1. Ketan Mittal Research Assistant University of Nevada, Reno Miles Greiner Professor of Mechanical Engineering University of Nevada, Reno Funded by the US Nuclear Regulatory Commission, Contract NRC-HQ- 12 -P- 02-0200 Packaging and Transportation of Radioactive Materials August 20, 2013 –San Francisco, California Ahti Suo-Anttila Computational Engineering Analysis LLC Albuquerque, New Mexico

2.  Consider a package designed to transport one used nuclear fuel assembly in proximity to a long- lasting, 12-m diameter jet fuel fire  If the package is centered over the pool, how long will it take before the fuel’s cladding reaches its possible burst temperature, 750°C?  How far must the package be from the pool’s center so that its cladding will not reach this temperature, even for an infinitely-long-lasting fire? (Safe distance)

3.  Models fuel block, steel-lead-steel construction surrounded by water tank  Inside package, heat generation within the fuel, conduction and surface- to-surface radiation heat transfer

5.  Simulations were performed for a range of modeling parameters  Calculated fire time of concern for the cladding t c (when the cladding reaches 750°C) is between 11.8 and 13.3 hours

6.  The fire time of concern for the cladding increases as the distance between the package and fuel centers increases  For S x > 6.4 m (package over the pool edge) the cladding temperature never reaches its burst condition.  This work helps risk analysts determine which actual fires have the potential to affect safety and require further study

8.  t c = 5.1 hour and 15.4 hour for T F = 800 °C and 1000 °C, respectively

9.  The fire time of concern for the cladding increases as the distance between the package and fuel centers increases  For S x = 6.4 m, (center near the fire pool edge) the cladding temperature never reaches its burst condition.

10.  Find the cladding time of concern with the package at other locations S X = 0, S Z = 0 S X = 3.4, S Z = 0 S X = 6.4, S Z = 0

12.  Uses Rosseland effective conductivity to calculate radiation heat transfer in highly sooty regions  Viewfactor radiation outside of heavily fire sooty regions Viewfactor radiation between fire surface and package

13.  Fuel heat generation, Solar heat flux  Natural convection and radiation heat transfer to 38 ° C environment  External surface temperature, hottest at center

16.  Use jet propellant (JP8) fuel fire from a 12-m-diameter pool  Determine the dependence of fire time of concern on the package location with respect to the fire

17.  Fire requirements:  Package must be fully engulfed  Package must be positioned 1 m over the surface of the fuel source  Fuel source must extend between 1 and 3 m beyond package surface Component Condition of Concern Temperature of Concern [°C] Fuel cladding Cladding burst rupture T BR = 750  Temperature of concern

18.  CAFE calculates fire behavior and relays heat transfer coefficient and bulk temperature data to ANSYS CAFE stand-alone run ANSYS runs CAFE runs Change in surface temperature (100°C) or elapsed time (60 sec) Relay heat transfer data for package surface

19.  Benchmarking of CAFE parameters had been done with package over the center of 8 m diameter pool fire under wind conditions  F PC – determines where the Rosseland effective conductivity will be used  0.08 suggested by previous experiments  0.1 used as the nominal-value  xwm – controls the way momentum equation solutions will be solved  1 suggested for xwm  0.25 used as the nominal-value

21. kmittal@anl.gov www.ketanmittal.com

23. ComponentCondition of Concern Temperature of Concern [°C] Fuel cladding Cladding burst rupture T BR = 750 O-ring Seal Thermal failure T TF = 427 Lead gamma shield Lead melt T LM = 316 Neutron shield tank Tank release valve opens due to liquid boiling T LB = 177

25. Seal

26. Gamma shield

27. Neutron shield

28.  Fuel Injection Rate:  Central disk of radius 4 m from which JP8 fuel vapor is injected into the domain at a rate of 0.01 kg/m 2 s.  Fuel is injected at a rate of 0.12 kg/m 2 s (12 times higher) in the outer 2-m-wide ring.  The higher rate in the outside ring is based on the higher heat transfer to that region from the fire, resulting in a higher rate of evaporation