Long-term product consistency test of simulated 90-19/Nd HLW glass

Chemical durability of 90-19/Nd glass, a simulated high-level waste (HLW) glass in contact with the groundwater was investigated with a long-term product consistency test (PCT). Generally, it is difficult to observe the long term property of HLW glass due to the slow corrosion rate in a mild condition. In order to overcome this problem, increased contacting surface (S/V = 6000 m⁻¹) and elevated temperature (150 °C) were employed to accelerate the glass corrosion evolution. The micro-morphological characteristics of the glass surface and the secondary minerals formed after the glass alteration were analyzed by SEM-EDS and XRD, and concentrations of elements in the leaching solution were determined by ICP-AES. In our experiments, two types of minerals, which have great impact on glass dissolution, were found to form on 90-19/Nd HLW glass surface when it was subjected to a long-term leaching in the groundwater. One is Mg-Fe-rich phyllosilicates with honeycomb structure; the other is aluminosilicates (zeolites). Mg and Fe in the leaching solution participated in the formation of phyllosilicates. The main components of phyllosilicates in alteration products of 90-19/Nd HLW glass are nontronite (Na_0.3Fe₂Si₄O₁₀(OH)₂·4H₂O) and montmorillonite (Ca_0.2(Al,Mg)₂Si₄O₁₀(OH)₂·4H₂O), and those of aluminosilicates are mordenite ((Na₂,K₂,Ca)Al₂Si₁₀O₂₄·7H₂O)) and clinoptilolite ((Na,K,Ca)₅Al₆Si₃₀O₇₂·18H₂O). Minerals like Ca(Mg)SO₄ and CaCO₃ with low solubility limits are prone to form precipitant on the glass surface. Appearance of the phyllosilicates and aluminosilicates result in the dissolution rate of 90-19/Nd HLW glass resumed, which is increased by several times over the stable rate. As further dissolution of the glass, both B and Na in the glass were found to leach out in borax form.     

Development and synthesis of durable self-glowing crystals doped with plutonium

Different crystalline materials doped with plutonium and other alpha-emitting radionuclides are characterized by self-glowing. Some of these materials, in particular, monocrystalline ones, which are highly chemically resistant, mechanically durable, and stable under radiation damage are promising for application in optical couplers, robotics and medicine. They might be used for a long time (from tens to hundreds years) in aggressive chemical media and space. Crystals with low content of radionuclides (less than 0.1 wt%) but intensive self-glowing are main subject of interest. Phosphate and silicate single crystals with zircon structure: xenotime, (Y,…)PO₄ and zircon, (Zr,…)SiO₄, were doped with ²³⁸Pu, ²³⁷Np and non-radioactive elements: Eu³⁺; In³⁺ and Tb³⁺. The most intensive self-glowing was obtained for xenotime crystals doped with 0.1 wt% ²³⁸Pu and Eu; and for zircon crystals doped with 0.01 wt% ²³⁸Pu and coupled admixture of In and Tb.     

Phase study in Sr-Th-P-O system: Structural and thermal investigations of quaternary compounds

The sub-solidus phase relations in Sr-Th-P-O quaternary system were determined at 1223 K in air. To confirm the formation and stability of reported phases, ternary and quaternary compounds in Sr-Th-O, Sr-P-O, Th-P-O and Sr-Th-P-O systems were synthesized by solid state reactions of SrCO₃, ThO₂ and NH₄H₂PO₄ in desired molar proportions at 1223 K. A pseudo-ternary phase diagram of SrO-ThO₂-P₂O₅ system was drawn on the basis of the phase analysis of various phase mixtures and phase fields were established by powder X-ray diffraction. In the phase diagram, three quaternary compounds SrTh(PO₄)₂, SrTh₄(PO₄)₆ and Sr₇Th(PO₄)₆ were identified. When heated in air at 1673 K, these compounds decompose to ThO₂. Structures of SrTh(PO₄)₂, SrTh₄(PO₄)₆ and Sr₇Th(PO₄)₆ were derived from X-ray powder data using the Rietveld refinement method. Thermal expansion behaviors of SrTh(PO₄)₂, SrTh₄(PO₄)₆ and Sr₇Th(PO₄)₆ were investigated using high-temperature X-ray diffraction in the temperature range of 298-1273 K.     

Effect of the preparation conditions of zirconium phosphate on the characteristics of Sr immobilization

The proton-type crystalline zirconium phosphate, HZr₂(PO₄)₃, was obtained by a thermal decomposition of NH₄Zr₂(PO₄)₃ at different temperatures from 400 to 800 °C, where NH₄Zr₂(PO₄)₃ was obtained in advance by a hydrothermal synthesis using a mixed solution of ZrOCl₂, H₃PO₄ and H₂C₂O₄ with different processing times from 5 to 72 h. Sr ion was immobilized to HZr₂(PO₄)₃ by treating the mixture of HZr₂(PO₄)₃ and Sr(NO₃)₂ aqueous solution in an autoclave at 250 °C. Immobilizing and leaching performance of St in HZr₂(PO₄)₃ were discussed.     

The high-temperature behaviour of PuPO4 monazite and some other related compounds

Thermal behaviour and lattice parameters of monazites MPO₄ (M³⁺ = Ce³⁺, Nd³⁺ and Pu³⁺) and cheralite CaTh(PO₄)₂ were studied using high-temperature X-ray diffraction. Heat treatment under inert atmosphere caused the decomposition of PuPO₄ and CaTh(PO₄)₂ into the corresponding oxides above 1473 K. The influence of the cation type within the crystallographic structure on the thermal expansion coefficient and the possible cation substitutions are discussed in the frame of nuclear waste management.     

Nuclear model calculations on the production of Sb via various nuclear reactions

Only very few radionuclides exist that decay exclusively by EC-mode without accompanying radiation, ¹¹⁹Sb is one of them. Auger emitter ¹¹⁹Sb (T_1/2 = 38.9 h, I_EC = 100%) is a potent nuclide for targeted radionuclide therapy based on theoretical dosimetry calculations at a subcellular scale. Auger electron emitting radionuclides in cancer therapy offer the opportunity to deliver a high radiation dose to the tumor cells with high radiotoxicity while minimizing toxicity to normal tissue.     

Effective atomic numbers of some composite mixtures including borax

Effective atomic numbers for (PbO and Na₂B₄O₇10H₂O) and (UO₂(NO₃)₂, and Na₂B₄O₇10H₂O) mixtures against changing contents of PbO, Na₂B₄O₇10H₂O, and UO₂(NO₃)₂ were measured in the X-ray energy range from 25.0 to 58.0 keV. The gamma rays emitted by a ²⁴¹Am annular source have been sent on the absorbers which emits their characteristic X-rays to be used in transmission arrangement. The X-rays were counted by a Si(Li) detector with a resolution of 146 eV at 5.90 keV. The changing compositions of the compounds were assigned to be 0, 0.167, 0.333, 0.500, 0.666, 0.833 and total masses of the mixtures were adjusted to be identical. Also, the total effective atomic numbers of each mixture were estimated by using the mixture rule. The measured values were compared with estimated values for the mixtures.     

Ageing of a phosphate ceramic used to immobilize chloride contaminated actinide waste

A process for the immobilization of intermediate level waste containing a significant quantity of chloride using Ca₃(PO₄)₂ as the host material has been developed. Waste ions are incorporated into two phosphate-based phases, chlorapatite [Ca₅(PO₄)₃Cl] and spodiosite [Ca₂(PO₄)Cl]. Non-active trials performed using Sm as the actinide surrogate demonstrated the durability of these phases in aqueous solution. Trials of the process, in which actinide-doped materials were used, were performed at PNNL which confirmed the wasteform resistant to aqueous leaching. Initial leach trials conducted on ²³⁹Pu/²⁴¹Am loaded ceramic at 313 K/28 days gave normalized mass losses of 1.2 × 10⁻⁵ g m⁻² and 2.7 × 10⁻³ g m⁻² for Pu and Cl, respectively. In order to assess the response of the phases to radiation-induced damage, accelerated ageing trials were performed on samples in which the ²³⁹Pu was replaced with ²³⁸Pu. No changes to the crystalline structure of the waste were detected in the XRD spectra after the samples had experienced an α radiation fluence of 4 × 10¹⁸ g⁻¹. Leach trials showed that there was an increase in the P and Ca release rates but no change in the Pu release rate.     

A comprehensive study on neutronics of a lead–bismuth eutectic cooled accelerator-driven sub-critical system for long-lived fission product transmutation

The aim of this study is to investigate the high-level waste (HLW) transmutation and fissile breeding potentials of a lead–bismuth eutectic (LBE) cooled accelerator-driven system (ADS) for the various configurations (the target radius, R_T = 10–50 cm and the radial thickness of the sub-critical core, δ_SC = 50–80 cm) and for the various fuel compositions (the fuel volume fraction, VF_F = 10%, 12%, 15% and 20% and the fissile fraction, FF = 10–24%) under sub-critical condition. The long-lived fission products (LLFPs: ⁹⁹Tc, ¹²⁹I and ¹³⁵Cs nuclides) and the uranium mono carbide (UC) ceramic fuel are considered as the HLW and the fissile fuel, respectively. The neutronic calculations have been performed per the incident proton (1000 MeV) with the high-energy Monte Carlo code MCNPX in coupled neutron and proton mode using the LA150 library. The numerical results bring out that the case of R_T = 30 cm, δ_SC = 80 cm, VF_F = 10% and FF = 23% is the optimum configuration and fuel composition, from the energy gain point of view, and has a high neutronic performance for an effective LLFP transmutation and fissile breeding.     

Measurement of natural radioactivity and radon exhalation rate from rock samples of Jaduguda uranium mines and its radiological implications

The Singhbhum shear zone is a 200 km long arcuate belt in Jharkhand state situated in eastern India. The central part between Jaduguda-Bhatin-Nimdih, Narwapahr-Garadih-Turamdih is rich in uranium. Presence of uranium in the host rocks and the prevalence of a confined atmosphere within mines could result in enhanced concentration of radon (²²²Rn) gas and its progeny. Inhalation of radon daughter products is a major contributor to the radiation dose to exposed subjects. By using high resolution γ-ray spectroscopic system various radionuclides in the rock samples, collected from different places of Jaduguda uranium mines have been identified quantitatively based on the characteristic spectral peaks. The activity concentrations of the natural radionuclides, uranium (²³⁸U), thorium (²³²Th) and potassium (⁴⁰K) were measured in the rock samples and radiological parameters were calculated. Uranium concentration was found to vary from 123 ± 7 Bq kg⁻¹ to 40,858 ± 174 Bq kg⁻¹. Activity of thorium was not significant in the samples, whereas, few samples have shown potassium activity from 162 ± 11 Bq kg⁻¹ to 9024 ± 189 Bq kg⁻¹. Radon exhalation rates from these samples were also measured using “Sealed Can technique” and found to vary from 4.2 ± 0.05 to 13.7 ± 0.08 Bq m⁻² h⁻¹. A positive correlation was found between the radon exhalation rate and the uranium activity. The absorbed dose rates vary from 63.6 to 18876.4 nGy h⁻¹, with an average value of 7054.2 nGy h⁻¹. The annual external effective dose rates vary from 0.7 to 23.2 mSv y⁻¹. Radium equivalent activities (Ra_eq) varied from 134.3 to 40858.0 Bq kg⁻¹. Value of external hazard index (H_ex) varied from 0.4 to 110.4 with an average value of 41.2.     

Kr ion irradiation study of the depleted-uranium alloys

Fuel development for the reduced enrichment research and test reactor (RERTR) program is tasked with the development of new low enrichment uranium nuclear fuels that can be employed to replace existing high enrichment uranium fuels currently used in some research reactors throughout the world. For dispersion type fuels, radiation stability of the fuel-cladding interaction product has a strong impact on fuel performance. Three depleted-uranium alloys are cast for the radiation stability studies of the fuel-cladding interaction product using Kr ion irradiation to investigate radiation damage from fission products. SEM analysis indicates the presence of the phases of interest: U(Al, Si)₃, (U, Mo)(Al, Si)₃, UMo₂Al₂₀, U₆Mo₄Al₄₃ and UAl₄. Irradiations of TEM disc samples were conducted with 500 keV Kr ions at 200 °C to ion doses up to 2.5 × 10¹⁹ ions/m² (∼10 dpa) with an Kr ion flux of 10¹⁶ ions/m²/s (∼4.0 × 10⁻³ dpa/s). Microstructural evolution of the phases relevant to fuel-cladding interaction products was investigated using transmission electron microscopy.     

Thermal conductivity of (U,Pu,Np)O2 solid solutions

The thermal conductivities of (U_,Pu_,Np)O₂ solid solutions were studied at temperatures from 900 to 1770 K. Thermal conductivities were obtained from the thermal diffusivity measured by the laser flash method. The thermal conductivities obtained below 1400 K were analyzed with the data of (U,Pu,Am)O₂ obtained previously, assuming that the B-value was constant, and could be expressed by a classical phonon transport model, λ = (A + BT)⁻¹, A(z₁, z₂) = 3.583 × 10⁻¹ × z₁ + 6.317 × 10⁻² × z₂ + 1.595 × 10⁻² (m K/W) and B = 2.493 × 10⁻⁴ (m/W), where z₁ and z₂ are the contents of Am- and Np-oxides. It was found that the A-values increased linearly with increasing Np- and Am-oxide contents slightly, and the effect of Np-oxide content on A-values was smaller than that of Am-oxide content. The results obtained from the theoretical calculation based on the classical phonon transport model showed good agreement with the experimental results.     

Cross-sections for alpha particle produced radionuclides on natural silver

Alpha particle-induced nuclear reactions for the generation of radionuclides on natural silver targets were investigated with the stacked foil activation technique up to E_α = 40 MeV. Elemental excitation functions are reported for the reactions ^natAg(α,xn)^{108,109,110,111}In, ^natAg(α,2pxn)^{105,106,110,111}Ag and ^natAg(α,pxn)^111mCd. The experimental cross-sections were compared with available data. Thick target yields have been deduced using the reported excitation functions.     

Synthesis of rare earth phosphates in molten LiCl-KCl eutectic: Application to preliminary treatment of chlorinated waste streams containing fission products

The precipitation of rare earth phosphates (RE = La, Ce, Pr, Nd, and Lu), from RECl₃ was investigated in molten LiCl-KCl eutectic at 500 °C in air. Ammonium dihydrogenphosphate (NH₄H₂PO₄) was used as the phosphorus precursor. X-ray diffraction analysis indicated the formation of compounds with monazite (La, Ce, Pr, and Nd) or xenotime (Lu) structures. ³¹P NMR spectroscopy measurements confirmed that lanthanum formed pure monazite, which indicates a LaCl₃ → LaPO₄ conversion factor near 100%. These results demonstrate that the stoichiometric addition of NH₄H₂PO₄ is sufficient to obtain quantitative precipitation at 500 °C of anhydrous rare earth phosphates in molten LiCl-KCl. The use of this type of precursor, which has the advantage of not modifying the chemical composition of the medium after recovery of the rare earth phosphates, could be considered during the first step of purification of chlorinated baths containing fission products arising from spent fuel reprocessing by a pyrochemical process.     

Reactivity of hydrogen peroxide towards Fe3O4, Fe2CoO4 and Fe2NiO4

The kinetics of CRUD oxidation by H₂O₂ has been studied using aqueous suspensions of metal oxide powder. Fe₃O₄, Fe₂CoO₄ and Fe₂NiO₄ were used as model compounds for CRUD. In addition, the activation energies for the reaction between H₂O₂ and the three CRUD models were determined. The rate constants at room temperature were determined to 6.6 (±0.4) × 10⁻⁹, 3.4 (±0.4) × 10⁻⁸ and 1.6 × 10⁻¹⁰ m min⁻¹ for Fe₃O₄, Fe₂CoO₄ and Fe₂NiO₄, respectively. The corresponding activation energies are 52 ± 4, 44 ± 5 and 57 ± 7 kJ mol⁻¹, respectively. The mechanism of the reaction is briefly discussed indicating that the final solid product in all three cases is Fe₂O₃. In addition to the experimental studies, the theoretical grounds for kinetics of reactions in particle suspensions are discussed. The theoretical discussion is also used to explain the somewhat unexpected trends in reactivity observed experimentally.     

On the radiolysis of iodide, nitrate and nitrite ions in aqueous solution: An experimental and modelling study

High radiation fields are predicted in the atmospheres in the reactor containment under postulated severe accident conditions. In particular, an experimental and modelling project (PARIS) has provided results, which show that nitrogen dioxide was the dominant measured species at high doses (>1 kGy) in air/steam mixtures. In addition, nitrite and nitrate ions were measured in the post-test containment sumps in some Phebus FP in-reactor integral experiments; but their separate effects on iodine volatility from irradiated aqueous solutions of iodide using appear unreported in open literature.To address this issue, this paper presents an overview of the results of an experimental and modelling study carried out at PSI, Switzerland. The experimental study consisted of small-scale irradiations of CsI, boric acid and tracer containing aqueous solutions. Tests were first carried out without nitrate or nitrite ions to obtain results to confirm expected iodine behaviour by correlation with predicted results, which were generated by concurrently developed code (PSIodine). The solutions were sparged with N₂O, argon and air to provide different net oxidation systems and to remove volatile iodine for measurement. Since the radiation chemistry of N₂O-saturated iodide solutions is well established and the measured I₂ yields and final pH correlate very well with the PSIodine code predictions, the effect of added nitrite ions to these solutions has provided results, which support the correct choice of relevant reactions for inclusion in the nitrate-model.Both experimental and predicted results clearly show that nitrate or nitrite ions in argon-sparged and irradiated iodide solutions (conc., 10⁻⁴ mol dm⁻³) containing boric acid lower % I₂ yields up to an initial NO₃⁻ concentration of ∼5.0 × 10⁻³ mol dm⁻³. Using a low CsI concentration (4.0 × 10⁻⁵ mol dm⁻³) estimated in containment sump during a postulated severe-accident, an initial nitrate concentration (10⁻³ mol dm⁻³) and pH 7.1, ∼3.6% I₂ was produced by argon sparging at a dose of 20.5 kGy. In contrast, 80% I₂ was formed at a dose of 12 kGy in the absence of nitrate ions.Irradiated and air-sparged CsI solutions, due to the lower net oxidation, gave the expected lower % I₂ yields than their argon-sparged counterparts. However, the reduction of volatile iodine species by radiation products of nitrate ions was enhanced. For example, using CsI solutions (conc., 10⁻⁴ mol dm⁻³), initial pH 4.6 and a range of nitrate ion concentrations (0, 10⁻⁴, 10⁻³ and 10⁻² mol dm⁻³), the % I₂ yields at a dose of 2 kGy have lowered from 26.9% to 25.6%, 3.2% and 2.8%, respectively. In the latter experiment, only ∼6% I₂ at a dose of ∼20 kGy was produced. In the absence of nitrate ions, a yield of ∼93% I₂ at only 5 kGy dose was obtained. By comparison, the % I₂ yields from their Ar-sparged counterpart experiments were lowered from ∼88% to ∼72%, 11% and 22% in the same nitrate concentration range. Therefore, apart from the lower net oxidation in O₂-containing solutions, the results indicate that the reduction of volatile iodine species by products of nitrate ion irradiation is enhanced in the presence of dissolved O₂.     

Effect of external gamma irradiation on dissolution of the spent UO2 fuel matrix

Leaching experiments were performed on UO₂ pellets doped with alpha-emitters (^238/239Pu) and on spent fuel, in the presence of an external gamma irradiation source (A⁶⁰Co = 260 Ci,  Gy h⁻¹). The effects of α, β, γ radiation, the fuel chemistry and the nature of the cover gas (aerated or Ar + 4%H₂) on water radiolysis and on oxidizing dissolution of the UO₂ matrix are quantified and discussed. For the doped UO₂ pellets, the nature of the cover gas clearly has a major role in the effect of gamma radiolysis. The uranium dissolution rate in an aerated medium is 83 mg m⁻² d⁻¹ compared with only 6 mg m⁻² d⁻¹ in Ar + 4%H₂. The rate drop is accompanied by a reduction of about four orders of magnitude in the hydrogen peroxide concentrations in the homogeneous solution. The uranium dissolution rates also underestimate the matrix alteration rate because of major precipitation phenomena at the UO₂ pellet surface. The presence of studtite in particular was demonstrated in aerated media; this is consistent with the measured H₂O₂ concentrations (1.2 × 10⁻⁴ mol L⁻¹). For spent fuel, the presence of fission products (Cs and Sr), matrix alteration tracers, allowed us to determine the alteration rates under external gamma irradiation. The fission product release rates were higher by a factor of 5-10 than those of the actinides (80-90% of the actinides precipitated on the surface of the fragments) and also depended to a large extent on the nature of the cover gas. No significant effect of the fuel chemistry compared with UO₂ was observed on uranium dissolution and H₂O₂ production in the presence of the ⁶⁰Co source in aerated conditions. Conversely, in Ar + 4%H₂ the fuel self-irradiation field cannot be disregarded since the H₂O₂ concentrations drop by only three orders of magnitude compared with UO₂.     

Synthesis and characterization of low-temperature precursors of thorium-uranium (IV) phosphate-diphosphate solid solutions

Several compositions of new precursor of thorium-uranium (IV) phosphate-diphosphate solid solutions (Th_4−xU_x(PO₄)₄P₂O₇, called β-TUPD) were synthesized in closed PTFE containers either in autoclave (160 °C) or on sand bath (90-160 °C). All the samples appeared to be single phase. From XRD data and TEM observations, the diffraction lines matched well with that of pure thorium phosphate-hydrogenphosphate hydrate (TPHPH), Th₂(PO₄)₂(HPO₄) · H₂O, which confirmed the preparation of a complete solid solution between pure thorium and uranium (IV) compounds. TGA/DTA experiments showed that samples of thorium-uranium (IV) phosphate-hydrogenphosphate hydrate (TUPHPH) prepared at 150-160 °C were monohydrated leading to the proposed formula Th_2−x/2U_x/2(PO₄)₂(HPO₄) · H₂O. The variation of the XRD diagrams versus the heating temperature showed that TUPHPH remained crystallized and single phase from room temperature to 200 °C. After heating between 200 °C and 800 °C, the presence of diphosphate groups in the solid was evidenced. In this range of temperature, the solid was transformed into the low-temperature monoclinic form of thorium-uranium (IV) phosphate-diphosphate (α-TUPD). This latter compound finally turned into well-crystallized, homogeneous and single-phase β-TUPD (orthorhombic form) above 930-950 °C for x values lower than 2.80. For higher x values, a mixture of β-TUPD, α-Th_1−zU_zP₂O₇ and U_2−wTh_wO(PO₄)₂ was obtained. By this new chemical route of preparation of β-TUPD solid solutions, the homogeneity of the samples is significantly improved, especially considering the distribution of thorium and uranium.     

Incorporation of cerium and neodymium in uranyl phases

The potential for incorporating rare earth elements (REE) into/onto crystalline compounds has been evaluated by precipitating uranyl phases from aqueous solutions containing either cerium or neodymium. These REEs serve both as monitors for evaluating the potential repository behavior of REE radionuclides, and as surrogate elements for actinides (e.g., Ce⁴⁺ and Nd³⁺ for Pu⁴⁺ and Am³⁺, respectively). The present experiments examined the behavior of REE in the presence of ianthinite , becquerelite (Ca(UO₂)₆O₄(OH)₆(H₂O)₈), and other uranyl hydroxide compounds commonly noted as alteration products during the corrosion of UO₂, spent nuclear fuel, and naturally occurring uraninite. The results of these experiments demonstrate that significant quantities of both cerium (K_d = 1020) and neodymium (K_d = 840) are incorporated within the uranium alteration phases and suggest that ionic substitution and/or adsorption to the uranyl phases can play a key role in the limiting the mobility of REE (and by analogy, actinide elements) in a nuclear waste repository.     

Experimental study of the Ho(d, 2n) and Ho(d, p) nuclear reactions up to 20 MeV for production of the therapeutic radioisotopes Er and Ho

The radioisotope ¹⁶⁵Er (T_1/2 = 10.36 h) is a candidate for Auger-electron therapy. The β⁻-emitting ^166gHo (T_1/2 = 26.83 h) is now being explored for various therapeutic applications. In the frame of our systematic study of charged particle production routes of therapeutic radionuclides the excitation functions of the ¹⁶⁵Ho(d, 2n)¹⁶⁵Er and ¹⁶⁵Ho(d, p)^166gHo reactions were measured up to 20 MeV by using a stacked foil irradiation technique and X/γ-ray spectroscopy. The excitation function of the ¹⁶⁵Ho(d, 2n)¹⁶⁵Er reaction was measured for the first time while for the ¹⁶⁵Ho(d, p)^166gHo reaction only a single dataset of earlier measured cross-sections was found. The measured excitation functions were compared to the results of different nuclear reaction model codes. The calculated thick target yield of the ¹⁶⁵Ho(d, 2n) reaction is significantly higher over the optimal energy range than that for the ¹⁶⁵Ho(p, n) reaction investigated earlier by us. The integral yield of the ¹⁶⁵Ho(d, p)^166gHo reaction is rather low compared to the established ¹⁶⁵Ho(n, γ)¹⁶⁶Ho reaction in a nuclear reactor.