# Resurgence of a Nation's Radiation Science Driven by Its Nuclear Industry Needs
## 3 Exemplar Results
### Sensing of Gases Produced by Radiolysis  
One major area of interest for the nuclear industry is the production of hydrogen from radiolysis of water that is in the presence of metal oxides. Such systems are important in both plutonium stewardship and decommissioning of Magnox waste ponds. The sludge in Sellafield's Magnox waste ponds contain Brucite (Mg(OH)2) which is subject to radiation emanating from the radioactive species present in the waste. Proper understanding of both the production of hydrogen and the rheological properties of these sludges is important for the storage, transport, and processing of this legacy waste. Understanding the role of water-oxide interfaces in radiolytic hydrogen production and the evolution if gases in contact with the oxide also underpins safe plutonium stewardship--the UK's stockpile of plutonium dioxide is currently stored in sealed cans. Since work on plutonium would require specialist active handling facilities, surrogates can be used at DCF, which will add insight into the wider field of radiolysis in the presence of an oxide surface. Recent developments in hydrogen probe technology [31] have provided new means to detect hydrogen. However, since these probes are highly sensitive to radiation, it is necessary to ensure they are not subject to the direct radiation field [32]. These probes have been used as an economic, parallelizable, and compact alternative to gas chromatographs in a range of experiments. Further work involves the calibration of the gas probes to also quantify amounts of oxygen. Examples of the kinds of measurements being undertaken in a series of ongoing research programs concerning the role of the role of water-oxide interfaces in radiolytic hydrogen production are shown in Figure 5.  
Electrochemical hydrogen gas probes have been used to measure the production of hydrogen from a magnesium hydroxide/water mixture by proton irradiation (mimicking the alpha irradiation field produced by decay of uranium). For this experiment, the sample mixture was sealed in a metal sample chamber with a 5 \(\upmu\)m aluminum window and a Unisense hydrogen probe [31] was attached via a Swagelok fitting. The sample chamber was placed so that the radiation beam passes directly through the foil window. The samples were irradiated with 5 MeV protons with a 1.3 nA current. This irradiation was performed with the chamber full of a mixture (11 \(\pm\) 5) % (\(w/w\)) of magnesium hydroxide and water. A separate experiment was performed on a 0.1 mM potassium bromide solution. The response of the hydrogen probe to four sequential ion irradiations of the sample is plotted in Figure 5a. The hydrogen probe response is clearly delayed after the start of irradiation indicating that the hydrogen takes time to diffuse out of the sample into the headspace of the chamber i.e., to reach equilibrium between the liquid and the gas. Although each irradiation is essentially identical, there is a clear decline in the hydrogen production rate, indicating radiation-induced hydrogen consumption. This experiment  
Figure 5: Results of radiolytic gas analysis experiments carried out on the particle accelerator using Unisense hydrogen probes to collect data. (**a**) The response of the hydrogen probe in mV during irradiations. Periods of irradiation are marked on the plot in red. (**b**) A linear trend is seen from experiments with fresh solutions of either magnesium hydroxide or potassium bromide. shows the hydrogen probe's potential for real-time hydrogen monitoring and measurement of hydrogen yields from ion irradiations. Figure 5b shows results from both the magnesium hydroxide and potassium bromide solutions. The increase in the hydrogen probe signal per unit energy deposited in for the magnesium hydroxide sample was 5.69 \(\pm\) 0.03 times the increase when the bromide solution was irradiated. Gas probes, off-line gas chromatography, and Orbisphere sensors are routinely used at DCF to determine radiation-induced changes in gas composition.