ML18341A029
| ML18341A029 | |
| Person / Time | |
|---|---|
| Site: | 07109338 |
| Issue date: | 12/06/2018 |
| From: | William Allen Spent Fuel Licensing Branch |
| To: | Ashley Ferguson Croft Associates Limited |
| Allen W | |
| References | |
| EPID L-2018-LLA-0137 | |
| Download: ML18341A029 (8) | |
Text
December 6, 2018 Mr. Alex Ferguson Licensing Engineer Croft Associates Limited Building 4F, Culham Science Centre Culham, Abingdon Oxfordshire, OX14 3DB, United Kingdom
SUBJECT:
REQUEST FOR ADDITIONAL INFORMATION FOR REVIEW OF THE MODEL NO. 3977A PACKAGE
Dear Mr. Ferguson:
By letter dated March 31, 2018 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML18136A484), as supplemented on July 24, 2018 (ADAMS Accession No. ML18213A130), Croft Associates Limited submitted an application to amend Certificate of Compliance No. 9338 for the Model No. 3977A package to add contents to the Model No. 3977A package, add licensing drawings and other miscellaneous changes. To assist with our review, the U.S. Nuclear Regulatory Commission staff (the staff) needs the information identified in the enclosure to this letter. Discussion of this request for additional information and a response date occurred on November 28, 2018.
We request that you provide this information by January 31, 2019. Inform us at your earliest convenience, but no later than January 24, 2019, if you are not able to provide the information by that date. If you are unable to provide a response by January 31, 2019, please propose a new submittal date with the reasons for the delay.
Please reference Docket No. 71-9338 and EPID No. L-2018-LLA-0137 in future correspondence related to this amendment request. The staff is available to discuss these questions as well as your proposed responses. If you have any questions regarding this matter, feel free to contact me at (301) 415-6877.
Sincerely,
/RA John McKirgan Acting for/
Chris Allen, Project Manager Spent Fuel Licensing Branch Division of Spent Fuel Management Office of Nuclear Material Safety and Safeguards Docket No. 71-9338 EPID No. L-2018-LLA-0137
Enclosure:
Request for Additional Information
A. Ferguson 2
SUBJECT:
REQUEST FOR ADDITIONAL INFORMATION FOR REVIEW OF THE MODEL NO. 3977A PACKAGE DOCUMENT DATE: December 6, 2018 DISTRIBUTION: SFST r/f RPowell, RI SWalker, RII MKunowski, RIII JKatanic, RIV DMarcano G:\SFST\Allen\Part 71\Safkeg\9338\RAI\Correspondence\Letter.docx ADAMS No.: ML18341A029 OFC: SFM SFM SFM SFM SFigueroa VWilson TAhn NAME: WAllen via e-mail via e-mail via e-mail DATE: 10/24/18 10/25/18 10/24/18 10/30/18 OFC: SFM SFM SFM SFM JSolis TTate CBajwa MRahimi NAME:
via e-mail via e-mail via e-mail via e-mail DATE: 10/25/18 11/16/18 11/16/18 11/19/18 OFC: SFM JMcKirgan NAME:
via e-mail DATE: 12/6/18 OFFICIAL RECORD COPY
Request for Additional Information Docket No. 71-9338 Model No. 3977A Package By letter dated March 31, 2018 (ADAMS Accession No. ML18136A484), as supplemented on July 24, 2018 (ADAMS Accession No. ML18213A130), Croft Associates Limited submitted an application to amend Certificate of Compliance No. 9338 for the Model No. 3977A package to add contents to the Model No. 3977A package, add licensing drawings and other miscellaneous changes. This RAI letter identifies information needed by the staff in connection with its review of the application. NUREG-1609, Standard Review Plan for Transportation Packages for Radioactive Material," was used by the staff in its review of the application.
Each individual RAI describes information needed by the NRC staff to complete its review of the application to determine whether the applicant has demonstrated compliance with the regulatory requirements.
General Information Review 1.1 Revise the free volume description in safety analysis report (SAR) Table 1-3-6.
In SAR Table 1-3-6, the applicant states that the product container and spacers shall be so designed as to leave a free volume of 225 cc within the [containment vessel] cavity.
This statement neither identifies the free volume if the thorium target were shipped without a product container, as Table 1-3-6 allows, nor is consistent with the free volume description in proprietary calculation CS2018/01.
This information is necessary to satisfy the requirements in Title 10 of the Code of Federal Regulations (10 CFR) 71.33(a).
Materials Review 2.1 Correct and revise, if necessary, the pyrophoric description of the proposed contents in SAR Table 1-3-6.
SAR Table 1-3-6 states The are not pyrophoric. (ADAMS Accession No. ML18136A487)
The applicant confirmed that the statement should read The contents are not pyrophoric.
(ADAMS Accession No. ML18226A238) However, the U.S. Department of Energy Handbook, Primer on Spontaneous Heating and Pyrophoricity, FSC-6910, identifies that thorium can be pyrophoric under certain conditions (e.g., a critical surface area in the presence of water). Therefore, the applicant needs to provide information which demonstrates that the proposed contents will not spontaneously combust. NRC staff also requests the applicant revise SAR Table 1-3-6 for clarity.
This information is necessary to satisfy the requirements in 10 CFR 71.43(d).
2.2 Analyze the changes caused by radiation from the irradiated thorium target in the package containment vessel (CV).
SAR Section 2.2.3 only discusses the effects of radiation on package materials associated with the containment vessel. It does not discuss the impact of radiation on package components which are inside the containment boundary (e.g., the CV plug seal and the Enclosure
plastic product container) which are closer to the radiation source. In addition, since the applicant does not inert the CV cavity during loading operations, radiation from the thorium target may produce a combustible combination of gases due to the presence of water vapor. The applicant needs to provide a bounding assessment of (i) the radiation effects on components which are inside the containment boundary, and (ii) the amount of gas production due to radiolysis of moisture in the CV.
This information is necessary to satisfy the requirements in 10 CFR 71.43(d).
2.3 Assess the impact of radiation embrittlement of Inconel on the package shielding capabilities and update the shielding analyses if necessary.
The applicant states in SAR Table 1-3-6 that the thorium target may be shipped in a product container. However, a proprietary drawing submitted by the applicant shows a configuration in which the thorium target is encased in Inconel and shipped outside of a product container. It is understood that Inconel may be susceptible to embrittlement by proton irradiation. For example, Carsughi et al. (1999) investigated Inconel 718 irradiated with 800 MeV protons, and found that the mechanical properties of Inconel 718 degraded after approximately 20 hours2.314815e-4 days <br />0.00556 hours <br />3.306878e-5 weeks <br />7.61e-6 months <br /> of irradiation at dose rates of 0.57 - 0.78 Sv/hour. If Inconel embrittlement occurs due to proton bombardment, normal conditions of transport (NCT) could damage the Inconel housing allowing either pieces of Inconel or pieces of thorium to relocate and produce increased radiation levels.
This information is necessary to satisfy the requirements in 10 CFR 71.43(f).
Thermal Review 3.1 Clarify the maximum decay heat value for content type CT-6, and provide NCT and HAC thermal evaluations for content type CT-6 if applicable.
Page 3-4 of the SAR states The package temperatures for Contents Type CT-6 (thorium target located at mid height of the CV cavity) would be bounded by those calculated for the higher maximum heat output of 30 W, as determined for the Inserts. This gives the impression that the Contents Type CT-6 have a lower decay heat which is inconsistent with SAR Table 1-3-6 that provides the maximum decay heat of 30 W for the new contents. Also, page 17 of SARP Update Matrix for Thorium Target (CTR 2018/01) states that the heat output is less than 1 W which shows another inconsistency in the application.
The staff needs this information to determine that predicted temperatures are below allowable limits for all package components.
This information is needed to determine compliance with 10 CFR 71.33(b)(7), 71.71(a),
71.71(c)(1), and 71.73(c)(4).
Shielding Review 5.1 Provide justification for using Ac-225 activity to define the content nuclides for CT-6 (activated thorium) within SAR Table 1-3-6.
Although many radionuclides are present, Table 1-3-6 only provides Ac-225 activity limits for the activated thorium content. The applicant explains its intent by the statement in Appendix B of SARP Update Matrix for Thorium Target. which states: It is proposed that only the activity of Ac-225 (being the principal radionuclide of interest) be reported on the shipping labels and documentation and the there is no need to the shipper to establish that the limit for the radionuclides calculated to be in the thorium target are less than specified limits.
Section 2 of the shielding assessment (Document 5163778-HS-REP-001) states: The 3977A Type B SAFKEG-HS package is required to contain a thorium target consisting of a radioactive thorium disc surrounded by a thin Inconel housing. The source contains a host of radionuclides present in both the thorium disc and the Inconel housing. These radionuclides are listed in Table 7-1 and were provided by Reference [1].
Section 5.5.2, Radiation Source, of NUREG-1609 states: Confirm that the contents used in the shielding analysis are consistent with those specified in the General Information section of the application. If the package is designed for multiple types of contents, ensure that the contents producing the highest external dose rate at each location are clearly identified and evaluated.
The applicant needs to demonstrate the nuclide profile and activity used is bounding of any Inconel incased proton activated thorium target that would produce 7.9 GBq (0.2 Ci).
Specifically, the staff requests the following:
- 1. Provide Reference 1 from Document 5163778-HS-REP-001,
- 2. Justify that the activation and decay assumptions from SAR Section 5.5.4.3 are bounding for all proton activated thorium contents,
- 3. Justify how the radionuclide profile was determined and state if daughter products of radionuclides were considered, and
- 4. Justify the amounts of thorium, Inconel and impurities (e.g., cobalt within the Inconel) used to simulate the target are bounding.
This information is needed to verify compliance with 10 CFR 71.33(b)(1), 71.47 and 71.51(a)(2).
5.2 Justify the use of nominal dimensions for the shielding components.
The staff compared the dimensions shown in Tables 7-2 and 7-3 of the shielding assessment (Document 5163778-HS-REP-001) to that of the drawings 0C-7942, 0C-7943 and 1C-7946. The staff finds use of nominal dimensions non-conservative. The staff requests that the applicant provide additional justification demonstrating that using nominal rather than minimum dimensions does not cause the package to exceed regulatory dose rate limits.
Section 5.5.1.1 of NUREG-1609 states: Design features important to shielding include Dimensions, tolerances, and densities of material for neutron or gamma shielding, including those packaging components considered in the shielding evaluation. Section 5.5.3.1 of NUREG-1609 states: Verify the dimensions of the source and packaging used in the shielding models. The staff does not find that the previously submitted uncertainty analyses address this item for the following reasons: (1) the content and analysis method are completely different from that of the initial approval, and (2) the staffs acceptance of the previous uncertainty analysis (ADAMS Accession No. ML14092A086) was based on conservatisms and margins to regulatory limits associated with the application for initial issuance of the certificate. The current analysis has removed some of those conservatisms (e.g., the source is no longer a point source and the cork material is now being credited within the analysis). Further, since the staff did not locate the dose rates (see RAI 5-7), the staff cannot determine if there is sufficient margin to the regulatory dose rate limit to compensate for this uncertainty.
This information is needed to verify compliance with 10 CFR 71.47 and 71.51(a)(2).
5.3 Discuss how the effects from NCT and HAC were incorporated into the shielding evaluation.
The applicants shielding evaluation does not discuss effects to the package due to NCT and HAC. However, SAR Section 2.7.8 indicates that there is deformation to the package as a result of the side puncture test and the 10.2 meter drop. In addition, both SAR pages 3-10 and 3-11 state: Under HAC conditions the cork reaches a maximum temperature of 788oC. Cork ablates under high temperatures and leaves a low density carbonaceous layer which provides insulation equivalent to still CO2. The applicant needs to discuss how these effects are accounted for within the shielding evaluation.
Section 5.5.3, Shielding Model of NUREG-1609 states: Review the Structural and Thermal Evaluation sections of the application to determine the effects that the tests for normal conditions of transport and hypothetical accident conditions have on the packaging and its contents. Verify that the models used in the shielding calculation are consistent with these effects. Section 5.5.3.1 of NUREG-1609 states: Ensure that any changes in configuration (e.g., displacement of source or shielding, reduction in shielding) resulting under normal conditions of transport or hypothetical accident conditions have been included, as appropriate. The staff did not find that the previously submitted uncertainty analyses address this item for the following reasons: (1) the content and analysis method are completely different than that of the initial approval, and (2) the staffs acceptance of the previous uncertainty analysis (ADAMS Accession No. ML14092A086) was based on conservatisms and margins to regulatory limits associated with the application for initial issuance of the certificate. The current analysis has removed some of those conservatisms (e.g., the source is no longer a point source and the cork material is now being credited within the analysis). Further, since the staff did not locate the dose rates (see RAI 5-7), the staff cannot determine if there is sufficient margin to the regulatory dose rate limit to compensate for this uncertainty.
This information is needed to verify compliance with 10 CFR 71.47 and 71.51(a)(2).
5.4 Provide minimum dimensions for the activated thorium source and Inconel housing or justify that the analyzed dimensions are bounding.
Section 5.3.3.1 of NUREG-1609 states: Verify the dimensions of the source and packaging used in the shielding models. ensure that the location and physical properties of the contents used in the evaluation are those resulting in the maximum external radiation levels. Ensure that any changes in configuration (e.g., displacement of source or shielding, reduction in shielding) resulting under normal conditions of transport or hypothetical accident conditions have been included, as appropriate.
The applicant did not provide the minimum dimensions of either the activated thorium source or the Inconel housing within Table 1-3-6 of the application SAR. The minimum dimensions of the source are needed to determine if the amount of self-shielding assumed within the shielding evaluation is appropriate and conservative. In addition, the Inconel housing dimensions are needed to determine if the source could potentially relocate or stay within the shoring material assumed within the shielding evaluation. The staff requests that the applicant provide the minimum dimensions or alternatively provide justification showing the source modeling described in Section 3.2.3 of the shielding assessment (Document 5163778-HS-REP-001) to be conservative with respect to all possible source dimensions that can be shipped within the SAFKEG-HS 3977A. The applicant also needs to justify that the source will retain its analyzed geometry and will not be separated from its Inconel housing under NCT or HAC.
This information is needed to verify compliance with 10 CFR 71.33(b)(3), 71.47 and 71.51(a)(2).
5.5 Provide the distances from the package surface used to evaluate regulatory dose rates.
The staff was unable to locate the distances that the applicant used to evaluate the regulatory dose rate limits. The staff requires this information to be able to verify that the locations used for evaluating dose rates under NCT are consistent with the distances prescribed in 10 CFR 71.47(b) for exclusive use and 10 CFR 71.51(a)(2).
This information is needed to verify compliance with 10 CFR 71.47 and 71.51(a)(2).
5.6 Provide a representative Monte Carlo N-Particle (MCNP) input and output file.
The applicant did not provide an MCNP input or output file. The staff uses these files to verify if package design information has been properly input into the code, to ensure that proper convergence is achieved and that the calculated dose rates from the output files agree with those reported in the application.
Section 5.5.4.2 of NUREG-1609 states: The application should also include representative input files used in the analyses. Verify, as appropriate, that the information from the shielding models is properly input into the code. At least one representative output file (or key sections of the file) should generally be included in the application.
Ensure that proper convergence is achieved and that the calculated dose rates from the output files agree with those reported in the text.
This information is needed to verify compliance with 10 CFR 71.47 and 71.51(a)(2).
5.7 Provide calculated dose rate levels.
SAR Table 5-15, Summary Table of package base external dose rates from MCNP calculations for the Nuclide Activities in LANL calculations for a typical target activated to produce 0.2 Ci Ac-225 states: See Atkins report 5163778-HS-REP-001-001 (Section 5.5.6). Neither the Atkins report nor the SAR has a Section 5.5.6. Column 12 in SAR Table 1-4-6 reported a maximum surface dose rate; however, this value exceeds the regulatory dose rate limit of 10 mSv/hr in 10 CFR 71.47(b)(1).
Section 5.5.4.4 of NUREG-1609 states: Confirm that the external radiation levels under normal conditions of transport and hypothetical accident conditions agree with the summary tables discussed in Section 5.5.1.2 and that they meet the limits in §71.47(a) or
§71.47(b), as appropriate, and §71.51(a)(2).
This information is needed to verify compliance with 10 CFR 71.47 and 71.51(a)(2).
Operations Review 7.1 Revise steps 5 and 8 of SAR Section 7.1.4.
Steps 5 and 8 of SAR Section 7.1.4 do not direct the user to perform an action. If the information in these steps is important to package operations, the applicant should either revise steps 5 and 8 to direct the user what action to perform or reformat the information (e.g., provide the information as a Note). In addition, the information in step 8 associates 225 cc only with the use of spacers while with the information provided in Table 1-3-6 associates 225 cc with the use of spacers and a product container. If the applicant chooses to retain the information in step 8, the applicant needs to make the information in Table 1-3-6 consistent with the information in step 8.
This information is needed to verify compliance with 10 CFR 71.87(f).
7.2 Clarify the instructions associated with inserts in the sealed split lid configuration.
SAR Sections 7.1.4, 7.2.4 and 7.3.3 each contain steps associated with inserts. However, the applicant did not provide insert drawings for the sealed split lid package configuration, and other SAR Sections do not discuss the use of an insert with the sealed split lid package configuration. Therefore, the applicant should either remove these steps, or if the applicant wishes to retain the flexibility to use inserts with the split lid configuration, the applicant should modify these instructions to identify under what circumstances they need to be performed.
This information is needed to ensure compliance with 10 CFR 71.87(f).
References
- 1. F. Carsughi, H. Derz, P. Ferguson, G. Pott, W. Sommer and H. Ullmaier, Investigations on Inconel 718 Irradiated with 800 MeV Protons, J. of Nuclear Materials, 264 (1999), pp. 78
- 88.
- 2. U.S. Department of Energy (DOE), DOE Handbook, Primer on Spontaneous Heating and Pyrophoricity, FSC-6910, DOE.
- 3. U.S. Nuclear Regulatory Commission (NRC), Engineering Drawings for 10 CFR Part 71 Package Approvals.
- 4. Parker (Parker Hannifin Corporation, O-Ring Division), Parker O-Ring Handbook, ORD 5700.