Other sealed sources - DOE-HDBK-1141-2001

Radiological Assessor Training

DOE-HDBK-1141-2001

Student's Guide

Neutron sources have a variety of applications and

are commonly used in moisture gauges (e.g.,

determining moisture content in raw materials such

as gravel, wood chips, etc.). The fast neutrons

emitted by the source are moderated by the

hydrogen atoms in the material being measured,

and can then be detected with a neutron detector.

Of course, the more moisture contained in the

material, the more hydrogen atoms will be present.

Neutron sources are also used to some extent for

radiography of very dense materials like lead or

steel, which otherwise would require very high

energy photons to radiograph.

Californium-252 emits neutrons after undergoing

spontaneous fission, and therefore serves as a

neutron source. Neutrons can also be produced

fairly easily by nuclear reactions in certain materials

such as beryllium.

The primary hazard from beta and neutron sources

is from the external radiation fields they generate.

These sources would only become an internal

hazard should the source rupture or leak and

radioactive material subsequently is inhaled or

ingested. An additional hazard of neutron activation

exists around neutron sources.

10 CFR 835 Subpart M "Sealed Radioactive Source

Control" establishes requirements for accountable

sealed radioactive sources. Requirements include

provisions for (at intervals not to exceed 6 months):

inventory

leak testing

Module 12 - 7