# Resurgence of a Nation's Radiation Science Driven by Its Nuclear Industry Needs
### Recirculation Loop  
Water radiolysis and corrosion under extreme conditions of high temperature and high pressure (HTHP) can be investigated using a water recirculation loop, shown in Figure 3a, which was purpose-built by Cormet(tm) Oy (Vantaa, Finland). Researchers at DCF commissioned the recirculation loop with four irradiation autoclaves; two are designed for gamma irradiation while the other two are dedicated for ion beam irradiations. The recirculation loop is a mobile station, which can be easily moved between the \({}^{60}\)Co irradiator room and ion beam target rooms.  
Figure 3b shows a schematic diagram of the recirculation loop. The flow system incorporates a 10 L feed tank. Dissolved oxygen or hydrogen concentration can be measured in the range of 0-1000 ppb using Hach(tm) Orbisphere sensors. Water conductivity is measured using two conductivity amplifiers from ABB(tm), accurate up to 10 \(\upmu\)S/cm. All four autoclaves incorporate temperature monitoring and control and are able to withstand temperatures up to 350 \({}^{\circ}\)C and 220 bar of pressure.  
Figure 3: The Cormet(tm) My recirculation loop. (**a**) A photograph of the equipment which is about 1.8 m tall by 1.5 m wide. (**b**) A simplified schematic diagram of recirculation loop. Sensors labelled D[H\({}_{2}\)], D[O\({}_{2}\)] and EC monitor dissolved hydrogen (ppb), dissolved oxygen (ppb), and electrical conductivity, respectively.  
Advanced control of the fluid flow enables different modes of operation. The simplest case is system conditioning. In this mode, an aqueous solution is continuously sparged with the gas of choice, e.g., high-purity argon, nitrous oxide, etc.; and the liquid simply circulates in a closed loop until equilibrium conditions are reached. Alternatively, irradiated liquid can be collected for analysis using the once-through operation mode. For corrosion tests, water flow can be directed through a mixed bed ion exchange column in order to generate highly deionized water. If radiolytic gas formation is to be evaluated, irradiated aqueous solution can be first accumulated in a gas stripping device and then purged with suitable high purity carrier gas, e.g., argon, to allow for dissolved gas extraction and subsequent mass-spectrometric analysis of extracted gases.  
The wetted parts of each autoclave and all components in the high-temperature part of the recirculation loop are made of Hastelloy C-267 alloy. This alloy is known for its resistance to oxidation and stress corrosion cracking (SCC), and excellent chemical durability at high temperatures. The autoclave shown in Figure 4a has a capacity of 50 mL and has been designed for gamma radiolysis experiments. It features two temperature sensors (K-type thermocouples) and inlet and outlet water lines. The pressure sensor and the safety valve are located outside of the \({}^{60}\)Co irradiation chamber. A heater band surrounds the autoclave body and a K-type thermocouple on the heating element monitors the temperature. Hot parts of the autoclave are made of corrosion-resistant Hastelloy C-276.  
Figure 4: Autoclaves used with the recirculation loop. (**a**) Autoclave used for gamma radiolysis experiments. (**b**) Irradiation cell for ion beam experiments, where (1) is a closing nut, (2) ceramic washer, (3) metallic foil window; (4) water outlet line; (5) water inlet line; (6) temperature sensor.  
The autoclave design for ion beam irradiations is shown in Figure 4b. This cell has capacity of only 6 mL. The autoclave has been designed to allow the passage of a proton beam through a thin window (a few tens of microns thick) that separates the beamline and the aqueous solution at HTHP inside the autoclave. The window is a metallic foil made of either C-276 (for radiolysis experiments) or a material under study (for corrosion testing).