Underwater Repair of Nuclear Reactors

An innovative approach to maintenance and repair inside reactor vessels without dewatering has been accomplished by the utilization of underwater technicians. The presence of water provides shielding to the workers thereby reducing both the radiation dosage and the dose rate and permits much longer stay time in the repair area. This provides several distinct benefits: (1) the number of people exposed to radiation during a repair operation is reduced by an order of magnitude or more; (2) the overall duration of the repair operation is usually shortened drastically; (3) quality standards are more easy to maintain; and (4) the individual radiation dosage is reduced to unprecedented levels for repair operations. Present experience with underwater technicians indicates clearly that virtually all kinds of Jobs can be accomplished under water. This includes determination of the problem, repair, and quality assurance check up which are all done with greater safety because of the shielding effect of the coolant.