Na-22 (Sodium-22) Radiation Safety Data
Published: Aug 21, 2023
Source: Ionactive Radiation Protection Resource
Na-22 (Sodium-22)
Half life: 2.6 years
Specific activity: 2.31×1014 Bq/g
Decay product: Ne-22 (non radioactive)
Significant emissions (keV) [Na-22 (Sodium-22)]
In the data below, % refers to the probability of emission of a particular type of radiation at a specified energy
Gamma / x-ray: 511 keV (181%) [i.e. due to two 511 keV photons being released per annihilation event]. 1275 keV (100 %).
Beta (Emax): 546 keV (90 %)
Electrons: n/a
Alpha particles: n/a
External exposure (in air) [Na-22 (Sodium-22)]
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 : 0.101 mSv/h (beta)
Point source : 0.00364 mSv/h (gamma "photon") - use this for radiation protection purposes
Infinite place source (at 10 cm)
Beta (HP 0.07) : 0.072 mSv/h
Photon (HP 0.07) : 0.014 mSv/h
Photons (HP 10) : 0.013 mSv/h
External exposure (arising from personal contamination) [Na-22 (Sodium-22)]
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: 1.70 mSv/h
0.05ml droplet on the skin: 0.70 mSv/h
[Note: For Na-22 special care is required to avoid direct contamination of the body. Consider a 1MBq droplet on the skin. Using the data given that will yield a dose rate of 0.7 Sv/h or 11.7 mSv/min. Consider a 1 GBq droplet on the skin. That will yield 700 Sv/h or 11.7 Sv/min to the skin. These are significant and could produce deterministic effects, and would certainly lead to dose limits being exceeded in a matter of seconds].
Shielding (external radiation) [Na-22 (Sodium-22)]
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: 0.8m
Plastic: 1.4mm
Typical PPE (glove): will provide minimal attention to beta (-) radiation. Note that for Na-22 extremity dose is dominated by the annihilation 511 keV photons.
Gamma / x-ray radiation (TVT and HVT)
Lead: 10mm (HVT) and 27mm (TVT) [Note this is higher than for the F-18 positron emitter since there is also a 1275 keV gamma ray photon as well as the annihilation radiation].
Steel: 31mm (HVT) and 80mm (TVT)
Internal exposure [Na-22 (Sodium-22)]
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 [Na-22(Sodium-22)] 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): 0.5 MBq
Ingestion dose (1 mSv): 0.315 MBq
Workplace Monitoring and Dosimetry [Na-22 (Sodium-22)]
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 [Na-22 (Sodium-22)]
- Proportional counter (e.g. Berthold LB 124 B Xenon detector) - about 17% efficiency (for contamination monitoring)
- Ion chamber (e.g fluke 451 ion chamber) - useful for dose rate monitoring
- Sodium Iodide (NaI) scintillation probe (e.g. Mini 44A or 44B) - useful for contamination spot checks
Dosimetry [Na-22 (Sodium-22)]
- Passive dosimetry - TLD / film for whole body dose monitoring (essential)
- Passive dosimetry - TLD extremity (finger) dosimeter for measuring potential exposures to the hand
- Active dosimetry - use of real time (EPD / PED etc) essential for real time dose control (also relevant for use in a cyclotron vault - see below)
Occurrences and uses [Na-22 (Sodium-122)]
Occurrences
- Not found in nature (artificially produced)
- Na-22 is created in a cyclotron (particle accelerator)
- Formed during atomic (nuclear) explosions
- A product of nuclear fission (i.e. in a nuclear reactor)
Uses
- PET (positron emission tomography) - calibration source. With a 2.6 year half-life, and being a positron emitter, Na-22 is an ideal radioisotope for use as a calibration source in a PET scanner.