Radiation and Hazardous Material

DOE-STD-6003-96

2. RADIATION AND HAZARDOUS MATERIAL

The neutron flux in a fusion facility will result in activation of the first wall and structure,

resulting in the production of radioactive materials. The level of activation is a function of power

level, fuel cycle [deuterium-deuterium (D-D) vs deuterium-tritium (D-T)], and materials choice.

Fusion experiments and power plants presently envisioned will also use strong magnetic fields,

radio-frequency heating, and some potentially hazardous materials such as beryllium and

vanadium. This section summarizes general guidance regarding radiological, magnetic field,

and hazardous material concerns expected to be present at fusion facilities.

Chemically hazardous materials are sometimes specified in the design of a fusion power

core because of their mechanical or nuclear properties. The most prominent of these materials

are beryllium, used as a first wall coating and as a neutron multiplier, and vanadium, used as a

first wall and blanket structure material.

2.1 Dose Definitions

The effective dose E has associated with it the same probability of the occurrence of

cancer and genetic effects whether received by the whole body via uniform irradiation or by

partial or individual organ irradiation. Although an assumption of uniformity may be a sufficient

approximation in many external irradiation cases, in others more precise evaluation of individual

tissue doses will be necessary. With external irradiation, differences may arise with depth in the

body and with orientation of the body in the generally nonuniform radiation field. When irradia-

tion is from radionuclides deposited in various tissues and organs, nonuniform or partial body

exposures usually occur. Tissues also vary in their sensitivity to radiation. The effective dose E

is a concept similar to the effective dose equivalent HE used by ICRP Publication 26 (ICRP

1977) and NCRP Report No. 91 (NCRP 1987). However, they are conceptually different. The

effective dose E is intended to provide a means for handling nonuniform irradiation situations, as

did the earlier dose equivalent.

The effective dose E is the sum of the weighted equivalent doses for all irradiated tissues

or organs. The tissue weighting factor wT takes into account the relative detriment to each organ

and tissue including the different mortality and morbidity risks from cancer, the risk of severe

hereditary effects for all generations, and the length of life lost due to these effects. The risks for

all stochastic effects will be the same whether the whole body is irradiated uniformly or

nonuniformly if

E = ∑ wTHT ,

(1)

where wT is the tissue weighting factor representing the proportionate detriment (stochastic)

tissue T when the whole body is irradiated uniformly, and HT is the equivalent dose received by

tissue T. For further explanation see NCRP Report No. 116 (NCRP 1993).

Doses mean the 50-yr committed effective dose (CED) unless otherwise stated. The

exposure times and exposure pathways to be included in the calculation of CED should be