ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Carbohydrazide as an alternative decontamination agent for magnetite dissolution in PHWR systems

Miguta Faustine Ngulimi, Sion Kim, Kamal Asghar, Bum Kyoung Seo, and Changhyun Roh

Nuclear Facility Cleanup Technology Division, Korea Atomic Energy Research Institute, Daejeon, Korea

E-mail: chroh@kaeri.re.kr

Received: 11 May 2025  Accepted: 26 June 2025

Abstract:

In nuclear power plants (NPPs), contamination primarily results from the neutron activation of corrosion products, leading to the formation of radionuclides that are deposited on internal surfaces, particularly within the piping systems. These deposits increase radiation exposure risks for workers, especially during decommissioning. To mitigate this, chemical decontamination is employed to reduce surface radioactivity. However, many existing decontamination processes face limitations, including low oxide removal efficiency and significant corrosion of base metal surfaces. This study evaluates the potential of CHZ as an alternative decontamination agent, focusing on its magnetite dissolution efficiency and its corrosive impact on carbon steel SA106 Grade B, which simulates the feeder pipes of pressurized heavy water reactors. Batch experiments were conducted to assess both magnetite powder dissolution and metal corrosion using CHZ-based formulations. Results were compared with the Canadian Decontamination and Remediation (CANDEREM) process. CHZ-based reagents demonstrated superior dissolution performance, achieving up to 206.6 ppm of dissolved iron after 9 h, compared to 116.6 ppm for the CANDEREM formulation. Furthermore, the corrosion induced by CHZ on SA106 Gr B was significantly lower than that observed with CANDEREM, suggesting a less corrosive property. CHZ-based reagent performance is enhanced by creating a reducing environment which facilitates the Fe³⁺ to Fe²⁺ conversion. CHZ is presented as a safer, more effective alternative for decontamination in NPPs.

Keywords: Magnetite; Dissolution; Carbohydrazide; Canadian decontamination and remediation process; Decontamination

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-025-04281-4

Chemical Papers 79 (11) 7703–7712 (2025)