Determination of plutonium radioactivity in Mururoa lagoon water

This study presents the plutonium radioactivity levels measured in Mururoa lagoon water during the 1985–1991 period.The low radioactivity levels recorded, from 10^–2 to 1.5 Bq/m³ are due to the slow solubilization of plutonium deposited in lagoon sediments following atmospheric experiments which took place from 1966 to 1974. The average concentrations of the lagoon water tend to decrease from one year to the next. However, the influence of the weather conditions is discussed.The Mururoa lagoon being open to the ocean, plutonium radioactivity traces are still detectable in the immediate vicinity of the atoll.