Decommissioning of Nuclear Storage Basin
Nuclear Storage Basin – Radioactive Sludge and Debris Removal
Underwater removal & packaging of highly radioactive material (DOE Decommissioning Project – applicable to both government and commercial nuclear facilities)
Over 300 dives were performed with no skin contaminations. Radiological conditions were extreme with contact dose rates in the sludge ranging from 0.050 Rem/hr to 30 Rem/hr and averaging about 2 Rem/hr. Divers encountered debris with dose rates of up to 600 Rem/hr on contact. To put this in perspective, high radiation is considered to be a dose rate exceeding 0.100 Rem/hr. An actual whole body exposure of 400 to 600 Rem can result in acute radiation poisoning causing death within 30 days.
Taking advantage of the shielding provided by the water and other dose mitigation techniques, we were able to keep the diver in a 0.001 to 0.005 Rem/hr field during the majority of the work. Even though brief excursions into high dose areas were necessary, an average exposure rate of 0.006 Rem/hr was maintained for the entire dive team for the course of the project. This includes Divers, Tenders, and support personnel. Divers typically averaged 0.003 Rem/hr during diving operations keeping total exposure well below expected levels.
Over 10,000 pounds of basin debris was managed and relocated. Divers operated a desludging system to collect approximately 1,500 ft3 of sludge in a fraction of the planned task duration. Overall, it was successfully demonstrated that, on a task by task basis, divers could work more efficiently while receiving significantly less radiation exposure than topside workers using remote tools or extension poles. Much of the work performed underwater would not have been possible without the shielding afforded by the water barrier and direct access by the divers.