Source Term cont'd - h3010v10299

DOE-HDBK-3010-94

7.0 Application Examples; Liquid Storage and Ion Exchange Examples

Even using the same very conservative assumptions about accident progression, and

adding an additional conservatism in the form of the boiling liquid release, the initial

source term can go down by a factor of five by simply changing the time in the

overall process at which the incident occurs.

The remaining source term calculations examine more extreme conditions by

assuming the Pyrex ion exchange columns are constructed out of steel, thus allowing

significantly higher pressures before vessel failure. If the degree of superheat is

greater than 50 oC but less than 100 oC, the associated ARF x RF of 7E-2 is seven

times greater than the ARF x RF for burning resin. The worst case for flashing spray

release is an exotherm shortly following initiation of the elution cycle, when columns

are fully loaded with plutonium in solution and significant plutonium remains on

resin. For the normal case (i.e., columns 1 and 2 loading), 1140 g of plutonium is in

solution in all of the columns with 5360 g absorbed on the resin. For the abnormal

case (columns 2 and 3 loading) 2280 g of plutonium is in solution in the columns,

with 4220 g still absorbed on the resin. The maximum initial source terms are:

Normal: (6500 g * 0.18 * 0.1 * 0.7) + (6500 g * 0.82 * 1E-2 * 1.0) = 135 g

Abnormal: (6500 g * 0.35 * 0.1 * 0.7) + (6500 g * 0.65 * 1E-2 * 1.0) = 201.5 g

Even these may not be worst-case values for steel vessels. System pressures as high

as 10.3 MPa (1500 psia) have been recorded at the onset of vessel or flange failure in

steel systems. The fact that the example system, if made of steel, could support such

pressures is apparent from simple calculations. Such a column would essentially act

like a straight pipe under internal pressure. A correlation to estimate the minimum

thickness of pipewall for a given design pressure is (Perry and Chilton, 1973):

T = PD/[2*(SE + PY)] + C

(7-7)

where:

T = minimum required thickness (in) = typical vessel thickness of 0.3 in.

P = design pressure (psi)

D = outside diameter (in) = average of 6.6 in for 6 in inner diameter and

0.3 in thickness

S = maximum allowable material stress (psi) = average of 15,000 for

stainless steel at 400 oF.

E = weld joint efficiency factor = assume 1.0

Y = variable temperature coefficient to account for redistribution

circumferential stress = 0.4

C = Allowance for corrosion = assume 10% of thickness = 0.03 in

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