Material-at-Risk (MAR)

DOE-HDBK-3010-94

1.0 Introduction

pathway will dominate the (overall) dose" (NUREG-1140). The airborne source term is

typically estimated by the following five-component linear equation:

Source Term = MAR x DR x ARF x RF x LPF

(1-1)

where:

MAR

= Material-at-Risk (curies or grams),

= Damage Ratio,

ARF

= Airborne Release Fraction (or Airborne Release Rate for

continuous release),

= Respirable Fraction, and

LPF

= Leakpath Factor.

The initial source term and initial respirable source term are products of the first three factors

and first four factors respectively. A depleted source term after a subsequent stage of

deposition or filtration is a product of the initial source term multiplied by the leakpath factor

of the specific stage.

This handbook assesses ARF and RF values separately for sources of airborne material

generated from accidents involving gases, liquids, solids, and surface contamination. All of

the above factors may need to be determined for particulate releases. Some of them,

however, will collapse to values of one for special cases (e.g., gaseous releases).

Material-at-Risk (MAR)

The material-at-risk is the amount of radionuclides (in grams or curies of activity for each

radionuclide) available to be acted on by a given physical stress. For facilities, processes,

and activities, the MAR is a value representing some maximum quantity of radionuclide

present or reasonably anticipated for the process or structure being analyzed. Different

MARs may be assigned for different accidents as it is only necessary to define the material in

those discrete physical locations that are exposed to a given stress. For example, a spill may

involve only the contents of a tank in one glovebox. Conversely, a seismic event may

involve all of the material in a building.

Damage Ratio (DR)

The damage ratio is the fraction of the MAR actually impacted by the accident-generated

conditions. A degree of interdependence exists between the definitions of MAR and DR. If

it is predetermined that certain types of material would not be affected by a given accident,

some analysts will exclude this material from the MAR.

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