Behavior of Triiodide Accumulation in Aqueous Iodine Solution.

Tsukaue, Yasoji; Takimoto, Yoshinori; Yoshida, Kunio

doi:10.3327/jnst.32.1192

Cited by 1 publication

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“…The Rokkasho Reprocessing Plant is a commercial 800 t/d reprocessing plant in Japan. Since the release of 129 I into the environment is strictly regulated, studies were performed to evaluate the iodine species in spent fuel solutions and the methods of expelling this iodine to the DOG, where it could be captured, and so it would not contaminate the downstream processes (Sakurai et al 1987;Sakurai et al 1989;Sakurai et al 1996a;Sakurai et al 1991bSakurai et al , 1992Sakurai et al 1996b;Takeshita and Azegami 2004; Tanigaki et al 1992; Tsukaue et al 1994;Tsukaue et al 1995). From this work, it was determined that colloids of silver iodide (AgI) and palladium iodide (PdI 2 ) played an important role in the behavior of iodine in the dissolution stage (Sakurai et al 1989(Sakurai et al , 1995aSakurai et al 1996a;Sakurai et al 1991bSakurai et al , 1992Sakurai et al , 1993Sakurai et al 1996b).…”

Section: Plant Experience -Dissolver and Dissolver Off-gasmentioning

confidence: 99%

Iodine Pathways and Off-Gas Stream Characteristics for Aqueous Reprocessing Plants ? A Literature Survey and Assessment

Jubin¹,

Strachan²,

Soelberg³

2013

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Used nuclear fuel is currently being reprocessed in only a few countries, notably France, England, Japan, and Russia. The need to control emissions of the gaseous radionuclides to the air during nuclear fuel reprocessing has already been reported for the entire plant. But since the gaseous radionuclides can partition to various different reprocessing off-gas streams, for example, from the head end, dissolver, vessel, cell, and melter, an understanding of each of these streams is critical. These off-gas streams have different flow rates and compositions and could have different gaseous radionuclide control requirements, depending on how the gaseous radionuclides partition. This report reviews the available literature to summarize specific engineering data on the flow rates, forms of the volatile radionuclides in off-gas streams, distributions of these radionuclides in these streams, and temperatures of these streams. This document contains an extensive bibliography of the information contained in the open literature.Iodine removal has always been primarily focused on the head-end off-gas operations. But, in light of the estimated iodine emissions control efficiencies of up to 99.9% or higher needed to meet US regulatory requirements, the control of iodine in the dissolver off-gas is insufficient. Operating experience and tests with actual nuclear fuel show that iodine evolution from the dissolver solution into the dissolver off-gas ranges between 95 and 99%. Iodine evolution from the dissolver solution can be improved to >95% with NO 2 sparging, addition of KIO 3 to the dissolver, and addition of iodate. Several studies have shown that much of the residual iodine in the dissolver solution is in the form of colloidal iodine (AgI and PdI 2 ); organic iodides formed in the dissolver also factor into the iodine retention. Even if the iodine in the dissolver off-gas is efficiently controlled, the iodine in other reprocessing facility off-gas streams may also need to be controlled.

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