ML20315A428
| ML20315A428 | |
| Person / Time | |
|---|---|
| Site: | 07201042 |
| Issue date: | 10/29/2020 |
| From: | Orano TN Americas, TN Americas LLC |
| To: | Office of Nuclear Material Safety and Safeguards |
| Shared Package | |
| ML20315A417 | List: |
| References | |
| E-57418, EPID L-2019-LLA-0078 | |
| Download: ML20315A428 (11) | |
Text
RAIs and Responses - Public Enclosure 12 to E-57418 RAI 4-7:
Provide the time limits and the appropriateness of the time periods associated with required action A.2 and A.3 of limiting conditions for operation (LCO) 3.1.3.
- a. The technical specification for LCO 3.1.3 indicated that the 61BTH Type 2 DSC time limits to ensure safe operation when completing the DSC transfer are not available. The technical specifications, which form part of the CoC approval, are to be completed prior to NRC certification to ensure there is adequate performance.
- b. The appropriateness of the time limits should be discussed relative to the sensitivity of the ambient temperature during transfer, as noted in Technical Specification 5.1.2(g).
This information is needed to determine compliance with 10 CFR 72.11 and 72.236(f).
Revised Response to RAI 4-7:
In order to provide the time limits and the appropriateness of the time periods associated with Technical Specifications (TS) Required Actions A.2 and A.3 of Limiting Conditions for Operation (LCO) 3.1.3, a computational fluid dynamics (CFD) evaluation of the 61BTH Type 2 Dry Shielded Canister (DSC) in the OS197 Transfer Cask (TC) during transfer operations has been added in the new UFSAR Section B.4.5.6.
UFSAR Sections B.4, B.4.3, B.4.5, B.4.5.1, B.4.5.1.1, B.4.5.1.2, B.4.5.1.3.2, B.4.5.1.4, B.4.5.2, B.4.5.2.2 and B.4.5.2.3 have been clarified to ensure that new analyses were presented in Section B.4.5.6 of this application in addition to those previously evaluated in CoC 1004 for transfer operations.
A list of computer files associated with the thermal evaluations in Section B.4.5.6 is provided as , and the thermal input/output files are provided in Enclosure 10 of the submittal package.
Impact:
TS LCO 3.1.3 has been updated as described in the response.
UFSAR Sections B.4, B.4.3, B.4.5, B.4.5.1, B.4.5.1.1, B.4.5.1.2, B.4.5.1.3.2, B.4.5.1.4, B.4.5.2, B.4.5.2.2 and B.4.5.2.3 have been updated as described in the response.
UFSAR Section B.4.5.6, Tables B.4-9 through B.4-11, and Figures B.4-9 through B.4-13 have been added as described in the response.
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RAIs and Responses - Public Enclosure 12 to E-57418 RAI 6-4:
Clarify if fuel assemblies (FAs) containing reconstitution rods are allowed to be loaded in the peripheral locations of the DSC and revise the UFSAR and/or TS to reflect these limits as necessary.
On page 1-24 of the HSM-MX UFSAR, the applicant states: Reconstituted assemblies containing up to five replacement irradiated stainless steel rods per assembly or an unlimited number of low enriched or natural uranium fuel rods or unirradiated non-fuel rods are acceptable for storage in an EOS-89BTH DSC as intact FAs.
On page 2-6 of the same UFSAR, the applicant states: Fuel assemblies are evaluated with five irradiated stainless steel rods per assembly, 40 rods per EOS-37PTH DSC, and 100 rods per EOS-89BTH DSC. The cooling time is the same as unreconstituted FAs. The reconstituted rods can be at any location in the FAs. There is no limit on the number of reconstituted FAs per DSC; the FAs containing irradiated stainless steel reconstituted rods are modeled in the inner compartments as shown in Figure 6-1 for EOS-37PTH and Figure 6-2 for EOS-89BTH of Chapter 6.
However, the staff notes that Table 1-1t of the CoC No. 1004 TS states that the maximum number of irradiated stainless steel rods in reconstituted assemblies per the 61BTH Type II DSC is 40, the maximum number of irradiated stainless steel rods per reconstituted fuel assembly is 10, and the maximum number of reconstituted assemblies per DSC with unlimited number of low enriched UO2 rods or Zr rods or Zr pellets or unirradiated stainless steel rods is 61.
The staff also notes that the TS for amendment 2 of the HSM-MX system includes: Number of RECONSTITUTED FUEL ASSEMBLIES [per the 61BTH Type II DSC [is] 61. However, information on the maximum number of irradiated stainless steel rods in reconstituted assemblies per the 61BTH Type II DSC and the maximum number of irradiated stainless steel rods per reconstituted fuel assembly is missing from both the TS and UFSAR for the HSM-MX system.
The staff needs this information to determine if the HSM-MX meet the regulatory requirements of 10 CFR 236(d).
Revised Response to RAI 6-4:
UFSAR Section B.6.2.6 is revised to provide fuel assembly source terms for reconstituted fuel assemblies containing both 5 and 10 irradiated stainless steel rods per fuel assembly. The OS197 TC and HSM-MX analyses documented in UFSAR Sections B.6.4.3 and B.6.4.4, respectively, are updated to address 24 reconstituted fuel assemblies with 5 irradiated stainless steel rods per fuel assembly on the basket periphery (total of 120 irradiated stainless steel rods per DSC). Results Tables B.6-13, B.6-14, B.6-16, and B.6-17 are updated. New UFSAR Tables B.6-18 through B.6-26 are added to support the reconstituted fuel analysis.
Due to the dose rate increase, the occupational exposure estimate in UFSAR Section B.11.2 is updated, including UFSAR Tables B.11-1 and B.11-2.
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RAIs and Responses - Public Enclosure 12 to E-57418 The fuel assembly source terms for reconstituted fuel assemblies containing 10 irradiated stainless steel rods per fuel assembly are used in a sensitivity study to demonstrate that dose rates are approximately the same for the 5 and 10 irradiated stainless steel rod reconstituted fuel assemblies when the number of irradiated stainless steel rods per DSC is held constant at 120, see UFSAR Tables B.6-25 and B.6-26. A limit of 120 irradiated stainless steel rods per DSC is added to the Technical Specifications (TS), Section 2.3.
MCNP input and output files are included in Enclosure 9.
Impact:
TS Section 2.3 has been revised as described in the response.
UFSAR Sections B.6.2.6, B.6.4.3, B.6.4.4, and Section B.11.2 have been revised as described in the response.
UFSAR Tables B.6-13, B.6-14, B.6-16, B.6-17, B.11-1 and B.11-2 have been revised as described in the response.
UFSAR Tables B.6-18 through B.6-26 have been added as described in the response.
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RAIs and Responses - Public Enclosure 12 to E-57418 RAI 6-5:
Justify that the specific power used in the source term calculations is appropriate or revise the source terms and shielding calculations for the HSM-MX system using a more appropriate specific power.
The applicant provides the fuel depletion parameters used in generating the source terms for the BWR fuel. The staff notes that the applicant states that it used the specific power as used in NUREG/CR-7194 for BWR fuel source term calculations. However, the staff notes that NUREG/CR-7194 used three different specific powers, 25 Watts/gram (W/g), 35 W/g, and 45 W/g. It used these different specific powers for sensitivity study rather than asserting these are the actual values of the BWR core operating parameters. The staff also notes that NUREG/CR-6700 states the specific power used for BWR fuel source analyses is 35 W/g. In addition, the staff found that the Standard NUHOMS Certificate of Compliance (CoC) 1004 design used 35 W/g in its design basis source term calculations for BWR fuel. Based on the information in the cited documents, it is not clear if the specific power used by the applicant in the source term calculation is conservative. Because using a specific power lower than the actual value in the depletion calculation will give lower source terms, the staff is concerned with whether the value used by the applicant bounds all the BWR fuels to be stored in the 61BTH DSC.
The staff needs this information to determine if the NUHOMS EOS system with the requested amendments meets the regulatory requirements of 10 CFR 72.236(d).
Revised Response to RAI 6-5:
UFSAR Section B.6.2.2 has been revised to make reference to newly added UFSAR Section B.6.2.9, Sensitivity Study on Specific Power. UFSAR Tables B.6-27 through B.6-30 have been added to support UFSAR Section B.6.2.9. It is demonstrated that a specific power of 30 MW/MTU has a negligible effect on dose rates. In addition, Section B.6.5.2 has been modified to add a new reference to NUREG/CR-6176.
Impact:
UFSAR Sections B.6.2.2 and B.6.5.2 have been revised, Section B.6.2.9 has been added. And Tables B.6-27 through B.6-30 have been added as described in the response.
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RAIs and Responses - Public Enclosure 12 to E-57418 RAI 8-4:
Provide the following information with respect to the analysis shown in Tables 4-29, 4.9.6-6, 4.9.7-5 and 4.9.7-7 where the maximum DSC shell temperature is greater than 600°F.
- 1. Provide mechanical properties for the SA-240/SA-479 Type 2205 / SA-182 Gr F60 (UFSAR Table 8-7) and SA-240 UNS S31803 / SA-182 Gr F51 (UFSAR Table 8-8) at temperatures that encompass the use of these materials under the conditions identified in UFSAR Table 4.9.7-7.
- 2. Explain the recovery actions for the analysis shown in Table 4.9.7-7 where the maximum DSC shell temp could exceed 600°F. The maximum DSC shell temperature of 717°F based on a steady state analysis for the accident condition with the EOS-37PTH DSC and HLZC 10 with 6 damaged fuel assemblies using shown in Table 4.9.7-7 is 117°F greater than the American Society of Mechanical Engineers (ASME) code allowable for a Unified Numbering System (UNS) S31803 duplex stainless steel using ASME Code Case N-635-1. Previous analysis show that significant alteration of the microstructure and mechanical properties can occur when duplex stainless steel are exposed to temperatures above 600°F (Weng et al.
2003; Taveres et al., 2005; Della Rovere et al., 2013).
This information is needed to determine compliance with 10 CFR 72.236(b).
References Della-Rovere, C.A., F.S. Santos, R. Silva, C.A.C. Souza, and S.E. Kuri, Influence of Long-Term Low-Temperature Aging on the Microhardness and Corrosion Properties of Duplex Stainless Steel, Corrosion Science, Vol. 68, pp. 84-90, 2013.
Taveres, S.S.M., V.F. Terra, P. De Lima Neto, and D.E Matos, Corrosion Resistance Evaluation of the UNS S31803 Duplex Stainless Steels Aged at Low Temperatures (350 to 550 °C) using DLEPR Tests, Journal of Materials Science, Vol. 40, pp. 4023-4028, 2005.
Weng, L.W., T.H. Chen, and J.R. Yong, The High-Temperature and Low-Temperature Aging Embrittlement in a 2205 Duplex Stainless Steel, Bulletin of College Engineering, No. 89, pp. 45-61, 2003.
Revised Response to RAI 8-4:
Response to Question 1 Material properties are provided in ASME Section II Part D for Alloy 2205 Sy and Su through 650 °F, and S31803 through 600 °F. For material properties above these limits, the Design for Stainless Steels Handbook, Table 8.1 provides rate of reduction factors for Duplex stainless steels, including S32205 through 1000 °C with respect to the room temperature properties [1].
While S31803 is not explicitly addressed, S31803 and S32205 are commonly dual-certified when purchased as Alloy 2205. Therefore, both Tables 8-7 and 8-8 of the UFSAR have been updated for the S32205 and S31803 properties, respectively, based on the rate of reduction for S32205 provided in [1].
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RAIs and Responses - Public Enclosure 12 to E-57418 Response to Question 2 Recovery actions for an accident condition where the neutron shield and air circulation are lost would include the following actions as soon as possible after an accident.
- 1. Reinstate neutron shielding to protect workers on the site and restart air circulation to control the fuel cladding and the DSC temperatures, if necessary based on the heat load of the DSC.
- a. If the neutron shield panels are punctured or damaged to the point that the neutron shielding cannot be refilled, appropriate supplementary shielding should be utilized, considering air flow, TC/DSC temperatures, and type of shielding required. This may include lead blankets, concrete barriers, metal sheeting, or other neutron shielding mechanisms. Section 12.3.1 has been updated to allow flexibility in determining the appropriate shielding for the specific accident.
- b. If the initial blower was damaged in the accident, the air circulation system is equipped with a redundant blower to facilitate engagement of air circulation. The air circulation system is designed utilizing off-the-shelf components such that ducting and blower components can expediently be replaced. Air circulation should be initiated for a time period as determined by a transient analysis considering accident specifics as discussed above, to reduce the DSC shell temperature to the maximum possible extent.
- 2. Evaluate the TC and DSC condition to determine if they are safe to move. This evaluation should include a transient thermal evaluation to determine the time the air circulation and neutron shield water, or both, should be in place to cool the DSC to a safe condition for transfer. The evaluation would consider the accident specifics, such as the decay heat load, the ambient temperature, and the time from loss of cooling or neutron shield water to the time the cooling or water are re-introduced. This will reduce the temperatures and provides additional margins to allow for safe transfer.
- 3. Return the TC/DSC to the fuel building or other acceptable location for evaluation of continued service after evaluations have determined that the TC is safe to move. Upright the TC and fill the annulus with water. Monitor the annulus water as required to ensure continued DSC cooling until a determination regarding continued serviceability of the TC, DSC, and contents is reached.
The direction provided in UFSAR Sections 12.3.1, 12.3.4, and 12.3.8 has been revised to add further discussion on the DSC inspection after an accident as described above.
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RAIs and Responses - Public Enclosure 12 to E-57418 (UFSAR Figure 4.9.7-5)
[
] The strength properties at 400 °C (752 °F) for S32205, namely the Su and Sy, equal 73.8 ksi and 39.0 ksi, respectively. The Su and Sy for 304 stainless steel at 750 °F are 63.3 ksi and 17.2 ksi, respectively, which are significantly lower than the duplex stainless steel strength properties.
Based on the strength properties, the 304 stainless steel is the limiting material in this load case; therefore, the evaluation is performed considering the 304 stainless steel material properties at 750 °F, even though shell materials of 304 stainless steel are assumed to maintain structural function through 800 °F. [
]
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RAIs and Responses - Public Enclosure 12 to E-57418 Proprietary Information on This Page Withheld Pursuant to 10 CFR 2.390 Page 8 of 11
RAIs and Responses - Public Enclosure 12 to E-57418 As part of the recovery and corrective actions, the air circulation would be initiated as discussed previously in this RAI response to reduce the DSC shell temperature to the maximum possible extent as determined by a transient analysis considering the accident-specific conditions.
Therefore, the DSC would be handled at temperatures lower than the maximum shell temperature reported in UFSAR Table 4.9.7-7 of 717 °F. [
]
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RAIs and Responses - Public Enclosure 12 to E-57418 Proprietary Information on This Page Withheld Pursuant to 10 CFR 2.390 Page 10 of 11
RAIs and Responses - Public Enclosure 12 to E-57418 Impact:
UFSAR Sections 3.9.1.2, 3.9.1.5, 8.7, 12.3.1, 12.3.4, and 12.3.8 have been revised as described in the response.
Tables 2-5, 3.9.1-5, 3.9.1-7, 3.9.1-7B, 8-7 and 8-8 of the UFSAR have also been updated as described in the response.
References:
- 1. The Steel Construction Institute, Design Manual for Structural Stainless Steel, 4th Edition, 2017.
- 2. Roberts, R; Newton, C, Interpretive Report on Small Scale Correlations with KIc Data, Welding Research Council Bulletin, February 1981.
- 3. 475 °C Embrittlement in a Duplex Stainless Steel UNS S31803, Materials Research, Vol.
4, No. 4, 237-240, 2001.
- 4. EOS01-1011-SAR, Rev. 3, NUHOMS EOS System Transportable Canister 37PTH Basket Transition Rails.
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