H-3 (Tritium) Radiation Safety Data

Source: Ionactive Radiation Protection Resource

H-3 (Tritium)

Half life: 12.3 years

Specific activity: 3.57×1014 Bq/g

Decay product: He-3 (non radioactive)

Significant emissions (keV) [H-3 (Tritium)]

In the data below, % refers to the probability of emission of a particular type of radiation at a specified energy

Gamma / x-ray: n/a

Beta (Emax): 19 keV (100 %)

Electrons: n/a

Alpha particles: n/a

External exposure (in air) [H-3 (Tritium)]

The values below are specified as mSv/h for either 1 MBq of activity or an area source of 1 MBq/m2 depending on the geometry. Unless specified below, any bremsstrahlung dose rate is not specified. (HP 0.07) represents a skin dose rate and (HP 10) represents an 'at depth' tissue dose rate (> 10mm).

Point source (at 30cm)

Point source : 0.0 mSv/h


Infinite place source (at 10 cm)

Beta (HP 0.07) : 0.0 mSv/h

Photon (HP 0.07) : 0.0 mSv/h

Photons (HP 10) : 0.0 mSv/h

External exposure (arising from personal contamination) [H-3 (Tritium)]

The values below are either for uniform contamination on the skin (for 1 kBq/cm2) or as a single droplet (1 kBq) and are specified in mSv/h. It is assumed that no PPE is being worn which would attenuate the radiation.

Uniform deposit on the skin: 0.0 mSv/h

0.05ml droplet on the skin: 0.0 mSv/h

Shielding (external radiation) [H-3 (Tritium)]

In the data below beta shielding is specified as mm of material to provide 100% absorption of the beta particle (or electron). Gamma (and x-ray) shielding is specified in terms of mm of material relating to 1 TVT or 1 HVT. The TVT is the thickness of material (in mm) which will reduce the radiation intensity (dose rate) down to 1/10 of the pre-shielded dose rate. The HVT is the thickness of material (in mm) which will reduce the radiation intensity down to 1/2 of the pre-shielded dose rate

Beta radiation (for 100% absorption)

Glass: << 0.1mm

Plastic: << 0.1 mm

Typical PPE (glove): total absorption


Gamma / x-ray radiation (TVT and HVT)

Pure beta emitter - TVT and HVT are not relevant for primary radiation.

Internal exposure [H-3 (Tritium)]

The data featured below is derived for employees who work with ionising radiation (and are therefore subject to dose limits specified by the Ionising Radiations Regulations 2017 in the UK, and similar regulation around the world). Whilst not directly applicable to public exposure (e.g. exposure resulting from environmental releases - either planned or accidental), the data will provide a good indication of likely exposures and is therefore adequate for general research, illustration and asking 'what if?' type questions. If you need professional advice, please consider consulting a Radiation Protection Adviser (RPA).

Internal radiation exposure generally means the intake of a radioactive substances by inhalation, ingestion or through cuts (or absorption) in the skin. For this resource assume cuts / absorption are similar to the ingestion values.

This data provides the dose delivered (committed effective dose equivalent) for an intake of [H-3 (Tritium)] by inhalation or ingestion to yield 1mSv effective dose. The dose value provided assumes that all the dose is delivered in the first year of intake, in reality this will vary greatly with radioisotope due to a combination of physical half-life, biological half-life and the biochemical behaviour of the particular radioactive substances in the body.

[Note: in the case of H-3 there is quite some difference between the dose delivered from an intake of elemental H-3 compared to tritiated water or organically bound tritium. This resource provides values for tritiated water which is similar to organically bound tritium and is by far the most common means of exposure].

Target organ: Whole body

Inhalation dose (1 mSv): 24.5 MBq

Ingestion dose (1 mSv): 24 MBq

Workplace Monitoring and Dosimetry [H-3 (Tritium)]

General comment

Workplace monitoring means using techniques to detect ionising radiation sources in the working environment (e.g. on benchtops, floors, walls, drains and similar). The monitoring can be direct (e.g. using a radiation detector to gain real time measurements of dose rate and / or activity) or indirect (where a smear / wipe of an area is made and this is then offered up to a radiation monitoring probe or placed in scintillation fluid for liquid scintillation counting).

Dosimetry is used to measure personal exposure from a source of ionising radiation. Passive dosimetry (e.g. film badge, thermoluminescent dosimeter - TLD etc) is worn on the body (e.g. trunk / extremities / near eyes) and measures total integrated dose over time. Active dosimetry (e.g. electronic personal dosimeter - EPD, personal electronic dosimeter - PED etc) is worn on the trunk of the body and provides real time accumulated dose (and sometimes dose rate) - audible dose and dose rate alarms may also be available. Biological monitoring [bioassay] (e.g. urine sampling, faecal sampling etc) takes biological samples from the body where they are analysed in a sensitive detector to determine activity of radionuclides in the body (usually due to the intake of radioactive material by inhalation, ingestion or through absorption / cuts in the skin).

Workplace monitoring [H-3 (Tritium)]
  • Area wipes following by liquid scintillation counting
Dosimetry [H-3 (Tritium)]
  • Urine sampling followed by laboratory assessment (bioassay)

Occurrences and uses [H-3 (Tritium)]

Occurrences
  • H-3 is formed naturally in the upper atmosphere (via cosmic rays interacting with nitrogen in the air).
  • Formed during atomic (nuclear) explosions.
  • A product of nuclear fission (i.e. in a nuclear reactor). Can be considered a waste product and / or a useful by-product (see below).
Uses
  • Tritium light devices - combining H-3 with a phosphor to produce luminescence (sometimes known as beta lights). Less popular now, but have been used in clocks, watches, compasses, fire escape signage, airport runway lights, railway rear carriage lights, London underground trains, sights on military weaponry. Generally radioactivity is in the 10's of GBq and higher.
  • Tracer radionuclides - used in environmental studies, used as a marker in research (i.e. radiolabelling of molecules that can then be tracked through chemical and biological processes). Generally radioactivity is in the 37 kBq - 37 MBq range for most studies.

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