Radiation Protection Today - Spring 2022 - Page 18

SOAPBOX sources for the calibration of radiation instruments .

Gary Teague is CEO of Gemini Technology , which specialises in the design and manufacture of dosimetry , calibration and specialist equipment for radiation laboratory , research and industrial applications . In this article he expresses his personal opinion on the challenges facing users and suppliers of Cs-137 sources , and suggests a possible way to avert a crisis .
Due to concern over the risks from a dirty bomb or other terrorist threat , the USA has made a stand to eradicate the production of Cs-137 ( CsCl ) used to manufacture high activity sources ( e . g . those used for blood irradiation ) and replace the technology with the use of X -ray irradiators .
The knock-on effect from the USA stance , and the potential for Europe and the rest of the world to follow suit , is that the demand for Cs-137 has dwindled to the point that the only global manufacturer has closed its plant until the demand picks back up .
All sealed sources have a working life certified by the manufacturer , based on the design integrity of the capsule which contains the radioactive material . The current situation means that across the world , Cs-137 sealed sources over their 15-year working life cannot be replaced with sources of matching activity because these are no longer available . The largest Cs-137 source that can be purchased globally right now is 300 GBq , which is less than 10 % of the activity required by 90 % of the UK facilities which use Cs-137
Many UK sites are still using Cs-137 sealed sources over 30 years old , and justify this by completing wipe tests to ensure capsule integrity . However , these sources have now gone through a full half-life , and can no longer achieve the required dose-rate . The other real problem is that most of the UK ' s irradiators which use Cs-137 sources are over 30 years old , and will need replacement in the near future . This again is a problem , since most UK sites will still need to calibrate monitoring instruments for at least another 50 years .
An ideal situation would be for old Cs-137 sources to be re-certificated with an extended working life . They could then potentially be transferred between sites that require these sources , rather than having to spend a fortune on their disposal , particularly since there is no Cs-137 available right now to replace them .
The current situation is not sustainable , and we are heading towards a crisis . We must either allow the re-certification of old sources for re-use , or accept a move away from Cs-137 altogether and change the standards to allow the use of X-rays for calibration of radiation monitoring instruments .
In my opinion , regulators and metrology labs need to get together to discuss how we can move forward on this issue , and find a sensible solution .
If you have an opinion on a radiological protection related issue which you would like to bring to the attention of the profession and make the case for change , please email RPToday @ srp-uk . org . We will consider publishing your letter or Soapbox article in a future issue .
18 Radiation Protection Today www . srp-rpt . uk