What is Tritium ? Tritium (3H) is a radioactive isotope of hydrogen, whose specific activity is 358 TBq.g-1. Only tiny proportions of 3H are in a natural state – there is approximately 1 tritium atom for every 1018 hydrogen atoms. Every year, approximately 70,000 TBq (0.2 kg) of tritium is produced through interactions between cosmic radiation and various atmospheric components. The radioactive halflife of tritium is 12.3 years and the total natural tritium inventory is estimated to be 1,300 PBq11 (3.5 kg). Tritium exits in various different chemical forms: tritiated water (HTO), tritium gas (HT) and organically bound tritium (OBT). Tritium is a low-energy beta emitter (mean energy 5.7 keV) and is generally considered to be an element with low radiotoxicity. It follows the hydrogen cycle and is diluted within it. The most commonly-found form in the biosphere is tritiated water, whose biological half-life following ingestion is estimated to be 10 days in an adult. The most common tritium exposure route is ingestion. An annual dose of approximately 0.01 μSv is caused by exposure to naturally occurring 3H. Tritiumworking groups Objectives and approach Dr Patrick Smeesters, Chairman of the “Tritium Impact” group Mr Roland Masse, Chairman of the “Tritium: Defence in Depth” group In 2008, the French Nuclear Safety Authority (ASN) decided to set up two working groups to review current scientific knowledge about the environmental and health impact of tritium (“Tritium Impact” group) and to review the sources and impact of tritium (“Tritium: Defence in Depth” group) and to issue recommendations, where necessary. From the very outset, the desire for a pluralistic approach was at the heart of the composition of these groups. They are broadly made up of French stakeholders – authorities, expert bodies, research organisations, operators and civil society groups. All these bodies had the opportunity to express their opinions through a presentation and discussions and to issue a written text, which is reproduced in full in this white book. The texts express the point of view of their authors only. The summaries that follow set forth the main points discussed and present the various points of view. If there was disagreement on any point, this is stated. The summaries are concluded with a series of recommendations from the working groups. The specific brief the groups received was to explore the following topics: the potential for tritium accumulation along the food chain and whether there is a need to reassess the health effects of beta radiation from tritium (“Impact” group), consequences of the future increase in tritium discharges, and industrial solutions for tritium separation and sequestration from liquid or gaseous discharges (“Defence in Depth” group). 1 Main multiples of units used herein: 103 kilo k; 106 mega M; 109 giga G; 1012 tera T; 1015 peta P; 1018 exa E
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