ML23006A270
| ML23006A270 | |
| Person / Time | |
|---|---|
| Site: | 07201032 |
| Issue date: | 01/06/2023 |
| From: | Holtec |
| To: | Office of Nuclear Material Safety and Safeguards |
| Shared Package | |
| ML23006A263 | List: |
| References | |
| 5018101, CAC 001028, EPID L-2021-LLA-0053 | |
| Download: ML23006A270 (1) | |
Text
Holtec Letter 5018101 Attachment 6 31-1 31-2 31-3 31-4 1-52-1 1-62-2 1-73-5 1-83-6 1-93-7 1-102-3 1-112-4 1-122-5 1-132-6 1-143-8 1-212- 1-223-1-153-9 1-162-7 1-172-8 1-181-1 1-192 1-202-9 10 10 1-233- 1-242- 1-252- 1-282- 1-292- 1-303-1-261-3 1-274 11 11 12 13 14 12 1-313- 1-322- 1-332- 1-342- 1-352- 1-363-13 15 16 17 18 14 1-373- 1-383- 1-392- 1-402- 1-413- 1-423-15 16 19 20 17 18 1-433- 1-443-19 20 Figure 1.2.1d: MPC-44 Basket Cell Identification HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 Proposed Revision 10G9 1-95 1 of 10
Holtec Letter 5018101 Attachment 6 certain necessary alternatives, as discussed in Section 2.2. The principal exception to the above Code pertains to the MPC lid, vent and drain port cover plates, and closure ring welds to the MPC lid and shell, as discussed in Section 2.2. In addition, Threaded Anchor Locations (TALs) in the MPC lid are designed in accordance with the requirements of NUREG-0612 for critical lifts to facilitate handling of the loaded MPC.
The MPC closure welds are partial penetration welds that are structurally qualified by analysis in Chapter 3. The MPC lid and closure ring welds are inspected by performing a liquid penetrant examination in accordance with the drawings contained in Section 1.5. The integrity of the MPC lid-to-shell weld is further ensured by performing a progressive liquid penetrant examination of the weld layers, and a Code pressure test.
The structural analysis of the MPC, in conjunction with the redundant closures and nondestructive examination, pressure testing, and helium leak testing (helium leak testing not required for redundant port cover design) provides assurance of canister closure integrity in lieu of the specific weld joint configuration requirements of Section III, Subsection NB.
Compliance with the ASME Code, with respect to the design and fabrication of the MPC, and the associated justification are discussed in Section 2.2. The MPC design is analyzed for all design basis normal, off-normal, and postulated accident conditions, as defined in Section 2.2.
The required characteristics of the fuel assemblies to be stored in the MPC are limited in accordance with Section 2.1.
Thermal The thermal design and operation of the MPC in the HI-STORM FW System meets the intent of the review guidance contained in ISG-11, Revision 3 [2.0.1]. Specifically, the ISG-11 provisions that are explicitly invoked and satisfied are:
- i. The thermal acceptance criteria for all commercial spent fuel (CSF) authorized by the USNRC for operation in a commercial reactor are unified into one set of requirements.
ii. The maximum value of the calculated temperature for all CSF under long-term normal conditions of storage must remain below 400ºC (752ºF). For short-term operations, including canister drying, helium backfill, and on-site cask transport operations, the fuel cladding temperature must not exceed 400ºC (752ºF) for high burnup fuel (HBF) and 570ºC (1058ºF) for moderate burnup fuel.
iii. The maximum fuel cladding temperature as a result of an off-normal or accident event must not exceed 570ºC (1058ºF).
iv. For HBF, operating restrictions are imposed to limit the maximum temperature excursion during short-term operations to 65ºC (117ºF) and the number of excursions to less than 10.
HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 Proposed Revision 10G 2-2 2 of 10
Holtec Letter 5018101 Attachment 6 TABLE 2.2.14 List of ASME Code Alternatives for Multi-Purpose Canisters (MPCs) clearances are satisfied. The dimensions required to be met in fabrication are chosen to meet the functional requirements of the dry storage components. Thus, although the post-forming Code cylindricity requirements are not evaluated for compliance directly, they are indirectly satisfied (actually exceeded) in the final manufactured components.
MPC Enclosure NB-4122 Implies that with the MPCs are built in lots. Material traceability Vessel exception of studs, bolts, nuts on raw materials to a heat number and and heat exchanger tubes, corresponding CMTR is maintained by CMTRs must be traceable to a Holtec through markings on the raw specific piece of material in a material. Where material is cut or component. processed, markings are transferred accordingly to assure traceability. As materials are assembled into the lot of MPCs being manufactured, documentation is maintained to identify the heat numbers of materials being used for that item in the multiple MPCs being manufactured under that lot. A specific item within a specific MPC will have a number of heat numbers identified as possibly being used for the item in that particular MPC of which one or more of those heat numbers (and corresponding CMTRS) will have actually been used. All of the heat numbers identified will comply with the requirements for the particular item.
MPC Lid and NB-4243 Full penetration welds MPC lid and closure ring are not full Closure Ring required for Category C Joints penetration welds. They are welded Welds (flat head to main shell per independently to provide a redundant seal.
NB-3352.3)
MPC Closure NB-5230 Radiographic (RT) or Root (if more than one weld pass is Ring, Vent and ultrasonic (UT) examination required) and final liquid penetrant Drain Cover required. examination to be performed in accordance Plate Welds with NB-5245. The closure ring provides independent redundant closure for vent and drain cover plates. Vent and drain port cover plate welds are helium leakage tested.
If the redundant port cover design is used, a helium leakage test is not required.
MPC Lid to NB-5230 Radiographic (RT) or Only progressive liquid penetrant (PT)
Shell Weld ultrasonic (UT) examination examination is permitted. PT examination required. will include the root and final weld layers and each approx. 3/8" of weld depth.
HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 Proposed Revision 10G 2-112 3 of 10
Holtec Letter 5018101 Attachment 6 2.3 SAFETY PROTECTION SYSTEMS 2.3.1 General The HI-STORM FW System is engineered to provide for the safe long-term storage of spent nuclear fuel (SNF). The HI-STORM FW will withstand all normal, off-normal, and postulated accident conditions without release of radioactive material or excessive radiation exposure to workers or members of the public. Special considerations in the design have been made to ensure long-term integrity and confinement of the stored SNF throughout all cask normal and off-normal operating conditions and its retrievability for further processing or ultimate disposal in accordance with 10 CFR 72.122(l) and ISG-2 [2.3.1].
2.3.2 Protection by Multiple Confinement Barriers and Systems 2.3.2.1 Confinement Barriers and Systems The radioactivity which the HI-STORM FW System must confine originates from the spent fuel assemblies and, to a lesser extent, any radioactive particles from contaminated water in the fuel pool which may remain inside the MPC. This radioactivity is confined by multiple engineered barriers.
Contamination on the outside of the MPC from the fuel pool water is minimized by preventing contact, removing the contaminated water, and decontamination. An inflatable seal in the annular gap between the MPC and HI-TRAC VW, and the elastomer seal in the HI-TRAC VW bottom lid (see Chapter 9) prevent the fuel pool water from contacting the exterior of the MPC and interior of the HI-TRAC VW while submerged for fuel loading.
The MPC is a seal welded enclosure which provides the confinement boundary. The MPC confinement boundary is defined by the MPC baseplate, MPC shell, MPC lid, closure ring, port cover plates, and associated welds.
The MPC confinement boundary has been designed to withstand any postulated off-normal operations, accident conditions, or external natural phenomena. Redundant closure of the MPC is provided by the MPC closure ring welds which provide a second barrier to the release of radioactive material from the MPC internal cavity. Therefore, no monitoring system for the confinement boundary is required.
Confinement is discussed further in Chapter 7. MPC field weld examinations, helium leakage testing of the port cover plate welds (if applicable), and pressure testing are performed to ensure the confinement function. Fabrication inspections and tests are also performed, as discussed in Chapter 10, to verify the integrity of the confinement boundary.
HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 Proposed Revision 10G 2-114 4 of 10
Holtec Letter 5018101 Attachment 6 used to remove all liquid water from the MPC. For MPCs with high burn-up fuel and higher heat loads, cyclic vacuum drying may be performed in accordance with Chapter 4 of this FSAR and ISG-11 Rev. 3. The annular gap between the MPC and HI-TRAC is filled with water during vacuum drying to promote heat transfer from the MPC and maintain lower fuel cladding temperatures. The internal pressure is reduced and held in accordance with Technical Specifications to ensure that all liquid water is removed.
An FHD system may also be used for high-burn-up fuel at higher decay heat heats as well as for moderate burn-up fuel and HBF at lower heat loads to remove residual moisture from the MPC.
Gas is circulated through the MPC to evaporate and remove moisture. The residual moisture is condensed until no additional moisture remains in the MPC. The temperature of the gas exiting the system demoisturizer is maintained in accordance with Technical Specification requirements to ensure that all liquid water is removed.
Following MPC moisture removal, by VDS or FHD, the MPC is backfilled with a predetermined amount of helium gas. The helium backfill ensures adequate heat transfer during storage, and provides an inert atmosphere for long-term fuel integrity. Cover plates are installed and seal welded over the MPC vent and drain ports with liquid penetrant examinations performed on the root and final passes (for multi-pass welds). The cover plate welds are then leak tested.
An option available on all MPCs is the addition of a second cover plate on the drain and vent ports. Only the inner cover plate is leak tested. The outer cover plate is installed in a counterbored recess directly over the inner port cover. The outer port cover is welded with visual and liquid penetrant examinations performed on the root, final, and at least one intermediate weld pass.
The MPC closure ring is then placed on the MPC and aligned, tacked in place, and seal welded providing redundant closure of the MPC confinement boundary closure welds. Tack welds are visually examined, and the root and final welds are inspected using the liquid penetrant examination technique to ensure weld integrity.
The annulus shield (if utilized) is removed and the remaining water in the annulus is drained.
The MPC lid and accessible areas of the top of the MPC shell are smeared for removable contamination. HI-TRAC VW surface dose rates are measured in accordance with the technical specifications. The MPC lift attachments are installed on the MPC lid. The MPC lift attachments are the primary lifting point on the MPC. MPC slings are installed between the MPC lift attachments and the lift yoke.
MPC transfer may be performed inside or outside the fuel building. The empty HI-STORM FW overpack is inspected and positioned with the lid removed. Next, the mating device is positioned on top of the HI-STORM FW and HI-TRAC VW is placed on top of it. The mating device assists in the removal of the HI-TRAC VW bottom lid and helps guide the HI-TRAC VW during its placement on the HI-STORM FW. The MPC slings are attached to the MPC lift attachments.
The MPC is transferred using a suitable load handling device.
HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 Proposed Revision 10G9 9-9 5 of 10
Holtec Letter 5018101 Attachment 6 If using redundant port cover plates, install the redundant port cover plate, perform the multi-pass welds, and perform NDE on the redundant port cover plates with approved procedures (See 9.1 and Table 2.2.14). Repair any weld defects in accordance with the sites approved Code weld repair procedures.
9.10. If not using a redundant port cover plate, PpPerform a leakage test of the MPC vent port cover plate and drain port cover plate in accordance with the following and site-approved procedures. When using a redundant port cover plate, only the inner cover plate is leak tested.:
- a. If necessary, remove the cover plate set screws or plugs.
- b. Flush the cavity with helium to remove the air and immediately install the set screws or plugs recessed below flush of the top of the cover plate.
- c. Plug weld the recess above each set screw or plug to complete the penetration closure welding in accordance with the licensing drawings using approved procedures.
Repair any weld defects in accordance with the applicable Code and re-perform the NDE until the weld meets the required acceptance criteria.
- d. Flush the area around the vent and drain cover plates with compressed air or nitrogen to remove any residual helium gas.
- e. Perform a helium leakage rate test of vent and drain cover plate welds in accordance with the Mass Spectrometer Leak Detector (MSLD) manufacturers instructions and leakage test methods and procedures of ANSI N14.5 [9.1.2]. The MPC Helium Leak Rate acceptance criterion is provided in LCO 3.1.1.
If using redundant port cover plates, install the redundant port cover plate, perform the multi-pass welds, and perform NDE on the redundant port cover plates with approved procedures (See 9.1 and Table 2.2.14). Repair any weld defects in accordance with the sites approved Code weld repair procedures.
10.11. Weld the MPC closure ring as follows:
- a. Install and align the closure ring.
- b. Weld the closure ring to the MPC shell and the MPC lid, and perform NDE in accordance with the licensing drawings using approved procedures. Repair any weld defects in accordance with the applicable code and re-perform the NDE until the weld meets the required acceptance criteria.
- c. If necessary, remove the AWS.
9.2.5 Preparation for Storage HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 Proposed Revision 10G9 9-20 6 of 10
Holtec Letter 5018101 Attachment 6 10.1.4 Leakage Testing Leakage testing shall be performed in accordance with written and approved procedures and the leakage test methods and procedures of ANSI N14.5 [10.1.5], as follows.
Helium leakage testing of the MPC base metals (shell, baseplate, and MPC lid) and MPC shell to baseplate and shell to shell welds is performed on the unloaded MPC. The acceptance criterion is leaktight as defined in ANSI N14.5. Shop leakage tests of the base metals and enclosure welds may be performed using automated leak test equipment to minimize the need for operator actions and interpretations. Automated leak test equipment design and computer software programs shall be reviewed and approved by a Level III Leak Test specialist qualified in accordance with ANSI N14.5. Maintenance and calibration of the equipment and testing of the software shall be performed by individuals qualified in accordance with ANSI.N14.5 using written procedures produced under the licensees quality program. The placement of the MPC components in the test equipment and recording of the test data in the documentation package for the equipment shall be performed by personnel trained and qualified in accordance with the licensees quality program. The helium leakage test of the vent and drain port cover plate welds shall be performed using a helium mass spectrometer leak detector (MSLD). If a leakage rate exceeding the acceptance criterion is detected, then the area of leakage shall be determined and the area repaired per ASME Code Section III, Subsection NB, Article NB-4450 requirements. Re-testing shall be performed until the leakage rate acceptance criterion is met.
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 plate welds when required shall be performed after welding of the cover plates and subsequent NDE. For instances where redundant port covers have been installed, leakage testing is onlynot required on inner port cover. The description and procedures for these field leakage tests are provided in Chapter 9 of this FSAR and the acceptance criteria are defined in the Technical Specifications for the HI-STORM FW system.
HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 Proposed Revision 10G9 10-12 7 of 10
Holtec Letter 5018101 Attachment 6 Table 10.1.1 (continued)
MPC INSPECTION AND ACCEPTANCE CRITERIA Function Fabrication Pre-operation Maintenance and Operations Structural a) Assembly and welding of MPC a) None. a) A multi-layer liquid components is performed per penetrant (PT)
ASME Code Section IX and III, examination of the MPC Subsection NB, as applicable. lid-to-shell weld is performed per ASME b) Materials analysis (steel, Section V, Article 2.
neutron absorber, etc.), is Acceptance criteria for performed and records are kept the examination are in a manner commensurate with defined in Subsection "important to safety" 10.1.1, and in the classifications. Licensing Drawings.
b) ASME Code NB-6000 pressure test is performed after MPC closure welding.
Acceptance criteria are defined in the Code.
Leak Tests a) Helium leakage testing of the a) None. a) Helium leakage testing is MPC base metal (shell, performed on the vent baseplate and MPC lid),MPC and drain port cover shell to baseplate welds and plates to MPC lid field MPC shell to shell welds is welds and the cover plate performed on the unloaded base metals.. If the MPC. Acceptance criterion is redundant port cover in accordance with leaktight design is used on the definition in ANSI N14.5. vent and drain ports, helium leak testing is onlynot required on inner port cover. See Technical Specification for guidance on acceptance criteria.
Criticality a) The boron content is verified at None. None.
Safety the time of neutron absorber material manufacture.
b) The installation of MPC cell panels is verified.
Shielding a) Material compliance is verified None. None.
Integrity through CMTRs.
b) Dimensional inspection of MPC lid thickness is performed.
HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 Proposed Revision 10G9 10-21 8 of 10
Holtec Letter 5018101 Attachment 6 Table 10.1.4 HI-STORM FW MPC NDE REQUIREMENTS NDE Acceptance Criteria Weld Location Applicable Code Requirement (Applicable Code)
Shell longitudinal RT ASME Section V, RT: ASME Section III, Subsection NB, seam Article 2 (RT) Article NB-5320 PT (surface) ASME Section V, PT: ASME Section III, Subsection NB, Article 6 (PT) Article NB-5350 Shell RT ASME Section V, RT: ASME Section III, Subsection NB, circumferential Article 2 (RT) Article NB-5320 seam PT (surface) ASME Section V, PT: ASME Section III, Subsection NB, Article 6 (PT) Article NB-5350 Baseplate-to- RT ASME Section V, RT: ASME Section III, Subsection NB, shell Article 2 (RT) Article NB-5320 PT (surface) ASME Section V, PT: ASME Section III, Subsection NB, Article 6 (PT) Article NB-5350 Lid-to-shell PT (root and final pass) ASME Section V, PT: ASME Section III, Subsection NB, and multi-layer PT. Article 6 (PT) Article NB-5350 PT (surface following pressure test)
Closure ring-to- PT (final pass) ASME Section V, PT: ASME Section III, Subsection NB, shell Article 6 (PT) Article NB-5350 Closure ring-to- PT (final pass) ASME Section V, PT: ASME Section III, Subsection NB, lid Article 6 (PT) Article NB-5350 Closure ring PT (final pass) ASME Section V, PT: ASME Section III, Subsection NB, radial welds Article 6 (PT) Article NB-5350 Port cover plates- PT (root and final pass) ASME Section V, PT: ASME Section III, Subsection NB, to-lid Article 6 (PT) Article NB-5350 (Single port cover plate option) PT (final pass) ASME Section V, PT : Clean White Port cover plates- Article 6 (PT) to-lid (when in conjunction with redundant port cover plate)
Port cover plates- Inner Plate: PT (root and ASME Section V, PT: ASME Section III, Subsection NB, to-lid (Redundant final pass only) Article 6 (PT Article NB-5350. In addition, the PT Port Ccover Outer Plate: PT (root, final of the Inner Plate shall produce a clean, pPlates to lid and at least one White result to indicate a lack of Option) intermediate pass) porosity Lift lug and lift PT (surface) ASME Section V, PT: ASME Section III, Subsection NB, lug baseplate Article 6 (PT) Article NB-5350 Vent and drain PT (surface) ASME Section V, PT: ASME Section III, Subsection NB, port cover plate Article 6 (PT) Article NB-5350 plug welds HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 Proposed Revision 10G9 10-28 9 of 10
Holtec Letter 5018101 Attachment 6 Multi-Purpose Canister B 3.1.1 BASES SURVEILLANCE Cooling provided by normal operation of the forced helium REQUIREMENTS dehydration system ensures that the fuel cladding temperature (continued) remains below the applicable limits since forced recirculation of helium provides more effective heat transfer than that which occurs during normal storage operations.
The conditions and requirements for drying the MPC cavity based on the burnup class of the fuel (moderate or high), heat load, and the applicable short-term temperature limit are given in the CoC/TS Appendix A, Table 3-1. The temperature limits and associated cladding hoop stress calculation requirements are consistent with the guidance in NRC Interim Staff Guidance (ISG)
Document 11.
Having the proper quantity of helium in the MPC ensures adequate heat transfer from the fuel to the fuel basket and surrounding structure of the MPC and precludes any overpressure event from challenging the normal, off-normal, or accident design pressure of the MPC.
Meeting the helium leak rate limit prior to TRANSPORT OPERATIONS ensures there is adequate helium in the MPC for long term storage and that there is no credible effluent dose from the MPC.
MPCs that utilize the redundant port cover design exhibit increased confinement boundary reliability. Each port cover plate is subjected to NDE to ensure absence of porosity in the material and is welded to the MPC lid in the same manner as in the non-redundant design. Each cover plate weld is subjected to similar NDE acceptance criteria, where successful NDE will verify the associated welds integrity to maintain the MPC confinement boundary. As such, this surveillance does not need to be performed for MPCs that utilize the redundant port cover design.
All of these surveillances must be successfully performed once, prior to TRANSPORT OPERATIONS to ensure that the conditions are established for SFSC storage which preserve the analysis basis supporting the MPC design.
REFERENCES 1. FSAR Chapters 1, 4, 7 and 9
- 2. Interim Staff Guidance Document 11, Rev. 3
- 3. Interim Staff Guidance Document 18, Rev. 1 HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 Rev. 10G98 13.A-16 10 of 10