Radiation Protection Today - Winter 2022 Issue 4 - Page 22

measurements of radon concentration can show dramatic variations over a 24-hour period . The radon levels in one old luminising plant were found to vary between

3 3
~ 1,000 Bq / m and 13-15,000 Bq / m ( see figure ). Concentrations were lower during the day due to doors and windows being opened and the use of an air-moving unit but rose rapidly when this was switched off at the end of a shift and the facility locked up . Mitigation of worker risk therefore requires both the management of area ventilation and the use of appropriate Respiratory Protective Equipment ( RPE ).
The Ionising Radiations Regulations 2017 apply for any work performed in an atmosphere containing Rn-222 gas at an annual average activity concentration in air
3 exceeding 300 Bq / m .
It is fairly easy to identify a radium dial when still intact , but visually recognising historic radium contamination can be much more challenging , especially if the item was burnt
200 µ Sv / h dose rate from aircraft signage
prior to disposal ( a common practice ). In such cases , it is necessary to rely primarily on radiation monitoring . The physical form of radium contamination from incinerated items can range from a dial fragment to a tiny speck of loose material , with the dose rate not necessarily proportionate to the physical size . In addition to external dose , small particulate contamination also carries the risk of internal dose if inhaled or ingested .
Daily variation in radon concentration in air in an old luminising facility
Museums are one location where radium might be present in significant quantity , either as individual luminised dials or signs , or as gauges installed in larger equipment . A single aircraft cockpit could contain numerous radium dials , giving rise to a significant dose rate – although this was probably not the most immediate hazard of concern when flying a Spitfire in World War Two !
Fragment of a radium dial being monitored
Small radium particle
Radium dials in an aircraft cockpit
Dealing with historic radium contamination can be complex , with the specific radiological risks and radiation field varying dependent upon the particular scenario . For this reason , it is important to seek advice from suitably qualified radiation protection professionals before commencing work where radium could be present .
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