E6-11408. Omaha Public Power District Independent Spent Fuel Storage Installation; Environmental Assessment and Finding of No Significant Impact

AGENCY:

Nuclear Regulatory Commission.

ACTION:

Issuance of an Environmental Assessment and Finding of No Significant Impact.

FOR FURTHER INFORMATION CONTACT:

Joseph M. Sebrosky, Senior Project Manager, Spent Fuel Project Office, Office of Nuclear Material Safety and Safeguards, U.S. Nuclear Regulatory Commission, Washington, DC 20555. Telephone: [phone]; Fax number: [phone]; E-mail: [e-mail].

SUPPLEMENTARY INFORMATION:

The U.S. Nuclear Regulatory Commission (NRC or Commission) is considering issuance of an exemption to Omaha Public Power District (OPPD) pursuant to 10 CFR 72.7, from specific provisions of 10 CFR 72.48(c)(2)(viii), 72.212(a)(2), 72.212(b)(2)(i)(A), 72.212(b)(7), and 72.214. The licensee wants to use the Transnuclear, Inc. (TN) Standardized NUHOMS® Storage System, Certificate of Compliance No. 1004 (CoC or Certificate) Amendment No. 8 (32PT dry shielded canister), to store spent nuclear fuel under a general license in an Independent Spent Fuel Storage Installation (ISFSI) associated with the operation of the Fort Calhoun Station (FCS), located in Washington County, Nebraska. OPPD is requesting an exemption from CoC No. 1004 and NRC regulations to allow changes to the transfer cask (TC) dose rate measurements, an earlier start time for vacuum drying and use of a method of thermal analysis that is a departure from the methodology described in the Standardized NUHOMS® updated final safety analysis report (FSAR).

Environmental Assessment (EA)

Identification of Proposed Action: The proposed action would exempt OPPD from the requirements of 10 CFR 72.48(c)(2)(viii), 72.212(a)(2), 72.212(b)(2)(i)(A), 72.212(b)(7), and 72.214 and enable OPPD to use a light weight TC and allow the use of an earlier start time for vacuum drying in conjunction with the Standardized NUHOMS® Storage System, CoC 1004, at the FCS. Sections 10 CFR 72.212(a)(2), 72.212(b)(2)(i)(A), 72.212(b)(7), and 72.214 specifically require storage in casks approved under the provisions of 10 CFR part 72 and compliance with the conditions set forth in the CoC for each dry spent fuel storage cask used by an ISFSI general licensee. The TN NUHOMS® CoC provides requirements, conditions, and operating limits in Attachment A, Technical Specifications (TSs). The proposed action would exempt OPPD from the requirements of 10 CFR 10 CFR 72.212(a)(2), 10 CFR 72.212(b)(2)(i)(A), 10 CFR 72.212(b)(7) and 10 CFR 72.214 in order to permit changes from TSs in Amendment 8 to CoC No. 1004 which would allow changes to the TC dose rate measurements, and allow an earlier start time for vacuum drying. Specifically, the exemption would be from CoC No. 1004 Attachment A, TSs, 1.2.1, “Fuel Specification,” 1.2.11, “Transfer Cask Dose Rates with a Loaded 24P, 52B, 61BT, or 32PT Dry Shielded Canister,” and 1.2.17a, “32PT Dry Shielded Canister Vacuum Drying Duration Limit.” In addition, the proposed action would exempt OPPD from requirements of 10 CFR 72.48(c)(2)(viii), which requires that a general licensee request that the certificate holder obtain a CoC amendment prior to implementing a change that would result in a departure from a method of evaluation described in the FSAR for the design. The method of evaluation for which OPPD is seeking an exemption involves the thermal analysis associated with the TC while it is inside the transfer trailer radiological shielding.

OPPD committed in its June 9, 2006, submittal to a maximum decay heat load per dry shielded canister (DSC) of 11 kilowatts (kW). This is less than the CoC No. 1004 Attachment A, Technical Specification, Table 1-1e maximum decay heat limit of 24 kW per DSC. In addition, in its July 3, 2006, supplement OPPD indicated that the minimum cooling time for the fuel that it intended to load is 16.2 years. This time is greater than the minimum amount of time specified in TS Table 1-1e.

The NRC has determined that the exemption, if granted, will contain the following four conditions: (1) OPPD will be limited to loading a total of four 32PT DSCs, (2) OPPD shall limit the decay heat level per DSC to 11 kW to ensure cask loadings are bounded by the analyses supporting the TN CoC No. 1004, Amendment No. 8, (3) OPPD shall limit the cooling time of the fuel that it intends to load to a minimum of 16.2 years to ensure that the radiological source term for fuel that is loaded in the light weight TC is kept as low as reasonably achievable, and (4) the TS 1.2.11 dose rate limit/specification are substituted with the limit of 170 mrem/hr in the axial direction and 110 mrem/hr in the radial direction. The axial dose rate limit of 170 mrem/hr is to be taken under the conditions in Table 1 below. The radial dose rate limit of 110 mrem/hr is to be taken under the conditions in Table 2 below.

32PT DSC inside the OS197L inside the decon sleeve/bell

Water drained from the DSC

TC/DSC annulus full (within approximately 1 foot of the top)

TC neutron shield full

Top shield plug in place and included in axial shielding

Inner top cover plate in place and included in axial shielding

Automated welding system (AWS) with integral shield in place and included in axial shielding

Measurement taken at vertical centerline of DSC, 3 feet from AWS shield

32PT DSC inside OS197L inside decon sleeve/bell

water drained from the DSC

TC/DSC annulus full (within approximately 1 foot of the top)

TC neutron shield full

6 inch nominal thickness carbon steel decon sleeve/bell in place and included in radial shielding

measurement taken at outside surface (contact) of decon sleeve/bell

The proposed action is in accordance with the licensee's request for exemption dated June 9, 2006, as supplemented July 3, 2006, July 7, 2006, and July 12, 2006.

Need for the Proposed Action: The proposed action is needed because the FCS will lose full core offload after the 2006 refueling outage. During this refueling outage, major components of the reactor coolant system will be replaced including two steam generators, the reactor vessel head and the pressurizer. The large amount of reactor coolant system components being replaced during the outage raises the likelihood that foreign material could be introduced into the reactor vessel and potentially deposited under the core support plate. This scenario would require the core to be offloaded to the spent fuel pool and the reactor core barrel to be removed to allow removal of the foreign material. In addition, allowing four DSCs to be loaded prior to the beginning of the refueling outage would allow better management of decay heat loads within the spent fuel pool (including minimization of fuel handling activities) and would also allow the receipt and storage of new fuel prior to the refueling outage. Regarding receipt and storage of the new fuel, OPPD intends to inspect 44 new fuel assemblies and 49 new control rods to support the 2006 refueling outage. Once inspections are complete the assemblies are transferred from the new fuel storage rack into the spent fuel pool. This fuel handling operation requires more resources, presents more radiological challenges, and is more complicated than normal intra-spent fuel pool fuel movements. Consequently, it is OPPD's practice to perform these operations prior to a refueling outage before the spent fuel from the core is offloaded into the spent fuel pool.

The proposed action is necessary because the NRC has not received an amendment to CoC No. 1004 to allow changes to the TC dose rate measurements, an earlier start time for vacuum drying and the use of a method of thermal analysis that is a departure from the methodology described in the Standardized NUHOMS® updated FSAR. The staff would have to review such an amendment request and only after making the appropriate findings would the staff initiate a 10 CFR 72.214 rulemaking to implement the change. This process typically takes at least 10 months from the receipt of the amendment request for simple license amendments. Complex license amendments can take over 30 months. Therefore, an amendment to allow changes to the TC dose rate measurements, an earlier start time for vacuum drying and the use of a method of thermal analysis that is a departure from the methodology described in the Standardized NUHOMS® updated FSAR can not be completed in time to support OPPD's stated needs.

Environmental Impacts of the Proposed Action: The NRC has completed its evaluation of the proposed action and concludes that there will be no significant environmental impact if the exemption is granted. The staff has determined that the proposed action would not endanger life or property. The potential environmental impact of using the NUHOMS® system was initially presented in the Environmental Assessment (EA) for the Final Rule to add the TN Standardized NUHOMS® Horizontal Modular Storage System for Irradiated Nuclear Fuel to the list of approved spent fuel storage casks in 10 CFR 72.214 (59 FR 65898, dated December 22, 1994).

The staff performed a safety evaluation of the proposed exemption. The staff has determined that the exemption to allow changes to the TC dose rate measurements, an earlier start time for vacuum drying and the use of a method of thermal analysis that is a departure from the methodology described in the Standardized NUHOMS® updated FSAR meets the requirements of 10 CFR part 72 for granting an exemption. Regarding the changes to the TC dose rate measurements, OPPD is seeking an exemption from TS 1.2.1, and 1.2.11. The exemption from TS 1.2.1 and 1.2.11 relate to the wording in these TSs for the TC dose rates. OPPD proposes to use a light weight TC that has reduced shielding including the elimination of all the lead shielding from previous versions of the TC. The reduced shielding results in a lower weight for the TC. The OS197L TC was developed by TN to be used at plants with reduced spent fuel pool building crane capacity. The OS197L TC is intended for plants that are limited to a 75 ton spent fuel pool building crane capacity. The TC that the OS197L TC replaces (which TN designates as the OS197 TC) requires a 100 ton spent fuel pool building crane capacity. Because the OS197L TC has less shielding (including the elimination of all the lead shielding) than the OS-197, the OS197L TC surface dose rates are higher than the OS197 TC with lead shielding. To reduce personnel doses, crane operations associated with the OS197L TC are done remotely and supplemental shielding is provided in the decontamination area where the DSC is welded and on the transfer trailer that is used to transport the OS197L TC to the horizontal storage module. The TS 1.2.1 and TS 1.2.11 exemptions involve the use of supplemental shielding in addition to the shielding provided by the OS917L TC to meet the intent of the TSs. TS 1.2.11 involves the measurement of the TC surface dose rates in the axial and radial direction. The objective of taking these dose rate measurements is to ensure that the DSC has not been inadvertently loaded with fuel not meeting specification (i.e., a fuel misload), and to maintain dose rates ALARA.

In the safety evaluation report (SER) the staff provides the following reasons for granting the exemptions to TS 1.2.1 and 1.2.11: (1) Use of fuel with a minimum cooling time of 16.2 years ensures that the OS197L TC surface dose rate will be significantly lower than it would be for bounding type fuel, (2) appropriate ALARA precautions are being taken at the FCS given the use of the OS197L TC, and (3) use of the OS197L TC is limited to four DSCs and is found to be acceptable at the FCS due to the extenuating circumstances that are described in OPPD's exemption request (e.g., limited to use of a 75 ton crane, loss of full core offload capability, allow receipt and storage of new fuel, and allow better management of decay heat loads within the spent fuel pool). Additional reasons cited in the SER for granting the exemption to TS 1.2.11 include: (1) OPPD calculated TS limits specifically for the axial and radial directions and the calculations in the radial direction included the supplemental shielding, (2) OPPD's calculated values are consistent with the TS 1.2.11 values, and (3) the applicant demonstrated that the appropriate procedures will be in place to identify a fuel misloading and maintain doses ALARA. Based on the technical information provided in the exemption request, and the reasons provided above, the staff finds that there is reasonable assurance the applicant meets the shielding and dose requirements of 10 CFR part 72 and 10 CFR part 20.

Regarding an earlier start time for vacuum drying, the staff reviewed OPPD's request to change TS 1.2.17a. OPPD will start the time limit for completing vacuum drying earlier in the loading sequence and will use helium as the backfill gas. In the current FSAR, draining up to 750 gallons of water from the DSC prior to it leaving the spent fuel pool is allowed to reduce the weight on the crane. The DSC is then placed in the decontamination area where the inner top cover plate is welded. During the welding process approximately 750 gallons of water remains in the DSC. After the welding is completed and the weld examinations are successfully performed, the remaining water in the DSC is removed and vacuum drying is started. Unlike what is currently described in the FSAR, OPPD plans to remove the majority of the water from the DSC prior to it leaving the spent fuel pool. OPPD plans to perform the welding of the DSC inner top cover plate with the DSC in the drained condition. To support draining the DSC earlier in the process than currently described in the FSAR, OPPD proposes to start the time limit associated with completing vacuum drying at the time that the initial 750 gallon drain down from the canister is achieved, which is prior to movement of the cask/canister to the decontamination area.

The time limits of TS 1.2.17a were selected to ensure that the maximum cladding temperature is within the acceptable limit of 752 °F during vacuum drying. These time limits also ensure that the cladding temperature meets the thermal cycling criteria of 117 °F during drying, helium backfilling, and transfer operations. The staff's basis for concluding that the exemption is appropriate, as documented in the staff's SER, is that starting the time limit for vacuum drying earlier in the loading sequence is bounded by the thermal analysis previously performed. Therefore, based on its review of the representations and information supplied by the applicant the staff concludes that the change to the sequence to drain the DSC earlier in the process and the corresponding change to the start of the vacuum drying time has been adequately described and evaluated by the applicant, and finds reasonable assurance that these changes meet the thermal requirements of 10 CFR part 72.

Regarding the change in method of evaluation related to the modeling of the heat transfer for the OS197L TC while it is inside the transfer trailer temporary shielding, OPPD intends to limit the loading of the DSCs to a total heat load of 11 kW. The supplemental shielding on the transfer trailer causes an impediment to heat transfer. Limiting the heat load of the DSC to 11 kW ensures that this configuration is bounded by the design basis fuel assemblies thermal analysis previously evaluated by the staff. The 11 kW limit is less than the CoC No. 1004 Attachment A, Technical Specification, Table 1-1e maximum decay heat limit of 24 kW and is therefore bounding. Based on its review of the representations and information supplied by the applicant the staff concludes that the thermal design for the TC inside the transfer trailer has been adequately described and evaluated by the applicant, and finds reasonable assurance that by limiting the heat load to 11 kW the thermal requirements of 10 CFR part 72 are met.

The proposed action to allow changes to the TC dose rate measurements, an earlier start time for vacuum drying and the use of a method of thermal analysis that is a departure from the methodology described in the Standardized NUHOMS® FSAR do not increase the probability or consequences of accidents, and no changes are being made in the types of any effluents that may be released offsite. Occupational exposures will not increase adversely because of the use of remote handling techniques for the OS197L TC and the additional supplemental shielding provided in the decontamination area and on the transfer trailer. Likewise public radiation exposure will not increase adversely due to the additional shielding provided on the transfer trailer. For an accident condition a complete loss of the OS197L TC neutron shield and the transfer trailer supplemental shielding was postulated. The dose rate at the site boundary assuming bounding fuel in a 32PT canister and a 100 meter site boundary is approximately 13 mrem/hour. This equates to a 104 mrem dose at the site boundary assuming an 8 hour recovery period. This dose is well below the 10 CFR 72.106 regulatory limit of 5000 mrem for accident conditions. Therefore, there are no significant radiological environmental impacts associated with the proposed action.

The exemption only affects the requirements associated with TC dose rate measurements, an earlier start time for vacuum drying, and the use of a different thermal analysis of the TC on the transfer trailer and does not affect non-radiological plant effluents or any other aspects of the environment. Therefore, there are no significant non-radiological impacts associated with the proposed action.

Accordingly, the Commission concludes that there are no significant environmental impacts associated with the proposed action.

Alternative to the Proposed Action: Because there is no significant environmental impact associated with the proposed action, alternatives with equal or greater environmental impact were not evaluated. As an alternative to the proposed action, the staff considered denial of the proposed action. Denial of the exemption would result in no change in the current environmental impact.

Agencies and Persons Consulted: This exemption request was discussed with Julia Schmitt of the Nebraska Health and Human Services Regulation and Licensure Radiation Control Program Office on July 5, 2006. The State official had no comments regarding the environmental impact of the proposed action. The NRC staff has determined that a consultation under Section 7 of the Endangered Species Act is not required because the proposed action will not affect listed species or critical habitat. The NRC staff has also determined that the proposed action is not a type of activity having the potential to cause effects on historic properties. Therefore, no further consultation is required under Section 106 of the National Historic Preservation Act.

Conclusion: The staff has reviewed the exemption request submitted by OPPD. Allowing changes to the TS TC dose rate measurements, an earlier start time for vacuum drying, and a different method of thermal analysis of the TC on the transfer trailer would have no significant impact on the environment.

Finding of No Significant Impact

The environmental impacts of the proposed action have been reviewed in accordance with the requirements set forth in 10 CFR part 51. Based upon the foregoing Environmental Assessment, the Commission finds that the proposed action of granting the exemption from specific provisions of 10 CFR 72.48(c)(2)(viii), 72.212(a)(2), 72.212(b)(2)(i)(A), 72.212(b)(7), and 72.214 to allow OPPD to make changes to the TS TC dose rate measurements, an earlier start time for vacuum drying, and a different method of thermal analysis of the TC on the transfer trailer, subject to conditions, will not significantly impact the quality of the human environment. Accordingly, the Commission has determined that an environmental impact statement for the proposed exemption is not warranted.

In accordance with 10 CFR 2.390 of NRC's “Rules of Practice,” final NRC records and documents regarding this proposed action are publically available in the records component of NRC's Agencywide Documents Access and Management System (ADAMS). The request for exemption dated June 9, 2006, and supplemented July 3, 2006, July 7, 2006, and July 12, 2006, was docketed under 10 CFR part 72, Docket No. 72-54. These documents may be inspected at NRC's Public Electronic Reading Room at http://www.nrc.gov/​reading-rm/​adams.html. These documents may also be viewed electronically on the public computers located at the NRC's Public Document Room (PDR), O1F21, One White Flint North, 11555 Rockville Pike, Rockville, MD 20852. The PDR reproduction contractor will copy documents for a fee. Persons who do not have access to ADAMS or who encounter problems in accessing the documents located in ADAMS, should contact the NRC PDR Reference staff by telephone at 1-800-397-4209 or [phone], or by e-mail to [e-mail].

Dated at Rockville, Maryland, this 13th day of July, 2006.

For the Nuclear Regulatory Commission.

Joseph M. Sebrosky,

Senior Project Manager, Spent Fuel Project Office, Office of Nuclear Material Safety and Safeguards.