interconnected systems were discussed in the original LAR.
Any leakage from the RO System piping will be collected by the floor drains or will run over the floor until another pathway is found to lower levels if a floor drain is not directly available. The floor drains are likely to be the path of choice because of their number and location throughout the auxiliary building. If there is no or little water that flows through a floor drain, the impact on safety-related equipment due to flooding is also less. This is because the safety-related equipment at the lowest elevation is located in the LPI/BS Pump Rooms, and also because a smaller leakage rate is implied. The main way that water can reach these rooms (in all Oconee Units) is through the floor drain system. The access to these pump rooms is protected by curbs such that the water would
LAR No. 2010-03, Supplement 2 - Duke Energy Response to NRC RAI Received March 16, 2011 May 12, 2011 Page 2 have to pond several inches before overflowing the curbs. Since there is a large floor area outside of the curb, this large area would have to contain the leakage before the water level could exceed the curb height. There would be many functional floor drains within the flooded area in that event due to the number of floor drains in a typical area of the Auxiliary Building floor. The November 15, 2010, LAR discussed the other aspects of responding to indications of Auxiliary Building flooding, such as the flow and response time requirements. Any leakage from the RO System piping will be detected in sufficient time to allow isolation prior to affecting safety-related equipment. The LAR also discussed the seismic design of the RO System piping in several areas that were not served by normally open floor drains, to prevent leakage caused by an earthquake from causing unacceptable consequences. The LAR also states that administrative controls will be in place to shutdown and isolate the RO System from the SFPs when ONS is placed under a tornado watch or warning because these same areas are vulnerable to tornado missiles.
LIST OF REGULATORY COMMITMENTS
LAR No. 2010-03, Supplement 2 - List of Regulatory Commitments May 12, 2011 Page 1 The following commitment table identifies those actions committed to by Duke Energy Carolinas, LLC (Duke Energy) in this submittal. Other actions discussed in the submittal represent intended or planned actions by Duke Energy. They are described to the Nuclear Regulatory Commission (NRC) for the NRC's information and are not regulatory commitments.
.Commitment C
Completion Date 1
Duke Energy will restrict fuel movement and cask handling Prior to aligning the activities during operation of the RO System until such time RO System to a calculations are completed that demonstrate the transport of SFP SFP water with radioactivity concentrations resulting from FHA does not prevent the access required to shutdown the RO system when required.
2 Duke Energy will add a TCOA to isolate the RO System to Prior to aligning the preclude intake of post LOCA fluids into the RO system.
RO system to a BWST.