ML110550616
| ML110550616 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 02/18/2011 |
| From: | Gillespie T Duke Energy Carolinas |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| LAR 10-003 | |
| Download: ML110550616 (8) | |
Text
T. PRESTON GILLESPIE, Jr.
Duker Vice President Ener~gy, Oconee Nuclear Station Duke Energy ONOl VP / 7800 Rochester Hwy.
Seneca, SC 29672 864-873-4478 864-873-4208 fax February 18, 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 Site, 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 1 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. By electronic mail dated December 20, 2010, NRC requested Duke Energy to supplement this LAR with additional information. The enclosure provides the additional information.
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 February 18, 2011.
Sincerely, T. Preston Gillespie, Jr., Vice President Oconee Nuclear Site
Enclosure:
Duke Energy Response to NRC Request for Additional Information www.duke-energy.com f f.
Nuclear Regulatory Commission February 18, 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 DUKE ENERGY RESPONSE TO NRC REQUEST FOR ADDITIONAL INFORMATION
LAR No. 2010-03, Supplement 1 Enclosure - Duke Energy Response to NRC Request for Additional Information February 18, 2011 Page 1 NRC RAI I It is not clear from the licensee's application that the structural design and analysis, including the seismic evaluation, where required (including "2 over 1" considerations), of systems structures and components (SSCs) affected and or newly introduced (including RO skid mounting) by the proposed change, have been completed which show that these SSCs are structurally capable to perform their intended design function. Therefore, the staff requests verification, from the licensee, that these items (designs and analyses of SSCs, as mentioned above) have been completed (e.g.,
pipe stress, pipe support design and analysis, anchorage, skid mounting).
Duke Energy Response to RAI I The design requirements for the Reverse Osmosis (RO) system are described in Section 2.0 of the LAR enclosure. The RO System piping is non-Quality Assurance Condition 2 (Radwaste)
Duke Energy Class E (USAS B31.1, non-seismic) piping, except as described in Section 2.0. The exceptions are where portions of the RO system are seismic Class D and where the RO system ties into Class C piping in the Spent Fuel Purification Loops.
The structural analysis of the piping is complete except for the seismic design of the piping going through the Hot Machine Shop. This piping will be designed as appropriate for this location so that existing analyses or SSCs are not affected. The other piping hangers and other structural features have been designed. While the RO unit itself is not seismically designed or mounted, it has been mounted permanently in a rugged manner. There is no safety-related equipment near the RO unit that would be damaged by it coming loose during an earthquake. The antimony capture vessel, part of the overall RO System, is also not seismically designed or mounted. It is located in the Hot Machine Shop, which is part of the Auxiliary Building, away from any possible impact with safety-related equipment. Duke Class E piping at the Spent Fuel Pools, although not normally seismically supported, is seismically supported in this area to prevent the piping from falling into the Spent Fuel Pools in the event of an earthquake. QA Condition 4 (Seismic) barriers have been installed for some Class E piping to prevent it from damaging safety-related cable trays below the pipe routing. RO piping in the Unit 3 Purge Equipment Room and the Unit 3 West Penetration Area Room is Duke Class D as discussed in the original submittal. The piping analysis and support design work for this piping is also part of the completed design work. Additional analysis and supports design work may occur as the piping is installed and implemented; however, the design will be remain consistent with existing design requirements.
LAR No. 2010-03, Supplement 1 Enclosure - Duke Energy Response to NRC Request for Additional Information February 18, 2011 Page 2 NRC RAI 2 The proposed change indicates that the new RO system will be included in the FSAR as a high energy system outside containment and it has addressed "Evaluation of Postulated Pipe Rupture in High Energy Portions of the RO System." It is not clear that the HELB analyses and evaluations, specifically the postulation of piping failures (including dynamic affects associated with these piping failures) of the RO system that could affect other plant critical or safety-related SSCs or postulation of piping failures of other piping systems that could affect the new RO system, have been performed. Therefore, the staff requests verification from the licensee that these items (HELB analyses and evaluations, as mentioned above) have been completed.
Duke Energy Response to RAI 2 The HELB analyses and evaluations for the new RO system have been completed. The results of the postulated pipe ruptures in the high energy portion of the RO system are described in section 3.2 of the license amendment request (LAR).
The proposed routing of the non-high energy RO system piping through areas of the plant where breaks in the RO system piping could result in release of radioactivity was reviewed against the postulated pipe ruptures in other high energy piping systems in those locations. The areas of concern are the Hot Machine Shop, the Unit 3 Ventilation (Purge) Equipment Room, and the Unit 3 West Penetration Room (see section 3.6 of the LAR). There were no postulated high energy line breaks in these areas that would impact the RO system piping.
NRC RAI 3 The LAR does not quantitatively address the potential for boron dilution of the SFPs and BWSTs as a result of the reverse osmosis operation and the adequacy of the existing boric acid concentration surveillance interval in detecting potential dilution in a timely manner. In accordance with 10 CFR 50.36(c)(40), surveillance requirements are requirements related to testing that assure that the limiting condition for operation (e.g., SFP and BWST boric acid concentrations) will be met. Provide a quantitative evaluation of dilution potential to allow the staff to assess whether the current surveillance interval would be adequate to satisfy the requirements of 10 CFR 50.36.
Duke Energy Response to RAI 3 Section 2.3 of the LAR enclosure states that ONS procedures will require more frequent monitoring of boron concentration and volume to verify the required Technical Specification (TS) limits continue to be met during RO System operation. The justification for not decreasing the TS surveillance test interval (STI) during RO system operation is based on NUREG-1430 not requiring additional monitoring during batch additions that could affect boron concentration or level. Makeup or Batch addition to adjust boron concentration and water level as a result of normal RO System operation are required to maintain the boron concentration and water level within TS limits.
Procedures controlling RO System operation will limit operation to a specified time period to prevent the boron concentration in the Borated Water Storage Tank (BWST) or Spent Fuel Pool (SFP) from going below TS limits.
LAR No. 2010-03, Supplement 1 Enclosure - Duke Energy Response to NRC Request for Additional Information February 18, 2011 Page 3 Duke Energy calculated the maximum time period the RO system can be operated before boron concentration or water level needs to be adjusted. The Oconee calculation assumes the BWST and SFP boron concentration are at 2650 ppm and the initial water levels are at the maximum level for normal operation at the start of RO system processing. For initial silica concentrations above 4 ppm for the SFP and above 3 ppm for the BWST, the maximum time period that the RO system can operate without makeup is limited by water inventory rather than boron concentration.
For lower initial silica concentrations, RO System operation will be limited to a maximum of 7 days.
Changes in water level can be easily recognized by plant personnel and low level is alarmed prior to decreasing below the TS limit.
Prior to operating the RO System, the SFP or BWST level will be adjusted to the initial maximum water level and the boron concentration increased to at least 2650 ppm (Note: These values may be changed if the Oconee calculation is revised to support the change.). The maximum time period that the RO unit can be operated without makeup is then determined by the initial silica concentration. The higher the silica concentration the higher the reject flow and the shorter period of time the RO unit can operate without water inventory makeup. After the end of an RO system operating period, the initial conditions (2650 ppm boron concentration and maximum water level for normal operation) will be re-established and the RO unit operated for the maximum time allowed based on the silica reading at the beginning of the next period of operation. RO system operating periods will be repeated as necessary until the desired silica concentration is reached.
As time progresses, the lower initial silica levels at the start of the operating period will allow longer operating periods that will result in a lower boron concentration at the end of the period (refer to table below). In all cases the boron concentration stays above the TS minimum boron concentration prior to reaching the low water level alarm level or at the end of the 7 days, which will be specified as the maximum RO operating period.
LAR No. 2010-03, Supplement 1 Enclosure - Duke Energy Response to NRC Request for Additional Information February 18, 2011 Page 4 Time Limits for Operation of the Reverse Osmosis Unit SFP I-BWST Starting Boron Concentration =
2650 ppm Starting Boron Concentration =
2650 ppm Silica ppm Hours Boron Elevation Silica ppm Hours Boron Level 30 35 2570 839.23 30 22 2610 47.30 29 36 2568 839.21 29 22 2610 47.34 28 37 2566 839.21 28 23 2608 47.32 27 39 2562 839.21 27 24 2606 47.33 26 40 2560 839.22 26 25 2604 47.32 25 42 2556 839.20 25 26 2602 47.31 24 43 2554 839.21 24 27 2600 47.31 23 46 2548 839.20 23 28 2598 47.33 22 47 2546 869.22 22 29 2596 47.33 21 49 2541 839.22 21 31 2592 47.30 20 51 2537 839.20 20 32 2590 47.31 19 55 2529 839.21 19 34 2586 47.32 18 58 2523 839.20 18 36 2582 47.31 17 60 2519 839.22 17 38 2577 47.30 16 65 2509 839.21 16 41 2571 47.30 15 69 2500 839.21 15 43 2567 47.31 14 73 2492 839.21 14 46 2561 47.30 13 78 2482 839.21 13 49 2555 47.30 12 87 2463 839.20 12 54 2545 47.31 11 93 2451 839.21 11 58 2537 47.31 10 101 2435 839.20 10 63 2527 47.31 9
116 2404 839.20 9
72 2508 47.31 8
116 2404 839.20 8
72 2508 47.31 7
128 2379 839.20 7
80 2492 47.30 6
152 2330 839.20 6
95 2461 47.30 5
168 2297 839.24 5
109 2433 47.30 4
168 2299 839.54 4
138 2374 47.30 3
168 2300 839.73 3
168 2313 47.31 2
168 2301 840.02 2
168 2314 47.71 1
168 2301 840.02 1
168 2314 47.71 0
168 2301 840.02 0
168 2314 47.71 High Water Level Alarm =
840.7' 49.0' Maximum Water Level for Normal Operation =
840.6' 48.5' RO unit Initial Water Level =
840.6' 48.5' RO unit Final Water Level =
839.2' 47.3' Minimum Water Level for Normal Operation =
839.4' 47.5' Low Water Level Alarm =
839.0'
<47.0' Maximum Boron Concentration(1) =
2950 ppm 3000 ppm Minimum COLR Boron Concentration =
2220 ppm 2220 ppm Regulatory Low Level (indicated) =
838.0"2) 47.0' (1) For BWST the maximum is specified in the COLR (2) TS SR 3.7.11 requirement is > 21.34', which is 837.82" (actual)
(3) TS SR 3.5.4.2 requirement is > 350,000 gallons, which is 46.0" (actual)
LAR No. 2010-03, Supplement 1 Enclosure - Duke Energy Response to NRC Request for Additional Information February 18, 2011 Page 5 Oconee procedures will specify the maximum continuous period of time the RO system can process SFP or BWST water prior to inventory and boron makeup. A change to the TS SR frequency is not warranted given the use of the RO system will be controlled by plant procedure and that changes in boron and water inventory evolve over relatively long periods of time as demonstrated above.
NRC RAI 4 On page six, the licensee states that "water from the SFPs will be sent to the RO unit and the majority of the water will be returned to the respective supply source." On page 7, the licensee intends on batch additions in order to maintain boron concentration above technical specifications during the reverse osmosis procedure. How does the licensee intend to measure the isotopic composition of the resulting boron to ensure the appropriate weight percent of B-1 0 is maintained?
What effect would an altered isotopic composition have on shutdown margin and spent fuel pool criticality calculations?
Duke Energy Response to RAI 4 RO unit operation to remove silica from the SFP or BWST water also reduces the boron concentration of the water. Silica is removed by passing water through a series of membranes.
The membranes remove silica by filtering and as a side effect also remove boron. According to the vendor, the membranes are not capable of differentiating between B-10 and B-1 1, therefore the isotopic composition is not expected to change.
Since the vendor has no test results to substantiate this statement, Duke Energy will confirm that the RO unit membranes do not preferentially remove B-1 0 during the initial testing of the RO System. If the RO unit membranes are found to preferentially remove B-1 0, the Duke Energy calculation described in response to issue 3 will be revised to establish limits for operating the RO unit based on the test results so that the necessary concentration of B-10 is maintained.