Dmitri G. Medvedev

Development of a large scale production of 67Cu from 68Zn at the high energy proton accelerator: closing the 68Zn cycle.

A number of research irradiations of (68)Zn was carried out at Brookhaven Linac Isotope Producer aiming to develop a practical approach to produce the radioisotope (67)Cu through the high energy (68)Zn(p,2p)(67)Cu reaction. Disks of enriched zinc were prepared by electrodeposition of (68)Zn on aluminum or titanium substrate and isolated in the aluminum capsule for irradition. Irradiations were carried out with 128, 105 and 92 MeV protons for at least 24h. After irradiation the disk was chemically processed to measure production yield and specific activity of (67)Cu and to reclaim the target material. The recovered (68)Zn was irradiated and processed again. The chemical procedure comprised BioRad cation exchange, Chelex-100 and anion exchange columns. Reduction of the oxidation degree of copper allowed for more efficient Cu/Co/Zn separation on the anion exchange column. No radionuclides other than copper isotopes were detected in the final product. The chemical yield of (67)Cu reached 92-95% under remote handling conditions in a hot box. Production yield of (67)Cu averaged 29.2 μCi/[μA-h×g (68)Zn] (1.08MBq/[μA-h×g (68)Zn]) in 24h irradiations. The best specific activity achieved was 18.6 mCi/μg (688.2 MBq/μg).

Activation of natural Hf and Ta in relation to the production of 177Lu.

The isotope (177)Lu is used in nuclear medicine and biology for in vivo applications as a radioactive label of various targeting agents. To extend the availability of no-carrier added (177)Lu, we investigated the feasibility of its production in a proton accelerator. Tantalum and Hf targets were irradiated and chemically processed to determine the radioisotope yield and cross-sections. The largest cross-sections (approximately 20 mb) were found for the Hf target at 195 MeV; however, the presence of co-produced Lu isotopes may limit the product applications. The results are in good agreement with theoretical data calculated using computer codes MCNPX and ORIGEN2S. Production of relevant medical isotopes such as (167)Tm and (169)Yb from the above targets is discussed as well.

Large scale accelerator production of 225Ac: Effective cross sections for 78–192 MeV protons incident on 232Th targets

Actinium-225 and 213Bi have been used successfully in targeted alpha therapy (TAT) in preclinical and clinical research. This paper is a continuation of research activities aiming to expand the availability of 225Ac. The high-energy proton spallation reaction on natural thorium metal targets has been utilized to produce millicurie quantities of 225Ac. The results of sixteen irradiation experiments of thorium metal at beam energies between 78 and 192MeV are summarized in this work. Irradiations have been conducted at Brookhaven National Laboratory (BNL) and Los Alamos National Laboratory (LANL), while target dissolution and processing was carried out at Oak Ridge National Laboratory (ORNL). Excitation functions for actinium and thorium isotopes, as well as for some of the fission products, are presented. The cross sections for production of 225Ac range from 3.6 to 16.7mb in the incident proton energy range of 78-192MeV. Based on these data, production of curie quantities of 225Ac is possible by irradiating a 5.0gcm-2 232Th target for 10 days in either BNL or LANL proton irradiation facilities.

Irradiation of strontium chloride targets at proton energies above 35 MeV to produce PET radioisotope Y-86

Abstract Proton irradiation of natural and enriched SrCl2 targets was used to produce PET radioisotope 86Y. The proton energy was degraded from the incident 117.8 MeV to induce the 88Sr(p,3n) reaction. For the irradiation three pellets made of natSrCl2 (6.61 and 74.49 g) and 88SrCl2 (5.02 g) were pressed and individually encapsulated in stainless steel target bodies. The two smaller targets were irradiated for 0.5–1 h at the energy ∼ 46→37 MeV to take advantage of the peak in the excitation function of the 88Sr(p,3n) reaction. The larger target was irradiated at 66.4→44.6 MeV. The irradiated pellets were chemically processed to selectively separate 86Y radioisotope using Eichrom DGA (N,N,N´,N´-tetra-n-octyldiglycolamide) resin. The production yields of 86Y were determined to be 10–13 mCi/μA h. Coproduction of 87mY in the final product was 34% for natSrCl2 and 54% for 88SrCl2 target. The chemical separation yield of yttrium reached 88–92%. The developed chemical procedure allows for the same day processing and shipment of the isotope to users.

Proton-induced production and radiochemical isolation of 44Ti from scandium metal targets for 44Ti/44Sc generator development

Scandium-44g (half-life 3.97h) shows promise for application in positron emission tomography (PET), due to favorable decay parameters. One of the sources of 44gSc is the 44Ti/44gSc generator, which can conveniently provide this radioisotope on a daily basis at a diagnostic facility. Titanium-44 (half-life 60.0 a), in turn, can be obtained via proton irradiation of scandium metal targets. A substantial 44Ti product batch, however, requires high beam currents, long irradiation times and an elaborate chemical procedure for 44Ti isolation and purification. This study describes the production of a combined 175MBq (4.7mCi) batch yield of 44Ti in week long proton irradiations at the Los Alamos Isotope Production Facility (LANL-IPF) and the Brookhaven Linac Isotope Producer (BNL-BLIP). A two-step ion exchange chromatography based chemical separation method is introduced: first, a coarse separation of 44Ti via anion exchange sorption in concentrated HCl results in a 44Tc/Sc separation factor of 102-103. A second, cation exchange based step in HCl media is then applied for 44Ti fine purification from residual Sc mass. In summary, this method yields a 90-97% 44Ti recovery with an overall Ti/Sc separation factor of ≥106.

Specific activity and isotope abundances of strontium in purified strontium-82

A linear accelerator was used to irradiate a rubidium chloride target with protons to produce strontium-82 (Sr-82), and the Sr-82 was purified by ion exchange chromatography. The amount of strontium associated with the purified Sr-82 was determined by either: ICP-OES or method B which consisted of a summation of strontium quantified by gamma spectroscopy and ICP-MS. The summation method agreed within 10% to the ICP-OES for the total mass of strontium and the subsequent specific activities were determined to be 0.25–0.52 TBq mg−1. Method B was used to determine the isotope abundances by weight% of the purified Sr-82, and the abundances were: Sr-82 (10–20.7%), Sr-83 (0–0.05%), Sr-84 (35–48.5%), Sr-85 (16–25%), Sr-86 (12.5–23%), Sr-87 (0%), and Sr-88 (0–10%). The purified strontium contained mass amounts of Sr-82, Sr-84, Sr-85, Sr-86, and Sr-88 in abundances not associated with natural abundance, and 90% of the strontium was produced by the proton irradiation. A comparison of ICP-OES and method B for the analysis of Sr-82 indicated analysis by ICP-OES would be easier to determine total mass of strontium and comply with regulatory requirements. An ICP-OES analytical method for Sr-82 analysis was established and validated according to regulatory guidelines.

Evaluation of SynPhase Lanterns for capturing Ac-225 from bulk thorium

Proton irradiation of a thorium (Th) target can produce Actinium-225 (Ac-225), but the irradiated thorium fissions results in the production of 100’s of other isotopes. SynPhase Lanterns containing sulfonic acid groups were evaluated for the purification of Ac-225 from Th and other fission metals. The SynPhase Lanterns were able to quantitatively and selectively capture Ac-225 and lanthanum (La) over Th. A second purification step would be needed to purify Ac-225 from trace amounts of Th and other fission products. The results from these studies were compared to similar studies performed with cation exchange resins, and the resins were superior at removing impurities.

Tailoring medium energy proton beam to induce low energy nuclear reactions in 86 SrCl 2 for production of PET radioisotope 86 Y

This paper reports results of experiments at Brookhaven Linac Isotope Producer (BLIP) aiming to investigate effective production of positron emitting radioisotope (86)Y by the low energy (86)Sr(p,n) reaction. BLIP is a facility at Brookhaven National Laboratory designed for the proton irradiation of the targets for isotope production at high and intermediate proton energies. The proton beam is delivered by the Linear Accelerator (LINAC) whose incident energy is tunable from 200 to 66 MeV in approximately 21 MeV increments. The array was designed to ensure energy degradation from 66 MeV down to less than 20 MeV. Aluminum slabs were used to degrade the proton energy down to the required range. The production yield of (86)Y (1.2+/-0.1 mCi (44.4+/-3.7) MBq/μAh) and ratio of radioisotopic impurities was determined by assaying an aliquot of the irradiated (86)SrCl2 solution by gamma spectroscopy. The analysis of energy dependence of the (86)Y production yield and the ratios of radioisotopic impurities has been used to adjust degrader thickness. Experimental data showed substantial discrepancies in actual energy propagation compared to energy loss calculations.