Restraint effect of coexisting nitrite ion in simulated high level liquid waste on releasing volatile ruthenium under boiling condition

ABSTRACT

In the ‘evaporation and dryness due to the loss of cooling functions,’ which is one of the severe accidents at reprocessing plants in Japan, volatile ruthenium (Ru) compound is possible to be produced and released from high level liquid waste (HLLW) in the storage tank to the environment. This cause is considered that the volatile Ru compound is produced from ruthenium nitrosyl nitrate by oxidizability of HNO₃ in HLLW and released. We consider that the release of the volatile Ru compound from the HLLW can be restrained by coexisting nitrite ion because of its reduction power. To confirm the effect of nitrite ion on the release behavior of the volatile Ru compound, four experiments of heating the simulated HLLW (SHLLW) with setting the concentration of nitrite ion in the SHLLW as a parameter were carried out. As a result, the release of the volatile Ru compound was seemed to be restrained by adding sodium nitrite as a source of nitrite ion under certain boiling condition. This result may contribute to improve source term analysis in the evaporation and dryness due to the loss of cooling functions.

KEYWORDS:

• Ruthenium
• nitrite ion
• evaporation
• high level liquid waste
• reprocessing
• severe accident

Acknowledgments

The authors wish to thank Kouji Watanabe of JES Techno System for technical support to composing the apparatus, and all members of the Fuel Cycle Research Group of Japan Atomic Energy Agency for their contributions.

This work includes the experimental results under the auspices of the Nuclear Regulation Authority.

Disclosure statement

No potential conflict of interest was reported by the authors.