Reactor production of promethium-147
Introduction
There is growing interest in the availability of low energy beta emitters for variety of important applications in defense, homeland security, and industry. These applications include beta batteries and other low-power, long-lived power sources including pacemakers, luminescence devices, electron capture detectors, and thickness gauges (Lieberman et al., 2007, Roberts and Van Tuyl, 1965, Walko et al., 1991). Light produced from luminescence devices is used directly in visual devices to produce signals that require dependable operation, and it is used indirectly in photocells converting the energy into an electric current. Low-energy beta emitters also show promise as a heat source and auxiliary power for satellites and space probes in a multitude of future NASA scientific missions. The list of potential radioisotopes for the above applications is quite limited and includes 3H (t1/2 = 12.3 y), 63Ni (t1/2 = 100 y), 147Pm (t1/2 = 2.62 y), 155Eu (t1/2 = 4.76 y), and 171Tm (t1/2 = 1.92 y). As these radionuclides are all are neutron-rich, the Oak Ridge National Laboratory (ORNL) High Flux Isotope Reactor (HFIR) represents a unique and powerful resource for their production. At present, 3H and 63Ni are the only radioisotopes from the above list that are routinely produced. For applications in micro-devices, however, a much higher specific activity is required, which only can be provided by 147Pm,155Eu, and 171Tm, which have much shorter half-lives than 3H and 63Ni. Although rather large quantities of 147Pm can be produced from 235U fission [Pressly 1960], 155Eu and 171Tm can only be synthesized at a large scale by neutron capture reactions on stable 154Sm and 170Er, following the β– decay of the short-lived intermediate radionuclides 154Sm(22.8%)[n,γ]155Sm(t1/2 = 22.8 m, β–)155Eu and 170Er(14.9%)[n,γ]171Er(t1/2 = 7.52 h, β–)171Tm, respectively.
Promethium-147 β− decays with a half-life of 2.6 years, and 99.994% of the time, this decay feeds to the ground state of 147Sm, and consequently the decay of 147Pm is followed by emission of an extremely weak γ-ray at 121.64 keV with an intensity of only 2.85 × 10−3%. The maximum energy of the β− particles from 147Pm is 224.5 keV, with an average energy of ~62 keV (Firestone and Shirley, 1996, Brown et al., 1986).
Traditionally, 147Pm has been isolated in large amounts from fission products from nuclear fuel processing (the yield from 235U fission to isobar 147 is 2.232%, International Atomic Energy Agency, 2006). Until the 1970s, ORNL had a large inventory of 147Pm that had been isolated from fission products at the Hanford nuclear facility in Washington state (Pressly et al., 1960). Since nuclear fuel is no longer processed in the United States, the ORNL inventory has long been exhausted, and there is currently no domestic source of significant amounts of 147Pm (147Pm is currently imported from the Russian Federation). However, similar to 155Eu and 171Tm, 147Pm can be also produced via β– decay of a short-lived predecessor, in this case 147Nd (t1/2 = 10.98 d), which is produced by irradiating enriched 146Nd in a nuclear reactor via the 146Nd[n,γ]147Nd(t1/2 = 10.98 d, β–)147Pm nuclear reaction (Jarrett and Van Tuyl, 1970). The approach requires separation of microgram quantities of Pm from grams of Nd target (Knapp et al., 2008).
In this paper, we describe the production yields and level of impurities from several targets that consisted of milligram quantities of highly enriched 146Nd as oxide irradiated at the ORNL HFIR for durations ranging from 24 to 180 h. We also report new values for the 147Pm burnup cross-sections using a highly purified sample of 147Pm as the target material. A comparison between theoretical and experimental data are also presented, illustrating that large neutron capture cross-sections of 147Pm limit the amount of 147Pm which can be produced even at the highest neutron flux available at the HFIR. Further, attempts are made to empirically evaluate the neutron capture cross-sections of 41.3-d 148mPm and 5.4-d 148gPm. In this work, we also describe the development of the chemical process based on extraction and ion-exchange chromatography for separation of 147Pm from milligram quantities of 146Nd targets and other impurities. The method described defines a selective means to prepare large quantities of 147Pm suitable for applications in beta voltaic batteries. The level of radioisotopic impurities in the final product are also briefly described.
Section snippets
Irradiation facility
The HFIR is a nuclear reactor with the capability and facilities for a wide range of irradiations in near steady-state thermal neutron fluxes up to 2.1 × 1015 n cm−2 s−1. The reactor has been in use since 1965 with the original purpose of producing transuranic isotopes and material irradiation, and a current objective focusing on neutron scattering. HFIR currently operates at an 85 MW power level with a refueling cycle of ~24 days. A hydraulic tube (HT) facility, consisting of a singular bundle
Assay of 147Pm in the presence of 147Nd
As stated earlier, the 0.76 keV energy difference between 120.50 keV from 147Nd and 121.26 keV from 147Pm, are within the ~1 keV energy resolution of our solid-state HPGe γ-ray spectrometers. Consequently, the detection of freshly synthesized 147Pm in the presence of a rather large level of 147Nd activity is hampered because the presence of the more abundant 120.50 keV (0.4%) γ-ray from 147Nd decay. Therefore, complete decay of 147Nd is necessary prior to direct assay of 147Pm activity without
Summary and future studies
The first step for large scale production of 147Pm was to re-evaluate the yield and burnup cross-section of 147Pm. For a one-cycle irradiation, 147Pm yield reaches a maximum value of 101.8 MBq/mg (2.75 mCi/mg) at 60 days post-EOB. Large neutron capture cross-sections of 147Pm result in a significant burnup of the 147Pm, consequently, the yield does not significantly increase with longer irradiation. Our estimates of the thermal neutron capture cross-section and resonance integral for 146Nd at
Acknowledgments
This research was supported by the US Department of Energy, Office of Nuclear Physics. The authors acknowledge the efforts and support of the High Flux Isotope Reactor staff, especially Greg Hirtz, for scheduling irradiations of the targets. The author thanks Drs. Susan Hogle, Dominic Giuliano and Benjamin Lewis for their critical review of the manuscript.
References (23)
- et al.
Half-lives of some fission product nuclides
J. Inorg. Nucl. Chem.
(1971) - et al.
Flux characterization of a peripheral target position in the High Flux Isotope Reactor
Appl. Radiat. Isot.
(2003) - et al.
Reactor production of thorium-229
Appl. Radiat. Isot.
(2016) - et al.
IsoChain: a user-friendly, two-group nuclear transmutation and decay code
Trans. Am. Nucl. Soc.
(2006) Demonstration of a radiation resistant, high efficiency SiC betavoltaic
Appl. Phys. Lett.
(2006)Radioisotopic Impurities in Promethium-147 Produced at the ORNL High Flux Isotope Reactor. Masters thesis
(2010)- International Atomic Energy Agency, 2006. Cumulative Fission Yields. 〈https://www-nds.iaea.org/sgnucdat/c3.htm〉 and...
- et al.
Promethium Isotopic Power Data Sheets, Report No. BNWL-1309 UC-23
(1970)
Cited by (11)
Characteristics comparison and Monte-Carlo simulation of isotopes used in betavoltaics for MEMS application
2022, Applied Radiation and IsotopesNuclear Data Sheets for A=147
2022, Nuclear Data SheetsNuclear data for reactor production of <sup>131</sup>Ba and <sup>133</sup>Ba
2021, Applied Radiation and IsotopesCitation Excerpt :This technique requires measurements of the yields of the radionuclide of interest for various irradiation periods at an ideally constant neutron flux. The calculated yields, based on known neutron capture cross sections, as a function of irradiation time is then fitted to the experimental data by varying the burnup cross section while keeping all other variables constant (Ersöz et al., 2018; Broderick et al., 2018). In this study, we report two group neutron capture cross sections for 130Ba(n,γ)131Ba and 131Ba(n,γ)132Ba reactions via irradiations of several highly enriched 130Ba targets in Oak Ridge National Laboratory's (ORNL's) High Flux Isotope Reactor (HFIR).
Hydrogen Loading System for Thin Films for Betavoltaics
2023, Journal of Nuclear Engineering and Radiation ScienceEffect of Lanthanide Ions Stress on Lactic Acid Fermentation Performance of Streptococcus thermophilus during Milk Processing
2023, AIP Conference ProceedingsDemonstration of Hydrogen Loading in Lithium Thin Films for Betavoltaics
2023, Transactions of the American Nuclear Society
- 1
Current addresses: Siemens Healthineers, Knoxville, TN 37932, USA.
- 2
Current addresses: Department of Energy, Office of Nuclear Physics, Isotope Program, SC-26/Germantown Building, 1000 Independence Ave., SW, Washington, DC 20585, USA.