ML082960227
| ML082960227 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 10/17/2008 |
| From: | Brandon M Tennessee Valley Authority |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| TAC MD5263, TAC MD5264, TVA-BFN-TS-418 | |
| Download: ML082960227 (18) | |
Text
Tennessee Valley Authority, Post Office Box 2000, Decatur, Alabama 35609-2000 October 17, 2008 TVA-BFN-TS-418 10 CFR 50.90 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Mail Stop OWFN, P1-35 Washington, D. C. 20555-0001 In the Matter of
)
Docket Nos. 50-260 Tennessee Valley Authority
)
50-296 BROWNS FERRY NUCLEAR PLANT (BFN) - UNITS 2 AND 3 - TECHNICAL SPECIFICATIONS (TS) CHANGE TS-418 - EXTENDED POWER UPRATE (EPU) -
RESPONSE TO ROUND 21 REQUEST FOR ADDITIONAL INFORMATION (RAI) ON CHANNEL BOW (TAC NOS. MD5263 AND MD5264)
By letter dated June 25, 2004 (ADAMS Accession No. ML041840301), TVA submitted a license amendment application to the NRC for EPU operation of BFN Units 2 and 3. The pending EPU amendment increases the maximum authorized power level by approximately 14 percent from 3458 megawatts thermal (MWt) to 3952 MWt.
On October 9, 2008, NRC issued a Round 21 RAI (ML082820038), which included two RAIs on steam dryer analysis methods for Units 1 and 2, and one RAI on channel bow for Units 2 and 3 EPU. The steam dryer RAIs were answered in the TVA submittal dated October 3, 2008. This submittal responds to the channel bow RAI from Round 21. is a proprietary response to the Round 21 RAI and contains information that AREVA NP, Inc. (AREVA) considers to be proprietary in nature and subsequently, pursuant to 10 CFR 9.17(a)(4), 2.390(a)(4) and 2.390(d)(1), AREVA requests that such information be withheld from public disclosure. Enclosure 2 is a redacted version of with the proprietary material removed and is suitable for public disclosure. contains an affidavit from AREVA supporting this request for withholding from public disclosure.
U.S. Nuclear Regulatory Commission Page 2 October 17, 2008 TVA has determined that the additional information provided by this letter does not affect the no significant hazards considerations associated with the proposed TS changes. The proposed TS changes still qualify for a categorical exclusion from environmental review pursuant to the provisions of 10 CFR 51.22(c)(9).
No new regulatory commitments are made in this submittal. If you have any questions regarding this letter, please contact James Emens at (256)729-7658.
I declare under penalty of perjury that the foregoing is true and correct. Executed on this 17th day of October, 2008.
Sincerely, Michael K. Brandon Interim Manager of Licensing and Industry Affairs
Enclosures:
- 1. Response to Round 21 Request for Additional Information (RAI) on Channel Bow (Proprietary Information Version)
- 2. Response to Round 21 Request For Additional Information (RAI) on Channel Bow (Non-Proprietary Information Version)
- 3. Areva Affidavit
U.S. Nuclear Regulatory Commission Page 3 October 17, 2008
Enclosures:
cc (Enclosures):
Ms. Eva Brown, Project Manager U.S. Nuclear Regulatory Commission (MS 08G9)
One White Flint, North 11555 Rockville Pike Rockville, Maryland 20852-2739 Eugene F. Guthrie, Branch Chief U.S. Nuclear Regulatory Commission Region II Sam Nunn Atlanta Federal Center 61 Forsyth Street, SW, Suite 23T85 Atlanta, Georgia 30303-8931 NRC Resident Inspector Browns Ferry Nuclear Plant 10833 Shaw Road Athens, Alabama 35611-6970 State Health Officer Alabama Dept. of Public Health RSA Tower - Administration Suite 1552 P.O. Box 303017 Montgomery, AL 36130-3017
NON-PROPRIETARY INFORMATION ENCLOSURE 2 TENNESSEE VALLEY AUTHORITY BROWNS FERRY NUCLEAR PLANT (BFN)
UNITS 2 AND 3 TECHNICAL SPECIFICATIONS (TS) CHANGE TS-418 EXTENDED POWER UPRATE (EPU)
RESPONSE TO ROUND 21 REQUEST FOR ADDITIONAL INFORMATION (RAI)
ON CHANNEL BOW (NON-PROPRIETARY INFORMATION VERSION)
This enclosure provides TVA's response to the channel bow RAI from NRC's October 9, 2008, Round 21 RAI (ML082820038) on EPU.
NON-PROPRIETARY INFORMATION NRC RAI SRXB-128 (Units 2 and 3)
Provide a discussion of the impact of channel bow on the critical power performance for Units 2 and 3 at EPU conditions. This discussion should include the following:
SRXB-1 28.a The effect of the EPU neutron spectrum on channel -bow mechanisms, Response to SRXB-128.a EPU operation will [
]. To assess the impact of this difference on channel bow, a detailed channel bow model that calculates the bow effect due to
[
].
This bow model is described in the RODEX4 topical report (Reference SRXB-128.1) and is included as an option in MICROBURN-B2. Channel bow is a function of [
E2-1
NON-PROPRIETARY INFORMATION
-J Figure SRXB-128.1: Average and Maximum Channel Bow for CLTP and EPU Equilibrium Cycle Designs (Excluding the Peripheral Assemblies) 1.
SRXB-1 28.b The appropriateness of the channel bow statistics, Response to SRXB-128.b Channel bow statistics used for the Safety Limit Minimum Critical Power Ratio (SLMCPR) analysis are derived from channel bow measurements. Measurement data are [
E2-2
NON-PROPRIETARY INFORMATION
] measurement data is used.
Figure SRXB-128.2 displays existing D-lattice bow measurement data from [
]. This difference will be discussed in more detail later in these responses.
r Figure SRXB-128.2: AREVA D-Lattice Channel Bow Measurement Data (Signed Values)
E2-3
NON-PROPRIETARY INFORMATION Figure SRXB-128.3 shows the same bow data except the absolute value is taken of the bow measurements. The SLMCPR analysis makes use of the statistics derived from the absolute values of bow measurement data.
r-J Figure SRXB-128.3: AREVA D-Lattice Channel Bow Measurement Data (Absolute Values)
More recent measurements have been obtained for comparison. The EPRI Fuel Reliability Program included an initiative to obtain a more modern characterization of fuel vendor channel performance (Reference SRXB-128.2). As part of this program, AREVA acquired data on I
]. A statistically relevant sample of [ ] fuel channels ([
] bow measurements) was measured by selecting assemblies over a range of operating conditions with exposures from [
]. No special design guidelines to mitigate channel bow were used for the core design during the time the measured fuel channels resided in
]. The fuel operated in 24-month cycles.
The C
] data is shown overlaid in Figure SRXB-128.3. In the plot, lines showing the mean bow and the mean plus two times the standard deviation bow are shown on the plot for comparison purposes. Data are grouped in exposure "bins" for calculating the mean bow and sample standard deviation as a function of exposure. The more recent bow data falls well within the bounds of the existing data and there is no significant difference in bow between the [
].
The bow statistics are applicable to the BFN units at EPU because:
The data was obtained from plants with the same D-lattice core geometry as the BFN units.
E2-4
NON-PROPRIETARY INFORMATION A sufficient quantity of data is available that extends to the licensed discharge exposure limit.
The measurements are on channels from the same vendor.
SRXB-1 28.c Characterization of the susceptibility of Units 2 and 3 to abnormal channel bow, Response to SRXB-128.c Industry operating experience indicates that D-lattice plants appear to not be susceptible to abnormal channel bow. Recent industry channel bow problems have occurred primarily in BWR reactors with C/S-lattice cores. Similar incidences of cell friction problems have not been reported in D-lattice plants except for a single recent incident at Monticello. The BFN units have not encountered any signs of cell friction as evidenced by normal control rod maneuvers and during the TS control rod operability surveillance testing.
A control rod that experienced friction at Monticello was confirmed to have been caused by channel bow. However, the operation of the fuel in the cell was atypical. Three of the four fuel assemblies in the cell were in their fourth cycle of operation. The other fuel assembly was in its third cycle. The cycle lengths underwent a transition to two-year cycles during this time. So the overall residence time for the three assemblies was equivalent to approximately 3-1/3 2-year cycles. Prior operation involved some level of control (i.e., exposure to an inserted control rod) and operation in one of the outer three rows of the core.
Although AREVA does not possess detailed information on the Monticello event, the abnormal bow was primarily attributed to shadow corrosion bow caused by early control. The operating condition of the fuel bears some resemblance to the conditions that caused recent problems with AREVA fuel in core peripheral locations in C-lattice plants. That is, the operation included higher exposure (greater fast fluence), high residence time, and peripheral cell operation (higher fluence gradient). [
For discussion purposes, abnormal bow observed in C/S-lattice cores is divided into two categories as outlined below. Note that expected or "normal" behavior is considered to be predictable bow arising from fast fluence gradients.
- [
E2-5
NON-PROPRIETARY INFORMATION As evidenced by a lack of reported control rod friction issues, there is an extensive amount of industry operating experience demonstrating that abnormal bow due to early control (shadow corrosion) is not occurring to any significant degree in D-lattice plants. The reason for the lack of shadow corrosion bow is [
] is a likely contributor to the lack of cell friction problems relative to C/S-lattice plants.
]. Still, the occurrence of the single Monticello event points to a much lower incidence of abnormal bow in D-lattice plants.
To further evaluate recent operation at the BFN units with AREVA fuel, the amount of early control and exposures of the AREVA channels were examined. The amount of early control is characterized as the [
]. However, Unit 3 Cycle 13 operated to EOC and shutdown with no control rod friction issues and no indications of slow-to-settle rods. A similar review was made for the current operating cycles, Unit 2 Cycle 15 and Unit 3 Cycle 14. In the current cycles, the fuel channels in [
]. Although Unit 3 is still relatively early in Cycle 14, recent scrams and subsequent restarts on both units provide evidence that none of the control rods in the cores have significant cell friction. The evaluation of the [
E2-6
NON-PROPRIETARY INFORMATION
]. However, industry operating experience along with AREVA experience provides confidence there is not a widespread problem with abnormal bow at higher exposures in D-lattice plants including the BFN units.
In response to recent channel bow problems in C/S-lattice plants with Zircaloy-2 material, the BFN units [
] in C/S-lattice plants provides additional assurance that abnormal bow will not be a problem in future cycles in the BFN units.
The foregoing discussion is not dependent on EPU. [
].
SRXB-128.d Any channel bow monitoring methods, address inward and outward bow, Response to SRXB-128.d Based on the favorable industry experience, TVA has not instituted formalized testing or surveillance programs specifically designed to detect abnormal cell friction due to channel bow in the BFN cores. Additionally, the fuel vendors have not made recommendations for routine friction testing. While there is no formal bow monitoring program, there are routine plant surveillance tests that can detect excessive friction. Among these are the periodic scram time test and the control rod exercise surveillance test, both of which are required by TS. One of the rod exercise tests specifically targets partially inserted rods; so this test provides an opportunity to detect abnormal friction in cells where the blade would have significant contact area with the surrounding channels. In this test, a partially inserted rod is moved in one notch and is then withdrawn back to the original position. Since the BFN cores are designed with a conventional core design (all four control rod sequences are utilized), a significant number of the interior core cells would be sampled during the cycle by the partially inserted rod exercise test.
Abnormal cell friction also can be detected by the periodic scram time surveillance testing. In this test, a representative sample of fully withdrawn rods is individually scrammed to measure the insertion times to various specified positions. If sufficient control rod interference is present due to channel bow, the test will reveal a slower scram time compared to the average of the rods tested.
Most of the control rods in the core (including the edge and near edge rods) are withdrawn during startup. In addition, there are a significant number of rod movements each time a control rod sequence exchange is performed, which occurs every few months during the cycle. These rod movements provide additional opportunities to detect any developing channel bow issues that could be creating excessive interference. If a control rod failed to properly settle during any rod movement, the operators will receive a rod drift alarm, which will prompt documentation and investigation.
E2-7
NON-PROPRIETARY INFORMATION Hence, it is very unlikely that a systematic issue with abnormal channel bow can occur without indications of control rod friction. [
]. Thus, the observation of control rod operation during surveillance testing and routine operation should be effective in identifying the onset of a channel bow problem.
SRXB-1 28.e Any conservatism in the treatment of channel bow in the safety analysis in regard to thermal margin.
Response to SRXB-128.e Conservatisms are discussed throughout the AREVA topical report on critical power methodology (Reference SRXB-128.3). In summary the conservatisms are:
[
E2-8
41 NON-PROPRIETARY INFORMATION SRXB-1 28.f The measures taken in regard to Service Information Letter 320, and Response to SRXB-128.f Core designs for the BFN units have followed SIL-320 Supplement 3 (Reference SRXB-128.4).
The core design guide avoids an unfavorable combination of fluence gradient bow in core peripheral locations. There are options in the guide for C-lattice and D-lattice cores. The requirements are less restrictive in the case of a D-lattice core. For recent core designs, TVA
[
]. At a minimum, the BFN units will continue to use SIL-320 Supplement 3 or future improved means to limit the impact of fluence gradients on cell friction.
SRXB-1 28.q Any future plans to manage greater than expected bow based on the monitoring.
Response to SRXB-128.q As noted above, industry operating experience indicates abnormal bow is not expected for D-lattice plants. However, in the event unexpected bow is encountered; a similar process currently used for C-lattice plants would be used. An outline of the steps is provided below.
- 1. Following the identification of cell friction, perform settle time tests to determine the extent of cell friction in the core. Perform additional testing if necessary to narrow the cause to channel bow.
- 2. For cells that fail the settle time testing, subject the control rod to a scram time insertion test.
Evaluate the control rod(s) for continued surveillance and operability based on the test results and establish the status (inoperable or continued surveillance frequency).
E2-9
NON-PROPRIETARY INFORMATION
- 3. An evaluation would be performed to determine the impact of channel bow on thermal limits.
Based on current experience, the evaluation would investigate the need to increase the channel bow assumed in the SLMCPR analysis beyond the standard values, and if needed, derive an administrative CPR penalty based on a revised analysis.
- 4. Implement periodic surveillance of susceptible cells. Depending on the outcome of the settle tests, it might be necessary to identify susceptible cells by application of more conservative C/S-lattice surveillance criteria.
- 5. It is likely that channel bow measurements would be made following the conclusion of the cycle. The measurements would be used to [
References:
SRXB-128.1 BAW-1 0247PA Revision 0, Realistic Thermal-Mechanical Fuel Rod Methodology for Boiling Water Reactors, AREVA NP Inc., April 2008.
SRXB-128.2 Poolside Measurement of AREVA BWR Fuel Channels, EPRI, Palo Alto, CA:
2004. 1008097.
SRXB-128.3 ANF-524(P)(A) Revision 2 and Supplements 1 and 2, ANF Critical Power Methodology for Boiling Water Reactors, Advanced Nuclear Fuels Corporation, November 1990.
SRXB-128.4 Services Information Letter, Mitigation of the Effects of Peripheral Core Location on Fuel Channel Bowing, SIL No. 320 Supplement 3, GE Nuclear Energy, April 2003.
E2-10
ENCLOSURE 3 TENNESSEE VALLEY AUTHORITY BROWNS FERRY NUCLEAR PLANT (BFN)
UNITS 2 AND 3 TECHNICAL SPECIFICATIONS (TS) CHANGE TS-418 EXTENDED POWER UPRATE (EPU)
RESPONSE TO ROUND 21 REQUEST FOR ADDITIONAL INFORMATION (RAI)
ON CHANNEL BOW AREVA AFFIDAVIT This enclosure provides AREVA's affidavit for Enclosure 1.
AFFIDAVIT COMMONWEALTH OF VIRGINIA
)
) ss.
CITY OF LYNCHBURG
)
- 1.
My name is Gayle F. Elliott. I am Manager, Product Licensing, for AREVA NP Inc. (AREVA NP) and as such I am authorized to execute this Affidavit.
- 2.
I am familiar with the criteria applied by AREVA NP to determine whether certain AREVA NP information is proprietary. I am familiar with the policies established by AREVA NP to ensure the proper application of these criteria.
- 3.
I am familiar with the AREVA NP information contained in Engineering Information Record 51-9093756-000, "Response to RAI for BFN EPU Round 21 SRXB 128,"
dated October 2008, and referred to herein as "Document." Information contained in this Document has been classified by AREVA NP as proprietary in accordance with the policies established by AREVA NP for the control and protection of proprietary and confidential information.
- 4.
This Document contains information of a proprietary and confidential nature and is of the type customarily held in confidence by AREVA NP and not made available to the public. Based on my experience, I am aware that other companies regard information of the kind contained in this Document as proprietary and confidential.
- 5.
This Document has been made available to the U.S. Nuclear Regulatory Commission in confidence with the request that the information contained in this Document be withheld from public disclosure. The request for withholding of proprietary information is made in accordance with 10 CFR 2.390. The information for which withholding from disclosure is
requested qualifies under 10 CFR 2.390(a)(4) "Trade secrets and commercial or financial information."
- 6.
The following criteria are customarily applied by AREVA NP to determine whether information should be classified as proprietary:
(a)
The information reveals details of AREVA NP's research and development plans and programs or their results.
(b)
Use of the information by a competitor would permit the competitor to significantly reduce its expenditures, in time or resources, to design, produce, or market a similar product or service.
(c)
The information includes test data or analytical techniques concerning a process, methodology, or component, the application of which results in a competitive advantage for AREVA NP.
(d)
The information reveals certain distinguishing aspects of a process, methodology, or component, the exclusive use of which provides a competitive advantage for AREVA NP in product optimization or marketability.
(e)
The information is vital to a competitive advantage held by AREVA NP, would be helpful to competitors to AREVA NP, and would likely cause substantial harm to the competitive position of AREVA NP.
The information in the Document is considered proprietary for the reasons set forth in paragraphs 6(b) and 6(c) above.
- 7.
In accordance with AREVA NP's policies governing the protection and control of information, proprietary information contained in this Document have been made available, on a limited basis, to others outside AREVA NP only as required and under suitable agreement providing for nondisclosure and limited use of the information.
- 8.
AREVA NP policy requires that proprietary information be kept in a secured file or area and distributed on a need-to-know basis.
- 9.
The foregoing statements are true and correct to the best of my knowledge, information, and belief.
SUBSCRIBED before me this day of __0____
, 2008.
Sherry L. McFaden NOTARY PUBLIC, COMMONWEALTH OF VIRGINIA MY COMMISSION EXPIRES: 10/31/10 Reg. # 7079129 SHERRY L. MCFADIN Notary Public Commonwealth of Virglnli a 7079129010 My Commission E.xpires Oct 31. 201,0 1
v-r.
I__