ML18150A330
| ML18150A330 | |
| Person / Time | |
|---|---|
| Site: | HI-STORE |
| Issue date: | 05/24/2018 |
| From: | Holtec |
| To: | Office of Nuclear Material Safety and Safeguards |
| Shared Package | |
| ML18150A319 | List: |
| References | |
| 5025024 | |
| Download: ML18150A330 (5) | |
Text
Document ID 5025024 Safety Analysis Report (SAR), Chapter 2- "Site Characteristics" RAI 2 Provide an assessment of the annual hazard to the proposed CIS Facility from any flight-related activities at nearby airports and aircraft flying through the nearby airways (e.g.,
IR 192/194, IR 128/180, V291, and V102), as given in SAR Rev. OB Section 2.2.3 Air Transportation.
The assessment should consider, at a minimum, the following flight-related information:
a) Any holding pattern close to the proposed site associated with nearby airports; b) The distance of the proposed site of the CIS Facility from each nearby airway (e.g., centerline or edge of the airway) based on a reliable source (e.g., Federal Aviation Administration);
c) The width of each airway near the proposed CIS Facility; d) The annual number of transits by each type of civilian and commercial aircraft through each of the nearby airway; e) The types of military aircraft traversing the nearby airways and their flight-related activities while in the vicinity of the proposed site (e.g., normal and special flight mode-related activities);
f) Any ordnance carried onboard any military aircraft while traversing these airways, including hung ordnance; g) The effective area for each of the important to safety structures at the proposed facility, taking into account the footprint area of the structures, the shadow area, and the skid area of the structures for each type of aircraft with specific crash-related characteristics, and; h) The historical crash rate for each type of aircraft in a particular flight phase and in a particular enroute flight mode (i.e., normal or special) for a military aircraft.
The assessment should provide the cumulative annual number of aircraft crashes at the proposed facility from all flight-related activities, and the potential consequences from onboard ordnance, if any, to the proposed facility, after considering the above information.
Alternatively, the applicant may use alternative approaches to assess the flight-related activities near the proposed CIS Facility and estimate the annual aircraft crash hazard with the associated justifications.
This information is necessary to determine compliance with 10 CFR 72.24(a), 72.90(a) through (d), 72.94, and 72.98.
Document ID 5025024 Holtec Response:
Holtec evaluated the annual aircraft hazard using a probabilistic assessment of flight related activities near the proposed CIS Facility. NUREG-0800 Section 3.5.1.6, Aircraft Hazards, was used as guidance for the basis of the probabilistic assessment. All nearby air traffic infrastructure has been identified including airports, holding and approach patterns, federal airways, Military Training Routes (MTRs), and Military Operation Areas (MOAs) as well as their relevant attributes. The Acceptance Criteria listed in NUREG-0800 Section 3.5.1.6 state that all requirements are met if the probability of an aircraft crash is less than an order of magnitude of 10-7 per year. It also provides criteria, which if met, specify that the probability can be considered less than an order of magnitude of 10-7 by inspection. These criteria will hereby be referred to as screening criteria.
Each of the nearby airports, holding or approach patterns, federal airways and MOAs pass the screening criteria by inspection and are considered to be negligible hazards. Of the four (two sets of two) nearby MTRs, IR-192/194 meet the screening criteria and are therefore considered negligible hazards, as the probability of a crash is less than 10-7 by inspection. IR-128/180 passes directly above the proposed CIS site and does not pass by inspection.
Further evaluation of IR-128/180 was performed to determine the potential hazard of this flight path. Following the guidance of the NUREG-0800 Section 3.5.1.6 equation for airway crash probability, the flight density on IR-128/180 would have to be greater than 1011 flights per year in order for the probability to be greater than 10-7. Dyess Air Force Base, who controls this MTR has stated they do not use the portion of IR-128/180 within 5 miles of the CIS Facility and do not plan to use it in the future. Therefore, it is reasonable to assume that the flight density will remain less than 1011 flights per year and the probability of a crash will remain less than 10-7.
Since the probability of a crash will remain less than 10-7, the route is a negligible hazard.
Although this information was verbally received, the lead airspace analyst at Air Force Headquarters (AF/A3TI) in the Pentagon is gathering the data as requested in this RAI and will formally transmit it to Holtec International shortly.
By inspection and probabilistic assessment, the annual aircraft crash hazard is determined to be a negligible hazard.
Chapter 2 Section 2.2.3 of the SAR has been revised to include a probabilistic assessment of the aircraft crash hazard at the CIS Facility. Figures 2.2.6 and 2.2.7 as well as Tables 2.2.4 through 2.2.9 were added to support these descriptions.
RAI 2 Provide assessments, using site-measured geotechnical properties, to demonstrate that the soils at the subgrade and under-grade of the storage pads and the Canister Transfer Facility (CTF) would be able to withstand the loading assumed in the certification of the HI-STORM UMAX Canister Storage System. The assessments should provide, at a minimum, the following information:
- 1. Information and analyses to estimate the bearing capacity of the soils at the subgrade
Document ID 5025024 and under-grade of the storage pads and the CTF. Specifically, provide a description of the methodologies selected, the site-measured geotechnical property data used, and the effects of any spatial variation of the in-situ geotechnical properties on the estimated bearing capacity. The analyses should demonstrate that the "subgrade and under-grade soil properties at the HI-STORE CIS site are uniformly better than those assumed for the general certification of the HI-STORM UMAX system," as stated in SAR Rev. 08, Section 4.3.2.1, "Structural."
- 2. Information and analyses to estimate the immediate and the long-term settlement of the soils at the subgrade and under-grade of the storage pads and the CTF.
Specifically, provide a description of the methodologies selected, the site-measured geotechnical property data used, and the effects of any spatial variation of the in-situ geotechnical properties on the estimated immediate and long-term settlement. The analyses should demonstrate that the estimated immediate and long-term settlements at the storage pad area and the CTF, including any differential settlement, would not exceed the assumed settlements in the certification of the HI-STORM UMAX, as discussed in SAR Rev. 08, Section 4.3.2.1, "Structural."
- 3. A description of the piling design envisioned to achieve the equivalent stiffness of Space C material, as stated in SAR Rev. 08, Table 4.3.3, which specifies that Space C "[...]
Holtec Response:
- 1. Holtec Report HI-2188143, Revision 0, added to Chapter 19 as reference 4.3.5, provides the bearing capacity and settlement calculations and methodologies. The soil under the UMAX ISFSI has allowable bearing capacities of 170 ksf and 255 ksf for static and seismic loading conditions, respectively. The soil under the CTF has allowable bearing capacities of 89 ksf and 133 ksf for static and seismic loading conditions, respectively.
These allowable bearing capacities are calculated using conservative parameters and assumptions. The allowable bearing capacities are greater than the computed bearing pressures under static and seismic loading conditions.
- 2. Holtec Report HI-2188143, Revision 0, added to Chapter 19 as reference 4.3.5, provides the bearing capacity and settlement calculations and methodologies. Elastic/immediate settlement and long-term settlement will occur under the UMAX ISFSI and Canister Transfer Facility (CTF). There is no restraining value associated with elastic settlement for either system per the HI-STORE FSAR or the UMAX FSAR. The values of 3.931 inches and 0.376 inches of elastic settlement for UMAX and CTF, respectively, are reasonable considering the size of the UMAX field that will be constructed. The UMAX FSAR states the maximum long-term permissible settlement of the SFP is 0.2 inches.
The calculated long term settlement for the UMAX ISFSI is 0.074 inches, therefore the requirement is met. A The calculated long-term settlement for the CTF is 0.047 inches,
Document ID 5025024 Although there is no requirement for the CTF, the 0.047 inches of long term settlement is small and can be considered negligible for the system.
- 3. Geotechnical explorations and evaluations revealed/confirmed that the HI-STORE CIS Site Value for strain compatible effective shear wave velocity in Space C (~1,000 ft/sec minimum) is greater than the HI-STORM Generic License Value (485 ft/sec minimum).
Therefore, pilings are not needed for support of the UMAX system and the language has been removed from Table 4.3.3.
- 4. Section 2.6.6 has been added to Chapter 2 to include the following information about the excavation and construction process. During the construction of Phase 1 of the HI-STORE CISF, there will be multiple areas where excavation will be required to accommodate and install the underground facilities; specifically, the Canister Transfer Facilities (CTF) which are located in the Cask Transfer Building (CTB), and the UMAX field. In both cases, the expected total excavation depth is approximately twenty-five (25) feet.
According to the geotechnical borings, there are two layers of subsurface material that will be encountered during construction excavations. The native Caliche layer, which is approximately 12 feet in depth from top of existing grade, and the native residual soil layer, which makes up approximately 13 feet of depth for the remaining required excavation depth for site facilities. In no instance is it expected that construction excavations will encounter the native Chinle layer.
In order to accommodate construction vehicle access and maintain industry wide safety standards, it is expected that construction practices will utilize a minimum 1:1 slope around the extents of the excavation pits. This method will create ~124,000 cubic yards (CY) of caliche spoils and ~121,500 CY of residual soil spoils; some of which (~24,000 CY) will be utilized to backfill the excavation area. The residual soil spoils will be utilized for the backfill material as it meets the minimum density and shear wave velocity requirements for Space B, referenced in Figure 4.3.1.
Once the areas have been excavated, the supporting soil will be prepared to receive the reinforced concrete Support Foundation Pad (SFP). The residual soil surfaces shall be proof rolled by a heavy vibrating compactor, prior to the placement of compacted fill or foundations. Careful observation shall be made by a professional engineer licensed in New Mexico or their approved representative during proof rolling in order to identify any areas of soft, yielding soils that may require over-excavation and replacement. Once the subsurface has been prepared and compacted, the supporting residual soil fill (Space C) shall be confirmed to have reached a compaction of 95 percent (minimum) of the modified Proctor maximum dry density (in accordance with ASTM D1557). The compaction should be conducted at or close to the optimum moisture content indicated by the modified Proctor test procedure (ASTM D1557).
Upon completion of subgrade preparation/compaction, placement of the reinforced concrete Support Foundation Pad (SFP) and UMAX Cavity Enclosure Containers
Document ID 5025024 (CECs), backfilling of Spaces A and B (Figure 4.3.1) will commence. Space A will consist of a Controlled Low Strength Material (CLSM) or lean concrete that has a minimum compressive strength and density of 1,000 psi and 120 pcf, respectively, as referenced in Table 4.3.3. Since the backfilling process is iterative, as the fill materials are brought back up to finished grade, the sloped areas of the excavation pit that make up Space B of the UMAX lateral subgrade, will be composed of the aforementioned residual soil. Again, it is expected that for Phase 1 of the HI-STORE CISF, and all subsequent phases, ~24,000 CY of this residual soil will be required to fill out the Space B portion of the excavated area.