ML14071A167

Enclosure 2: Presentation Slides - North Anna ISFSI TN-32 Cask and Pad 1 Assessments Following August 23, 2011, Central Virginia Earthquake

ML14071A167
Person / Time
Site:	North Anna
Issue date:	01/28/2014
From:	Dominion
To:	NRC/NMSS/SFST/LID/LB
Davis B
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ML14071A145	List: ML14071A167
References
TAC LA0479
Download: ML14071A167 (20)

Text

North Anna ISFSI TN-32 Cask and Pad 1 Assessments following August 23, 2011 Central Virginia Earthquake Richard Ridder January 28, 2014

Agenda Purpose

Background

Observations at ISFSI Pad 1 Pad 1 Structural Analysis TN-32 Evaluations Structural Thermal Shielding Summary Cask Spacing TN32 Cask and Pad 1 Assessments following August 23, 2011 Central Virginia Earthquake 2

Purpose of Meeting Describe the results of the observations and evaluations of North Anna ISFSI Pad 1 and the TN-32 casks following 8/23/11 earthquake Discuss Dominions proposed resolution to the as-left TN-32 cask spacing compared with the Technical Specification Design Features Description TN32 Cask and Pad 1 Assessments following August 23, 2011 Central Virginia Earthquake 3

Background

August 23, 2011 Central Virginia Earthquake 5.8 magnitude Recorded Accelerations Exceeded Design Basis Earthquake (DBE)

Values Strong motion duration 3.1 seconds TN32 Cask and Pad 1 Assessments following August 23, 2011 Central Virginia Earthquake 4

TN32 Cask and Pad 1 Assessments following August 23, 2011 Central Virginia Earthquake 5 Observations at ISFSI Pad 1 Detailed Visual and Performance Inspections No damage or cracking to pad surface from earthquake No visible structural damage to TN-32 casks No damage to electrical conduit, only slight displacement No damage to pressure monitoring systems, including the remote monitoring panel TN32 Cask and Pad 1 Assessments following August 23, 2011 Central Virginia Earthquake 6

Additional Observations No cask monitoring system alarms during or following earthquake.

No loss of electrical power at the ISFSI No change to cask surface dose rates No abnormalities or drift in setpoints for six randomly selected pressure switches inspected on August 30, 2011. Interseal helium monitoring pressures were normal.

TN32 Cask and Pad 1 Assessments following August 23, 2011 Central Virginia Earthquake 7

TN-32 Cask Movement 25 of 27 casks showed indication of slight movement from pre-earthquake positions 41/2 inches maximum No obvious preferential direction N S 2 2.5 3 3.5 2.5 2.25 1.25 2.5 2.5 2 1 1 49 43 37 29 23 16 13 10 19 26 30 41 47 52 3.5 2

1.5 1 1.5 4.5 3 1.5 1.5 2.5 0.5 45 38 36 20 14 12 06 21 24 32 42 48 53 1 4 2 0.75 TN32 Cask and Pad 1 Assessments following August 23, 2011 Central Virginia Earthquake 8

Indications of Sliding TN32 Cask and Pad 1 Assessments following August 23, 2011 Central Virginia Earthquake 9

Spacing Measurements Center to center spacing varies from 15 feet 21/4 inches to 16 feet 111/4 inches 16 feet nominal spacing described in Tech Specs 163 161 16 162 152 164 158 165 161 1511 1511 163 162 1610 1611 1610 165 163 163 162 162 169 169 168 1610 1610 N S 49 43 37 29 23 16 13 10 19 26 30 41 47 52 45 38 36 20 14 12 06 21 24 32 42 48 53 1511 1510 163 163 1511 1510 162 162 16 162 158 164 TN32 Cask and Pad 1 Assessments following August 23, 2011 Central Virginia Earthquake 10

TN-32 Spacing The casks moved slightly, but showed no other indications of adverse effects, and no damage.

Dominion concludes that leaving the casks in their current positions makes sense Analyze Pad and revisit TN-32 analyses Address spacing description in Tech Specs TN32 Cask and Pad 1 Assessments following August 23, 2011 Central Virginia Earthquake 11

Pad 1 Structural Analysis Purpose Confirm visual inspection results which showed no damage, and confirm no damage in inaccessible areas Anticipate the condition of Pad 1 if another 8/23/11 earthquake occurs Enveloped Response Spectra Peak Spectral (@ Top of Pad #1 & C.G. of Casks)

Soil Structure Interaction Acceleration (SSI) Analysis: Frequency Acc.

Time Amplified TimeHistories Layers of Rock & Soil Acceleration Time Recorded TimeHistories TN32 Cask and Pad 1 Assessments following August 23, 2011 Central Virginia Earthquake 12

Pad 1 Structural Analysis Static Coefficient Analysis Using amplified response spectra from SSI, peak seismic accelerations were applied in a static coefficient analysis Casks assumed to remain pinned to pad Casks located at 14 ft center-to-center spacing Cask loads modeled as point loads to address any cask edge loading Pad analyzed in accordance with ACI 349-01 Seismic load demand approximately 75% of design code capacity using above conservatisms Sufficient margin in Pad 1 to withstand the moments and shear forces from the 8/23/11 earthquake and another 8/23/11 earthquake or a DBE as presently licensed TN32 Cask and Pad 1 Assessments following August 23, 2011 Central Virginia Earthquake 13

TN-32 Structural Evaluation Cask structural analysis used 1g lateral and 2g vertical accelerations Cask basket structurally evaluated for a 1g lateral acceleration and 3g vertical acceleration Cask and basket evaluated for 18 inch drop onto pad (50g acceleration downwards) and tipover (50g)

Peak enveloped seismic accelerations from SSI at cask center of gravity are bounded by these previously analyzed conditions Sliding Evaluation Minimum acceleration to slide:

0.284g horizontal, vertical 0.189g, coefficient of friction 0.35 Sliding would be expected for event of 8/23/11 magnitude TN32 Cask and Pad 1 Assessments following August 23, 2011 Central Virginia Earthquake 14

TN-32 Thermal Evaluation Current licensed thermal analysis Cask maximum heat load - 32.7 kW 16 feet minimum center-to-center spacing Previous licensed thermal analysis Cask maximum heat load - 27.1 kW 16 feet nominal center-to-center spacing All cask heat loads were less than 27.1 kW prior to 8/23/11 TN32 Cask and Pad 1 Assessments following August 23, 2011 Central Virginia Earthquake 15

TN-32 Thermal Evaluation Transnuclear performed sensitivity analysis for cask spacing 16, 15, and 14 feet center-to-center spacing Cask maximum heat load of 27.1 kW Vertical view factors calculated for each spacing Cask temperatures calculated for 27.1 kW heat load at 14 feet spacing are bounded by the current licensing basis Tmax, 16ft, 32.7 kW (°F) Margin to Component Tmax, 14ft, 27.1 kW (°F)

(licensing basis) licensing basis (°F)

Outer Surface 240 237.5 2.5 Radial Neutron Shield 280 257.6 22.4 (Resin/Aluminum)

Seal/Lid 256 237.1 18.9 Fuel Compartment 527 466.1 60.9 Fuel Cladding 565 501.4 63.6 TN32 Cask and Pad 1 Assessments following August 23, 2011 Central Virginia Earthquake 16

TN-32 Radiological Assessment No indications of damage to TN-32 casks No detection of local radiation leakage or streaming as confirmed by radiological surveys No change in surface dose rates as confirmed by radiological surveys Insignificant change in offsite dose rates due to cask movement The analysis assumes fully loaded pad, essentially transforming the pad into a line source for evaluation of offsite dose to public. Movement of the casks a few inches from their nominal locations would have an insignificant effect on offsite dose rates at the site boundaries TN32 Cask and Pad 1 Assessments following August 23, 2011 Central Virginia Earthquake 17

Summary No observed damage to TN-32 casks or Pad 1 Pad 1 - sufficient margin to withstand the 8/23/11 earthquake and another 8/23/11 earthquake or a DBE as presently licensed TN-32 structural evaluation - no damage predicted; accelerations due to earthquake bounded by existing analyses TN-32 shielding assessment - surface dose rates unchanged, offsite dose rate change insignificant TN-32 thermal analysis - temperature increases at 14 feet center-to-center spacing bounded by current licensing basis TN32 Cask and Pad 1 Assessments following August 23, 2011 Central Virginia Earthquake 18

Cask Spacing TS Design Features Description (4.2.3):

The SSSCs in each row will be spaced a nominal 16 feet apart center-to-center. Each row of SSSCs will be spaced a nominal 16 feet apart center-to-center. For SSSCs whose heat load exceeds 27.1 KW the spacing shall be a minimum of 16 feet apart center-to-center.

Spacing currently varies from 15 21/4 to 16 111/4 Propose formal clarification on the Docket of nominal spacing TN32 Cask and Pad 1 Assessments following August 23, 2011 Central Virginia Earthquake 19

Objective Document that the TN-32 cask spacing following earthquake meets design and regulatory requirements Allow the casks to remain in their current positions TN32 Cask and Pad 1 Assessments following August 23, 2011 Central Virginia Earthquake 20