Criticality - HDBK-1145-2001new0115

Radiological Safety Training for Plutonium Facilities

DOEHDBK11452001

Student's Guide

4. Criticality

A criticality event can produce a life-

threatening dose of radiation to those who

are in the immediate vicinity.

Example: A burst of 1018 fissions in a metal

system may produce doses of 600 rad up to

a distance of 30 feet and 100 rad up to

around 70 feet (assuming there is no

shielding). Also, there may be enough heat

generated to melt the system containing the

plutonium. The fission products produced

will create residual contamination and

lasting radiation problems.

LD 50/30: lethal dose at which 50% of an

irradiated population dies with 30 days.

B. Internal exposure hazards

Plutonium is a heavy metal that is chemically

toxic as well as radioactive. Many other heavy

metals such as arsenic, lead, and uranium are also

chemically toxic.

Plutonium is primarily an alpha emitter and is

particularly hazardous if taken into the body. Alpha

particles do not travel far in material, which means

they lose all of their energy in a short distance.

Alpha particles cannot penetrate the dead layer of

skin on the body. However, when they are in direct

contact with our living cells, such as in our lungs,

they are a hazard. Other alpha emitters include

natural radon, which is also an inhalation concern.