Sources of STCs

DOE-HDBK-1184-2004

the primary physical forms considered are particles, liquids/vapors and large solid

forms.

Radiological controls for STC particles that are considered to be insoluble should

be based on the controls used for radioactive particles rather than the controls used

for HT, HTO, or vaporous forms of OBTs. Such tritiated particles are called

insoluble tritiated particulates (ITPs). Examples of ITPs are tritiated metals, and

metal oxides; the large molecule component of OBT oil; and solid OBTs such as

flyash, nylon, and organic dust.

Soluble types of particulates rapidly release their bound tritium. For these types of

triated particles, radiation protection measures should be based on those for HT or

HTO. In addition, the detection problems that arise from the binding of tritium within

the host particle are not an issue (see section 3.1). Examples of such particles are

metal tritides of palladium and uranium.

STCs that are liquids and vapors are primarily comprised of OBTs. Soluble OBT

can be incorporated into the body by inhalation, ingestion, or absorption through

skin. Soluble OBT distributes throughout the body causing a whole body dose.

ICRP 78 (ICRP 1998b) categorizes the dissolution rate for soluble vaporous OBT

as Type V (very fast dissolution). Solvents are considered to be soluble.

Radiological protection measures for vaporous OBTs are identical to those used for

HT and HTO. When establishing controls for liquid forms of OBTs, it is important to

consider absorption of the OBT through the skin, the vapor pressure of the liquid,

the possibility that the liquid is composed of more than one OBT, and dispersal

mechanisms that could aerosolize the liquid. An example of a liquid OBT is tritiated

oil that has been used in pumps and air compressors.

Tritiated oils are a type of OBT that contains both soluble and insoluble

components. Oils can be taken into the body by inhalation when they are in

particulate form or can be absorbed through the skin. Because tritiated oils

primarily consist of insoluble components (see section 4.4.3) tritiated oils will be

treated in this handbook as insoluble particulates when they become airborne

droplets.

The term "large solid forms" denotes the types of STCs that cannot be easily taken

into the body, such as a piece of tritiated metal. Radiological controls for these

types of tritides consist primarily of planning for situations in which portions these

materials could be converted to airborne particles. Otherwise, standard radiation

protection measures for the control of radioactive materials should be applied to

these types of STCs. See section 3.2.1.2 for additional guidance that may be

applicable to large solid forms of STCs.

2.4 Sources of STCs

As discussed previously, tritium, including that contained in STCs, is not considered an

external exposure hazard. However, particulate tritiated materials, both metals and organic

materials, can be ingested or inhaled, creating an internal exposure hazard. Solid

particulate OBTs, such as plastic, nylon, organic dust, or the large molecule component of

OBT oil, can become airborne by dispersal mechanisms. Equipment that can impart

energy to oil through motion or release of pressure (e.g. pumps and air compressors) can

cause an oil mist aerosol to be generated.