Other sealed sources cont'd

Radiological Assessor Training

DOE-HDBK-1141-2001

Instructor'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

Fast neutrons moderated (slowed

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

down) to slow neutrons, which are

emitted by the source are moderated by the

detected.

hydrogen atoms in the material being measured,

and can then be detected with a neutron detector.

When an alpha-emitting material is

Of course, the more moisture contained in the

combined with beryllium, the

material, the more hydrogen atoms will be present.

alpha/beryllium reaction results in

the formation of Carbon-12 and a

neutron. Some common sources of

Neutron sources are also used to some extent for

this type are combinations of

radiography of very dense materials like lead or

Americium-241 and Beryllium (AmBe

steel, which otherwise would require very high

sources) and Plutonium-239 and

energy photons to radiograph.

Beryllium (PuBe sources). Another

nuclear reaction that can produce

neutrons is the photo-neutron

Californium-252 emits neutrons after undergoing

reaction. For this reaction to occur,

spontaneous fission, and therefore serves as a

a gamma-emitting material is

neutron source. Neutrons can also be produced

combined with beryllium, resulting in

fairly easily by nuclear reactions in certain materials

the production of neutrons. An

such as beryllium.

example of this type of neutron

source is the combination of

Antimony-124 and Beryllium (SbBe

The primary hazard from beta and neutron sources

source).

is from the external radiation fields they generate.

These sources would only become an internal

Neutron activation can produce

hazard should the source rupture or leak and

gamma-emitters (external dose

concern).

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

Review definition of accountable

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

sealed radioactive source.

inventory

Discuss 10 CFR 835.3(e) provision

to allow 30 day grace period for

certain time intervals.

posting

leak testing

Module 12 10