[en] Sulphate is known to be the probably most important chemical contamination in producing intergranular stress corrosion cracking (IGSCC) in boiling water reactors (BWRs). It is hence very important to minimise the sulphate concentration in order to reduce the costs for inspection, repair, and extended outages due to IGSCC. There are two main sources to the sulphate in the BWR. The first is the natural cooling water, which is used to provide the cooling of the condenser. Depending on the sulphate concentration of the natural river or sea water, or the more concentrated water in a cooling tower, in combination with the possible leaks of condenser tubes will be a threat for sulphate (and chloride) intrusions to the BWR coolant. A well-designed and well-maintained condensate clean-up system (CCU) can impede the sulphate levels in the reactor water. Ironically, the second main source of sulphate is generally the anionic resins used in the clean-up systems in the LWR, and many other water polishing applications. The anionic resins normally consist of a partially cross-linked polystyrene structure, with sulfonic acid (-SO₃) groups, providing the retention capability for anions. The organic structure is, however, sensitive to elevated temperature, and some chemical species present in the BWR coolant, and may hence decompose, releasing fragments of the resin to the reactor pressure vessel (RPV). Barsebaeck-2 is a Swedish BWR that has been in operation with hydrogen water chemistry (HWC) for 8 years. The purpose of the HWC is to mitigate the crack growth, which requires an aggressive water chemistry, generally a combination of oxidising conditions and some sulphate or other anionic contaminant. The HWC operation is normally successive in that a low electrochemical corrosion potential (ECP) (well below -230 mV vs. SHE) and low concentrations of oxygen and hydrogen peroxide can be maintained. A successful HWC operation implies that the short periods of operation without hydrogen injection will be relatively more important, since despite being short periods, transients in anionic contaminants can be significant, especially during start-up and shutdown conditions, when typically the hydrogen injection is shut off. A considerable effort has been made to minimise the relative impact of the non-HWC periods, especially by reducing the sulphate concentration released from the resins. In this work it was found that not only the CCU resin is important but also the reactor water clean-up (RWCU) resin. A radiolysis modelling code has been developed and this code has been applied in the modelling of various operational conditions in several Swedish BWRs. (authors)