External and Internal Hazards - HDBK-1145-2001new0114

Radiological Safety Training for Plutonium Facilities

DOEHDBK11452001

Student's Guide

IV. External and Internal Hazards

A. External exposure hazards

1. Alpha radiation

Alpha radiation is not an external dose concern

because it will not penetrate the dead layer of

skin. Alpha radiation is primarily a concern if it

is introduced inside the body.

2. Gamma and x-ray radiation

All plutonium nuclides emit large quantities of

low-energy x-rays, and the "in growth" of Am-

241 emits higher-energy gamma rays. These

contribute to external exposure and especially

extremity exposure.

3. Neutron radiation

Several plutonium nuclides emit neutron

radiation through spontaneous fission

(notably from Pu-238, Pu-240, and Pu-

242). The rate at which these neutrons

are emitted is different with different

nuclides of the plutonium.

Neutron radiation is also produced by an

alpha-neutron reaction. When alpha

particles interact with the nucleus of an

atom of a lighter element (such as

beryllium or lithium), the nucleus is left in

an excited state. To return to the ground

state, the atom emits a neutron with an

energy of about 2.5 MeV.

An alpha particle emitted by a plutonium

atom may penetrate the nucleus of a

fluorine atom in the compound PuF4.

The excited nucleus decays by emitting a

neutron. The neutron yield and energy

of the alpha-neutron reaction are

dependent on the alpha energy and the

material.