Full system decontamination at PWR Biblis unit A + B with ASDOC_D-MOD process - 000076

Full System Decontamination (FSD) with ASDOC_D-MOD has especially been developed for nuclear reactor systems including besides austenitic steels also martensitic and limited for ferritic materials. The ASDOC-D-MOD process is characterized by several short decontamination cycles with comparably low concentrations of chemicals. The latter guarantees a smooth dissolution of oxide layers and a minimum output of waste. The ASDOC_D-MOD process uses methane sulfonic acid (MSA) to adjust the pH-value of the decontamination solution in order to avoid precipitation of iron ions from the solution. Permanganic acid (HMnO₄) is used as a strong oxidant and oxalic acid (C₂H₂O₄) as a chelating agent. The number of required single decontamination cycles is in the order of 15 to 20. In 2016 and 2017/18 ASDOC_D-MOD FSD was conducted at PWR units Biblis A and B. In these projects mean decontamination factors of 90 and 85 were achieved. Less than 12.75 m³ of secondary waste (ion exchange resins) were required for deposition of metal ions. (authors)