ML13268A423
| ML13268A423 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 09/03/2013 |
| From: | Batson S Duke Energy Carolinas |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| Download: ML13268A423 (10) | |
Text
ENERGY, DUKE Scot L. Batson Vice President Oconee Nuclear Station Duke Energy ONOIVP 17800 Rochester Hwy Seneca, SC 29672 10 CFR 50.90 o: 864.873.3274 f.864.873.4208 September 3, 2013 Scott.Batson@duke-energy.com Attn: Document Control Desk U. S. Nuclear Regulatory Commission 11555 Rockville Pike Rockville, MD 20852-2746
Subject:
Duke Energy Carolinas, LLC Oconee Nuclear Station, Units 1, 2 and 3 Renewed Facility Operating License Numbers DPR-38, 47 and 55; Docket Numbers 50-269, 50-270 and 50-287; Response to Request for Additional Information Associated with License Amendment Request for Reverse Osmosis System Operation, License Amendment Request No. 2012-05, Supplement 3 On October 30, 2012, Duke Energy Carolinas, LLC (Duke Energy) submitted a License Amendment Request (LAR) requesting Nuclear Regulatory Commission (NRC) approval to operate a Reverse Osmosis (RO) System to remove silica from the Borated Water Storage Tanks (BWSTs) and Spent Fuel Pools (SFPs) during Unit operation. The LAR also requested approval of associated proposed new Technical Specifications (TSs) and Bases that impose new requirements for RO System operation and isolation. Duke Energy submitted supplemental information on January 21, 2013, in response to additional information requested during the NRC Acceptance Review. On June 11, 2013, Duke responded to a request for additional information (RAI) made by the NRC in letter dated April 12, 2013. The NRC requested Duke Energy to provide additional information by letter dated July 18, 2013. responds to the request for additional information. In response to RAI 16, Duke Energy will install automatic isolation valves in Spent Fuel Pool Cooling (SFPC) system piping upstream of the RO system BWST suction connections that will isolate the RO system supply piping before initiation of recirculation to prevent unanalyzed amounts of post loss-of-coolant accident (LOCA) fluids from entering the RO system. In May 2011, a similar concern was identified by Duke Energy regarding the use of the SFPC purification for BWST recirculation when performing Technical Specification required BWST boron sampling. Due to that concern, Oconee Nuclear Station (ONS) discontinued use of the SFPC purification system for BWST recirculation. As a result, ONS must now use a Low Pressure Injection (LPI) or Reactor Building Spray (BS) train to re-circulate each unit's BWST when performing Technical Specification required BWST boron sampling. This makes one train of LPI or BS inoperable thus making a train of an engineered safeguards feature inoperable. By installing the new automatic isolation valves in the line upstream of the branch line to the RO system, these valves will be used to isolate both the RO system and the SFPC purification system to prevent unanalyzed radiological releases from either system.
As such, Duke Energy requests NRC approval to credit the new automatic isolation valves to isolate the RO System BWST suction connection as well as the SFPC systems before initiation of reactor building sump recirculation to prevent post LOCA fluids from entering these systems.
www.duke-energy.com
U. S. Nuclear Regulatory Commission September 3, 2013 Page 2 Duke Energy will provide revised proposed Technical Specifications to address the new configuration using automatic isolation valves and a revised significant hazards consideration to address the crediting of the new automatic valves for the recirculation path by October 18, 2013.
A list of Regulatory Commitments is provided in Enclosure 2.
Inquiries on this submittal should be directed to Boyd Shingleton, Oconee Regulatory Affairs Group, at (864) 873-4716.
I declare under penalty of perjury that the foregoing is true and correct. Executed on September 3, 2013.
Sincerely, Scott L, Batson Vice President Oconee Nuclear Station
Enclosures:
- Duke Energy Response to Request for Additional Information - List of Regulatory Commitments
U. S. Nuclear Regulatory Commission September 3, 2013 Page 3 cc w/enclosures:
Mr. Victor McCree, Regional Administrator U. S. Nuclear Regulatory Commission - Region II Marquis One Tower 245 Peachtree Center Ave., NE, Suite 1200 Atlanta, GA 30303-1257 Mr. Richard Guzman, Acting Project Manager (by electronic mail only)
Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission 11555 Rockville Pike Mail Stop O-8C2 Rockville, MD 20852-2746 Mr. Eddy Crowe NRC Senior Resident Inspector Oconee Nuclear Site Ms. Susan Jenkins, Manager Radioactive & Infectious Waste Management Division of Waste Management South Carolina Department of Health and Environmental Control 2600 Bull St.
Columbia, SC 29201
U. S. Nuclear Regulatory Commission September 3, 2013 Page 4 bcc w/
Enclosures:
K. R. Alter J. A Patterson L. S. Nichols V. B. Bowman M. B. Lynch R. A. Heineck T. L. Patterson R. D. Hart - CNS J. N. Robertson - MNS D. B. Alexander- NRI&IA Dan Westcott - CR3 Lee Grzeck - BNP Dave Corlett - HNP Richard Hightower - RNP S. N. Severance NSRB, EC05N ELL, ECO50 File - T.S. Working ONS Document Management
ENCLOSURE I Duke Energy Response to Request for Additional Information
License Amendment Request No. 2012-05, Supplement 3 September 3, 2013 Page 1 Enclosure I Duke Energy Response to Request for Additional Information NRC Background Duke Energy Carolinas, LLC (Duke or the licensee) originally submitted a license amendment request (LAR) dated November 15, 2010 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML103220101) requesting approval to operate a reverse osmosis (RO) purification system at Oconee Nuclear Station (ONS), Units 1, 2, and 3, to purify the borated water storage tanks and the spent fuel pools during power operation. Duke then submitted responses to the Nuclear Regulatory Commission's (NRC's) request for additional information (RAI) on the following dates: February 18, 2011 (ADAMS Accession No. ML110550616), May 12, 2011 (ADAMS Accession No. ML11137A112), August 2,2011 (ADAMS Accession No. ML11215A198), October 10, 2011 {ADAMS Accession No. ML11285A302),
and December 15, 2011 {ADAMS Accession No. ML11354A253}. Based on discussions between Duke and the NRC, by letter dated April 3,2012, Duke requested to withdraw this LAR, and the NRC staff agreed by letter dated April 12, 2012. In a letter dated October 30, 2012 (ADAMS Accession No. ML12307A219), as supplemented on January 21,2013 (ADAMS Accession No. ML13025A254), and June 11,2013 (ADAMS Accession No. ML13172A043),
Duke submitted a revised LAR for the use of the RO system. The Nuclear Regulatory Commission (NRC) staff is reviewing the submittals and has the following questions.
RAI-16 (Follow-up to previous RAI 7)
In lieu of automatically actuated isolation valves, the LAR proposes to use a time critical operator action (TCOA) to ensure the RO system supply piping boundary valves are manually closed before initiation of recirculation to prevent post loss-of-coolant accident (LOCA) fluids from entering the RO system.
Regulatory Guide 1.183, Regulatory Position 5.1.2 states that:
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.
The licensee has not provided adequate justification for why these boundary valves do not need to be automatically actuated. The proposed boundary valves are manually operated and both located in the same room. A dedicated operator will not be used to ensure the valves are closed when directed by the emergency operating procedures and no remote indication has been provided in order to verify the valves are closed. During the recirculation phase, these valves isolate the reactor coolant system from the environment similar to containment isolation valves, which must be locked closed or automatically isolated (General Design Criteria 56/57). As discussed in Generic Letter (GL) 91-08, normally closed isolation valves may be opened for limited time periods under administrative controls, which includes stationing of a dedicated operator. As discussed in Information Notice 97-78, if a dedicated operator is not provided, an evaluation of the impact of a single operator error should be performed, including the ability to
License Amendment Request No. 2012-05, Supplement 3 September 3, 2013 Page 2 recover from credible operator errors and the time required to make the recovery. Therefore, provide one of the following:
1, An analysis of the impact of not isolating the RO system on the radiological consequences of a design basis accident.
2, Automatically actuated RO system boundary valves.
3, A dedicated operator responsible for closing the RO system boundary valves, with the controls for maintaining operability of the RO system valves using the dedicated operator discussed in the TS Bases.
- 4. An evaluation of the impact of a single operator error on the ability to perform the TCOA within 33 minutes, including failure of the operator to be dispatched to perform the action, the ability of the operator to get to the valves using more than one pathway, and the impact of having no verification that the action has been performed.
Duke Energy Response Duke Energy will install automatically actuated isolation valves (QA-1, Duke Energy Class C -
United States of America Standard (USAS) B31.7, seismic) in the Spent Fuel Pool Cooling (SFPC) System upstream of the RO system Borated Water Storage Tank (BWST) suction connections. These valves will isolate the purification system from the BWST prior to Emergency Core Cooling System (ECCS) pump suction switchover to the Reactor Building Emergency Sump (RBES) (on low BWST recirculation header pressure equivalent to a BWST level before switchover). Actuation signals to close the valves will be from two redundant BWST pressure switches installed in the BWST recirculation header. The setpoint for the pressure instrument will prompt closure of the valves before the BWST reaches a point where ECCS pumps are aligned to the Reactor Building sump. Position indication for these two valves will be provided on the Operator Aid Computer (OAC) in the control room.
This installation of automatic isolation valves addresses two concerns: 1) unanalyzed radiological release pathway via the RO system should it be unisolated when a LOCA occurs, and 2) unanalyzed radiological release pathway via the SFPC purification system should the BWST recirculation pump be in use when a LOCA occurs.
A concern with BWST recirculation using the SFPC system was identified in May 2011 as part of an extent of condition review associated with the concern identified during the RO LAR review regarding post LOCA reactor building sump back leakage resulting in an unanalyzed release pathway. When used for BWST recirculation, the SFPC System also takes suction from the line downstream of LP-28 and discharges to the top of the BWST. Like the RO unit, if this mode of operation is not secured prior to completing suction swap from the BWST to RBES, the assumptions in the maximum hypothetical accident (MHA) dose analysis would be challenged.
Currently, to sample for BWST boron concentration, ONS re-circulates the BWST using a Low Pressure Injection (LPI) or Reactor Building Spray (BS) train to assure the contents are mixed prior to sampling. This makes one train of LPI or BS inoperable thus making a train of an engineered safeguards feature inoperable. The preferred method of recirculation is to use the SFPC purification system / BWST Recirculation Pump.
License Amendment Request No. 2012-05, Supplement 3 September 3, 2013 Page 3 Duke Energy is installing the automatic isolation valves in the line upstream of the branch line to the RO system so these valves can also be used to isolate the SFPC system from the BWST.
As such, Duke Energy requests NRC approval to credit the new automatic isolation valves to isolate the RO System and the SFPC System purification loop prior to completing suction swap from the BWST to RBES to prevent post LOCA fluids from entering these systems. Duke Energy will provide revised proposed Technical Specifications (TSs) to address the new configuration and a revised significant hazards consideration by October 18, 2013.
In response to Acceptance Review Issue 1 in letter dated January 21, 2013, Duke Energy agreed to add a redundant manual RO System supply isolation valve to the RO System design to address single failure concerns and revised the proposed TS to require two manual RO System supply isolation valves. Based on installing the two new automatic isolation valves, the redundant manual isolation valve is no longer required and will not be included in the design.
The proposed TS requirements for manual valves will be replaced with TS requirements for automatic valves.
RAI-17 (follow-up to previous RAI 9)
Explain why the spent fuel (SF) cooling and purification system will not become contaminated with post-LOCA back leakage, since the SF cooling and purification system connects to the borated water storage tank (BWST) with the valves open to carry the RO discharge flow back to the BWST, and the BWST itself is subject to post-LOCA back leakage.
Duke Energy Response The iodine release model in the Maximum Hypothetical Accident (MHA) dose analysis assumes post-LOCA sump back leakage enters the BWST below the water level in the tank, since the SFPC System and the RO system will be automatically isolated prior to sump recirculation.
Noble gases are not contained in the post-LOCA sump back leakage, since they are released into containment following the LOCA and, with the exception of iodine, all radioactive materials in the recirculating liquid are assumed to be retained in the liquid phase. Only a portion of the iodine in the sump back leakage becomes airborne. This airborne iodine is assumed to be released to the atmosphere via the large BWST vent which is open to the atmosphere.
Post-LOCA backleakage enters the BWST from the bottom of the tank. The RO System discharges to the top of the BWST through the overflow connection above 848 ft. elevation.
Therefore, considering the water level present at switchover and the location of the RO System return to the BWST, it would take more than 30 days at 5 gpm for water contaminated by post-LOCA backleakage to enter the discharge piping and leak back into the RO System piping or associated SFPC System piping and challenge the RO System discharge check valve/boundary valve or contaminate the SFPC System. Therefore, this leakage path is not subject to post-LOCA back leakage.
As stated in our response to Acceptance Review Issue 2 (Duke Energy letter dated January 21, 2013), the maximum allowable leakage from the LPI System components is currently limited to two gallons per hour (gph). Significant margin (as discussed in response to Acceptance Review Issue 3 is provided in the Alternative Source Term (AST) calculation to allow for additional
License Amendment Request No. 2012-05, Supplement 3 September 3, 2013 Page 4 leakage. In that response, Duke Energy indicated that a portion (6 gph maximum) of the conservatism would be assigned to the RO System supply manual isolation valves and the BWST Recirculation Pump suction valve. With the new configuration, proposed in response to RAI 16 above, Duke Energy will assign this portion to the two new SFPC System automatic isolation valves and other normally closed potential leakage paths that branch upstream of these new automatic isolation valves. This will limit any return flow that could leak through the supply side back to the top of the BWST via the RO system or the SFPC system to 6 gph, which is within the assumptions of the AST analysis.
- License Amendment Request No. 2012-05, Supplement 3 September 3, 2013 ENCLOSURE 2 REGULATORY COMMITMENTS 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 Completion Date 1 Duke Energy will provide the revised proposed Technical October 18, 2013 Specification.