Lesson 2/Learning Event 7
Degrees of Risk
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; from initial nuclear radiation
resulting from enemy or friendly weapons, or both; and from initial nuclear radiation resulting from
planned friendly supporting fires. Degrees of risk are defined in terms of percent incidences of either
casualties or performance degradation. From a radiation standpoint, the effect considered to cause
performance degradation (but not casualties) is vomiting, which is commonly termed a "nuisance"
effect. The three degrees of risk are discussed in the following paragraphs.
Negligible Risk. Troops receiving a negligible risk dose will not experience more than a 2.5 percent
incidence of vomiting. This dose will cause no casualties. The negligible risk dose is 50 cGy(rad) for
units with no previous dose (RS-0 units). It will be appropriately less for previously exposed units. A
negligible risk is acceptable in any case in which the use of nuclear weapons is desirable. Negligible
risk should not be exceeded unless significant advantage will be gained.
Moderate Risk. Troops receiving a moderate risk dose will not experience more than a 5 percent
incidence of vomiting. This dose will cause no casualties. A moderate risk dose is 70 cGy(rad) for units
with no previous dose. It will be appropriately less for previously exposed units. A moderate risk is
considered acceptable in close support operations. For example, to create a gap in enemy forward
positions or to halt an enemy attack. Moderate risk should not be exceeded if troops are expected to
operate at full efficiency after a friendly burst.
Emergency Risk. Troops receiving an emergency risk dose will not experience more than a 5 percent
incidence of casualties. The incidence of vomiting may be higher. An emergency risk dose is 150
cGy(rad) for units with no previous dose. It will be appropriately less for previously exposed units. An
emergency risk should be accepted only when it is absolutely necessary. It should be exceeded only in
extremely rare situations that might be loosely called "disaster" situations. No attempt is made to define
disaster situations. The commander must determine these extremely rare situations for himself and
decide which criteria are appropriate to use in attempting to salvage them.
Establishing an Operations Exposure Guide When the Total Cumulative Dose is NOT Known. A
battalion commander plans to conduct a survey in a radiologically contaminated area. The survey party
members come from different units within the battalion. The survey party's total cumulative dose is
unknown. The commander will accept a moderate risk. What Operation Exposure Guide will the
commander establish for this survey operation?
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