Mohd. Afzal

Ultrasonic decontamination of prototype fast breeder reactor fuel pins.

Fuel pin decontamination is the process of removing particulates of radioactive material from its exterior surface. It is an important process step in nuclear fuel fabrication. It assumes more significance with plutonium bearing fuel known to be highly radio-toxic owing to its relatively longer biological half life and shorter radiological half life. Release of even minute quantity of plutonium oxide powder in the atmosphere during its handling can cause alarming air borne activity and may pose a severe health hazard to personnel working in the vicinity. Decontamination of fuel pins post pellet loading operation is thus mandatory before they are removed from the glove box for further processing and assembly. This paper describes the setting up of ultrasonic decontamination process, installed inside a custom built fume-hood in the production line, comprising of a cleaning tank with transducers, heaters, pin handling device and water filtration system and its application in cleaning of fuel pins for prototype fast breeder reactor. The cleaning process yielded a typical decontamination efficiency of more than 99%.

Laser-Assisted Decontamination of Fuel Pins for Prototype Fast Breeder Reactor

Decontamination of fuel pins is an important process step in nuclear fuel fabrication. Decontamination assumes greater significance with respect to fuels containing plutonium, owing to both plutonium’s high radiotoxicity arising from its long biological half-life and its relatively short radioactive half-life. The advantages of using a laser to decontaminate such radioactive surfaces over conventional cleaning techniques are well recognized. This paper describes detailed process optimization and field implementation of laser-assisted decontamination of fuel pins of the Prototype Fast Breeder Reactor (PFBR). A short-pulsed Nd-YAG laser has been effectively used to decontaminate the fuel pins by exposing their outer surface to laser radiation of an appropriate fluence. The laser parameters were controlled to achieve the required cleaning without causing any clad surface damage. Achievement of such was confirmed by evaluating the laser-cleaned surface using scanning electron microscopy, chemical composition studies by electron probe microanalysis, and Vicker’s microhardness test.

Fabrication of (U-Pu) Mixed-Oxide Fuel for Pressurized Heavy Water Reactors

Indian pressurized heavy water reactors (PHWRs) have been operated over the years using natural UO2 bundles. An attempt has been made recently to use (U-Pu) mixed-oxide (MOX) fuel bundles containing 0.4% PuO2 to increase the burnup and reduce fuel inventory. This paper outlines the design changes made in the fuel elements and presents the important steps in fabrication of MOX fuel, the novel quality and process control procedures developed, and our experience during the fabrication of MOX fuel assemblies irradiated in one of the commercial PHWRs.