Se-75 (Selenium-75) Radiation Safety Data

Source: Ionactive Radiation Protection Resource

Se-75 (Selenium-75)

Half life: 119.8 days

Specific activity: 5.37×1014 Bq/g

Decay product: As-75 (stable)

Significant emissions (keV) [Se-75 (Selenium-75)]

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

Gamma / x-ray: 136 keV (59%), 265 keV (59%), 401 keV (12%)

Beta (Emax):

Electrons: 14 keV (6%), 85 keV (3%), 124 keV (2 %)

Alpha particles: n/a

Electron capture emitter.

External exposure (in air) [Se-75 (Selenium-75)]

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. (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 : 0.000740 mSv/h (0.74 micro Sv/h) [via gamma emissions].

Infinite place source (at 10 cm)

Beta / electrons (HP 0.07) : 0.00088 mSv/h (0.88 micro Sv/h)

Photon (HP 0.07) : 0.0074 mSv/h (7.4 micro Sv/h)

Photons (HP 10) : 0.0052 mSv/h (5.2 micro Sv/h)

External exposure (arising from personal contamination) [Se-75 (Selenium-75)]

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: 0.143 mSv/h (gamma dose rate)

0.05ml droplet on the skin: 0.0076 mSv/h (7.6 micro Sv/h) (gamma dose rate)

Shielding (external radiation) [Se-75 (Selenium-75)]

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: 0.2mm

Typical PPE (glove): negligible absorption (don't rely on gloves to shield for external radiation, they are a contamination control method).

Gamma / x-ray radiation (TVT and HVT)

Lead: <1mm (HVT) and 5mm (TVT)

Steel: 8mm (HVT) and 27mm (TVT)

Internal exposure [Se-75 (Selenium-75)]

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 [Ga-68 (Gallium-68)] 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.

Target organ: Lungs

Inhalation dose (1 mSv): 0.985 MBq

Ingestion dose (1 mSv): 0.385 MBq

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