ORIGINAL PAPER Corrosion monitoring of type 304L stainless steel in nuclear near-high level waste by electrochemical noise Girija Suresh • U. Kamachi Mudali • Baldev Raj Received: 12 July 2010 / Accepted: 23 May 2011 / Published online: 17 June 2011 Ó Springer Science+Business Media B.V. 2011 Abstract Electrochemical noise (EN) monitoring of 304L stainless steel (SS) and sensitized 304 SS in 3 N nitric acid and nuclear near-high level waste (HLW) solution was carried out using a three nominally identical electrode configuration under open circuit conditions. EN signals characteristics of passivation process was obtained for 304L SS in 3 N nitric acid throughout the measurement period, while in near-HLW solution, features of passivation and depassivation were observed. Potentiodynamic polar- ization of 304L SS in 3 N nitric acid and near-HLW showed spontaneous passivation. Noise resistance was evaluated from EN time record and this parameter was used in the present investigation to qualitatively assess the corrosion behavior during the immersion period. The average noise resistance was found to be lower in near- HLW solution when compared to 3 N nitric acid. The results of the investigation are presented in this article. Keywords 304L  Electrochemical noise  Corrosion monitoring  Near nuclear HLW 1 Introduction High level liquid waste is the liquid effluent generated from the reprocessing of the spent nuclear fuel [1, 2] and it consists of unrecovered uranium, plutonium transuranics, and other highly radioactive fission products generated during fission. The yield of these fission fragments depends on the type of fissile atom loaded in the reactor and the neutron energy for reactor applications. Most of the radioactive isotopes in HLW emit large amounts of radia- tion and decay heat and have extremely long half lives creating long time periods before the waste will settle to safe levels of radioactivity. The activity of HLW ranges from 3.7 9 10 9 Bq m -3 and above [1, 2]. In spite of having lower volume than low and intermediate level waste, HLW disposal is of great concern for the public. Thus, waste management and immobilization of HLW is required to safeguard the present and future generations. A three-stage strategy for management of HLW has been formulated in India. This involves immobilization of waste oxides in stable and inert solid matrices, also called as vitrification, followed by interim retrievable storage of the conditioned waste under continuous cooling and final disposal in geological repositories [1, 2]. The vitrification facilities are co-located near the reprocessing plants so as to avoid long-term transportation of HLW. HLW is stored in underground waste tank farm, housing high integrity stainless steel type 304L tanks of large capacity (250–500 m 3 each) provided with temperature, pressure, and level monitoring. HLW is transferred from here to vitrification plant through underground piping. Liquid storage is an interim step and requires cooling and con- tinuous surveillance [1–3]. Though liquid storage has been proved to be largely safe and acceptable for few decades, this cannot be considered as the ultimate system of storage and disposal of HLW. Conversion of HLW into a suitable solid matrix for vitrification has been studied extensively in many countries [1–3]. Corrosion and tank integrity are major issues concerning worker and environmental safety. Since corrosion, whether localized or uniform, could ini- tiate in these tanks, monitoring of corrosion is necessary. Several departments of energy sites in USA such as Hanford, Savannah River, Oak Ridge Reservation, and the G. Suresh  U. Kamachi Mudali (&)  Baldev Raj Indira Gandhi Centre for Atomic Research, Kalpakkam 603102, India e-mail: kamachi@igcar.gov.in 123 J Appl Electrochem (2011) 41:973–981 DOI 10.1007/s10800-011-0324-x