Removal of nitric acid from a simulated high level liquid waste by a safe chemical denitration

The heat and off-gas generation behavior was experimentally examined during a safe chemical denitration, pre- and mild-denitration, of simulated HLLW with a nitric acid concentration of 2 to 7.5 M. The maximum heat and off-gas generation were no more than 100 cal/s x l and about 0.8 l/min, respectively. The solution temperature does not reach boiling temperature and no solution was squirted out from the denitration vessel. The pre- and mild-denitration technique could be considered as one of safe methods for removing nitric acid from the HLLW with various nitric acid concentrations. The pre- and mild-denitration also has an advantage to improve the filtration characteristics of precipitates produced by the denitration of simulated HLLW. The denitration of HLLW with 7.5 M nitric acid concentration induced formation of 'very easy-to-filter' solid. Moreover, a good filter cake washing is possible. (author)