Abilities of helium immobilization by the UO₂ surface using the “ab initio” method

National Centre for Nuclear Research (NCBJ) - 7 Andrzeja Sołtana Str., 05-400 Otwock/Swierk, Poland

Received: 25 May 2016
Accepted: 30 September 2016

Abstract

We present density functional theory calculation results concerning the uranium dioxide crystals with a helium atom incorporated in the octahedral sites on a nano superficial layer of UO₂ fuel element. In order to quantify the capability of helium immobilization we propose a quantum model of adsorption and desorption which we compare with the classical model of Langmuir. Significant differences between the models are maintained in a wide temperature range including high temperatures of the order of 1000 K. By the proposed method of quantum isotherms it was established that the octahedral positions near the metal surface are good traps for helium atoms. While in a temperature close to 1089 K it predicts an intensive release of helium, which is consistent with the experimental results.