ML22304A217
| ML22304A217 | |
| Person / Time | |
|---|---|
| Site: | 07201042 |
| Issue date: | 10/31/2022 |
| From: | Narayanan P Orano USA |
| To: | Office of Nuclear Material Safety and Safeguards, Document Control Desk |
| Shared Package | |
| ML22304A216 | List: |
| References | |
| E-61677, CAC 001028, EPID L-2021-LLA-0055 | |
| Download: ML22304A217 (1) | |
Text
October 31, 2022 E-61677
U. S. Nuclear Regulatory Commission Columbia Office Attn: Document Control Desk 7160 Riverwood Drive One White Flint North Columbia, MD 21046 Tel: (410) 910-6900 11555 Rockville Pike
@Orano_USA Rockville, MD 20852
Subject:
Application for Amendment 3 to NUHOMS EOS Certificate of Compliance No. 1042, Revision 9 (Docket 72-1042, CAC No.
001028, EPID: L-2021-LLA-0055) - Clarifications Regarding Annul us Water, MX-LC Alignment, and Seismic Damping Values
Reference:
[1] Letter E-61137 from Prakash Narayanan, Applicati on for Amendment 3 to NUHOMS EOS Certificate of Compliance No.
1042, Revision 7 (Docket 72-1042, CAC No. 001028, EPID: L-2021-LLA-0055) - Clarification Regarding Annulus Temperatures During Vacuum Drying Operations, dated June 29, 2022
[2] Letter E-58840 from Prakash Narayanan, Application for Amendment 3 to NUHOMS EOS Certificate of Compliance No.
1042, Revision 1 (Docket 72-1042, CAC No. 001028, EPID: L-2021-LLA-0055) - Response to Request for Supplemental Information (New Scope) and Revised Responses to Request for Additional Information, dated June 23, 2021
[3] Letter from Christian Jacobs to Prakash Narayanan, TN Americas LLC Application for Certificate of Compliance No. 1042,
Amendment No. 3, to NUHOMS EOS System (Docket No. 72-1042, CAC No. 001028, EPID: L-2021-LLA-0055) - Request for Supplemental Information, dated May 20, 2021
[4] Letter E-58329 from Prakash Narayanan, Application for Amendment 3 to NUHOMS EOS Certificate of Compliance No.
1042, Revision 0 (Docket 72-1042), dated March 31, 2021
This submittal provides further clarification regarding the app roach to maintaining water in the annulus between the dry shielded canister (DSC) an d the transfer cask (TC) during loading operations. The item was initially addresse d in TN Americas LLCs (TN) response to Observation 4-9, in Reference [2]. TN pr ovided clarification to this item in Reference [1].
Enclosures transmitted herein contain SUNSI. When separated fr om enclosures, this transmittal document is decontrolled.
Document Control Desk E-61677 Page 2 of 3
This submittal also provides clarification regarding alignment of the Matrix Loading Crane (MX-LC) with the upper tier compartments of the Matrix horizontal s torage module (HSM-MX), and clarification regarding the seismic damping values used for the MX-LC and the HSM-MX retractable roller trays (RRTs).
As follow-up to Reference [1], the NRC and TN held conference c alls on September 15, 2002,
[ML22264A337] and on September 28, 2022, [ML22278A179], for the purpose of further discussions and clarification from the contents included in Ref erence [1]. Based on these interactions with the NRC, TN is providing further clarificatio n to address this issue.
provides a proprietary version of the additional in formation in response the clarification discussions held on the conference calls on Septe mber 15, 2002, and on September 28, 2022. Enclosure 9 provides a public version of th ese responses.
provides a listing of changed UFSAR pages resulting from this Revision 9 to the application for Amendment 3.
provides the UFSAR changed pages associated with th is Revision 9 to the application for Amendment 3. The changed pages include a footer annotated as 72-1042 Amendment 3, Revision 9, October 2022, with changes indicated by italicized text and revision bars. The changes are further annotated with gray shading or a gray box enclosing an added section, as well as a footer to distinguish the Amendment 3, Re vision 9 changes from previous Amendment 3 changes.
provides the public version of the Enclosure 4 UFSA R changed pages.
provides a listing of the computer files associated with CoC 1042 Amendment 3, Revision 9. Enclosure 7 contains the computer files associated with this amendment submittal.
The file structure of the computer files is not compatible with the NRC EIE application process and Enclosure 7 is therefore being submitted separately. Since Enclosure 7 contains entirely proprietary information, no public version is provided.
provides changes and clarifications not associated with the thermal and materials clarifications.
Certain portions of this submittal include proprietary informat ion, which may not be used for any purpose other than to support the NRC staffs review of the app lication. In accordance with 10 CFR 2.390, TN Americas LLC is providing an affidavit (Enclos ure 1), specifically requesting that this proprietary information be withheld from public discl osure.
Should the NRC staff require additional information to support review of this application, please do not hesitate to contact Mr. Glenn Mathues at 410-910-6538, o r by email at Glenn.Mathues@orano.group.
Sincerely,
Prakash Narayanan Chief Technical Officer
Document Control Desk E-61677 Page 3 of 3
cc: Chris Jacobs (NRC), Senior Project Manager, Storage and Tra nsportation Licensing Branch Division of Fuel Management
Enclosures:
- 1. Affidavit Pursuant to 10 CFR 2.390
- 2. Additional Information Regarding Clarification Questions (Pr oprietary)
- 6. Listing of Computer Files Contained in Enclosure 7
- 7. Computer Files Associated with Certificate of Compliance 104 2 Amendment 3, Revision 9 (Proprietary) (contained on one hard drive)
- 8. Additional Clarifications Not Associated with the Thermal an d Materials Clarifications
- 9. Additional Information Regarding Clarification Questions(Pub lic)
Enclosure l to E-61677
AFFIDAVIT PURSUANT -
TO 10 CFR 2.390
TN Americas LLC )
State ofMarylahd y-- ss.
County of Howard )
I, Prakash Narayanan, depose and say that I am Chief Technical Officer of TN Americas LLC, duly authorized to execute this affidavit, and have reviewed or caused to have reviewed the information that is identified as proprietary and referenced in the paragraph immediately below. I am submitting this affidavit in conformance with the provisions of 10 CFR 2.390 of the Commission's regulations for withholding this information.
The information for which proprietary treatment is sought is contained in the following enclosures, as listed below:
- Enclosure 2 -Portions of Additional Information Regarding Clarification
- Enclosure 4 -Portions of certain updated final safety analysis report (UFSAR) chapters
- Enclosure 7 -Certain Computer Files Associated with Certificate of Compliance 1042 Amendment 3, Revision 9
These documents have been appropriately designated as proprietary.
I have personal knowledge of the criteria and procedures utilized by TN Americas LLC in designating information as a trade secret, privileged or as confidential commercial or financial information.
Pursuant to the provisions of paragraph (b) (4) of Section 2.390 of the Commission's regulations, the following is furnished for consideration by the Commission in determining whether the information sought to be withheld from public disclosure, included in the above referenced document, should be withheld.
- 1) The information sought to be withheld from public disclosure involves certain portions of the additional information regarding clarification, portions of the UFSAR and analysis computer files, all related to the design of the NUHOMS EOS System, which are owned and have been held in confidence by TN Americas LLC
- 2) The information is of a type customarily held in confidence by TN Americas LLC, and not customarily disclosed to the public. TN Americas LLC has a rational basis for determining the types of information customarily held in confidence by it.
- 3) Public disclosure of the information is likely to cause substantial harm to the competitive position of TN Americas LLC, because the information consists of descriptions of the design and analysis of dry spent fuel storage systems, the application of which provide a competitive economic advantage. The availability of such information to competitors would enable them to modify their product to better compete with TN Americas LLC, take marketing or other actions to improve their product's position or impair the position of TN Americas LLC's product, and avoid developing similar data and analyses in support of their processes, methods or apparatus.
Further the deponent sayeth not.
Prakash Narayanan..
Chief Technical Officer
Subscribed a.J?:d sworn before me this ~ -th day of October 2022.
KHYNESYA TAYLOR
~~e? Notary Public Notary Public Howard County Maryland My Commission Expires J_jj_; _s_; _J/J_JS My Commission Expires Oct. 5, 2025
Page 1 of 1 Enclosure 2 to E-61677
Additional Information Regarding Clarification Questions Withheld Pursuant to 10 CFR 2.390
Enclosure 3 to E-61677
List of UFSAR Pages Involved in CoC 1042 Amendment 3, Revision 9
UFSAR Pages 1-16 1-17 4-91 4-92 4-106 4-107 9-4 9-8 9-11 9-12 9-20 13.A-22 A.2-9 A.2-20 A.9-3 B.4-26
Page 1 of 1 Enclosure 4 to E-61677
CoC 1042 Amendment 3, Revision 9 UFSAR Changed Pages Withheld Pursuant to 10 CFR 2.390
Enclosure 5 to E-616776
CoC 1042 Amendment 3, Revision 9 UFSAR Changed Pages (Public)
NUHOMS EOS System Updated Final Safety Analysis Report Rev. 4, 06/22
- 4. Fill TC/DSC Annulus with demineralized water and seal (Note that throughout the UFSAR, the term demineralized water includes any water that may be used for makeup to the reactor coolant system or spent fuel pool)
- 5. Fill DSC cavity with water (may be accomplished in step 6)
- 6. Lift TC and place in fuel pool
- 7. Load spent fuel, including top end caps/top lid if damaged or failed fuel is being loaded in the specified locations.
- 8. Place top shield plug
- 10. Seal inner top cover
- 11. Vacuum Dry and Backfill
- 12. Pressure test
- 13. Leak test
- 14. Seal outer top cover plate
- 16. Place loaded TC on transfer skid/trailer
- 17. Move loaded TC to EOS-HSM
- 18. Prepare and align TC/EOS-HSM
- 19. Insert DSC into EOS-HSM
- 20. Close EOS-HSM For operations (in sequence of occurrence) for the NUHOMS EOS System with the EOS-TC108 the following additional steps may be used to meet crane limits.
- Concurrent with Step 1 the TC108 neutron shield tank may be removed from the cask and positioned for installation onto the cask once it is loaded and removed from the fuel pool.
- Between Step 9 and Step 10, the neutron shield tank is reinstalled and filled with water.
October 2022 Revision 9 72-1042 Amendment 3 Page 1-16 NUHOMS EOS System Updated Final Safety Analysis Report Rev. 4, 06/22
These operations are described in the following paragraphs. The descriptions are intended to be generic and are described in greater detail in Chapter 9. Plant specific requirements may affect these operations and are to be addressed by the licensee.
Prepare TC:
Transfer cask preparation includes exterior washdown and interior decontamination.
These operations are performed on the decontamination pad/pit outside the fuel pool area. The operations are similar to those for a shipping cask, which are performed by plant personnel using existing procedures. For the TC108, this includes removing the neutron shield tank if required to meet crane capacity limits or cask loading space considerations.
Prepare DSC:
The internals and externals of the DSC are inspected and cleaned if necessary. This ensures that the DSC will meet plant cleanliness requirements for placement in the spent fuel pool. If the neutron shield tank is removed from the TC108, position the tank such that it can be installed onto the cask once the cask is loaded and removed from the fuel pool.
Insert bottom end caps and/or failed fuel canisters to specified locations
Bottom end caps are installed in specified locations if damaged fuel is being loaded.
Failed fuel canisters are installed in specified locations if failed fuel is being loaded.
Place DSC in TC:
The empty DSC is inserted into the TC.
Fill TC/DSC annulus with demineralized water and seal:
The TC/DSC annulus is filled with uncontaminated water and is then sealed prior to placement in the pool. This prevents contamination of the DSC outer surface and the transfer cask inner surface by the pool water.
Fill DSC cavity with water:
The DSC cavity is filled with pool water to prevent an in-rush of water as the transfer cask is lowered into the pool.
Lift TC and place in fuel pool:
The TC, with the water-filled DSC inside, is then lowered into the fuel pool. The TC125 and TC135 liquid neutron shield may be left unfilled to meet hook weight limitations.
October 2022 Revision 9 72-1042 Amendment 3 Page 1-17 NUHOMS EOS System Updated Final Safety Analysis Report Rev. 4, 06/22
EOS-37PTH DSC - Time Limits for Normal/Off-Normal Transfer Operations
Based on the results for Load Cases 8 and 10 in Section 4.5.3.2, steady-state transfer operations are permitted for the EOS-TC125 loaded with the EOS-37PTH DSC with heat loads 36.35 kW (HLZC 3).For heat loads > 36.35 kW and 50 kW (HLZCs 1 and 2), based on the results for Load Cases 1 and 3 in Section 4.5.3.1, steady-state transfer operations are not permitted, and a time limit of 14 hours1.62037e-4 days <br />0.00389 hours <br />2.314815e-5 weeks <br />5.327e-6 months <br /> is determined to complete both vertical and horizontal transfer operations.
At the end of the 14 hours1.62037e-4 days <br />0.00389 hours <br />2.314815e-5 weeks <br />5.327e-6 months <br /> transient transfer operation, the maximum fuel cladding temperature reaches 736 °F with sufficient margin to the fuel cladding temperature limit of 752 °F. However, to provide an additional margin and to ensure sufficient time for the initiation of recovery actions, a time limit of 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> is chosen for all transfer operations for heat loads > 36.35 kW and 50 kW (HLZCs 1 and 2). The maximum fuel cladding temperature at 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> after start of the transfer operations is 711 °F.
If transfer operations cannot be completed within the time limit of 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> and the TC/DSC is in a horizontal orientation, one of the recovery actions is to initiate air circulation within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> as noted in Technical Specifications [4-24].
If air circulation is initiated as a recovery option, it must be operated for a minimum duration of 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> to allow sufficient time for the TC/DSC components to cool down.
After 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> has elapsed with the blowers in operation, they can be turned off to complete the DSC transfer. The maximum fuel cladding temperature 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> after the air circulation is turned off is 737 °F, which has sufficient margin to the temperature limit of 752 °F as shown in Table 4-27. However, to provide additional margin, a time limit of 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> is chosen to complete the DSC transfer operations. The maximum fuel cladding temperature 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> after the air circulation is turned off is 733 °F, as shown in Table 4-27.
If air circulation cannot be initiated within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> of exceeding the 10-hour time limit specified in Table 4-31, the TC/DSC has to be returned to the cask handling area to be positioned in vertical orientation and then the TC/DSC annulus will be filled with demineralized water. As specified in the Actions for LCO 3.1.3 of the Technical Specifications [4-24], a total of 5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> is available to complete Action A.2 and Action A.3 of the LCO 3.1.3 with a maximum duration of 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> for Action A.2. The following evaluation considers the maximum duration allowed for Action A.2 (1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />) and the remaining duration of 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> allowed for Action A.3. However, in this instance, the total time from the beginning of transfer operations is 15 hours1.736111e-4 days <br />0.00417 hours <br />2.480159e-5 weeks <br />5.7075e-6 months <br /> as shown below.
Total Time for Transfer = T1 + T2 + T3 = 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> + 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> + 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> = 15 hours1.736111e-4 days <br />0.00417 hours <br />2.480159e-5 weeks <br />5.7075e-6 months <br />
where:
T1 = Transfer Time Limit after draining the water from the TC/DSC annulus
= 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> (See Table 4-31)
October 2022 Revision 9 72-1042 Amendment 3 Page 4-91 NUHOMS EOS System Updated Final Safety Analysis Report Rev. 4, 06/22
T2 = Time to Initiate Air Circulation = 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> (See Technical Specification)
T3 = Time to move the TC/DSC into the cask handling area to be positioned in Vertical orientation and to fill the TC/DSC annulus with demineralized water =
4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> (See Technical Specification)
It is very unlikely that air circulation cannot be initiated because of the redundant nature of the air circulation system, which includes redundant blower and power systems. Further, the entire air circulation system is assembled and verified to operate prior to transfer operation as indicated in the Technical Specifications [4-24] and in Chapter 9, Section 9.1.5.
In the extremely unlikely event that air circulation cannot be initiated, the 15 hours1.736111e-4 days <br />0.00417 hours <br />2.480159e-5 weeks <br />5.7075e-6 months <br /> duration to complete the refilling of the TC/DSC annulus with water exceeds the 14 hours1.62037e-4 days <br />0.00389 hours <br />2.314815e-5 weeks <br />5.327e-6 months <br /> considered for Load Case 1 and 3 (See Table 4-24). The result of transient analysis presented in Table 4-24 for Load Case 1 shows that the fuel cladding temperature is 724 °F at 12 hour1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> into the transfer operation and increases to 736 °F after an additional 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />. This shows that the fuel cladding temperature increases at most by 6 °F per hour during the transfer operation. Based on this information, the maximum fuel cladding temperature at the end of 15 hours1.736111e-4 days <br />0.00417 hours <br />2.480159e-5 weeks <br />5.7075e-6 months <br /> is:
Tmax,Fuel,15 hrs = Tmax,Fuel,14 hrs + T/hour = 736 °F + 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />
- 6 °F/hour = 742 °F
where:
Tmax,Fuel,14 hrs = Maximum temperature at the end of 14 hours1.62037e-4 days <br />0.00389 hours <br />2.314815e-5 weeks <br />5.327e-6 months <br /> into transfer operation
= 736 °F from Table 4-24 @ 14 hours1.62037e-4 days <br />0.00389 hours <br />2.314815e-5 weeks <br />5.327e-6 months <br /> for Load Case 1 Tmax,Fuel,12 hrs = Maximum temperature at the end of 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> into transfer operation
= 724 °F from Table 4-24 @ 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> for Load Case 1 T/hour = Temperature Increase per hour
= 6 °F (Tmax,Fuel,14 hrs - Tmax,Fuel,12 hrs / 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> = 6 °F/ hour)
Even for this worst-case condition, the maximum fuel cladding temperature remains below the allowable limit of 752 °F. In addition to the fuel cladding temperature, a review of the maximum temperatures in Table 4-24 shows large margins for other TC components. Therefore, the temperature limits specified for the TC/DSC in Section 4.2 will be satisfied for this condition.
October 2022 Revision 9 72-1042 Amendment 3 Page 4-92 NUHOMS EOS System Updated Final Safety Analysis Report Rev. 4, 06/22
Impact of Helium Injection on TC/DSC Annulus Water Temperature
Once the vacuum drying requirements per TS LCO 3.1.1 are satisfied, the DSC is pressurized up to 23 psig with helium as noted in Step 19 of Section 9.1.2 which increases the TC/DSC annulus water temperature.
October 2022 Revision 9 72-1042 Amendment 3 Page 4-106 NUHOMS EOS System Updated Final Safety Analysis Report Rev. 4, 06/22
TC/DSC Annulus Water Replenishment Requirements
The rate of evaporation within the TC/DSC annulus assuming all the heat is dissipated through the water can be calculated as:
where, Q = Heat Load of the DSC = 50 kW (Multiply by 3412.3 to convert to Btu/hr)
L = Latent heat of vaporization = 970.3 Btu/lbm 1 gallon of water is 8.34 lbm
A continues flow of fresh demineralized water with a flow rate of 0.35 gpm into the TC/DSC annulus for highest heat load of 50 kW will ensure that the fuel cladding temperature and the DSC component temperatures will remain bounded by the calculated temperatures in Section 4.5.11.
October 2022 Revision 9 72-1042 Amendment 3 Page 4-107 NUHOMS EOS System Updated Final Safety Analysis Report Rev. 4, 06/22
- 5. Remove the TC top cover plate and examine the TC cavity for any physical damage and ready the TC for service.
Note: Verify that a TC spacer of appropriate height is placed inside the TC to provide the correct airflow and interface at the top of the TC during loading, drying, and sealing operations for DSCs that are shorter than the TC cavity length.
- 6. Verify specified lubrication of the TC rails.
- 7. Examine the DSC for any physical damage that might have occurred since the receipt inspection was performed. The DSC is to be cleaned and any loose debris removed.
- 8. Record the DSC serial number that is located on the grapple ring. Verify the DSC type and basket type against the DSC serial number. Verify that the DSC is appropriate for the specific fuel loading campaign per the criteria specified in Section 2.1 (EOS-37PTH DSC) or Section 2.2 (EOS-89BTH DSC) of the Technical Specifications [9-5].
- 9. Using a crane, lower the DSC into the TC cavity by the internal lifting lugs and rotate the DSC to match the TC and DSC alignment marks.
- a. If damaged FAs or loaded failed fuel canisters (FFCs) are included in a specific loading campaign, verify that the appropriate basket type is used and place the required number of bottom end caps provided for damaged fuel or FFCs into the cell locations per Technical Specification 2.1. Optionally, this step may be performed at any prior time.
- b. Verify that the fuel spacers, if required, are present in the fuel cells.
Optionally, this step may be performed at any prior time.
- 10. Fill the TC/DSC annulus with demineralized water. Place the inflatable seal into the upper TC liner recess and seal the TC\\DSC annulus by pressurizing the seal with compressed air. The term demineralized water throughout the UFSAR includes any water that may be used for makeup to the reactor coolant system or spent fuel pool.
Note: A TC/DSC annulus pressurization tank filled with demineralized water is connected to the top vent port of the TC via a hose to provide a positive head above the level of water in the TC/DSC annulus. This is an optional arrangement, which provides additional assurance that contaminated water from the fuel pool will not enter the TC/DSC annulus, provided a positive head is maintained at all times.
- 11. Fill the DSC cavity with water from the fuel pool or an equivalent source that meets the requirements of Section 3.2.1 of the Technical Specifications [9-5] for boron concentration, if applicable.
October 2022 Revision 9 72-1042 Amendment 3 Page 9-4 NUHOMS EOS System Updated Final Safety Analysis Report Rev. 4, 06/22
9.1.3 DSC Drying and Backfilling
CAUTION: During performance of steps listed in Section 9.1.3, monitor the TC/DSC annulus water level and replenish if necessary. Boiling of TC/DSC annulus water is expected at high heat loads. Consider adding demineralized water from the top continuously and ensure that a portion of the TC/DSC annulus is open to atmosphere to allow water vapor to escape. A water flow rate of 0.35 gpm is recommended. The flow rate may be adjusted as required to ensure the water remains approximately twelve inches below the top edge of the DSC shell. In addition, a feed and bleed system with continuous flow of fresh water can also be used to control the boiling of annulus water for high heat load systems.
- 1. Place scaffolding around the TC so that any point on the surface of the TC is easily accessible to personnel. Decontaminate the exterior surfaces of the TC.
Temporary shielding may be installed as necessary to minimize personnel exposure.
- 2. Decontaminate the exposed surfaces of the DSC shell perimeter and the exposed annulus area of the TC; remove the inflatable TC/DSC annulus seal.
- 3. Connect the TC drain line to the TC, open the TC cavity drain port and allow water from the TC/DSC annulus to drain out until the water level is approximately twelve inches below the top edge of the DSC shell. Take swipes around the outer surface of the DSC shell and the exterior surfaces of the TC, and check for smearable contamination in accordance with Section 3.3.1 of the Technical Specification [9-5] limits.
CAUTION: Radiation dose rates are expected to be high at the drain and vent port locations. Use proper ALARA practices (e.g., use of temporary shielding, appropriate positioning of personnel, etc.) to minimize personnel exposure.
- 4. Prior to the start of welding operations, drain a minimum of 60 gallons of water from the DSC back into the fuel pool or other suitable location using the vacuum drying system (VDS) or an optional liquid pump. Alternatively, all the water from the DSC may be drained if precautions are taken to keep the occupational exposure ALARA. Consistent with ISG-22 [9-6] guidance and Technical Specification 3.1.1, helium at 1-3 psig is used to backfill the DSC with an inert gas (helium) as water is being removed from the DSC. Helium must be used to fill the space above the water inside the DSC.
Note: The tool for engaging the DSC internal drain tube may contain o-rings.
The o-rings may be lubricated. If up to two o-rings come off the tool inside the DSC cavity, loading operations may continue. This is evaluated in Chapter 8, Section 8.2.12.
- 5. Place the inner top cover plate (ITCP) onto the DSC. Verify proper fit-up of the ITCP with the DSC shell. Install the welding machine onto the ITCP.
October 2022 Revision 9 72-1042 Amendment 3 Page 9-8 NUHOMS EOS System Updated Final Safety Analysis Report Rev. 4, 06/22
- 19. Pressurize the DSC with helium to more than 18 psig, but do not exceed 23 psig and hold for 10 minutes. This pressure test may instead be performed after the second evacuation performed in Step 24.
Note: This is the ASME Code NB-6300 pressure test required per Section 4.4.4 of the Technical Specifications [9-5]. As provided in the Code alternative to NB-6324, the examination for leakage associated with the pressure test is performed via helium leak test method in Step 4 of Section 9.1.4.
- 20. NOT USED.
- 21. NOT USED.
- 22. Depressurize the DSC cavity by releasing the helium through the VDS to the plants spent fuel pool or radioactive waste system.
- 23. Seal weld the prefabricated plug over the vent port and perform root and final dye penetrant weld examinations in accordance with Section 4.4.4 of the Technical Specifications [9-5].
- 24. Re-evacuate the DSC cavity using the VDS. The cavity pressure should be reduced to between 3 and 0.75 mm Hg.
CAUTION: The addition of Helium into the DSC cavity will increase the temperature of water in the TC/DSC annulus. Therefore, continuously monitor the TC/DSC annulus for boiling while Helium is added to the DSC and add demineralized water continuously as required. A water flow rate of 0.35 gpm is recommended during the helium backfill. The flow rate may be adjusted as required to ensure the water remains approximately twelve inches below the top edge of the DSC shell. Ensure that a portion of the TC/DSC annulus is open to atmosphere to allow water vapor to escape. In addition, a feed and bleed system with continuous flow of fresh water can also be used to control the boiling of annulus water.
- 25. Open the valve allow helium to flow into the DSC cavity to pressurize the DSC to 2.5 +/- 1 psig and confirm stable for 30 minutes after filling in accordance with Section 3.1.2 of the Technical Specification [9-5] limits.
- 26. Close the valves on the helium source.
- 27. Decontaminate as necessary.
October 2022 Revision 9 72-1042 Amendment 3 Page 9-11 NUHOMS EOS System Updated Final Safety Analysis Report Rev. 4, 06/22
9.1.4 DSC Sealing Operations
CAUTION: During the performance of steps listed in Section 9.1.4, monitor the TC/DSC annulus water level and replenish, as necessary, to maintain cooling. Boiling of TC/DSC annulus water is expected at high heat loads. Consider adding demineralized water from the top continuously and ensure that a portion of the TC/DSC annulus is open to atmosphere to allow water vapor to escape. A water flow rate of 0.35 gpm is recommended. The flow rate may be adjusted as required to ensure the water remains approximately twelve inches below the top edge of the DSC shell. In addition, a feed and bleed system with continuous flow of fresh water can also be used to control the boiling of annulus water for high heat load systems.
- 1. Disconnect the VDS from the DSC. Seal weld the prefabricated cover plate over the drain port, inject helium into blind space just prior to completing welding, and perform root and final dye penetrant weld examinations in accordance with Section 4.4.4 of the Technical Specification [9-5] requirements.
- 2. Temporary shielding may be installed as necessary to minimize personnel exposure. Place the outer top cover plate (OTCP) onto the DSC. Verify proper fit up of the OTCP with the DSC shell. Install the welding machine onto the OTCP.
- 3. Tack weld the OTCP to the DSC shell. Place the OTCP weld. If the weld will be inspected by multi-layer PT, place only the root pass.
- 4. Helium leak test the inner top cover plate and vent/drain port plug/plate welds using the leak test port in the OTCP in accordance with Sections 4.4.4 and 5.1.2.f of the Technical Specification [9-5] limits. Verify that the personnel performing the leak test are qualified in accordance with SNT-TC-1A [9-3]. Alternatively, this can be done with a test head prior to installing and welding the OTCP. The use of a test head is recommended when the outer top cover will be welded by single pass HA-GTAW.
- 5. If a leak is found, remove the OTCP weld, the drain port cover and vent port plug welds, and repair the ITCP welds. Repeat procedure steps from Section 9.1.3 Step 14.
- 6. Perform dye penetrant examination of the OTCP root pass weld. Weld out the OTCP to the DSC shell. Perform root and multilayer dye penetrant examination in accordance with Section 4.4.4 of the Technical Specifications [9-5]. The OTCP-to-shell weld may instead be examined by UT per Section 4.4.4 of the Technical Specifications [9-5].
- 7. Seal weld the prefabricated plug over the OTCP test port and perform root and final dye penetrant weld examinations.
- 8. Remove the welding machine from the DSC.
October 2022 Revision 9 72-1042 Amendment 3 Page 9-12 NUHOMS EOS System Updated Final Safety Analysis Report Rev. 4, 06/22
CAUTION: Monitor the applicable time limits determined for the unloading operation in Step 11, Section 9.2.1 above, or Step 16 of Section A.9.2.1, until the TC/DSC Annulus is filled with water in Step 12 of Section 9.2.2. If the time limits for unloading cannot be met, initiate forced cooling. Boiling of TC/DSC annulus water is expected at high heat loads. Consider adding water from the top and ensure that a portion of the TC/DSC annulus is open to atmosphere to allow water vapor to escape. In addition, a feed and bleed system with continuous flow of fresh water can also be used to control the boiling of annulus water for high heat load systems.
- 1. Transfer the loaded TC from the ISFSI to inside the plant's fuel or reactor building along the designated transfer route.
- 2. Position and ready the trailer for access by the crane. The trailer is supported on the vertical jacks.
- 3. If required to meet crane weight limits, replace steel TC cover plate with the aluminum TC cover plate.
- 4. Attach the TC lifting yoke to the crane hook. Then engage the TC lifting yoke with the trunnions of the TC on the transfer trailer.
- 6. Lift the TC approximately one inch off the saddle supports. Verify that the yoke lifting arms are properly positioned on the trunnions.
- 7. Move the crane in a horizontal motion while simultaneously raising the crane hook vertically and lift the TC off the trailer. Move the TC to the TC designated area.
- 9. Clean the TC, if needed, to remove any dirt that may have accumulated on the TC during the DSC loading and transfer operations.
- 10. Place scaffolding around the TC.
- 11. Unbolt the TC cover plate and remove it.
- 12. Install temporary shielding to reduce personnel exposure as required. Fill the TC/DSC annulus with demineralized water. Place an inflatable seal into the upper TC liner recess and seal the TC\\DSC annulus by pressurizing the seal with compressed air.
- 13. Provide suitable protection for the TC during cutting operations.
October 2022 Revision 9 72-1042 Amendment 3 Page 9-20 NUHOMS EOS System Updated Final Safety Analysis Report Rev. 4, 06/22
B.3.3 RADIATION PROTECTION
B.3.3.1 DSC and TRANSFER CASK (TC) Surface Contamination
BASES
BACKGROUND Since the TC with DSC in its interior is placed in the spent fuel pool in order to load the spent fuel assemblies, the exterior of the surface of the TC and the outer top surface of the DSC may become contaminated from radioactive material in the spent fuel pool water. The TC/DSC annulus is filled with demineralized water and sealed prior to placement in the spent fuel pool; therefore, only the outer top 1-foot surface of the DSC and the exterior surfaces of the TC are susceptible to contamination by the water from the spent fuel pool. After placing the top shield plug onto the DSC, the loaded DSC with TC is lifted out of the pool into the decontamination area. The outer surface of the TC is decontaminated. The TC/DSC annulus area is decontaminated and the annulus seal is subsequently removed. After the draining of the TC/DSC annulus until the water level is approximately twelve inches below the top edge of the DSC shell, the DSC smearable surface contamination on the outer top 1-foot surface of the DSC and the exterior surface of the TC are checked. Contamination on these surfaces is removed to a level that is as low as reasonably achievable (ALARA) and below the LCO limits in order to minimize radioactive contamination to personnel and the environment.
APPLICABLE This radiation protection measure assures that the surfaces of the TC SAFETY and the DSC have been decontaminated. This keeps the dose to ANALYSYS occupational personnel ALARA.
LCO The contamination limits on the outer top 1-foot surface of the DSC and the exterior surface of the TC are based on the allowed removable external radioactive contamination specified for spent fuel shipping containers in 49 CFR 173.443 (as referenced in 10 CFR 71.87(i)). Consequently, these contamination levels are considered acceptable for exposure to the general environment. This level will also ensure that the contamination levels of the inner surfaces of the HSM and potential releases of radioactive material to the environment are minimized. In addition, the NUHOMS EOS storage system provides significant additional protection for the DSC surface than the transportation configuration. The HSM will protect the DSC from direct exposure to the elements and will, therefore, limit potential releases of removable contamination. The probability of any removable contamination being entrapped in the HSM airflow path released outside the HSM is considered extremely small.
October 2022 Revision 9 72-1042 Amendment 3 Page 13.A-22 NUHOMS EOS System Updated Final Safety Analysis Report Rev. 4, 06/22
Structural Design
In accordance with ASME NOG-1, the MX-LC is classified as a Type I crane, since it is used to handle a critical load. It is designed to retain control of and hold the load during and after a design basis seismic event. The design includes the stress analysis of the structural elements of the MX-LC and their connections, as well as a stability analysis to demonstrate that the MX-LC will not experience significant sliding or tipping under seismic loading.
For these seismic analyses, a pair of wheel chocks is provided for each of the four gantry boxes to restrain the gantry lower boom from sliding under seismic loading.
Retention brackets are also provided at each gantry box to prevent the wheels from leaving the rails during a seismic event. Connections between the upper boom and face of the HSM-MX are provided when in the raised configuration for loading the upper compartments, and a connection between the transfer skid and HSM-MX is also provided. The MX-LC upper boom assembly has four telescoping sections which are braced with viscous dampers to accommodate earthquake loads.
Seismic loads imposed on the MX-LC consider ground motions due to a safe shutdown earthquake (SSE) applied in all three orthogonal directions. The ground motions correspond to the enhanced RG 1.60 response spectrum [A.2-13] scaled to a ZPA of 0.3g in both the horizontal and vertical directions. The mass considered during a seismic event is the distributed mass of the MX-LC and the credible critical load. A structural damping value less than 7% can be conservatively applied for the seismic design of the MX-LC in lieu of 7% damping required in Section 4153.8 of NOG-1.
The structural evaluation of the MX-LC during lifting of the loaded transfer cask is performed for the load combinations specified in ASME NOG-1, Subsection 4140.
The credible critical load of 162 tons is combined with the crane deadload and SSE load for the most limiting extreme environmental load combination. Four configurations are considered for the MX-LC, with the upper boom both in the lowered and raised positions, and with the lift link assemblies both in the fully extended and fully retracted positions. The raised position governs the design due to the higher center of gravity for the load relative to the MX-LC structure.
October 2022 Revision 9 72-1042 Amendment 3 Page A.2-9 NUHOMS EOS System Updated Final Safety Analysis Report Rev. 4, 06/22
A.2.1.4.2.2 MX-RRT The MX-RRT is part of the NUHOMS transfer equipment and is a device used to support the DSC, during transfer operations. There are two MX-RRT beams inserted into opposing channels below the DSC opening on the HSM-MX. Each of the MX-RRT beams are removed upon completion of the loading operation and replaced with the HSM-MX shield door shielding blocks. The MX-RRT is designed in accordance with ASME B30.1 [A.2-15] as a combination power-operated jack with industrial rollers. For the seismic analysis of the MX-RRT, a damping value of 4% is used for welded steel structures per NRC Reg. Guide 1.61 [A.2-16]. Structural acceptance criteria of the MX-RRT is in accordance with ASME NOG-1 [A.2-7]. In addition, the MX-RRT is engineered as single-failure-proof per NUREG-0612
[A.2-9]. The MX-RRT function is twofold, one to accept the DSC during its insertion and second, to lower the DSC onto its permanent pillow blocks within the HSM-MX.
The MX-RRT is a Part 72 ITS piece of transfer equipment. The MX-RRT is considered ITS as it supports the DSC during its insertion and extraction both into and out of the HSM-MX, respectively, thus providing both a structural and retrieval function.
A.2.1.4.2.3 MX-RRT Handling Device The MX-RRT handling device is part of the NUHOMS Transfer Equipment and is a device used to allow insertion and extraction of the MX-RRT and the HSM-MX shield door shielding blocks. This is a NITS piece of equipment since it does not provide a safety function feature for the HSM-MX.
A.2.1.5 Auxiliary Equipment
No change to Section 2.1.5.
October 2022 Revision 9 72-1042 Amendment 3 Page A.2-20 NUHOMS EOS System Updated Final Safety Analysis Report Rev. 4, 06/22
- 3. Inspect the DSC, and MX-RRT support pads inside HSM-MX compartment.
- 4. For ALARA purposes, reinstall the HSM-MX door.
- 5. Inspect the HSM-MX air inlet and outlets to ensure that they are clear of debris. Inspect the screens on the air inlet and outlets for damage.
CAUTION: The insides of empty compartments have the potential for high dose rates due to adjacent loaded compartments. Proper ALARA practices should be followed for operations inside these compartments and in the areas outside these compartments whenever the MX-RRT operations are being performed.
- 6. Remove the MX-RRT cover plates and shield plugs.
- 7. Insert and install MX-RRT into HSM-MX. Extend the MX-RRT rollers, secure and verify that the rollers are extended.
- 8. Transport the TC from the plant's fuel/reactor building to the ISFSI along the designated transfer route.
- 9. Once at the ISFSI, move the transfer trailer inside the MX-LC at home position between the skid and the MX-LC grappling mechanism.
- 10. Use the MX-LC grappling mechanism to capture the skid along with TC, disengage the skid positioning system, move the skid up in the vertical direction to clear it from the transfer trailer, and then the transfer trailer is moved from MX-LC.
- 11. Remove the FC system, and install the ram cylinder assembly.
11a. If the HSM-MX upper compartment is to be loaded, install the MX-LC brackets to the embedments on each adjacent HSM-MX module.
- 12. Remove the HSM-MX door.
- 13. Unbolt and remove the TC top cover plate.
- 14. Move MX-LC along the rail in front of HSM-MX until the TC is completely against the face of HSM-MX.
- 15. The skid is moved until the target compartment is reached. If necessary, adjust the MX-LC position until the MX-LC is properly aligned with the targeted compartment. For alignment with the HSM-MX upper modules, the MX-LC Chocks may be temporarily adjusted by no greater than 1/4" while performing lateral alignment of the TC.
- 16. Secure the MX-LC/skid/cask to the front wall embedments of the HSM-MX using the restraints.
October 2022 Revision 9 72-1042 Amendment 3 Page A.9-3 NUHOMS EOS System Updated Final Safety Analysis Report Rev. 4, 06/22
B.4.5.1.3.3 Accident Transfer
There is no change to the accident transfer thermal results presented in Appendix T.4, Section T.4.5.3.3 of [B.4-2].
Based on the discussion in Appendix T.4, Section T.4.5.3.3 of [B.4-2], loss of neutron shield is the bounding accident condition. Table T.4-10 of [B.4-2] presents the peak component temperatures achieved under this accident at steady-state conditions.
B.4.5.1.4 Evaluation of OS197FC-B TC Performance
There is no change to the evaluation presented in Appendix T, Section T.4.5.4 of
[B.4-2] on the thermal performance of the OS197FC-B TC for normal, off-normal, and accident conditions of operation when heat loads are less than or equal to 22 kW.
For heat loads > 22kW and 31.2 kW, the transfer time limits of 26 hours3.009259e-4 days <br />0.00722 hours <br />4.298942e-5 weeks <br />9.893e-6 months <br /> and 13 hours1.50463e-4 days <br />0.00361 hours <br />2.149471e-5 weeks <br />4.9465e-6 months <br /> specified in Appendix T.4.5.4 of [B.4-2] are based on a 2 hour2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> recovery time.
However, to be consistent with the EOS-37PTH and EOS-89BTH DSCs the recovery time to complete the various action statements in LCO 3.1.3 of the Technical Specifications [B.4-3] is increased by 3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> to a total of 5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> with corresponding reduction in the transfer time limits. Therefore, the time limits for EOS-61BTH DSC are reduced to 23 hours2.662037e-4 days <br />0.00639 hours <br />3.80291e-5 weeks <br />8.7515e-6 months <br /> and 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> based on the HLZC.
Based on the discussion in Section 4.5.4, if air circulation cannot be initiated within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> after exceeding the transfer time limit, the TC/DSC has to be returned to the cask handling area to be positioned in vertical orientation and then the TC/DSC annulus will be filled with demineralized water. As discussed in Section 4.5.4, a total of 5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> is available to complete Action A.2 and Action A.3 of the LCO 3.1.3 of the Technical Specifications [B.4-3] with a maximum duration of 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> for Action A.2.
The allowable duration for the transfer operations (defined as from the time when the water in the TC-DSC annulus is drained to when the DSC is loaded into the storage module) will vary depending only on the DSC type and the heat load configuration.
For simplicity of operations, a single time limit is used for all ambient conditions and TC orientations (i.e., longer times are available for the non-controlling conditions).
The following table summarizes the permissible operational conditions:
DSC Heat Load Zoning Configuration Transfer Time Limit (1), (2) (4)
HLZCs 1, 2,3, 4 and 9 (5) ( 22 kW) No time limit HLZCs 5, 6 ( 31.2 kW) 23.0 Hours (3)
HLZCs 7, 10 (5) ( 31.2 kW) 10.0 Hours (3)
HLZC 8 ( 27.4 kW) 23.0 Hours (3)
Notes:
(1) Transfer time is defined as from the time when the TC/DSC annulus water is drained to when the DSC is loaded into the storage module.
(2) The listed allowable transfer times are valid for all ambient conditions and TC orientations.
(3) Initiate recovery operations such as air circulation if the operation time exceeds the limit per LCO 3.1.3 of Technical Specifications [B.4-3].
(4) The transfer operation time limit is reset only if the transfer cask annulus is refilled with water.
(5) Thermal evaluation of 61BTH DSC for HLZCs 9 and 10 is presented in Section T.4.6.10 of [B.4-2].
October 2022 Revision 9 72-1042 Amendment 3 Page B.4-26 Enclosure 6 to E-61677 Listing of Computer Files Contained in Enclosure 7
Disk ID No. Discipline System/Component File Series (topics) Number (size) of Files Enclosure 7 Section 4.5.11
Input and output files for the bounding loading One condition of EOS-37PTH DSC in EOS-TC125 with Computer 50 kW. Th ese file s pertain to the desig n basis Hard Drive steady-state thermal evalu atio n dis cussed in
- 37PTH DSC in Sectio n 4.5.11, and the result s presented in Ta ble Thermal EOSEOS-TC125 4-32. 12
- Subfolder HLZC1_Loading Thermal (2.11 GB)
Page 1 of 1 Enclosure 7 to E-61677
Computer Files Associated with Certificate of Compliance 1042 Amendment 3, Revision 9 Withheld Pursuant to 10 CFR 2.390
Enclosure 8 to E-61677
Additional Clarifications Not Associated with the Thermal and Materials Clarifications
TN Americas LLC is providing additional changes to the proposed Amendment 3 Updated Final Safety Analysis Report (UFSAR ) that are not related to the Thermal and Materials Clarifications.
The requested changes are discussed in the following sections of this enclosure and include a description of the change and a summary of the impact on the UFSAR.
- 1. MX-LC Chocks
Description:
In order for a proper alignment of the MX -L C with the upper HSM -MX modules, the MX-LC chocks may need to be temporarily adjusted by no greater than 1/4 inch during the lateral alignment process.
- UFSAR Impact: A sentence is added to UFSAR Chapter A.9, Step A.9.1.6.15 to allow operators to temporarily adjust the MX-L C Chocks during the lateral alignment process.
- 2. MX-LC and the MX -Retractable Roller Tray Damping Value
Description:
Provide the clarification in the UFSAR that the structural damping value used in the seismic analysis for the MX-LC may be conservatively applied at less than the 7%
damping value specified per Section 4153.8 of ASME NOG-1. Provide the clarification in the UFSAR that the structural damping value used in the seismic analysis for the retractable roller tray (MX-RRT) is 4%, per NRC Reg. Guide 1.61 for welded steel structures.
Page 1 of 1 Enclosure 9 to E-61677 Additional Information Regarding Clarification Questions - Public
As follow-up to the clarification calls with the NRC on September 15, 2022 and September 28, 2022, TN is providing the following additional information.
Materials Clarification Question #1:
With respect to the Materials clarification question and discission, the following is provided in regards to the term clean water used in the UFSAR.
The term clean water, when referring to the water in the TC/DSC annulus, is changed throughout the UFSAR to demineralized water. The annulus is filled initially with demineralized water and is also replenished with demineralized water in the case of water evaporation.
Discussions with various NRC licensees have also yielded the term primary grade water that is used interchangeably. Primary grade water is also used in the nuclear reactor coolant system.
As such, rather than limiting the licensees to strictly water termed demineralized water, which does not have a specific standard or definition, the UFSAR has been updated to allow for the term demineralized water to also include any water that is used for make -up to the reactor coolant system or spent fuel pool to be used in the DSC/TC annulus for both initial fill and replenishing. The water source for demineralized water is monitored as it pertains to the impact to the reactor coolant system and spent fuel pool which are regularly analyzed for conductivity, silica, pre-and post-ultraviolet (UV) chlorides and sulfates, total organic carbon (TOC) and gamma activity.
From operating experience, the annulus is typically replenished once per loading. The worst-case known scenario occurred when the field services operators had prepared the DSC/TC for transfer to the HSM, but transfer was delayed until the morning shift due to extreme weather conditions. The loaded DSC/TC sat overnight. During this time, operators continuously monitored the water level. The annulus was replenished twice during that shift, adding about 2 inches each time for a total of about 3 to 4 inches.
Prior to DSC transfer, the water in the annulus is completely drained; therefore, any contaminants that may exist in the water are removed each time the TC is used. The annulus is filled with water for only four days of the loading, and only one of those days involves fuel in the basket. This is not sufficient time to corrode the inner surface of the TC/outer surface of the DSC before draining. Additionally, the water is sampled when drained to ensure contaminant levels are below effluent limits. Any instances of high contaminants would be detected and addressed during this sampling. Since the draining occurs each loading, is refilled within two to three days later for the next DSC loading, and is decontaminated after each campaign, there is not sufficient time for the corrosion to occur.
Impact:
UFSAR Sections 1.2.3.1, 4.5.4, 9.1.1, 9.2.2, Chapter 13 Appendix A, B.3.3.1, and B.4.5.1.4 have been revised based on the discussion above.
Page 1 of 5 Enclosure 9 to E-61677 Additional Information Regarding Clarification Questions - Public
Thermal Clarification Question #1:
With respect to the first Thermal clarification question and discussion, the following update is provided. This update is presented in three parts.
Part 1 presents the the impact of helium injection on the TC/DSC annulus water temperature and also provides the background of rapid boiling observed at Davis Besse for DSC #009.
Part 2 presents a discussion on the uncertainty in the boiling correlations and provides an alternate approach to estimating the temperature difference between the water and the DSC surface.
Part 3 presents a discussion on the minimum flow rate required to be maintained to control any potential unforseen boiling.
Part 1: Impact of Helium Injection on the TC/DSC Annulus Water Temperature
Part 1A: DSC #009 at Davis Besse
During vacuum drying operations for DSC #009, stable vacuum pressures could not be maintained when the DSC was valved off from the vacuum pump. After attempting to vacuum-dry the DSC for many hours, and system troubleshooting (inspection for leaks), it was determined that the DSC cavity should be returned to atmospheric pressure and a suspect fitting/tool replaced. When helium was rapidly introduced into the DSC cavity to bring the DSC to atmospheric pressure, the temperature of the demineralized water in the DSC/TC annulus increased so that rapid boiling occurred in the annulus.
Page 2 of 5 Enclosure 9 to E-61677 Additional Information Regarding Clarification Questions - Public
Part 1B: Design Basis DSC at 50 kW
To mitigate the issue identified at Davis Besse, TN Americas LLC (TN) revised the operating procedure in the UFSAR to limit the lowest internal pressure within the DSC during vacuum drying operations to 0.75 Torr. Step 17 of Section 9.1.2 of the UFSAR clarifies this limit to the general licensees. This ensures that the thermal conductivity is maintained within the DSC during vacuum drying operations and eliminates the large temperature differential that was observed in DSC #009 that resulted in rapid boiling.
New Section 4.5.11.1 of the revised UFSAR presents a discussion on the impact of helium injection on the TC/DSC annulus water temperature.
Part 2: Uncertainty in the Boiling Correlations
The heat transfer correlation presented in Section 4.5.11 to estimate the temperature difference between the DSC shell and the water is a widely used equation to evaluate pool boiling. Based on the discussion in Section 10.2.2 of [2], this equation is dependent on the Prandtl number of the saturated liquid and the empirical constant for the surface. Since the Prandtl number for saturated water is well established, the empirical constant is the primary source of uncertainty.
As shown in Table 10.1 of [2], the highest value among the various surface finishes of water on stainless steel is used to estimate the temperature difference. This results in a conservative estimate of the temperature difference between the saturated water and the surface.
To compare this temperature difference, an alternate equation proposed by Collier as noted in Section 10.2.2 of [2] is used. Based on Equation 10.3, Section 10.2.2 of [2], the temperature difference can be estimated as:
1/3.33 q"
= T X 0.17 1.2 103.33 pp p 0.000481 1.8 4 10p pp p2.3 ++
cr cr cr cr C= 5.72 °F = 3.18 °
- where,
XT = Excess Temperature ( ° C)
p = Operating pressure (atm) = 1 atm
pcr = Critical pressure of water (atm) = 218.3 atm (see Table II, f - 90 of [3])
q " = Heat flux from DSC outer shell = 1,878 W/m 2
Page 3 of 5 Enclosure 9 to E-61677 Additional Information Regarding Clarification Questions - Public
The temperature difference between the saturated water and the DSC surface based on this alternative approach also provides additional assurance that any potential boiling will remain within the natural convection or nucleate boiling regime.
Part 3: TC/DSC Annulus Water Replenishment Requirements
Detailed feed and bleed instructions were not included, as this is one of the recommended approaches in addition to a feed option typically used to monitor the TC/DSC annulus water level. However, to provide additional guidance, Chapter 9 of the UFSAR has been updated to provide guidance on the flow rate to be maintained continuously based on the maximum heat load. New Section 4.5.11.2 of the revised UFSAR presents the flow rate to ensure a continuous stream of cold demineralized water to dissipate the heat.
In addition, similar procedures are employed in other systems. Step 7 of Section 9.2.3 [ 4]
provides a procedure similar to the caution statements provided in Chapter 9 of the UFSAR regarding boiling.
References
TN Calculation, Thermal Evaluation of EOS-37PTH DSC in EOS-TC125 During Vacuum Drying Process for the 2019 Davis-Besse Dry Cask Storage Loading Campaign, 503948-0405, Revision 1.
Kreith, Bohn, Principles of Heat Transf er, 4th Edition, 1986
Weast, Astle, CRC Handbook of Chemistry and Physics, 61st Edition, 1980- 1981.
HI-STORM FW System FSAR - Non-Proprietary, Rev.6, June 2019
Impact:
UFSAR Sections 4.5.11.1 and 4.5.11.2 have been added as discussed above. UFSAR Section 9.1 has been revised as discussed above.
Page 4 of 5 Enclosure 9 to E-61677 Additional Information Regarding Clarification Questions - Public
Thermal Clarification Question #2 :
With respect to the second Thermal clarification question and discussion, the following update is provided:
References
TN Calculation, Thermal Evaluation of EOS-37PTH DSC in EOS-TC125 During Vacuum Drying Process for the 2019 Davis -Besse Dry Cask Storage Loading Campaign, 503948-0405, Revision 1.
USNRC, Davis Besse Nuclear Power Station - Integrated Inspection Report 05000346/2021002 AND 07200014/2021001, August 12, 2021. (Adams # ML21224A237)
Impact:
UFSAR Sections 4.5.11.1 and 4.5.11.2 have been added as discussed above.
Page 5 of 5