ML18330A079
| ML18330A079 | |
| Person / Time | |
|---|---|
| Site: | HI-STORE |
| Issue date: | 11/21/2018 |
| From: | Cuadrado J R Spent Fuel Licensing Branch |
| To: | Yoira Diaz-Sanabria Division of Spent Fuel Management |
| Cuadrado J R | |
| Shared Package | |
| ML18330A078 | List: |
| References | |
| Download: ML18330A079 (13) | |
Text
Division of Spent Fuel Management, NMSSU.S. Nuclear Regulatory CommissionPublic Meeting with Holtec InternationalOctober 23, 2018Holtec HI-STORE CISF Review
-Discussion of 5/24/18 RAI Responses on Geotechnical Stability Assessment (Proprietary
)
Summary*March 28, 2018
-NRC issues request for additional information (RAI), Part 1:
-RAI 2-2 -Requests additional details on geotechnical stability assessment for HI
-STORE CISF site
- May 24, 2018 -Holtec submits response to RAI: HI
-STORE Bearing Capacity and Settlement Calculations (HI
-2188143)*NRC staff has identified concerns with Holtec's response:
-Site geotechnical parameters used
-Immediate soil settlement estimation
-Consolidation soil settlement estimation
-Secondary settlement estimation
-Effects of Construction sequence on settlement
-Pad interactions
-Spatial Variation of Soil Properties on Pad Settlement Issue 1 -Representativeness of Soil Parameters Used (Table 5.3)
- Only unit weight measured at site; Friction angle () and Elastic modulus (E) derived from Standard Penetration Test Blow Count (N), Poisson's ratio () from literature
- Response does not explain the applicability of the empirical relationship used for and E to conditions at site
- Response does not explain the applicability of Poisson's ratio () to conditions at the site
- E for Residual soil not explained: in Table 5.3 = 27.81 ksfbut in page A.2 = 39.68 ksf*E for Chinle Formation: not clear whether effects of fractures were considered
- Cohesion (C) for Residual Soil and Chinle Formation not explained; estimate assumes no friction
-Applicant later assumes that both materials are cohesionless Issue 2 -Immediate Soil Settlement Estimation
- Uses methodology suggested in Section 10.6.2.4.2, Settlement of Footings on Cohesionless Soils, of AASHTO LRFD Bridge Design Specification:
-Response does not explain why the selected method for cohesionless soils would be appropriate for cohesive soil
[CResidualSoil= 4000 psf, CChinleFormation= 8060 psf in Table 5.3]
- Uses weighting scheme for two
-layer system (Residual Soil and Chinle Formation) given by Bowles (1997):
-Response does not explain why depth causing settlement would be 5 x pad width when EChinle Formation/EResidual Soil98 or 69 (Criterion from Bowles is 10 for Chinle Formation to be "hard" to undergo immediate settlement)
Issue 3 -Consolidation Settlement Estimation
- Uses Consolidation Pressure
(), Compressive Ratio (), and Recompression/Swell Ratio ()from Chinle Formation to calculate settlement of Residual Soil:
-No explanation provided for why Chinle Formation values are appropriate
- Response does not explain how Consolidation Pressure was obtained, nor does it justify use of the formula to estimate consolidation settlement
- Consolidation Pressure
(), Compressive Ratio
(), and Recompression/Swell Ratio
()in Chinle Formation are measured from two different samples at 74 and 100 ft depth:
-No explanation provided for why the use of two different samples is appropriate Issue 3 -Consolidation Settlement Estimation (cont.)*Consolidation estimated for upper 6 ft of Residual Soil Layer using Chinle Formation parameters:
-No explanation provided for what prevents lower 6 ft of Residual Soil from undergoing consolidation settlement
- No explanation for why Chinle Formation would not undergo consolidation settlement when consolidation parameters are measured from samples of this formation
- No explanation for why weight of the vertical cask transporter (VCT) is not included in calculating the applied transient load causing settlement Issue 4 -Secondary Settlement Estimation
- No discussion is provided for why secondary settlement would be negligible Issue 5 -Effects of Construction Sequence in Settlement
- Response does not explain why the Immediate Settlements from placing the Controlled Low Strength Material (CLSM) (1.962e8 lbs), ISFSI Pad (3.006e7 lbs), and MPCs with closure lid (3.625e7 lbs) on top of the Support Foundation Pad, would not contribute toward the cumulative settlement against the Permissible Long
-Term Settlement of 0.2 in (Table 2.3.1 of UMAX FSAR)
-Pouring of CLSM, construction of top ISFSI Pad, and placement of MPCs into storage are expected to occur more than 7 days after construction of the Support Foundation Pad Issue 5 -Effects of Construction Sequence in Settlement (cont')
Issue 6 -Interaction Among Pads*Pad dimensions: 438 ft x 183 ft
- Pad-to-pad separation distance (along shorter dimension) = 35 ft Issue 6 -Interaction Among Pads(cont.)*Stress below the pads would not be uniform
-End closer to next pad would have larger stress than the far end; hence, settle more
- Pad tilting (rotation): Does not appear to be calculated Issue 7 -Spatial Variation of Soil Properties on Pad Settlement
- 5 boreholes in the pad area*No explanation whether difference in material properties would produce excessive differential settlement of the Spent Fuel Pad
- Part of RAI 2
-2 Conclusions
- NRC staff needs additional information to address RAIs on geotechnical stability and determine compliance with NRC's safety regulations
- Timely completion of NRC review of Holtec's HI
-STORE CISF application requires complete and high quality responses to NRC staff's questions
- NRC staff is open to additional discussion with applicant prior to submission of responses