After the second world war, radiobiological facilities were installed to advise on the safe disposal of radioactive substances at sea.

Officials said contamination resulted from practices in earlier years, when regulations for the handling and disposal of radioactive substances and other toxic chemicals were more lax.

To control by licence the custody, use, manufacture, importation, transportation, distribution, exportation and disposal of radioactive substances, irradiating apparatus and other sources of ionising radiation.

The tritium cleanup tops an array of problems that the 50-year-old lab faces as it tries to rebuild shaken public confidence in its ability to manage the 5,300-acre government complex, a Federal Superfund site since 1989 because of the disposal of radioactive substances and chemicals over many years.