3-6. Degree-of-Risk Concept. The degree-of-risk concept provides guidance to the commander in
establishing the OEG. There are three degrees of risk: negligible, moderate, and emergency. Each of
these can be applied to radiation hazards resulting from enemy or friendly weapons, or both. It can also
be applied to initial nuclear radiation resulting from planned friendly supporting fires.
a. Degrees of risk are defined in terms of the expected response of personnel who are exposed to
nuclear radiation. These responses are expressed as a percentage of casualties or reduction in
performance. Vomiting is one effect that is considered to cause reduction in performance. The radiation
aspects of degrees of risk are discussed in Lesson 1.
b. It is important for you to understand and remember that the negligible risk dose of 50 cGy,
moderate risk dose of 70 cGy, and emergency risk dose of 150 cGy are for units with no previous
radiation exposure. After a unit has been exposed to nuclear radiation, the risk dose will be less, as shown
in Table 3-2.
c. The commander can establish the OEG using the degree-of-risk exposure chart. When doing
this, the commander must consider the RES of subordinate units and the degree of risk that will be
(1) Use the degree-of-risk information. The possible exposure criteria for a single operation
and the dose criteria for a stated degree of risk are given in Table 3-2. The risk criteria for units in RES-1
and RES-2 are based on assumed average exposure (40 cGy for RES-1 and 110 cGy for RES-2). These
average criteria should be used only when the numerical value of the total past cumulative dose of a unit
is UNKNOWN. When the cumulative dose is KNOWN, the risk criteria are obtained by subtracting the
actual known dose from the RES-0 criterion. The following examples give calculations of the degree of
risk for both criteria:
(a) Calculate the degree of risk when the total cumulative dose is KNOWN. A unit is
known to have received a total cumulative dose of 30 cGy. How much more radiation can this unit
receive before exceeding a negligible risk?
Step 1. You know that the total cumulative dose of the unit is 30 cGy.
Step 2. You know that the commander does not want to exceed a negligible risk.