Appendix A: Category 2 Threshold Quantities of Radionuclides

DOE-STD-6003-96

Release fractions (RFs) were also taken from Attachment 1 and are given in the table

below.

Physical form

Gases (tritium, krypton, etc.)

1.0

Highly volatile (phosphorus, halides,

0.5

potassium, sodium, etc.)

102

Semivolatile (selenium, mercury, etc.)

103

Solid/powder/liquid

When a comparison was made between the quantities listed here and corresponding val-

ues in DOE 1992, some significant differences were noted. An investigation revealed that the

calculations supporting DOE 1992 appear to have used the highest dose conversion factors to

be found in DOE 1988b, whereas the calculations performed for this study used dose conver-

sion factors (also from DOE 1988b) corresponding to the oxide forms of the radionuclides, the

form expected to be found associated with fusion reactor materials. As a consequence of this

difference in approach, the DOE 1992 threshold quantities are sometimes orders of magnitude

less than those listed in this letter. Radionuclides showing significant differences for this reason

were 32P, 33P, 35S, 36Cl, 44Ti, 55Fe, 59Fe, 63Ni, 89Sr, 90Sr, 93Zr, 95Zr, 109Cd, 113Cd, 114MIn,

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Gd, 198Au, 203Hg, 227Ac, 230Th, 232Th, 238Pu, 239Pu, and 241Pu.

As a check, the dose conversion factors used in this study were compared with corre-

sponding factors found in Fetter 1988 and 1991. Fetter's calculated dose conversion factors

were intended to apply specifically to fusion reactor materials. The comparison showed general

agreement with the dose conversion factors used here.

It should also be noted that the DOE 1992 calculations for 36Cl used an RF of 1.0, while

an RF of 0.5 was used for this study to be consistent with the other halides. An order of magni-

tude difference in the threshold quantity for 75Se is due to the evident use in DOE 1992 of an

RF of 0.001, while this study used an RF of 0.01 to be consistent with the instructions in

Attachment 1 of DOE 1992.

There are also differences in some of the threshold quantities given in grams. These dif-

ferences can be traced to the use in DOE 1992 of values for specific activity (SA) that are 2 and

3 orders of magnitude higher than the values used here. The use of these SA values when cal-

culating threshold values in DOE 1992 appear to be due to error. The SA values used here were

found to agree with values given in Shleien 1992.

The discrepancy in the values for 52Mn is inexplicable. That was the only case in which

the value in DOE 1992 was significantly higher than the corresponding value calculated here,

and a reason could not be found for the difference.

In summary, the threshold quantities given in the Table A.1 are believed to apply accu-

rately to radioactive materials generated in fusion facilities. Until Category 3 threshold limits are

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