A radiochemical procedure was established to estimate the amount of volatile fission products nuclides released from UO2 pellet by the pulse neutron irradiation at the NSRR.
The 137Cs amounts in the fuel rods after irradiation at the NSRR were measured to clarify release behavior of fission products (137Xe and 137I) from oxide fuel under the reactivity initiated accident condition. The amounts of 137Xe and 137I released from the UO2 pellet were estimated from the measurement of 137Cs. All UO2 pellets before irradiation at the NSRR were fresh.
The nuclides of 137Xe and 137I generated in UO2 pellet of fuel rod by irradiation at the NSRR were released from the pellet in relation with the vaporization phenomenon after melting of UO2 pellet. At the deposition energy higher than 340-350cal./g UO2, about 60% of 137Xe and 137I were released from the pellet of fuel rod, at maximum. At the deposition energy lower than 340-350cal./g UO2, 137Xe and 137I in the UO2 pellet of fuel rod were scarcely released out.