ML19127A265
| ML19127A265 | |
| Person / Time | |
|---|---|
| Site: | 07201032 |
| Issue date: | 04/30/2019 |
| From: | Holtec |
| To: | Division of Spent Fuel Management |
| Shared Package | |
| ML19127A267 | List: |
| References | |
| 5018065 | |
| Download: ML19127A265 (3) | |
Text
Supplemental Information for RSI 6-1 Docket No. 72-1032 Certificate of Compliance No. 1032 Amendment No. 5 to the HI-STORM Flood/Wind (FW) Multipurpose Canister Storage System Chapter 6 - Shielding Evaluation 6-1 Provide the neutron and gamma source terms for the new decay heat patterns.
The proposed technical specifications (TS) for the HI-STORM FW amendment contain new decay heat loading patterns. The applicant states in the Safety Analysis Report (SAR) that it used these decay heat limits to calculate the radiation source terms for dose and dose rate evaluations of the transfer cask and the storage system design. It is not clear to the staff what source term was used to perform these evaluations.
The applicant provided information starting at the bottom of page 5-6 of the changed SAR pages to justify its approach. The staff finds that the information presented is insufficient for the staff to review and make a finding as to whether or not the HI-STORM FW will be capable of meeting the regulatory requirements of 10 CFR 72.236(d). The staff requests that the applicant provide specific information on the parameters (burnup, enrichment, cooling time, and depletion assumptions) used to generate the source terms that were used to calculate doses for each ne loading pattern. Although the staff recognizes there is some information in Table 5.2.18 of the SAR, this table states that this is only applicable to loading patterns: 37C1, 37C2, 37C3, 37D1, 37D2, 37D3, 37E1, 37E2, 37E3, 89A1, and 89A2.
Section 6.5.2 Radiation Source Definition of NUREG-1536 states: The reviewer should examine the description of the design-basis fuel in Chapter 2, Principal Design Criteria of the SAR to verify that the applicant calculated the bounding source term. The review confirms that the applicant examined all fuel designs and burnup conditions for which the cask system is to be certified, to ensure that the bounding fuel type and values are used.
This information is needed for the staff to evaluate the capability of the cask system to meet dose limits in 10 CFR 72.104 and 106 as required by 10 CFR 72.236(d).
Holtec Response:
Holtec is in the process of implementing the Fuel Qualification Tables (FQTs) approach as discussed with the NRC staff during recent conference calls and a meeting on March 19, 2019. In response to RSI-6, Holtec has implemented the proposed FQTs into the HI-STORM FW Amendment 5 FSAR and the FQTs are used to determine the radiation source terms for dose and dose rate evaluations. The FSAR Chapters 2 and 5 are revised to include this approach and the proposed changed pages are being submitted to the Staff to complete our response to this RSI. The same approach was implemented in HI-STORM FW Amendment 4 RAI 5-5 response, which was submitted by April 15th.
Letter 5018065 Attachment 1
In summary, the approach for determining the neutron and gamma source terms for the new decay heat load patterns in amendment 5 and supporting calculations are as follows:
The design basis of the fuel permitted to be loaded into the system, in terms of burnups and cooling times, is not a single burnup and cooling time combination, but an equation that allows the calculation of the minimum cooling time as a function of the assembly burnup. While the equation has some technical background (its loosely related to heat loads), it is, for the purpose of the FSAR, an arbitrarily selected equation, and is validated through dose rate calculations showing the maximum (bounding) dose rates that would correspond to the design basis. For this validation, a sufficient number of burnup and cooling times are selected based on the equation, dose rate calculations are then performed for each combination, and the maximum dose rates are established. Note that the combination of burnup and cooling time that results in the highest dose rate could be different for different dose locations. In general, the number and the values of the combinations are selected so there is reasonable assurance that the condition at or close to the maximum is identified.
For the enrichments used in the calculations in the FSAR, conservatively low values are used, based on a database of actual fuel assemblies at US reactor sites. The low enrichments are based on [1] and [2]. To determine the enrichments, the data is separated in burnup bins spanning 5 GWd/mtU (i.e. 0 to 5, 5 to 10, 10 to 15, etc.). Then for each bin, an enrichment value is determined that presents a lower bound value for most of the assemblies in that bin.
SCALE 6.2.1, along with the above methodology, is used to develop the source terms which are used to the update the shielding evaluations.
The HI-STORM FW Amendment 5 FSAR is revised to reflect this new approach.
References
[1] U.S. Energy Information Administration, Form GC-859, "Nuclear Fuel Data Survey" (2013).
[2] U.S. Energy Information Administration, Form GC-859, "Nuclear Fuel Data Survey" (2002).
Observations:
8-1 Table 1.2.5. Typo on specific gravity and density units. Closed parentheses are superscripted.
Holtec Response:
Typo was corrected in Table 1.2.5 on FSAR page 1-67.
Letter 5018065 Attachment 1
8-2 Table 1.2.10. Long fuel dimensions has no upper limit. There is a maximum limit based on the overall dimensions of the MPC. Provide the upper limit for the long fuel.
Holtec Response:
As stated in FSAR Chapter 1, the MPC external diameters are identical to allow the use of a single overpack design, however the height of the MPC, as well as the overpack and transfer cask, are variable based on the SNF to be loaded. Table 1.2.10 is used to define the categories of PWR fuel lengths. This table is not intended to provide a bounding length for the fuel. Table 3.2.2, provides the limiting parameters used for structural analyses and includes the maximum fuel assembly length.
8-3 SAR Section 1.A.2. Typo on the first line in this section.
Holtec Response:
Typo was corrected in Section 1.A.2 on FSAR page 1.A-2.
8-4 SAR Section 10.1.3. Typo in 3rd paragraph, 5th sentence starting with The procedures shall ensure The term mix rations should be mix ratios.
Holtec Response:
Typo was corrected in Section 10.1.3. on FSAR page 10-10.
Letter 5018065 Attachment 1