ML17054C788
| ML17054C788 | |
| Person / Time | |
|---|---|
| Site: | Vermont Yankee, Holtec  |
| Issue date: | 05/26/2017 |
| From: | Yen-Ju Chen Spent Fuel Licensing Branch |
| To: | |
| Chen Y | |
| References | |
| Download: ML17054C788 (10) | |
Text
UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 SAFETY EVALUATION REPORT DOCKET NOS.51-271, 72-59, 72-1014 EXEMPTION REQUEST FOR ENTERGY NUCLEAR OPERATIONS, INC.S VERMONT YANKEE NUCLEAR POWER STATION INDEPENDENT SPENT FUEL STORAGE INSTALLATION IN VERNON, VERMONT
SUMMARY
By application dated November 9, 2016, (Entergy 2016) and supplemented on January 9, 2017 (Entergy 2017a), Entergy Nuclear Operations, Inc. (Entergy) submitted a request to the U.S.
Nuclear Regulatory Commission (NRC) for an exemption, in accordance with Title 10 of the Code of Federal Regulations (10 CFR) 72.7, from the requirements of 10 CFR 72.212(a)(2),
72.212(b)(3), 72.212(b)(5)(i), 72.214, and the portion of 72.212(b)(11) that requires compliance with the terms, conditions, and specifications of the Certificate of Compliance (CoC) No. 1014 for spent fuel storage at the Vermont Yankee Nuclear Power Station (VYNPS) independent spent fuel storage installation (ISFSI). For this proposed exemption, Entergy requested relief from some requirements in Appendix B, Table 2.1-3, Note 19, of Amendment No. 10 to Holtecs CoC No. 1014. This exemption would allow Entergy to load certain lower enriched U-235 (up to 3.3 wt.% U-235) channeled fuel (specifically, crud induced localized corrosion (CILC) fuel),
classified as undamaged per the CoC No. 1014, Amendment No. 10, with higher enriched fuel (up to 4.8 wt% U-235) in the same HI-STORM 100 multipurpose canister (MPC) at the VYNPS site. Entergy proposed to revise the current Note 19 as follows:
In accordance with the definition of UNDAMAGED FUEL ASSEMBLY, certain assemblies may be limited to up to 3.3 wt.% U-235. When loading these fuel assemblies, all other undamaged fuel assemblies in the MPC are limited to enrichments as specified in this table [2.1-3].
In support of its exemption request, Entergy points to an application submitted by Holtec to the NRC for Amendment No. 11 of CoC No. 1014, dated January 29, 2016 (Holtec 2016a). If approved by the NRC, Amendment No. 11 of CoC No. 1014 would permit loading higher enriched fuel with the lower enriched undamaged spent fuel stored in the HI-STORM 100 cask system. Holtecs Amendment No. 11 request is more extensive in scope than Entergys exemption request. Entergy asserts that Holtecs application for Amendment No. 11 demonstrates that higher-enriched fuel can be safely loaded with lower-enriched undamaged fuel in the same MPC.
This safety evaluation report (SER) documents the NRC staffs (the staffs) review and evaluation of Entergys exemption request. The staffs evaluation is based on a review of Entergys application, as supplemented, and whether it meets the criteria for an exemption from
the requirements of 10 CFR Part 72, Licensing Requirements for the Independent Storage of Spent Nuclear Fuel, High-Level Radioactive Waste, and Reactor-Related Greater Than Class C Waste, (NRC 2016a) for dry storage of spent nuclear fuel.1 Section 72.7 of 10 CFR allows the Commission to grant exemptions from the requirements of 10 CFR Part 72 if the exemption is authorized by law and will not endanger life or property or the common defense and security and is otherwise in the public interest.
A. Authorized by Law Entergy plans to use Holtecs HI-STORM 100 cask system under CoC No. 1014, Amendment No. 10 (NRC 2016b), for dry storage of spent nuclear fuel in MPC-68M canisters at the VYNPS ISFSI. This exemption would allow Entergy to load certain (CILC fuel) lower enriched (up to 3.3 wt.% U-235) channeled boiling water reactor (BWR) fuel assemblies classified as undamaged per CoC No. 1014, Amendment No. 10, with higher enriched (planar-average initial enrichment up to 4.8 wt.% U-235) BWR fuel assemblies in the same MPC-68M canister. The provisions from which Entergy is requesting the exemption require Entergy to follow the conditions of CoC No. 1014, Amendment No. 10, that when loading certain lower enriched channeled undamaged BWR fuel, all fuels in the same MPC cannot exceed 3.3 wt.% U-235 maximum planar-average initial enrichment.
As explained in this SER, the proposed exemption will not endanger life or property, nor the common defense and security, and is otherwise in the public interest. Issuance of this exemption is consistent with the Atomic Energy Act of 1954, as amended, and not otherwise inconsistent with the NRCs regulations or other applicable laws. Therefore, issuance of the exemption is authorized by law.
B. Will Not Endanger Life or Property or the Common Defense and Security The staff reviewed Entergys exemption request and concludes, as discussed below, that the proposed exemption from certain requirements of 10 CFR Part 72 will not cause the HI-STORM 100 MPC-68M to encounter conditions beyond those for which it has been evaluated and demonstrated to meet the remaining safety and security requirements of 10 CFR Part 72. The staff followed the guidance of NUREG-1536, Revision 1, Standard Review Plan for Dry Cask Storage Systems at a General License Facility, July 2010 (NRC 2010); however, as explained below, the staffs evaluation includes only those areas of review that are relevant to the changes that would result from Entergys requested exemption.
1.0 GENERAL INFORMATION The proposed exemption would not alter the general description of the dry storage system thus no evaluation is necessary.
1 In an email dated March 16, 2017, (Vermont 2017) the State of Vermont provided comments on the draft environmental assessment for the proposed action of granting the exemption request. Several comments concerned the safety basis for the exemption. The NRC staff replied to Vermonts comments in a letter dated May 23, 2017, (NRC 2017) and has considered the issues raised in the comments in this SER.
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2.0 PRINCIPAL DESIGN CRITERIA EVALUATION The proposed exemption would not alter the principal design of the dry storage system thus no evaluation is necessary.
3.0 STRUCTURAL EVALUATION The proposed exemption would not alter the structure of the dry storage system thus no evaluation is necessary.
4.0 THERMAL EVALUATION The proposed exemption would not alter the thermal characteristics of the dry storage system thus no evaluation is necessary.
5.0 CONFINEMENT EVALUATION The proposed exemption would not alter the confinement boundary of the dry storage system thus no evaluation is necessary.
6.0 SHIELDING EVALUATION The objective of this review is to ensure that, with the requested exemption, the design of the HI-STORM 100 cask system continues to provide adequate protection against direct radiation to the onsite operating workers and members of the public, and that the ISFSI continues to satisfy the regulatory requirements during normal operating, off-normal, and design-basis accident conditions.
Entergy noted in its supplement to the exemption request that the VYNPS spent fuel pool contains a large number of potential CILC fuel assembliesapproximately 40 percent of all assemblies. The CILC fuel assemblies have an average cooling time of 35 years and average burnup of 25 GWD/MTU, and up to 3.3 wt.% U-235. The remaining 60 percent of the fuel has an average cooling time of 15 years and average burnup of 35 GWD/MTU, and most has an initial enrichment of 3.3 wt.% U-235 or more.
Based on calculations performed by Holtec and provided by Entergy in its supplement to the exemption request (Entergy 2017a), Entergy submitted that storing CILC fuel with higher enriched and higher burned fuel in the same cask would reduce dose rates.
The staff documented in the SER for CoC No. 1014, Amendment No. 9, Revision 1, (NRC 2015) that a CILC fuel assembly can be classified as undamaged if it meets part (b) of the definition for undamaged fuel assembly in CoC No. 1014, Appendix A, Section 1.1:
a BWR fuel assembly with an intact channel, a maximum planar average initial enrichment of 3.3 wt.% U-235, without known or suspected GROSSLY BREACHED SPENT FUEL RODS, and which can be handled by normal means.
The requested exemption would allow Entergy to load certain low enriched channeled fuel classified as "undamaged" per CoC No. 1014, such as CILC fuel, in the same MPC with higher enriched fuels.
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Holtec conducted analyses for Entergy to justify the exemption request from a shielding perspective, and to estimate the resulting reduction in dose rates. The results are documented in several proprietary reports and submitted in the supplement to the exemption request (Entergy 2017a) as discussed below.
Holtec used Casks #14 and #44, listed in Table 7.2 of Holtec proprietary Report HI-2167202, Revision 0, "Fuel Compatibility and Loading Plan Report for VYNPS," for the analysis, as these two casks are representative of the loading plan. Cask #14 contains solely undamaged fuel assemblies, limited to 3.3 wt.% U-235 and affected by CILC. Cask #44 contains higher enriched (up to 4.8 wt.% U-235) assemblies. The burnup, enrichment, and cooling time of the fuel assemblies used to calculate dose rates are averaged values from all assemblies in the respective cask regions. To simplify the calculations, Holtec rounded up the burnup to the nearest multiple of 5 GWD/MTU, rounded down the enrichment to one decimal place, and rounded down cooling times to whole years. The staff considers the rounding approach conservative for calculating dose rates because it assumes the most conservative source terms, that is, the highest burnup, the lowest enrichment, and the shortest cooling time. This is consistent with the guidance in NUREG/CR-6802, Recommendations for Shielding Evaluations for Transport & Storage Packages, May 2003 (NRC 2003).
Holtec performed a comparative analysis between VYNPSs loading under the existing Amendment No. 10 with the fuel restriction and the loading with the restriction removed as per the requested exemption. Holtec used the SAS2H and ORIGEN-S modules from the SCALE 5.1 code system from Oak Ridge National Laboratory to calculate the radiation source terms, which is acceptable as noted in NUREG-1536, Revision 1.
Holtec calculated the dose rates for Casks #14 and #44 under the current Note 19 and under the proposed revision to Note 19 to estimate the dose rate reduction. For calculating the dose rates for canisters with a mix of fuel enrichment levels, Holtec simulated swapping fuel from the inner region of Cask #14 with fuel from the outer region of Cask #44.
Table 2 in Entergys supplement to its exemption request presents a comparison of dose rates at 100-meter distance from the HI-STORM 100. The comparison shows that the combined dose rates from both casks are reduced when calculated based upon swapping fuel from the outer region of Cask #44 with fuel from the inner region of Cask
- 14. The projected total dose rate and annual total dose are within the regulatory limits in 10 CFR Part 72.104.
6.1 Findings
The staff reviewed the information provided by Entergy and Holtec that loading CILC fuel (at 3.3 wt.% U-235) and higher enrichment fuel (up to 4.8 wt.% U-235) in the same MPC will reduce the overall dose rates. The staff found these calculation results are within regulatory limits; therefore, the staff concludes that granting this exemption assures the VYNPS ISFSI continues to satisfy the requirements for the dose limits as specified in 10 CFR 72.104.
7.0 CRITICALITY EVALUATION
The criticality review and evaluation ensures that spent nuclear fuel to be placed into the dry storage system remains subcritical under normal, off-normal, and accident conditions 4
involving handling, packaging, transfer, and storage. The staff reviewed the applicable portion of the information submitted by Holtec in its application request for HI-STORM 100 cask, Amendment No. 11 (Holtec 2016b) as the safety bases for criticality review.
7.1 Criticality Design Criteria and Features The exemption does not involve any change to the criticality safety design criteria and features of the HI-STORM 100 cask system.
7.2 Fuel Specification Entergy stated when loading 10x10A, B, C, F, and G fuel assemblies into the MPC-68M, all other undamaged fuel assemblies in the MPC will be limited to the maximum planar average initial enrichments as specified in CoC Appendix B, Table 2.1-3, BWR Fuel Assembly Characteristics, rather than the 3.3 wt.% U-235 as required in Note 19.
7.3 Model Specification Entergy referenced supporting information submitted in Holtecs application for Amendment No. 11 to the HI-STORM 100 System (Holtec 2016b), to support the criticality analysis for this exemption request. The criticality analysis used the same models for the MPC basket and fuel assemblies when MPC-68M was initially evaluated and approved by the staff (NRC 2011, SER for Amendment No. 8 to CoC No. 1014).
The criticality analysis is based upon full three-dimensional calculations using the Monte Carlo N-Particle code MCNP4a and ENDF/B-V continuous energy library. The calculations modeled bare fuel rods without damaged fuel canisters at 3.3 wt.% U-235 in arrays of varying sizes occupying all cells within the MPC-68M. The array sizes considered and their corresponding results reference Table 6.III.4.9 of the CoC No. 1014, Amendment No. 11 application (Holtec 2016a). Furthermore, normal undamaged fuel mixed with lower enriched channeled BWR fuel is discussed by Holtec to be modeled as a bare fuel rod of varying array sized in a checkerboard configuration, and the referenced results listed are those in Table 6.III.4.10 of the CoC No. 1014, Amendment No. 11 application. In both cases, the calculations demonstrated that the system remains subcritical in the worst case scenario, including consideration of fuel and basket fabrication tolerances and other possible uncertainties and biases in the model and computer code. The results are bounded by the referenced undamaged fuel assembly reactivity, at its maximum planar average initial enrichment in all cells, listed in Table 6.III.4.2 of the Amendment No. 11 application. These bounding values were previously reviewed and approved by the NRC as part of CoC No. 1024, Amendment No. 8 (NRC 2011).
7.4 Findings
The staff reviewed the information provided by Entergy to support this exemption request and determined that it is in compliance with the requirements of 10 CFR 72.24, 72.124, and 72.236(c) and the reactivity is bounded by the undamaged fuel assembly reactivity previously reviewed and approved by NRC analysis (NRC 2011). The staff evaluated the adequacy of the description, methods, and analyses of the package related to the criticality evaluation, and has determined that, subject to Entergys requested exemption for CoC No. 1014 to support the storage of higher enrichments with low enriched channeled undamaged fuel in the MPC-68M, the dry storage system 5
at the VYNPS ISFSI will continue to meet the criticality safety requirements of 10 CFR Part 72.
Based on its review of the information provided in the exemption request and the acceptance criteria for criticality safety as defined in NUREG-1536, the staff concludes that the exemption request meets the regulatory requirements, i.e., the HI-STORM 100 Cask System as proposed will continue to remain subcritical under all credible normal, off-normal, and accident conditions and provide reasonable assurance for safe storage of spent fuel. This finding considered the regulation itself, appropriate regulatory guides, applicable codes and standards, and accepted engineering practices.
8.0 MATERIALS EVALUATION The proposed exemption would not alter the materials used in components of the dry storage system thus no evaluation is necessary.
9.0 OPERATING PROCEDURES EVALUATION The proposed exemption would not alter the operating procedures thus no evaluation is necessary.
10.0 ACCEPTANCE TESTS AND MAINTENANCE PROGRAM EVALUATION The proposed exemption would not alter the acceptance tests and maintenance program thus no evaluation is necessary.
11.0 RADIATION PROTECTION EVALUATION Entergy indicated that the exemption request would result in reduction in dose rates to workers and a lower dose rate at the site boundary.
As discussed in Section B.6, Shielding Evaluation, the staff found that loading CILC fuel (3.3 wt.% U-235) and higher enriched fuel (up to 4.8 wt.% U-235) in the same MPC would reduce the dose rates. Therefore, the staff concludes that there is reasonable assurance the VYNPS ISFSI continues to satisfy the requirements for the dose limits as specified in 10 CFR 72.104. This finding is reached on the basis of a review that considered the regulation in 10 CFR Part 72 and accepted practices.
12.0 ACCIDENT ANALYSES EVALUATION The proposed exemption would not affect Holtecs accident analyses thus no evaluation is necessary.
13.0 TECHNICAL SPECIFICATIONS AND OPERATING CONTROLS AND LIMITS The proposed exemption would not alter the technical specifications and operating controls and limits thus no evaluation is necessary.
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14.0 QUALITY ASSURANCE EVALUATION The proposed exemption would not alter the quality assurance program thus no evaluation is necessary.
Based on these evaluations, the staff has concluded that granting this exemption will be consistent with the requirements of 10 CFR Part 72 and will not endanger life or property.
The exemption requested by Entergy is not related to any security or common defense aspect of the VYNPS ISFSI. Therefore, granting the exemption would not result in any potential impacts to common defense and security.
C. Otherwise in the Public Interest In determining whether to grant the exemption is in the public interest, the staff considered the no-action alternative of denying the exemption request. Denial of the exemption request would require Entergy to load and store spent fuel in accordance with the current conditions of Amendment No. 10 of CoC No. 1014, which restrict loading higher-enriched fuel with the lower-enriched undamaged fuel in the same MPC. In addition, when loading the lower-enriched undamaged fuel, the maximum planar-average initial enrichment of all fuels in the MPC could not exceed 3.3 wt.% U-235.
The exemption proposed by Entergy would allow VYNPS to store spent fuel assemblies with higher and lower enrichments in the same MPC. Entergy provided data showing that this mixed-fuel arrangement reduces the operational dose rate at VYNPS. Specifically, the undamaged fuel assemblies are typically low-burned and long-cooled, and could be mixed with higher-enriched and higher-burned fuel in the same cask to reduce dose rates. Placing the low-burned, long-cooled assemblies on the periphery of the cask acts as shielding and blocks the radiation from the shorter-cooled, higher-burned fuels stored in the center of the cask.
In addition, Entergy requested this exemption to facilitate completion of its post-shutdown decommissioning activities. Holtec, the CoC holder, requested Amendment No. 11 to CoC No. 1014, by letter dated January 29, 2016 (Holtec 2016a) and the request is currently under review by the staff. Holtecs amendment requests, in part, the revision of Appendix B, Table 2.1-3, Note 19, of the CoC to allow the storage of higher and lower enriched fuel assemblies.
The NRC will not complete its review of Amendment No. 11 prior to the proposed initiation of VYNPSs 2017 loading campaign, as described in the Vermont Yankee Post-Shutdown Decommissioning Activities Report (Entergy 2014) as supplemented (Entergy 2017b).
Therefore, granting the exemption allows VYNPS to manage its spent fuel inventory and maintain its decommissioning schedule during its upcoming loading campaign.
The staff reviewed and confirmed the data provided by Entergy. Section B.6 of this SER finds that the exemption, if implemented, will result in more efficient spent fuel loading and a reduction of the operational dose rate. The staff concludes that granting the requested exemption continues to provide adequate protection of public health and safety. For these reasons, granting the exemption is otherwise in the public interest.
CONCLUSION The staff performed a comprehensive review of the exemption request. Based on the statements and representations provided by Entergy in its exemption request, as supplemented, 7
the staff concludes that the modification to the requirements in Appendix B, Table 2.1-3, Note 19 of Amendment No. 10 to the Holtec CoC No. 1014, does not affect the ability of the cask system to meet the requirements of 10 CFR Part 72.
This exemption request should be approved.
REFERENCES Entergy 2014. Vermont Yankee Post-Shutdown Decommissioning Activities Report. December 29, 2014. Agencywide Document Access and Management System (ADAMS) Accession No. ML14357A110.
Entergy 2016. Entergy Nuclear Operations, Inc. Letter from Entergy Nuclear Operations, Inc.
to NRC, Exemption Request from certain requirements of 10 CFR 72.212 and 10 CFR 72.214, Vermont Yankee Nuclear Power Station, License No. DPR-28, Docket Nos. 50-271, 72-59 and 72-1014, November 9, 2016, ADAMS Accession No. ML16319A102.
Entergy 2017a. Entergy Nuclear Operations, Inc. Letter from Entergy Nuclear Operations, Inc.
to NRC, Response to Request for Supplemental Information Related to Exemption Request from certain requirements of 10 CFR 72.212 and 10 CFR 72.214 Vermont Yankee Nuclear Power Station License No. DPR-28 Docket Nos. 50-271, 72-59 and 72-1014, January 9, 2017, ADAMS Accession No. ML17010A300.
Entergy 2017b. Entergy Nuclear Operations, Inc. Letter from Entergy Nuclear Operations, Inc.
to NRC, Notification of Schedule Change for Dry Fuel Loading Campaign, Vermont Yankee Nuclear Power Station, Docket No. 50-271, License No. DPR-28 April 12, 2017, ADAMS Accession No. ML17104A050.
Holtec 2016a. Letter from Holtec International to NRC, Holtec International HI-STORM 100 Multipurpose Canister Storage System Amendment Request 1014-11, January 19, 2016, ADAMS Accession No. ML16029A528.
Holtec 2016b. Letter from Holtec International to NRC, Supporting Information for License Amendment Request 11 (1014-11) to the HI-STORM 100 CoC, February 16, 2016. ADAMS Accession No. ML16069A246.
NRC 2003. U.S. Nuclear Regulatory Commission, Recommendations for Shielding Evaluations for Transport & Storage Packages, NUREG/CR-6802, May 2003. ADAMS Accession No. ML031330514.
NRC 2010. U.S. Nuclear Regulatory Commission, Standard Review Plan for Spent Fuel Dry Cask Storage Systems at a General License Facility, NUREG-1536, Revision 1, July 2010, ADAMS Accession No. ML101040620.
NRC 2011. U.S. Nuclear Regulatory Commission. Safety Evaluation Report, Docket No. 72-1014, Holtec International HI-STORM 100 Cask System, Certificate of Compliance No. 1014, Amendment No. 8, August 2011, ADAMS Accession No. ML112160627.
NRC 2015. U.S. Nuclear Regulatory Commission. Preliminary Safety Evaluation Report, Holtec International HI-STORM 100 Cask System, Certificate of Compliance No. 1014, Amendment No. 9, Revision No.1, ADAMS Accession No. ML15156B011.
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NRC 2016a. U.S. Nuclear Regulatory Commission. Code of Federal Regulations, Title 10, Energy, Part 72, Licensing Requirements for the Independent Storage of Spent Nuclear Fuel, High-Level Radioactive Waste, and Reactor-Related Greater Than Class C Waste.
Washington, D.C., 2016.
NRC 2016b. U.S. Nuclear Regulatory Commission. Letter from NRC to Holtec International, "Certificate of Compliance No. 1014, Amendment No. 10 for the HI-STORM 100 Cask System (CAC No. L24979), May 25, 2016, ADAMS Accession No. ML16144A177.
NRC 2017. U.S. Nuclear Regulatory Commission. Letter from NRC to Vermont Department of Health, Response: Draft Environmental Assessment: Exemption Request for Vermont Yankee Independent Spent Fuel Storage Installation, May 23, 2017, ADAMS Accession No. ML17144A045.
Vermont 2017. Email from Vermont Department of Health to NRC, RE: Followup: Draft Environmental Assessment: Exemption Request for Vermont Yankee Independent Spent Fuel Storage Installation, March 16, 2017, ADAMS Accession No. ML17080A475.
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ML17054C788 OFC NMSS/DSFM NMSS/DSFM NMSS/DSFM NMSS/DSFM NMSS/DSFM OGC NMSS/DSFM ASotomayor-NAME YChen WWheatley Rivera SGhrayeb TTate JMaltese JMcKirgan DATE 2/13/2017 2/21/2017 2/14/2017 1/25/2017 4/27/2017 5/25/2017 5/26/17