IAEAInternational Atomic Energy Agency

Use of radiation source in consumer products

Day 6 – Lecture 7

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Objective

• To describe the various types of consumer products that contain radioactive materials,

• To discuss the radiological protection principles and to show how they are applied to the regulation of consumer products

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Contents

• Early consumer products• Ionization Chamber Smoke Detectors• Time Pieces• Anti-static brushes and• Other products• Radiation Protection• Justified or unjustified uses• Exemptions• Disposal

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A long history

• When radiation and radioactivity were first discovered there was a rush to exploit this new “wonder of science”.

• The emphasis was on “benefit” or what was thought might be a benefit with little thought or awareness of harm.

• This lead to “products” available to the public – indeed heavily marketed – such as:-

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Early consumer products

• Radium compress for rheumatism• Radium shoe liners• Radium face cream• Radon “sparklets” bulbs to produce radon

water

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Glow-in-the-dark products

• Radium/phosphor paints used for:• Clocks and watches• Aircraft instrument dials• Bell pushes• Boat instruments and signs• Compasses• Car speedometers and dials• Thermostat dials

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Radiation protection

• In the 1950s came recognition that such widespread distribution of products with essentially no control was undesirable

• Justification was introduced – or at least avoidance of unnecessary exposure

• 1960s – 1970s re-examination of existing products and consideration of new products was at its height

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Products

• Before dealing with the application of radiation protection principles and the regulation of products it is useful to have more idea of the types of products available.

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Ionization Chamber Smoke Detectors

• The most widely used product• Uses an alpha source to increase sensitivity

to the out-of-balance current between a sealed chamber and one open to admit smoke

• Am-241 up to 40 kBq• Annual doses around 0.01-0.2 μSv

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Timepieces

• Alarm clocks and watches• Were very common but much less so now• Radium paint replaced by tritium or Pm-147• Annual dose to wearer around 0.1μSv

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Gaseous Tritium Light Sources (GTLS)

• Glass tubes coated internally with a phosphor and filled with tritium gas

• Primarily commercial uses such as EXIT signs

• Largest domestic use was in UK to illuminate circular “trimphone” dials

• Also used in watches, compasses, fishing floats, light switches, bell pushes

• Activity 10-15 GBq

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Lightening preventers

• An alpha source on the end of a lightening rod so the additional ionization would attract the lightening

• Effectiveness now seriously doubted• Removed for disposal where encountered

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Anti-static brushes

• Use an alpha source with a fine haired brush to dispel static electricity

• Used with records (vinyl) and photographic negatives

• 18 MBq Po-210 or 1 MBq Am-241• Popularity has declined recently

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Thoriated gas mantles

• For use in incandescent lamps for camping and caravanning, but also home lighting in some countries.

• Doses mainly from inhalation and ingestion during burning and from broken mantles during replacement

• Annual doses a few μSv but could be more for home lighting

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Coloured enamels

• Uranium salts are used to give a strong yellow colour to enamels

• Pottery, cloisonné jewellery, badges, key fobs etc

• Doses very low but for items kept in a pocket (key fobs) could be a few μSv

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Gemstones

• Irradiation can enhance the colour of gemstones and increase the value

• X-rays do not cause any subsequent dose• Neutron irradiation can induce activity,

minimised by choice of stones to avoid impurities and storage after irradiation for decay

• Doses to wearers claimed to be small

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Other products

• Camera lenses containing thorium• False teeth containing uranium

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Radiation Protection Principles

There are three main principles of radiation protection;• Justification• Optimisation• Dose limits

All are really used when dealing with consumer products

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Justification

• “No practice or source within a practice should be authorized unless the practice produces sufficient benefit to the exposed individuals or to society to offset the radiation harm that it might cause i.e. the practice should be justified, taking into account social, economic and other relevant factors”.

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Unjustified uses

• The following practices are deemed to be not justified :

• (a) practices involving food, beverages, cosmetics or any other commodity or product intended for ingestion, inhalation or percutaneous intake by, or application to, a human being; and

• (b) practices involving the frivolous use of radiation or radioactive substances in commodities or products such as toys and personal jewellery or adornments.”

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Also unjustified

• Distribution to the public of sources or radioactive substances not in a complete consumer product

• The use cannot be predicted -• so the benefit and detriment cannot be

assessed.

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Optimisation

Optimization requires the:

• magnitude of individual doses

• number of people exposed, and the

• likelihood of incurring exposures

to be kept As Low As Reasonably Achievable (the ALARA principle).

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Optimisation

• Optimisation is more qualitative and design-oriented:• Use most appropriate radionuclide for half-life,

radiation type, energy and minimum activity necessary for product to work

• Chemical and physical form for safety in use and accidents

• Mechanical construction to prevent access to source

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Dose limitation

• Dose limits should ensure that no individual faces an unacceptable risk in normal circumstances

• Dose limits for public apply but these cover several sources so normally for consumer products a small fraction of 1 mSv.

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Exemption

• The principles of exemption in the BSS have been used by some authorities for consumer products, but not unjustified products• Limit for each product 10 µSv individual dose to

user• Collective dose < 1 mSv per year

• If single product activity less than exemption levels in BSS then can be automatically exempted

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Labelling

• Safety of products should not depend on labelling so not essential requirement

• Desirable to identify product, inform consumer and reduce risk of misuse

• Label may be on package where impractical on product e. g. gas mantles

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Disposal

• Some authorities have tried to impose restrictions but not really practical for members of the public.

• Disposal in normal household refuse should be part of safety assessment and approval implies that this is safe.

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Conclusions

• Large numbers of consumer products in use in most countries

• Decision on whether to permit a particular product usually lies with National Regulatory Authority

• Permitted products need optimised design and good quality control.

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Where to Get More Information

International Atomic Energy Agency, Postgraduate Educational Course in Radiation Protection and the Safety of Radiation Sources (PGEC), Training Course

Series 18, Vienna (2002)

IAEA safety standards, Radiation Protection and Safety of Radiation Sources: International Basic Safety Standards, Interim Edition (GSR Part 3, 2011).