ML041680400
| ML041680400 | |
| Person / Time | |
|---|---|
| Site: | McGuire, Mcguire  |
| Issue date: | 06/09/2004 |
| From: | Gordon Peterson Duke Power Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| TAC MC0945, TAC MC0946 | |
| Download: ML041680400 (8) | |
Text
f Duke MWPowere A Duke Energy Company June 9, 2004 U.S. Nuclear Regulatory Commission ATTENTION:
Document Control Desk Washington, DC 20555-0001 GARY R. PETERSON Vice President McGuire Nuclear Station Duke Power MGOI VP / 12700 Hagers Ferry Road Huntersville, NC 28078-9340 704 875 5333 704 875 4809 fax grpeters@duke-energy.com
Subject:
Duke Energy Corporation (Duke)
McGuire Nuclear Station Units 1 and 2 Docket Numbers 50-369 and 50-370 Technical Specifications Amendment Request for Additional Information (RAI); TS 3.7.15 -
Spent Fuel Assembly Storage, and TS 4.3 -
Fuel Storage
Reference:
(1) Duke letter to NRC, dated September 29, 2003, and (2) NRC letter to Duke, dated April 21, 2004 (TAC NOS. MC0945 AND MC0946)
This letter provides additional information that was requested by the NRC staff in the above referenced NRC letter.
Duke's responses are provided in the following attachment.
Please contact Norman T. Simms of Regulatory Compliance at 704-875-4685 with any questions with respect to this matter.
Very truly yours, G. R. Peterson Attachment I't www.duke-energy. corn
U.S. Nuclear Regulatory Commission June 9, 2004 Page 2 xc: (w/attachment)
L.A. Reyes Administrator, Region II U.S. Nuclear Regulatory Commission Atlanta Federal Center 61 Forsyth Street, SW, Suite 23T85 Atlanta, GA.
30303 J.B. Brady NRC Senior Resident Inspector McGuire Nuclear Station J.J. Shea, Project Manager (addressee only)
Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission One White Flint North, Mail Stop O-7D1A 11555 Rockville Pike Rockville, MD 20852-2738 Beverly 0. Hall, Section Chief Radiation Protection Section 1645 Mail Service Center Raleigh, N.C.
27699-1645
U.S. Nuclear Regulatory Commission June 9, 2004 Page 3 Gary R. Peterson, being duly sworn, states that he is Vice President of McGuire Nuclear Station; that he is authorized on the part of Duke Energy Corporation to sign and file with the U.S. Nuclear Regulatory Commission these revisions to the McGuire Nuclear Station Facility Operating Licenses Nos. NPF-9 and NPF-17; and, that all statements and matters set forth therein are true and correct to the best of his knowledge.
Gary R. Peterson, Vice President McGuire Nuclear Station Duke Energy Corporation Subscribed and sworn to before me on ____________,2004.
Notary Public My Commission Expires: Aq/71 1
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ATTACHMENT
Attachment June 9, 2004 Page 1 Responses to Nuclear Regulatory Commission Request for Additional Information Related to McGuire Nuclear Station's License Amendment Request for No-Boraflex Credit Question 23 The staff notes that the defined Region 1 of the spent fuel pool (SFP) was reracked without prior NRC approval utilizing a Boral neutron poison material. Therefore, the staff requests a discussion of the procedures and tests used to ensure that the Boral panels in the racks have the minimum B-10 loading assumed in the analyses.
Response
In 2003, Duke Power replaced the Region 1 storage racks that contained Boraflex as a neutron poison material in the McGuire spent fuel pools with new racks containing Boral neutron poison material. All other key physical parameters and dimensions of the new rack modules remained identical to those of the old rack modules (including the minimum B-10 loading). This work was performed under a contract with Holtec International. Duke Power's procurement specification for the new Region 1 racks required the poison material to have a minimum B-10 loading of 0.020 glcm2. This was the same minimum B-10 loading (0.020 g/ cm2) assumed in the Duke Power analyses for the new Region 1 rack modules. However, the minimum B-10 loading requirement in the Holtec material purchase specification for the Boral plate material was 0.022 glcm2, thus providing an extra margin of conservatism for the poison plate material.
The Boral) was supplied to Holtec by AAR Manufacturing. The Boral panels supplied by AAR for the new McGuire Region 1 racks were manufactured in 2 batches in accordance with Holtec's Boral Technical Specification (SP-BORAL-1, Holtec Report HI-90523). This Boral Technical Specification required AAR to perform examinations and testing to assure and certify the BoralD dimensions comply with all the requirements in the specification in regard to materials, workmanship, boron content and markings. These examinations and tests were performed in accordance with the following AAR procedures:
- AAR-10012 QAP Boral In-process and Final Inspection Procedure
- AAR-11002 QAP Chemical Test of Boral to Verify Boron Loading The process for determining the boron loading of the Boral material was by chemical analysis.
The number of samples cut from each lot for density measurements and chemical analysis was in sufficient number to verify that the B-10 areal density was greater than the guaranteed minimum of 0.022 g/cm2 with a 95% probability and a 95% confidence level. The test procedures include oven drying of the boron carbide, placement of the boron carbide into a hydrochloric acid solution, filtering, washing and drying of the residue-this yields the total B4C. The B-10 loading per unit area is computed by multiplying the boron carbide weight per unit area by the B-10 percentage on the material certification. Results of the chemical testing were submitted to Duke along with a certification of compliance from the rack supplier. These test results showed an average B-10 loading of 0.024 g/cm and an actual minimum B-10 loading of 0.0226 g/cm2 in
Attachment June 9, 2004 Page 2 the 229 panels measured. All panels tested exceeded the certified minimum areal density of B-
- 10. Each piece of Boral was individually serialized and traceable to material and inspection documentation. Finally, the documentation required for the Boral material included:
- List of serial numbers
- Inspection data (minimum of dimensions, visual and B-10 loading)
- Wet chemistry results
- Certificate of Compliance to purchase order requirements (including Vendor's QA Manual revision used and specific certification to 10CFR21)
- Results of density measurements and chemical analysis of samples cut from each lot (as discussed above, in sufficient number to determine the boron content with a 95%
probability and a 95% confidence level)
- B4C particle size distribution for each lot of B4C powder
- Spectroscopic (or similar) analysis of the boron in each lot of B4C used
Question 24 Recently, incidents of Boral blistering have been reported and the impact on the expected performance of this material is not yet known. Therefore, the NRC staff requests the licensee to implement technical specification (TS) Boral coupon surveillance program to ensure consistent material performance assumed in its analyses. This program should monitor the physical and chemical properties in Boral over time and include the following:
- Description of the coupons used (e.g. from the same lot as the panels);
- Technique for measuring the initial BoronlO (B-10) content of the coupons;
- Frequency and its justification; and
- Tests to be performed on coupons (e.g., weight measurement, measurement of dimensions (length, width and thickness), and B-10 content)
In addition, please inform the NRC staff in writing if the coupons reveal a change in material performance from that assumed in the analyses.
Response
Boral consists of finely divided particles of boron carbide uniformly distributed in aluminum powder, clad in type 1100 aluminum and pressed and sintered in a hot-rolling process. For over 25 years Boral has been used as the neutron absorber in wet storage applications. Boral has been the material of choice in more than 30 units in the United States and many more overseas. Based on industry experience and other testing programs, Boral is a satisfactory material for reactivity control in spent fuel storage racks. Notwithstanding the stability and integrity for the Boral Panels, a surveillance program will be established at MNS to monitor certain physical properties
Attachment June 9, 2004 Page 3 of the Boral in order to detect the onset of any significant degradation in sufficient time to permit remedial action.
To this end, a total of twenty (20) Boral coupons were supplied to Duke along with the new spent fuel storage rack modules for use in a surveillance program. These coupons came from each of the two lots of Boral for the McGuire storage rack order. A minimum of two different Boral panels were used to obtain the test coupons from both lots of Boral manufactured. Holtec's Boral Technical Specification (SP-BORAL-1, Holtec Report HI-90523) specified the documentation required for these coupons. The dimensions of the coupons are 4" x 8" (+1-0.063"), and each panel from which a coupon was taken was tested for B-10 loading as discussed in the response to RAI Question 23.
In addition, a surveillance coupon tree containing ten Boral coupons is placed into a designated spent fuel pool storage cell for each Unit. The Boral coupon tree will be surrounded by freshly discharged fuel assemblies Procedures are being revised to ensure this aspect of the surveillance program. A prearranged number of coupons are removed from the tree on a prescribed schedule and certain physical and/or chemical properties are measured from which stability and integrity of the Boral in the storage cells may be inferred. One or more of the following measurements will be performed on the designated coupon removed from the tree:
- Visual Examination and photographic documentation of appearance
- Dimensional Measurements (length, width, and thickness)
- Weight and specific gravity
- Neutron Attenuation (B-10 areal density)
A Problem Investigation Process (PIP) would be initiated in the event that an acceptance criterion for one or more of the above measurement parameters is not met. Through this process, the impact that the deviation could have on the criticality analysis would be evaluated, and reviewed to determine if the condition meets NRC reporting requirements. The engineering evaluation performed would identify any further testing or any corrective actions that may be necessary. In addition to the PIP program, other appropriate programs/processes would be utilized, as warranted, to address and resolve the observed deviation.
Further, in addition to the tests for B-10 content (as discussed in response to RAI Question 23),
tests on representative coupons of Boral were performed to uncover any blistering or swelling by subjecting coupons to a water environment at elevated temperatures. At least two coupons from each lot of Boral (of width approximately equal to the Boral panel design and a length-to-width ratio of at least 2) were immersed in demineralized water at 1700F for a period of at least 45 days. The exposed coupons were then examined for evidence of swelling or delamination. All coupons tested under the Boral order pertinent to the fuel rack order showed no indications of swelling or delamination.
Consistent with other neutron poison material surveillance programs (at MNS, as well as other Licensees), the Boral surveillance program will be defined within station procedures and directives. There are no plans to include the Boral surveillance program within Technical Specifications. Historically, spent fuel pool neutron fixed-poison material surveillance programs have not been included within Technical Specifications. As operating experience has shown,
Attachment June 9, 2004 Page 4 these surveillance programs, even though not included in technical specifications, have been very effective in detecting the onset of any significant degradation with ample time to take corrective action as may be necessary. Accordingly, current procedures will be revised and new procedures developed to implement and control the irradiation, removal and testing of the Boral coupons.