ML20070H852

Freezing of Driver Fuel Upon Entry to Inner Blanket

ML20070H852
Person / Time
Site:	Clinch River
Issue date:	12/23/1982
From:	Epstein M FAUSKE & ASSOCIATES, INC.
To:
Shared Package
ML20070H826	List: ML20070H821 ML20070H832 ML20070H852 ML20070H869
References
NUDOCS 8212270254
Download: ML20070H852 (4)

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FREEZING OF DRIVER FUEL UPON ENTRY TO INNER BLANKET

_ Michael Epstein Fauske & Associates, Inc.

" 8212270254 821223 l PDR ADDCK 05000537 .

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FREEZING OF DRIVER FUEL UPON ENTRY TO INNER BLANKET ASSEMBLIES -

We consider a turbulent flow or jet of driver fuel at its freezing temperature flowing " radially" into an inner blanket assembly through a longitudinal failure (or slit) along its steel-hexcan boundary. Freezing of the molten driver fuel will take place on the surfaces of the relatively cold blanket rods as well as on the inner walls of the intact portion of the hexcan. It is of interest to determine whether the molten driver fuel can fill all the interstitial space within the ccmpact blanket-rod structure before solidification is complete between the blanket rods that occupy the .

outer row of the bundle matrix (" blanket inlet region"). The penetration and freezing of the molten driver fuel in the interstices of the bundle will

" weld" the blanket rods together and strengthe'n the blanket assembly against subsequent mechanical or thermal attack by driver fuel.

In keeping with our objective, we focus attention on a representative subchannel within the rod bundle and assume that it can be regarded as a simple parallel-plate channel of gap width 6 equal to the diameter of the wire wrap (minimum spacing between rods = 0.084 cm). An expression for the dis-tance X a solidifying liquid initially at its fusion temperature can pene~-

trate into a cold channel before the channel freezes shut in the inlet region is [1]

[AP+D l = 0.085 i ["}7/11 X

I (1) h (A ag l

( pv 2 j ,

where v and p are the liquid kinematic viscosity and density, respectively, a, is the thermal diffusivity of the solid phase that grows along the channel 1

1

~

wall, A is the solid phase growth constant [1], D = 26 is the hydraulic h

diameter of the freeze channel and AP is the driving pressure for liquid flow.

2 2 3 Taking v = 0.005 .cm /s, o, = 0.0064 cm /s, = 8.6 g/cm for the molten

, (driver) fuel properties; A = 0.5 for fuel crust growth on a solid (blanket) fuel wall; and a driving pressure AP = 0.5 atm corresponding to gravity-driver fuel flow, we get X = 20.4 cm P

Owing to the circuitous path the driver fuel must follow through the rod bundle matrix, the above-predicted penetration distance is egoivalent to a

" straight-line distance" of about 12.0 cm. This distance is somewhat greater than the width of the rod bundle (= 10 cm) and, therefore, the molten driver fuel should fill most of the space between blanket rods with frozen material.

Of course, if the driver fuel is initially superheated, it will readily penetrate the interstitial space between blanket rods, stagnate and then solidify in place.

Reference

1. M. Epstein, L. J. Stachyra, and G. A. Lambert, " Transient Solidification in Flow into a Rod Bundle," J. Heat Transfer, Vol. 102, No. 2, pp.

330-334, 1980. '

i Enclosure 6 This enclosure contains the response to item 9 of enclosure 1.

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