# Resurgence of a Nation's Radiation Science Driven by Its Nuclear Industry Needs
## 3 Exemplar Results
### Applications of the Re-Circulation Loop
#### 3.5.1 Radiation Chemistry in LWRs  
Neutron flux makes a major contribution to the radiation field in the core of water-cooled nuclear reactors. When neutrons interact with water molecules, energetic recoil protons are produced (there is also a small fraction of recoil oxygen atoms being formed), which, in turn, induce radiolysis of water by electrostatic interactions. It has been proposed that by using protons it would be possible to quantitatively determine the contribution of neutron radiation to the water radiolysis under LWR conditions [49]. Thus, an overall radiolytic effect for any specified neutron flux can be associated with corresponding proton recoils, for which the radiolytic product yields can be determined directly. Such information, along with data gathered from separate gamma irradiation experiments, would lead to the accurate modelling of the chemistry at high temperature and for reducing radicals where data are limited. At DCF, this goal is pursued by generating protons with energies of up to 10 MeV using the tandem ion accelerator to irradiate water with added scavengers. A series of gamma and proton radiolysis experiments is underway; an exemplar of obtained data is shown in Figure 10.  
The results shown in Figure 10a describe the verification of the Hach(tm)tM}@polisphere H2 sensor response to changes made to the flow rate through the autoclave (shown in Figure 4a during a single continuous test. There are two main reasons for performing recirculation loop experiments in dynamic mode, i.e., with a continuous flow: (1) displacing irradiated  
Figure 10: (**a**) Determined G-value of molecular hydrogen as a function of the fluid flow rate (kg/h) through the autoclave upon gamma irradiation of deaerated 1 mM KBr solution. (**b**) Radiation chemical yield of H2 from a scavenger system containing 1 mM NO3 –, 1 mM Br –, and 10 mM CHO2 – under deaerated conditions and room temperature irradiated with a proton beam as a function of particle energy. All irradiations were performed using 10 nA current with exposures lasting for 15 min. fluid from the autoclave to prevent excessive accumulation of radiolytic products; and (2) delivering formed products, e.g., H2, to the built-in sensors for analysis. A deaerated aqueous solution containing 1 mM KBr has been used in this gamma-irradiation test under room temperature conditions and the data were corrected to account for the time that the solution was flowing through the section of the loop located outside of the irradiation chamber. The radiation chemical yield of molecular hydrogen (G(H2)) is well-known for this system: gamma irradiation of 1 mM KBr produces H2 at 0.45 molecules/100 eV yield [50]. The results presented in Figure 10a indicate that the flow rates below 1.4 kg/h lead to the underestimation of the H2 concentration, whereas the flow rates above 2.0 kg/h result in the G(H2) overestimation. We interpret this as the sensor having an optimal flow range for detection of H2; hence, the \"sweet spot\" for the flow rate, giving correct hydrogen values, has been identified to be ca. 1.4 kg/h; this flow rate has been used in all subsequent experiments. Figure 10b shows the H2 production results from the proton beam irradiation of a scavenger system containing 1 mM NO3-, 1 mM Br-, and 10 mM CHO2- under deaerated conditions and room temperature. All irradiations were performed with the same beam current (10 nA) and were 15 min in duration. The results indicate that the hydrogen yield, G(H2), increases when the energy of incident protons is increased. These results are in agreement with the findings of [PERSON] et al. [51], who also reported a moderate increase of G(H2) in the proton beam energy range between 1 and 3 MeV under 25 C. Future experiments will be performed in the higher ion energy range (up to 6 MeV) to explore hydrogen formation trends as a function of decreasing track-average LET of H projectiles. Another promising scavenger system has been recently developed by [PERSON] et al.