ML11354A253
| ML11354A253 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 12/15/2011 |
| From: | Gillespie T Duke Energy Carolinas |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| LAR 2010-03, Suppl 5 | |
| Download: ML11354A253 (8) | |
Text
Duke T. PRESTON GILLESPIE, JR.
Vice President CEnergy Oconee Nuclear Station Duke Energy ON0I VP / 7800 Rochester Hwy.
Seneca, SC 29672 10 CFR 50.90 864-873-4478 864-873-4208 fax December 15, 2011 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 (ONS), Units 1, 2, and 3 Docket Numbers 50-269, 50-270, and 50-287 Additional Information Regarding License Amendment Request for Approval to Operate a Reverse Osmosis System during Unit Operation, License Amendment Request (LAR) No. 2010-03, Supplement 5 On November 15, 2010, Duke Energy Carolinas, LLC (Duke Energy) submitted a License Amendment Request (LAR) to request approval to operate a Reverse Osmosis (RO) System to remove silica from the Borated Water Storage Tanks and Spent Fuel Pools during Unit Operation at ONS. Duke Energy supplemented the LAR by letters dated February 18, 2011, May 12, 2011, August 2, 2011 and October 11, 2011. NRC requested Duke Energy to respond to two additional questions transmitted by email on October 31, 2011. The Enclosure provides Duke Energy's response to these questions.
Inquiries on this submittal should be directed to Boyd Shingleton, ONS Regulatory Compliance Group, at (864) 873-4716.
I declare under penalty of perjury that the foregoing is true and correct. Executed on December 15, 2011.
Sincerely, T. Preston Gillespie, Jr., Vice President Oconee Nuclear Station Enclosure
-AllL www. duke-energy. com
Nuclear Regulatory Commission December 15, 2011 Page 2 cc 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 Duke Energy Response to NRC Request for Additional Information
LAR 2010-03, Supplement 5 December 15, 2011 Page 1 ENCLOSURE Duke Energy Response to NRC Request for Additional Information NRC RAI 1 Over 99% of the radioactivity released during a fuel handling accident (FHA) is contained in the spent fuel pool water. The proposed change creates the potential for a new release pathway from the spent fuel pool water to the environment via the reverse osmosis (RO) system. This pathway is not currently considered in the FHA analyses because it did not exist prior to this proposed change. In the amendment request, the licensee does not analyze the safety significance (the impact on Title 10 of the Code of Federal Regulations (10 CFR), Section 50.67 analyses) of this pathway for a design basis FHA. Rather, the licensee proposes to revise the Updated Final Safety Analysis Report to include an operating restriction that no fuel movements or cask handling activities are allowed when the RO system is operating. The staff believes that this is an operating restriction that is assumed at the start of the FHA and continues throughout the duration of the accident and, therefore, meets 10 CFR 50.36, Criterion 2 which states:
(ii) A technical specification limiting condition for operation of a nuclear reactor must be established for each item meeting one or more of the following criteria: (B) Criterion 2. A process variable, design feature, or operating restriction that is an initial condition of a design basis accident or transient analysis that either assumes the failure of or presents a challenge to the integrity of a fission product barrier.
In addition Regulatory Guide 1.183, "Alternative Radiological Source Terms for Evaluating Design Basis Accident at Nuclear Power Reactors," (Adams Accession Number ML003716792), Regulatory Position (RP) 5.1.2 states:
Credit may be taken for accident mitigation features that are classified as safety-related, are required to be operable by technical specifications, and 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 proposed operating restriction is credited to mitigate the design basis FHA. If the system is not operating, there may still be a release pathway present through the piping. It is not clear if the license commitment also means that the RO system will be isolated. If the system is isolated, this should prohibit leakage to the environment via the RO system. Contrary to RP 5.1.2 above, credit for mitigation is proposed for a mitigation feature which prohibits a release through the RO system and is not controlled by technical specifications. Therefore, the staff is concerned that the credited operating restriction appears to be inconsistent with 10 CFR 50.36 and RP 5.1.2. Depending upon the licensee's course of action, please provide a response to one of the following requests for additional information.
- 1. State whether the proposed operating restriction meets RP 5.1.2. If it does not, please provide additional justification for crediting the proposed operating restriction. Justify why a commitment and a non-safety related system is appropriate rather than a technical specification
Enclosure-LAR 2010-03, Supplement 5 December 15, 2011 Page 2 and a safety-related system to ensure 10 CFR 50.67 continues to be met. Justify why securing the RO system isolates the spent fuel pool water from the RO system or state that the RO system is isolated from the spent fuel pool water using a valve. In addition, justify why the proposed operating restriction does not meet 10 CFR 50.36, Criterion 2.
- 2. Consistent with 10 CFR 50.67, please analyze the dose impact of the additional release pathway (through the RO system) after a design basis FHA. Please provide the analysis, any methods, inputs or assumptions used, and the results of the analysis.
- 3. Please provide a technical specification for the proposed operating restriction.
Duke Energy Response to RAI 1 The proposed operating restriction requires the RO System to be isolated from the spent fuel pool during fuel handling or cask handling operations using a closed manual isolation valve.
RP 5.1.2 of RG 1.183 is referring to accident mitigation features and is specifically directed at single active component failures. A closed manual isolation valve is passive by design and is not an accident mitigation feature since it is already closed. Regardless, the proposed operating restriction is not an accident mitigation feature since closure of the valve is not the only barrier that ensures 10 CFR 50.67 continues to be met. The RO System piping also serves as a barrier and would also have to fail before a potential additional release pathway could be created.
An event that would result in release of highly radioactive fluids not within the bounds of the FHA is unlikely to occur. Such an event would require one of the following:
two passive single failures (failure of the closed manual isolation valve and failure of the high pressure portion of the RO System piping) and one operator error (placing the RO System in operation) concurrent with a FHA two operator errors (RO system unisolated from SFP, i.e., manual isolation valves left in the open position and RO system placed in operation) and a single passive failure of the high pressure portion of the RO system piping concurrent with a fuel handling accident.
Duke Energy committed to include an operating restriction to require the non safety related RO System to be isolated from the SFP during Fuel or Cask Handling activities. This operating restriction will be included in the Selected Licensee Commitment (SLC) Manual. Locating this requirement in a SLC is appropriate and consistent with other existing SLCs that implement operating restrictions. For example, SLC 16.6.5, "Core Flood Tank (CFT) Discharge Valve Breakers, and SLC 16.6.7, "Borated Water Storage Tank (BWST) Outlet Valve Control" provide operating restrictions. SLC 16.6.5 requires the breakers associated with the CFT discharge valves to be locked open and tagged. If this requirement is not met, the breakers must be locked open and tagged within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> or the affected unit must be placed in MODE 3 in 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> and pressure reduced to _< 800 psig in 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />. SLC 16.6.7 requires manual valve LP-28 on the BWST discharge line to be locked open. If this requirement is not met the required action is to enter the applicable TS condition for the BWST being inoperable. These requirements, along with numerous others, were relocated to the SLC Manual during the
Enclosure-LAR 2010-03, Supplement 5 December 15, 2011 Page 3 Improved Technical Specification (ITS) conversion process. NRC approved these relocations by "NUREG-1430, Fr Notice of Issuance of Amends 300 to Licenses DPR-38, DPR-47 & DPR-55,respectively,reflecting Full Conversion of Current TSs to Set of TSs Based on [[NUREG" contains a listed "[" character as part of the property label and has therefore been classified as invalid.,rev 1|letter dated December 16, 1998]].
The control of the Oconee Nuclear Station selected licensee commitment program and manual is in accordance with approved directives. The manual is officially designated as Chapter 16 of the Oconee UFSAR. The original issue and subsequent revisions of the manual are approved by the station manager or his designee. Administrative requirements of the manual are the responsibility of the Site Regulatory Compliance Section.
Changes to these Selected Licensee Commitments are considered a change in an NRC commitment and can only be made in accordance with the approved directives and by use of the 10CFR50.59 Process.
Duke Energy evaluated the scenario where the operating restriction (i.e., RO system not isolated from SFP) is violated and a Fuel Handling Accident occurs and the RO system piping remains intact. Considering these assumptions, 10 CFR50.67 continues to be met as described below.
The UFSAR Chapter 15 Fuel Handling Accident (FHA) dose analysis analyzes two potential release locations for radioactivity released from the Spent Fuel Pool (SFP) water: the unit vent and the fuel handling building roll-up door. Releases of noble gases and iodines which partition out of the water could be released to the environment through either of these locations. No credit is taken for filtration, deposition, plateout, nor holdup prior to the release to the environment. No dilution of radioactivity in the SFP inventory is assumed. The timing of the release is assumed to occur over a two-hour period per Regulatory Guide 1.183.
Normal flow from the RO system is returned to the SFP. Reject flow from the reverse osmosis system goes to various tanks within the waste disposal system.
The intake for the RO system takes suction above the minimum T.S. water level. The FHA dose analysis takes credit only for iodine scrubbing in the water up to the T.S. minimum water level. Any water than enters the RO system would be further scrubbed by the additional water.
The FHA assumes exponential release of activity such that the vast majority is released in the first 30 minutes; whereas, handling and holdup of RO reject flow would delay releases.
Therefore, the FHA activity releases are bounding.
The unit vent is the bounding FHA release location, since it is closer to the control room air intakes, and therefore has a higher X/Q value. For Oconee, control room X/Qs are determined by postulating a release at any of the three units with dispersion to any of the control room air intakes. In this way, the X/Q used bounds any combination of a release out any unit vent to either control room at Oconee. Therefore, migration of radioactivity within the auxiliary building would not change the bounding X/Q, even if the release occurred from the unit vent on another unit.
Any gaseous radioactivity within the reverse osmosis system that is released into the auxiliary building would be ultimately released via the unit vent. Liquid waste would go to the miscellaneous waste holdup tanks located in the auxiliary building. Therefore, a new pathway
Enclosure-LAR 2010-03, Supplement 5 December 15, 2011 Page 4 from the spent fuel pool water to the environment is not created by the reverse osmosis system, because the bounding release location would still be the unit vent as assumed in the design basis FHA analysis.
Duke Energy also evaluated the scenario where the operating restriction is violated, the RO System piping fails, and no FHA occurs. A failure of the high pressure portion of the RO system piping, without a concurrent FHA, would be bounded by the dose consequences of the design basis Alternative Source Term (AST) FHA analysis.
The operating restriction is not an accident mitigation feature as described in RP 5.1.2 and does not meet the criteria cited for requiring a Technical Specification since it is not an initial condition of a design basis accident.
RAI 2
The licensee's evaluation of the large break loss of coolant accident (LOCA) includes sump back-leakage to the boron water storage tank (BWST). Since the proposed RO system takes suction from the BWST, the licensee proposed that a time critical operator action be added to the Emergency Operating Procedures to isolate the RO system from the BWST at the safety related Class C seismic boundary valve. The licensee concluded that with this action, the addition of the RO system does not impact the assumptions in the design basis LOCA dose analysis.
In the amendment request, the licensee does not analyze the safety significance (the impact on Title 10 of the Code of Federal Regulations (10 CFR), Section 50.67 analyses) of this pathway for a design basis LOCA. Rather, the licensee proposes to isolate the pathway prior to the radiation reaching the pathway. The staff believes that the proposed operator action describes the isolation of a component that is part of the primary success pathway which functions to mitigate the LOCA and, therefore, meets 10 CFR 50.36, Criterion 3.
The proposed isolation of the RO system credits a boundary valve to mitigate the design basis LOCA. It assumes that after the system is isolated that there will be no leakage to the environment via the RO system. Therefore, contrary to RP 5.1.2 above, credit for mitigation is proposed for a mitigation feature that is not required to be operable by technical specifications.
The staff is concerned that the credited action for isolation of the RO system appears inconsistent with 10 CFR 50.36 and RP 5.1.2. Depending upon the licensee's course of action, please provide a response to one of the following requests for additional information.
- 1. State whether the proposed operating action credits mitigation features that meet RP 5.1.2. If it does not, please provide an additional justification for crediting the proposed isolation. Justify why a technical specification for the isolation valve is not needed to ensure 10 CFR 50.67 continues to be met. In addition justify why the proposed isolation valve does not meet 10 CFR 50.36, Criterion 3.
- 2. Consistent with 10 CFR 50.67, please analyze the dose impact of the additional release pathway (through the RO system) after a design basis LOCA. Please provide the analysis, any methods, inputs or assumptions used, and the results of the analysis.
- 3. Please provide a technical specification for the credited isolation valve
Enclosure-LAR 2010-03, Supplement 5 December 15, 2011 Page 5 Duke Energy Response to RAI 2 Regulatory Guide 1.183, RP 5.1.2 states:
Credit may be taken for accident mitigation features that are classified as safety-related, are required to be operable by technical specifications, and 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 safety related boundary valve is an accident mitigation feature that will be explicitly addressed in EOPs as requiring to be closed to mitigate an accident. The valve is a branch valve off the LPI flow path that is required to be closed for LPI train OPERABILITY. TS LCO 3.5.3 Bases defines an LPI train as including the piping, instruments, pumps, valves, heat exchangers and controls to ensure an OPERABLE flow path. As such, the new valve is required to be OPERABLE per TS 3.5.3. For LPI train OPERABILITY the valve is required to be closed or capable of being closed within the required time (33 minute Time Critical Operator Action (TCOA)). Duke Energy is requesting the NRC to allow credit for closing a normally closed manual valve (actuation requirements explicitly addressed in the EOP) in lieu of an automatically isolated valve.
The valve that will be used to isolate the RO System from the BWST is a Class C seismic boundary valve. As such, the valve will be required to be tested in accordance with the Inservice Testing Program required by 10CFR50.55a. ONS Technical Specification (TS) 5.5 requires the IST Program be established, implemented, and maintained. Details of the IST Program are provided in ONS TS 5.5.9. The ONS IST program provides controls for inservice testing of ASME Code Class 1, 2, and 3 pumps and valves. This testing, which is required by 10CFR50.55a and Technical Specifications, provides assurance the seismic boundary valve will perform its intended safety function of being closed or capable of being closed when opened during RO operation. Failure to meet the requirements of the ONS IST program is a violation of Technical Specifications and 10CFR 50.55a.