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Journal Articles

Consideration of the dielectric response for radiation chemistry simulations

Toigawa, Tomohiro; Kai, Takeshi; Kumagai, Yuta; Yokoya, Akinari*

Journal of Chemical Physics, 160(21), p.214119_1 - 214119_9, 2024/06

https://doi.org/10.1063/5.0211089

The spur reaction is crucial for determining radiolysis or photolysis in liquid, but the spur expansion process has yet to be elucidated. One reason is the need to understand the role of the dielectric response of the solvating molecules surrounding the charged species generated by ionization. The dielectric response corresponds to the time evolution of the permittivity and might affect the chemical reaction-diffusion of the species in a spur expansion process. This study examined the competitive relationship between reaction-diffusion kinetics and the dielectric response by solving the Debye-Smoluchowski equation while considering the dielectric response. The Coulomb force between the charged species gradually decreases with the dielectric response. Our calculation results found a condition where fast recombination occurs before the dielectric response is complete. Although it has been reported that the primary G-values of free electrons depend on the static dielectric constant under low-linear-energy transfer radiation-induced ionization, we propose that considering the dielectric response can provide a deeper insight into fast recombination reactions under high-linear-energy transfer radiation- or photo-induced ionization. Our simulation method enables the understanding of fast radiation-induced phenomena in liquids.

Journal Articles

Chemical reaction of uranium oxide induced by water radiolysis

Kumagai, Yuta

Hoshasen (Internet), 49(1), p.15 - 17, 2024/03

https://doi.org/10.11470/houshasen.49.1_15

Water radiolysis induces oxidative dissolution of uranium oxides. Understanding of this process is a chemical basis for safety assessment of the deep geological repository of spent fuel and would serve as knowledge for retrieval and storage of fuel debris after a severe accident of nuclear power reactors. In order to evaluate the release rate of radioactive elements from the UO $_{2}$ matrix of spent nuclear fuel, several chemical kinetic models have been developed. However, the conventional reaction models were found out to be simplistic based on new insights obtained recent experimental studies. Therefore, the reaction mechanism of surface oxidation and dissolution of uranium is now a subject of revisit. Here, a few recent studies regarding the reaction mechanism are introduced.

Journal Articles

A Raman spectroscopy study of bicarbonate effects on UO $_{2+x}$

McGrady, J.; Kumagai, Yuta; Watanabe, Masayuki; Kirishima, Akira*; Akiyama, Daisuke*; Kimuro, Shingo; Ishidera, Takamitsu

Journal of Nuclear Science and Technology, 60(12), p.1586 - 1594, 2023/12

https://doi.org/10.1080/00223131.2023.2236104

Times Cited Count：0 Percentile：0.01(Nuclear Science & Technology)

Journal Articles

Current location of fuel debris chemistry

Sato, Nobuaki*; Kirishima, Akira*; Sasaki, Takayuki*; Takano, Masahide; Kumagai, Yuta; Sato, Soichi; Tanaka, Kosuke

Current Location of Fuel Debris Chemistry, 178 Pages, 2023/11

Considerable efforts have been devoted to the decommissioning of the TEPCO's Fukushima Daiichi Nuclear Power Station (1F) and now the retrieval of fuel debris is being proceeded on a trial basis. It can be said that the succession of science and technology related to debris, that is, human resource development, is important and indispensable. For that reason, we thought that a specific textbook on decommissioning is necessary. Regarding the 1F fuel debris, we still do not know enough, and it would be difficult to describe the details. However, 12 years have passed since the accident, and we have come to understand the situation of 1F to a certain extent. At this stage, it is essential for future development to organize the current situation by combining examples of past severe accidents. Therefore, we presented in this book the current state of fuel debris chemistry research from the perspectives of solid chemistry, solution chemistry, analytical chemistry, radiochemistry, and radiation chemistry.

Journal Articles

UO $_{2}$ dissolution in bicarbonate solution with H $_{2}$ O $_{2}$ ; The Effect of temperature

McGrady, J.; Kumagai, Yuta; Kitatsuji, Yoshihiro; Kirishima, Akira*; Akiyama, Daisuke*; Watanabe, Masayuki

RSC Advances (Internet), 13(40), p.28021 - 28029, 2023/09

https://doi.org/10.1039/D2RA08131H

Upon nuclear waste canister failure and contact of spent nuclear fuel with groundwater, the UO $_{2}$ matrix of spent fuel will interact with oxidants in the groundwater generated by water radiolysis. Bicarbonate (HCO $_{3}$ $^{-}$ ) is often found in groundwater, and the H $_{2}$ O $_{2}$ induced oxidative dissolution of UO $_{2}$ in bicarbonate solution has previously been studied under various conditions. Temperatures in the repository at the time of canister failure will differ depending on the location, yet the effect of temperature on oxidative dissolution is unknown. To investigate, the decomposition rate of H $_{2}$ O $_{2}$ at the UO $_{2}$ surface and dissolution of U $^{VI}$ in bicarbonate solution (0.1, 1, 10 and 50 mM) was analysed at various temperatures (10, 25, 45 and 60 $^{circ}$ C). At [HCO $_{3}$ $^{-}$ ] 1 mM, the apparent equilibrium concentration of U $^{VI}$ decreased with increasing temperature. This was attributed to the formation of U $^{VI}$ -bicarbonate species at the surface and a change in the mechanism of H $_{2}$ O $_{2}$ decomposition from oxidative to catalytic. At 0.1 mM, no obvious correlation between temperature and U dissolution was observed, and thermodynamic calculations indicated this was due to a change in the surface species. A pathway to explain the observed dissolution behaviour of UO $_{2}$ in bicarbonate solution as a function of temperature was proposed.

Journal Articles

Raman identification and characterization of chemical components included in simulated nuclear fuel debris synthesized from uranium, stainless steel, and zirconium

Kusaka, Ryoji; Kumagai, Yuta; Watanabe, Masayuki; Sasaki, Takayuki*; Akiyama, Daisuke*; Sato, Nobuaki*; Kirishima, Akira*

Journal of Nuclear Science and Technology, 60(5), p.603 - 613, 2023/05

https://doi.org/10.1080/00223131.2022.2128460

Times Cited Count：1 Percentile：27.23(Nuclear Science & Technology)

Journal Articles

Radiation-induced dissolution of uranium oxide materials in water

Kumagai, Yuta

Hoshasen Kagaku (Internet), (115), p.43 - 49, 2023/04

Oxidation and dissolution of uranium oxide materials has been a subject of numerous studies as a basis of the geological disposal technology for spent nuclear fuel. The understandings obtained by these studies provide useful suggestions for research and development regarding the retrieval and storage of nuclear fuel debris generated by a nuclear severe accident. Here, these research backgrounds of oxidative dissolution of uranium oxides are briefly reviewed and some studies relating to radiation-induced reactions will be introduced.

Journal Articles

Phase analysis of simulated nuclear fuel debris synthesized using UO $_{2}$ , Zr, and stainless steel and leaching behavior of the fission products and matrix elements

Tonna, Ryutaro*; Sasaki, Takayuki*; Kodama, Yuji*; Kobayashi, Taishi*; Akiyama, Daisuke*; Kirishima, Akira*; Sato, Nobuaki*; Kumagai, Yuta; Kusaka, Ryoji; Watanabe, Masayuki

Nuclear Engineering and Technology, 55(4), p.1300 - 1309, 2023/04

https://doi.org/10.1016/j.net.2022.12.017

Times Cited Count：2 Percentile：84.55(Nuclear Science & Technology)

Simulated debris was synthesized using UO $_{2}$ , Zr, and stainless steel and a heat treatment method under inert or oxidizing conditions. The primary U solid phase of the debris synthesized at 1473 K under inert conditions was UO $_{2}$ , whereas a (U,Zr)O $_{2}$ solid solution formed at 1873 K. Under oxidizing conditions, a mixture of U $_{3}$ O $_{8}$ and (Fe,Cr)UO $_{4}$ phases formed at 1473 K whereas a (U,Zr)O $_{2+x}$ solid solution formed at 1873 K. The leaching behavior of the fission products from the simulated debris was evaluated using two methods: the irradiation method, for which fission products were produced via neutron irradiation, and the doping method, for which trace amounts of non-radioactive elements were doped into the debris. The dissolution behavior of U depended on the properties of the debris and aqueous medium the debris was immersed in. Cs, Sr, and Ba leached out regardless of the primary solid phases. The leaching of high-valence Eu and Ru ions was suppressed, possibly owing to their solid-solution reaction with or incorporation into the uranium compounds of the simulated debris.

Journal Articles

Application of high-energy-resolution X-ray absorption spectroscopy at the U L $_{3}$ -edge to assess the U(V) electronic structure in FeUO $_{4}$

Yomogida, Takumi; Akiyama, Daisuke*; Ouchi, Kazuki; Kumagai, Yuta; Higashi, Kotaro*; Kitatsuji, Yoshihiro; Kirishima, Akira*; Kawamura, Naomi*; Takahashi, Yoshio*

Inorganic Chemistry, 61(50), p.20206 - 20210, 2022/12

https://doi.org/10.1021/acs.inorgchem.2c03208

Times Cited Count：4 Percentile：58.46(Chemistry, Inorganic & Nuclear)

FeUO $_{4}$ was studied to clarify the electronic structure of U(V) in a metal monouranate compound. We obtained the peak splitting of HERFD-XANES spectra utilizing high-energy-resolution fluorescence detection-X-ray absorption near edge structure (HERFD-XANES) spectroscopy at the U L $_{3}$ -edge, which is a novel technique in the U(V) compounds. Theoretical calculations revealed that the peak splitting was caused by splitting the 6d orbital of U(V). Such distinctive electronic states are of major interest to researchers and engineers working in various fields, from fundamental physics to the nuclear industry and environmental sciences for actinide elements.

Journal Articles

Study on the relation between the crystal structure and thermal stability of FeUO $_{4}$ and CrUO $_{4}$

Akiyama, Daisuke*; Kusaka, Ryoji; Kumagai, Yuta; Nakada, Masami; Watanabe, Masayuki; Okamoto, Yoshihiro; Nagai, Takayuki; Sato, Nobuaki*; Kirishima, Akira*

Journal of Nuclear Materials, 568, p.153847_1 - 153847_10, 2022/09

https://doi.org/10.1016/j.jnucmat.2022.153847

Times Cited Count：3 Percentile：63.91(Materials Science, Multidisciplinary)

FeUO $_{4}$ , CrUO $_{4}$ , and Fe $_{x}$ Cr $_{1-x}$ UO $_{4}$ are monouranates containing pentavalent U. Even though these compounds have similar crystal structures, their formation conditions and thermal stability are significantly different. To determine the factors causing the difference in thermal stability between FeUO $_{4}$ and CrUO $_{4}$ , their crystal structures were evaluated in detail. A Raman band was observed at 700 cm $^{-1}$ in all the samples. This Raman band was derived from the stretching vibration of the O-U-O axis band, indicating that Fe $_{x}$ Cr $_{1-x}$ UO $_{4}$ was composed of a uranyl-like structure in its lattice regardless of its "x"' value. Mssbauer measurements indicated that the Fe in FeUO $_{4}$ and Fe $_{x}$ Cr $_{1-x}$ UO $_{4}$ were trivalent. Furthermore, Fe $_{x}$ Cr $_{1-x}$ UO $_{4}$ lost its symmetry around Fe $^{mathrm{III}}$ with increasing electron densities around Fe $^{mathrm{III}}$ , as the abundance of Cr increased. These results suggested no significant structural differences between FeUO $_{4}$ and CrUO $_{4}$ . Thermogravimetric measurements for UO $_{2}$ , FeUO $_{4}$ , and CrUO $_{4}$ showed that the temperature at which FeUO $_{4}$ decomposed under an oxidizing condition (approximately 800 $^{circ}$ C) was significantly lower than the temperature at which the decomposition of CrUO $_{4}$ started (approximately 1250 $^{circ}$ C). Based on these results, we concluded that the decomposition of FeUO $_{4}$ was triggered by an "in-crystal" redox reaction, i.e., Fe $^{mathrm{III}}$ U $^{mathrm{V}}$ Fe $^{mathrm{II}}$ U $^{mathrm{VI}}$ , which would not occur in the CrUO $_{4}$ lattice because Cr $^{mathrm{III}}$ could never be reduced under the investigated condition. Finally, the existence of Cr $^{mathrm{III}}$ in FexCr $_{1-x}$ UO $_{4}$ effectively suppressed the decomposition of the Fe $_{x}$ Cr $_{1-x}$ UO $_{4}$ crystal, even at a very low Cr content.

Journal Articles

Structure, stability, and actinide leaching of simulated nuclear fuel debris synthesized from UO $_{2}$ , Zr, and stainless-steel

Kirishima, Akira*; Akiyama, Daisuke*; Kumagai, Yuta; Kusaka, Ryoji; Nakada, Masami; Watanabe, Masayuki; Sasaki, Takayuki*; Sato, Nobuaki*

Journal of Nuclear Materials, 567, p.153842_1 - 153842_15, 2022/08

https://doi.org/10.1016/j.jnucmat.2022.153842

Times Cited Count：5 Percentile：81.82(Materials Science, Multidisciplinary)

To understand the chemical structure and stability of nuclear fuel debris consisting of UO $_{2}$ , Zr, and Stainless Steel (SUS) generated by the Fukushima Daiichi Nuclear Power Plant accident in Japan in 2011, simulated debris of the UO $_{2}$ -SUS-Zr system and other fundamental component systems were synthesized and characterized. The simulated debris were synthesized by heat treatment for 1 to 12 h at 1600 $^{circ}$ C, in inert (Ar) or oxidative (Ar + 2% O $_{2}$ ) atmospheres. $^{237}$ Np and $^{241}$ Am tracers were doped for the leaching tests of these elements and U from the simulated debris. The characterization of the simulated debris was conducted by XRD, SEM-EDX, Raman spectroscopy, and Mssbauer spectroscopy, which provided the major uranium phase of the UO $_{2}$ -SUS-Zr debris was the solid solution of U $^{mathrm{IV}}$ O $_{2}$ (s.s.) with Zr(IV) and Fe(II) regardless of the treatment atmosphere. The long-term immersion test of the simulated debris in pure water and that in seawater revealed the macro scale crystal structure of the simulated debris was chemically very stable in the wet condition for a year or more. Furthermore, the leaching test results showed that the actinide leaching ratios of U, Np, Am from the UO $_{2}$ -SUS-Zr debris were very limited and less than 0.08 % for all the experiments in this study.

Journal Articles

Uranium dissolution and uranyl peroxide formation by immersion of simulated fuel debris in aqueous H $_{2}$ O $_{2}$ solution

Kumagai, Yuta; Kusaka, Ryoji; Nakada, Masami; Watanabe, Masayuki; Akiyama, Daisuke*; Kirishima, Akira*; Sato, Nobuaki*; Sasaki, Takayuki*

Journal of Nuclear Science and Technology, 59(8), p.961 - 971, 2022/08

https://doi.org/10.1080/00223131.2021.2023055

Times Cited Count：2 Percentile：48.47(Nuclear Science & Technology)

We investigated potential degradation of fuel debris caused by H $_{2}$ O $_{2}$ , which is the oxidant of major impact from water radiolysis. We performed leaching experiments on different kinds of simulated debris comprising U, Fe, Cr, Ni, and Zr in an aqueous H $_{2}$ O $_{2}$ solution. Chemical analysis of the leaching solution showed that U dissolution was induced by H $_{2}$ O $_{2}$ . Raman analysis after the leaching revealed that uranyl peroxides were formed on the surface of the simulated debris. These results demonstrate that uranyl peroxides are possible alteration products of fuel debris from H $_{2}$ O $_{2}$ reaction. However, the sample in which the main uranium-containing phase was a U-Zr oxide solid solution showed much less uranium dissolution and no Raman signal of uranyl peroxides. Comparison of these results indicates that formation of an oxide solid solution of Zr with UO $_{2}$ improves the stability of fuel debris against H $_{2}$ O $_{2}$ reaction.

Journal Articles

A Study of H $_{2}$ O $_{2}$ -induced oxidative degradation of simulated fuel debris

Kumagai, Yuta; Kusaka, Ryoji; Nakada, Masami; Watanabe, Masayuki; Akiyama, Daisuke*; Kirishima, Akira*; Sato, Nobuaki*; Sasaki, Takayuki*

Hoshasen Kagaku (Internet), (113), p.61 - 64, 2022/04

The severe accident at TEPCO's Fukushima Daiichi Nuclear Power Station resulted in generation of fuel debris. The fuel debris is in contact with water and the radiolysis of water can accelerate degradation of the debris. The analysis of particles sampled from inside or near the damaged reactors indicates the complicated compositions of the fuel debris. It is challenging to estimate the effect of water radiolysis on such a complicated material. Therefore, in this study, we investigated the potential degradation process by leaching experiments of simulated fuel debris in aqueous H $_{2}$ O $_{2}$ solution. The results show that the reaction of H $_{2}$ O $_{2}$ induced uranium dissolution from most of the samples and then formation of uranyl peroxides. In contrast, a sample that had U-Zr oxide solid solution as the major phase exhibited remarkable resistance to H $_{2}$ O $_{2}$ . These findings revealed that the degradation of the simulated debris reflects the reactivity and stability of the uranium phase in the matrices.

Journal Articles

Study on the mechanism of radiolytic degradation of an extractant for minor actinides separation

Toigawa, Tomohiro; Kumagai, Yuta; Yamashita, Shinichi*; Ban, Yasutoshi; Matsumura, Tatsuro

UTNL-R-0502 (Internet), 2 Pages, 2022/04

This report summarizes the results obtained in FY2020 at the Electron Linac Facility of the University of Tokyo. The radiolysis process of -hexaoctyl nitrilotriacetamide (HONTA), which is expected to be used as an extractant in a separation process for minor actinides, diluted in dodecane was investigated by pulse radiolysis experiments. The radical cation and the triplet-excited state of HONTA were observed in the nanosecond time region. The transition from the radical cation to the triplet excited state was slowed down by adding electron scavengers, and further, the reactivity of the triplet excited state was also suppressed.

Journal Articles

Radiation chemistry provides nanoscopic insights into the role of intermediate phases in CeO $_{2}$ mesocrystal formation

Li, Z.*; Piankova, D.*; Yang, Y.*; Kumagai, Yuta; Zschiesche, H.*; Jonsson, M.*; Tarakina, N. V.*; Soroka, I. L.*

Angewandte Chemie; International Edition, 61(6), p.e202112204_1 - e202112204_9, 2022/02

https://doi.org/10.1002/anie.202112204

Times Cited Count：5 Percentile：35.86(Chemistry, Multidisciplinary)

The role of intermediate phases in CeO $_{2}$ mesocrystal formation from aqueous Ce(III) solutions subjected to -radiation was studied. Radiolytically formed hydroxyl radicals convert soluble Ce(III) into less soluble Ce(IV). Transmission electron microscopy and X-ray diffraction studies of samples from different stages of the process allowed the identification of several stages in CeO $_{2}$ mesocrystal evolution following the oxidation to Ce(IV): (1) formation of hydrated Ce(IV)-hydroxides, serving as intermediates in the liquid-to-solid phase transformation; (2) CeO $_{2}$ primary particle growth inside the intermediate phase; (3) alignment of the primary particles into "pre-mesocrystals" and subsequently to mesocrystals, guided by confinement of the amorphous intermediate phase and accompanied by the formation of mineral bridges. Further alignment of the obtained mesocrystals into supracrystals occurs upon slow drying, making it possible to form complex hierarchical architectures.

Journal Articles

Zeolite-assisted radiolysis of aromatic chlorides mitigating influence of coexisting ions in water matrix

Kumagai, Yuta; Kimura, Atsushi*; Taguchi, Mitsumasa*; Watanabe, Masayuki

Radiation Physics and Chemistry, 191, p.109831_1 - 109831_8, 2022/02

https://doi.org/10.1016/j.radphyschem.2021.109831

Times Cited Count：0 Percentile：0.01(Chemistry, Physical)

In this study, we investigated and compared the effects of a high-silica zeolite (HMOR) on the radiation-induced degradation of three aromatic chlorides, 2-chlorophenol (2-ClPh), 2-chloroaniline (2-ClAn), and 2-chlorobenzoic acid (2-ClBA), in order to examine its potential to reduce the influence of ions in water matrix in the irradiation treatment of water-soluble organic compounds. In the presence of ions reactive to radicals, the degradation of 2-ClPh in water was inhibited, but the combined use of HMOR much improved the degradation yield. This improvement was attributed to high performance of HMOR in adsorption of 2-ClPh. Similarly, HMOR was effective for adsorption of 2-ClAn and facilitated the 2-ClAn degradation by irradiation. In contrast, HMOR was poor at adsorption of 2-ClBA and consistently the degradation of 2-ClBA in the water-HMOR mixture was inhibited by the radical scavenger. These results demonstrate that HMOR can mitigate the influence of radical scavengers in water.

Journal Articles

Measurement and evaluation of hydrogen production from mixtures of seawater and zeolite in decontamination of radioactive water

Kumagai, Yuta; Nagaishi, Ryuji; Kimura, Atsushi*; Taguchi, Mitsumasa*; Nishihara, Kenji; Yamagishi, Isao; Ogawa, Toru

Insights Concerning the Fukushima Daiichi Nuclear Accident, Vol.4; Endeavors by Scientists, p.37 - 45, 2021/10

Zeolite adsorbents are to be used for decontamination of radioactive water in Fukushima Dai-ichi Nuclear Power Station. Evaluation of hydrogen production by water radiolysis during decontamination is important for safe operation. Thus hydrogen production from the mixture of zeolite adsorbents and seawater was studied because seawater was urgently used as a coolant for the fuels. The hydrogen yield from the mixture decreased at a high weight fraction of zeolites. However, the measured yield was higher than the yield expected from the direct radiolysis of seawater in the mixture, which would decrease proportional to the weight fraction of seawater. The result suggests that the radiation energy deposited to zeolites was involved in the hydrogen formation. From the results, the hydrogen production rate was evaluated to be 3.6 mL/h per ton of radioactive water before decontamination. After the process, it was evaluated to be 1.5 L/h per ton of waste adsorbents due to the high dose rate.

Journal Articles

The Kinetics and mechanism of H $_{2}$ O $_{2}$ decomposition at the U $_{3}$ O $_{8}$ surface in bicarbonate solution

McGrady, J.; Kumagai, Yuta; Watanabe, Masayuki; Kirishima, Akira*; Akiyama, Daisuke*; Kitamura, Akira; Kimuro, Shingo

RSC Advances (Internet), 11(46), p.28940 - 28948, 2021/08

https://doi.org/10.1039/D1RA05580A

Times Cited Count：5 Percentile：35.86(Chemistry, Multidisciplinary)

Journal Articles

Distribution of studtite and metastudtite generated on the surface of U $_{3}$ O $_{8}$ ; Application of Raman imaging technique to uranium compound

Kusaka, Ryoji; Kumagai, Yuta; Yomogida, Takumi; Takano, Masahide; Watanabe, Masayuki; Sasaki, Takayuki*; Akiyama, Daisuke*; Sato, Nobuaki*; Kirishima, Akira*

Journal of Nuclear Science and Technology, 58(6), p.629 - 634, 2021/06

https://doi.org/10.1080/00223131.2020.1854881

Times Cited Count：7 Percentile：64.73(Nuclear Science & Technology)

Journal Articles

Radiation-induced effects on the extraction properties of hexa--octylnitrilo-triacetamide (HONTA) complexes of americium and europium

Toigawa, Tomohiro; Peterman, D. R.*; Meeker, D. S.*; Grimes, T. S.*; Zalupski, P. R.*; Mezyk, S. P.*; Cook, A. R.*; Yamashita, Shinichi*; Kumagai, Yuta; Matsumura, Tatsuro; et al.

Physical Chemistry Chemical Physics, 23(2), p.1343 - 1351, 2021/01

https://doi.org/10.1039/D0CP05720G

Times Cited Count：14 Percentile：81.66(Chemistry, Physical)

The candidate An(III)/Ln(III) separation ligand hexa--octylnitrilo-triacetamide (HONTA) was irradiated under envisioned SELECT (Solvent Extraction from Liquid waste using Extractants of CHON-type for Transmutation) process conditions using a solvent test loop in conjunction with cobalt-60 gamma irradiation. We demonstrate that HONTA undergoes exponential decay with increasing gamma dose to produce a range of degradation products which have been identified and quantified by HPLC-ESI-MS/MS techniques. The combination of HONTA destruction and degradation product ingrowth, particularly dioctylamine, negatively impacts the extraction and back-extraction of both americium and europium ions. The loss of HONTA was attributed to its reaction with the solvent (-dodecane) radical cation of (HONTA + R $^{.+}$ ) = (7.61 0.82) 10 $^{9}$ M $^{-1}$ s $^{-1}$ obtained by pulse radiolysis techniques. However, when this ligand is bound to either americium or europium ions, the observed -dodecane radical cation kinetics increase by over an order of magnitude. This large reactivity increase to additional reaction pathways occurring upon metal-ion binding. Lastly nanosecond time-resolved measurements showed that both direct and indirect HONTA radiolysis yielded the short-lived (100 ns) HONTA radical cation as well as a longer-lived (s) HONTA triplet excited state. These HONTA species are important precursors to the suite of HONTA degradation products observed.