P-33 (Phosphorus -33) Radiation Safety Data

Source: Ionactive Radiation Protection Resource

P-33 (Phosphorus-33)

Half life: 25.6 days

Specific activity: 5.72×1015 Bq/g

Decay product: S-33 (non radioactive)

Significant emissions (keV) [P-33 (Phosphorus-33)]

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): 249 keV (100 %) Beta (Eav): 83 keV

Electrons: n/a

Alpha particles: n/a

External exposure (in air) [P-33 (Phosphorus-33)]

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 (beta dose rate) [negligible above background]

Infinite place source (at 10 cm)

Beta (HP 0.07) : 0.049 mSv/h

Photon (HP 0.07) : 0.0 mSv/h

Photons (HP 10) : 0.0 mSv/h

External exposure (arising from personal contamination) [P-33 (Phosphorus-33)]

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: 0.87 mSv/h (beta dose rate)

0.05ml droplet on the skin: 0.137 mSv/h (beta dose rate)

[Note: Where possible working with P-33 will be preferable compared to working with P-32, as long as the experimental aims and objects are still achieved. P-33 is a considerably lower energy beta emitter compared to P-32}.

Shielding (external radiation) [P-33 (Phosphorus-33)]

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: 0.3 mm

Plastic: 0.3 mm

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

Gamma / x-ray radiation (TVT and HVT)

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

Internal exposure [P-33 (Phosphorus-33)]

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 [P-33 (Phosphorus-33)] 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: Whole body

Inhalation dose (1 mSv): 0.7 MBq

Ingestion dose (1 mSv): 4.15 MBq

Workplace Monitoring and Dosimetry [P-33 (Phosphorus-33)]

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 [P-33 (Phosphorus-33)]
  • Geiger-Mueller (GM) tube with thin end window (e.g. Mini E / EP15) - 10-30% efficiency
  • Beta Scintillation probe with large area window (e.g. Thermo HP-380B) - up to 28% efficiency
  • LB 124 SCINT probe - large area surface contamination monitor (170 cm2)
  • Area wipes following by liquid scintillation counting (usable results, but direct monitoring more useful)
Dosimetry [P-33(Phosphorus-33)]
  • Urine sampling followed by laboratory assessment (bioassay)

Occurrences and uses [P-33 (Phosphorus-33)]

  • P-33 is not found in nature (in any meaningful or useful activity)
  • P-33 is formed in a nuclear reactor (irradiation of P-31 with neutrons)
  • Formed during atomic (nuclear) explosions
  • Biomedical studies in plant and animal cells - radiolabelling cells with P-33 is a common research analytical technique, often favoured over P-32 due to its longer half life and lower beta energy (therefore lower extremity hazard).

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