Development of an On-line Analyzer for Vanadous Ion in Lomi Decontamination

Abstract

An automatic, repetitive titrimeter was developed for the determination of vanadous ion concentration during chemical decontamination of nuclear power plants by means of the LOMI method. The LOMI (an acronym for low oxidation state, metal ion) treatment is used during refueling shut-downs to reduce the exposure of plant personnel to radiation by removing radioactive deposits which have accumulated in pumps and piping. A dilute aqueous mixture of vanadous formate and picolinic acid (2-pyridine carboxylic acid) reduces, complexes, and dissolves oxide deposits which contain radioisotopes which were produced by neutron activation of the products of corrosion and wear. The titrimeter makes it possible to follow depletion of the V(II) concentration as the process proceeds. The instrument automatically withdraws samples of the circulating chemicals, performs a titration with Fe(III), and determines the end point by means of oxidation-reduction electrodes. Means were found to secure rapid and meaningful electrode response. That made it possible to design and assemble an instrument which was successful in laboratory simulations and field use.