ML21223A050
| ML21223A050 | |
| Person / Time | |
|---|---|
| Site: | Holtec |
| Issue date: | 08/11/2021 |
| From: | Holtec |
| To: | Office of Nuclear Material Safety and Safeguards |
| Shared Package | |
| ML21223A045 | List: |
| References | |
| 5014931, EPID L-2021-LLA-0039 HI-2002444, Rev 21A | |
| Download: ML21223A050 (6) | |
Text
Holtec Letter 5014931 Attachment 4
- l. Continue to raise the HI-TRAC under the direction of the plant's radiological control personnel. Continue rinsing the surfaces with demineralized water. When the top of the HI-TRAC reaches the same elevation as the reservoir, close the Annulus Overpressure System reservoir valve (if used). See Figure 8.1.14.
- m. Remove HI-TRAC from the spent fuel pool while spraying the surfaces with plant demineralized water.
ALARA Note:
Decontamination of HI-TRAC bottom should be performed using remote cleaning methods, covering or other methods to minimize personnel exposure. The bottom lid decontamination may be deferred to a convenient and practical time and location. Any initial decontamination should only be sufficient to preclude spread of contamination within the fuel building.
- n. Decontaminate HI-TRAC bottom and HI-TRAC exterior surfaces including the pool lid bottom. Remove the bottom protective cover, if used.
- o. If used, disconnect the Annulus Overpressure System from the HI-TRAC See Figure 8.1.14.
- p. Set HI-TRAC in the designated cask preparation area.
Note:
If the transfer cask is expected to be operated in an environment below 32 oF, and a minimum heat load requirement was not applied to loading the MPC, the water jacket shall be filled with an ethylene glycol solution (25% ethylene glycol). Otherwise, . However, users need to perform thermal evaluation using the site- specific heat loads and ambient conditions to determine the minimum heat load limit for using water without ethylene glycol in the HI-TRAC water jacket during transfer operations below 32°F. The thermal evaluation shall be performed using the models and methods consistent with those described in Section 4.5 of the FSAR the jacket shall be filled with demineralized water.
Depending on weight limitations, the neutron shield jacket may remain filled (with pure water or 25% ethylene glycol solution, as required). Users shall evaluate the cask weights to ensure that cask trunnion, lifting devices and equipment load limitations are not exceeded.
- q. If previously drained, fill the neutron shield jacket with plant demineralized water or an ethylene glycol solution (25% ethylene glycol) as necessary.
- r. Disconnect the lifting slings or Lid Retention System (if used) from the MPC lid and disengage the lift yoke. Decontaminate and store these items in an approved storage location.
Warning:
MPC lid dose rates are measured to ensure that dose rates are within expected values. Dose rates exceeding the expected values could indicate that fuel assemblies not meeting the CoC may have been loaded.
- s. Measure the dose rates at the MPC lid and verify that the combined gamma and neutron dose is below expected values.
- t. Perform decontamination and a dose rate/contamination survey of HI-TRAC.
HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL HI-STORM 100 FSAR Proposed Rev. 21A REPORT HI-2002444 8-20 Page 1 of 6
Holtec Letter 5014931 Attachment 4 Note:
If the HI-TRAC is expected to be operated in an environment below 32 oF, and a minimum heat load requirement was not applied to loading the MPC, the water jacket shall be filled with an ethylene glycol solution (25% ethylene glycol). Otherwise, tThe jacket shall can be filled with demineralized water. However, users need to perform thermal evaluation using the site-specific heat loads and ambient conditions to determine the minimum heat load limit for using water without ethylene glycol in the HI-TRAC water jacket during transfer operations below 32°F. The thermal evaluation shall be performed using the models and methods consistent with those described in Section 4.5 of the FSAR
- 4. If previously drained, fill the neutron shield jacket with plant demineralized water or an ethylene glycol solution (25% ethylene glycol) as necessary. Ensure that the fill and drain plugs are installed.
- 5. Engage the lift yoke to the HI-TRAC lifting trunnions.
- 6. Align HI-TRAC over HI-STORM and mate the overpacks. See Figure 8.1.31.
- 7. If necessary, install the MPC downloader.
- 8. Remove the transfer lid (or mating device) locking pins and open the doors (mating device drawer).
ALARA Warning:
If trim plates are not used, personnel should remain clear of the immediate door area during MPC downloading since there may be some radiation streaming during MPC raising and lowering operations.
- 9. At the users discretion, install trim plates to cover the gap above and below the door (drawer for HI-TRAC 100D, 125D, and 100G). The trim plates may be secured using hand clamps or any other method deemed suitable by the user. See Figure 8.1.33.
Caution:
Limitations for handling an MPC containing high burn-up fuel and total MPC heat load greater than the threshold heat load setting in Table 4.5.4 at the time of unloading in a HI-TRAC are evaluated and established on a canister basis to ensure that acceptable cladding temperatures are not exceeded. Refer to FSAR Section 4.5 for guidance. The Supplemental Cooling System (SCS) is used to prevent fuel cladding temperatures from exceeding ISG-11 Rev. 3 limits. Operation of the SCS is initiated in accordance with the TS and continues until MPC re-flooding operations have commenced. Staging and check-out of the SCS shall be completed prior to transferring the MPC to the HI-TRAC.
- 11. Raise the MPC into HI-TRAC.
- 12. Verify the MPC is in the full-up position.
HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL HI-STORM 100 FSAR Proposed Rev. 21A REPORT HI-2002444 8-102 Page 2 of 6
Holtec Letter 5014931 Attachment 4 An option available on all MPCs is the addition of a second cover plate on the drain and vent ports. The outer cover plate is installed in a counterbored recess directly over the inner port cover. The outer port cover is welded using a minimum of three weld passes that bridge the weld joint. Visual and liquid penetrant examinations shall be performed on the root, final and at least one intermediate weld pass. Helium leak testing is not required when the redundant port cover design is used Leakage testing of the field welded MPC lid-to-shell weld and closure ring welds are not required.
Leak testing results for the MPC shall be documented and shall become part of the quality record documentation package.
Leakage testing of the vent and drain port cover plates, when required, shall be performed after welding of the cover plates and subsequent NDE. The description and procedures for these field leakage tests are provided in FSAR Section 8.1 and the acceptance criteria are defined in the Technical Specifications in Appendix A to CoC 72-1014.
9.1.4 Component Tests 9.1.4.1 Valves, Rupture Discs, and Fluid Transport Devices There are no fluid transport devices or rupture discs associated with the HI-STORM 100 System.
The only valve-like components in the HI-STORM 100 System are the specially designed caps installed in the MPC lid for the drain and vent ports. These caps are recessed inside the MPC lid and covered by the fully-welded vent and drain port cover plates. No credit is taken for the caps' ability to confine helium or radioactivity. After completion of drying and backfill operations, the drain and vent port cover plates are welded in place on the MPC lid and are liquid penetrant examined and, when required, leakage tested to verify the MPC confinement boundary.
There are two pressure relief valves installed in the upper ledge surface of the HI-TRAC transfer cask water jacket. These pressure relief valves are provided for venting of the neutron shield jacket fluid under hypothetical fire accident conditions in which the design pressure of the water jacket may be exceeded. The pressure relief valves shall relieve at 60 psig and 65 psig. The HI-TRAC 100G pressure relief valves shall relieve at 50 psig and 60 psig.
9.1.4.2 Seals and Gaskets There are no confinement seals or gaskets included in the HI-STORM 100 System.
9.1.5 Shielding Integrity HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL HI-STORM 100 FSAR Proposed Rev.21A REPORT HI-2002444 9-10 Page 3 of 6
Holtec Letter 5014931 Attachment 4 Table 9.1.4 (continued)
HI-STORM 100 NDE REQUIREMENTS MPC Acceptance Weld Location NDE Requirement Applicable Code Criteria (Applicable Code)
Lid-to-shell PT (root and final pass) ASME Section V, Article 6 (PT) PT: ASME Section III, Subsection NB, and multi-layer PT (if UT is not Article NB-5350 performed).
PT (surface following pressure test)
UT (if multi-layer PT is not performed) ASME Section V, Article 5 (UT) UT: ASME Section III, Subsection NB, Article NB-5332 Closure ring-to-shell PT (final pass) ASME Section V, Article 6 (PT) PT: ASME Section III, Subsection NB, Article NB-5350 Closure ring-to-lid PT (final pass) ASME Section V, Article 6 (PT) PT: ASME Section III, Subsection NB, Article NB-5350 Closure ring radial welds PT (final pass) ASME Section V, Article 6 (PT) PT: ASME Section III, Subsection NB, Article NB-5350 Port cover plates-to-lid (Single port PT (root and final pass) ASME Section V, Article 6 (PT) PT: ASME Section III, Subsection NB, cover plate option) Article NB-5350 Port cover plates-to-lid (Redundant Inner Plate: PT (final pass) ASME Section V, Article 6 (PT) PT: ASME Section III, Subsection NB, Port Cover Plate Option) Outer Plate: PT (root, final and at Article NB-5350, In addition, the least one intermediate pass) PT oif the Inner Plate and the Outer Plate final weld surface shall produce a clean, White result to indicate a lack of porosity Lift lug and lift lug baseplate PT (surface) ASME Section V, Article 6 (PT) PT: ASME Section III, Subsection NG, Article NG-5350 Vent and drain port cover plate plug PT (surface) ASME Section V, Article 6 (PT) PT: ASME Section III, Subsection NG, welds Article NG-5350 HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL HI-STORM 100 FSAR Proposed Rev. 21A REPORT HI-2002444 9-27 Page 4 of 6
Holtec Letter 5014931 Attachment 4 11.IV.2.3.3 100% Fuel Rod Rupture Dose Calculations The MPC confinement boundary maintains its integrity. There is no effect on the shielding effectiveness, and the magnitude of the radiation source is unchanged. However, the radiation source could redistribute within the sealed MPC cavity causing a slight change in the radiation dose rates at certain locations. Therefore, there is no release of radioactive material or significant increase in radiation dose rates.
11.IV.2.3.4 100% Fuel Rod Rupture Accident Corrective Action As shown in the analysis of the 100% fuel rod rupture accident, the MPC confinement boundary is not damaged. The HI-STORM 100UVH System is designed to withstand this accident and continue performing the safe storage of spent nuclear fuel under normal storage conditions. No corrective actions are required.
11.IV.2.4 Burial-Under- Debris 11.IV.2.4.1 Postulated Cause of Burial under Debris Burial of the HI-STORM 100UVH System under debris is not a credible accident. During storage at the ISFSI, there are no structures over the casks. The minimum regulatory distance(s) from the ISFSI to the nearest site boundary and the controlled area around the ISFSI concrete pad precludes the close proximity of substantial amounts of vegetation. There is no credible mechanism for the HI-STORM System to become completely buried under debris. However, for conservatism, complete burial under debris is considered.
11.IV.2.4.2 Analysis of Effects and Consequences of Burial under Debris Burial of the HI-STORM System does not impose a condition that would have more severe consequences for criticality, confinement, shielding, and structural analyses than that performed for the other accidents analyzed. The debris would provide additional shielding to reduce radiation doses.
Burial under debris can affect thermal performance because the debris acts as an insulator and heat sink. This will cause the HI-STORM System and fuel cladding temperatures to increase. A thermal analysis has been performed to determine the time for the fuel cladding temperatures to reach the accident condition temperature limit during a burial under debris accident.
Structural The structural evaluation of the MPC enclosure vessel for accident internal pressure conditions bounds the pressure calculated herein. Therefore, the resulting stresses from this event are well within the allowable values, as demonstrated in Section 3.4.
HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2002444 Proposed Revision 21A 11.IV-9 Page 5 of 6
Holtec Letter 5014931 Attachment 4 Thermal The thermal consequences of burial-under-debris are presented in the Supplement Section 4.IV.6.
The evaluation demonstrates that the peak fuel cladding temperature remains below the ISG-11 Rev 3 limit and the confinement function of the MPC is not compromised. The evaluation demonstrates that the fuel cladding and confinement function of the MPC are not compromised when the debris is removed within the duration calculated in Section 4.IV.6. This time may be calculated on a site-specific basis using the heat load of the loaded casks.
Shielding There is no effect on the shielding performance of the system as a result of this event.
Criticality There is no effect on the criticality control features of the system as a result of this event.
Confinement There is no effect on the confinement function of the MPC as a result of this event. As discussed in the structural evaluation above, all stresses remain within allowable values, assuring confinement boundary integrity.
Radiation Protection Since there is no degradation in shielding or confinement capabilities as discussed above, there is no effect on occupational or public exposures as a result of this event.
Based on this evaluation, it is concluded that the burial under debris accident does not affect the safe operation of the HI-STORM 100UVH System, if the debris is removed within the specified time.
11.IV.2.4.3 Burial Under Debris Accident Corrective Action Analysis of the burial under debris accident in Supplement 4.IV shows that the temperatures and pressures are not exceeded even for an extended duration of burial. Upon detection of the burial under debris accident, the ISFSI operator shall assign personnel to remove the debris with mechanical and manual means as necessary. After uncovering the storage overpack, the storage overpack shall be visually and radiologically inspected for any damage. The sites emergency action plan shall include provisions for the performance of this corrective action.
HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2002444 Proposed Revision 21A 11.IV-10 Page 6 of 6