Enriched Molybdenum Research Articles

Absolute Mo96(p,n)Tc96m+g cross sections and a new branching for the Tc96m decay

Background: Radionuclides in the Mo-Tc region play an important role in modern medical diagnostics. These applications require a $\ensuremath{\gamma}$-emitting radioisotope that is injected into the patient. Various production methods of those radionuclides have been investigated in the past; among them are ($p,x$) reactions on natural or enriched molybdenum. Reliable estimations for the produced activity of the radionuclides and radioactive byproducts are required. Therefore, either precise theoretical calculations or a firm experimental database for the nuclear production reactions are needed. In addition, experimental cross-section data of proton-induced reactions on heavy nuclei are very valuable to test nuclear models that enter theoretical calculations of reaction rates relevant for nuclear astrophysics.Purpose: The present paper reports on experimental cross sections of the $^{96}\mathrm{Mo}(p,n)^{96m+g}\mathrm{Tc}$ reaction. The contribution of the ground-state population as well as for the population of the metastable state in $^{96}\mathrm{Tc}$ are determined individually. The obtained results are very valuable to test existing models that enter statistical model calculations. In addition, the present work aims at remeasuring the branching ratio of the decay of the metastable state $^{96m}\mathrm{Tc}$.Method: Highly enriched $^{96}\mathrm{Mo}$ targets were irradiated with protons at energies between ${E}_{p}=3.9\phantom{\rule{4pt}{0ex}}\mathrm{MeV}$ and ${E}_{p}=5.4\phantom{\rule{4pt}{0ex}}\mathrm{MeV}$, which are slightly above the ($p,n$) threshold (${E}_{th}=3.8\phantom{\rule{4pt}{0ex}}\mathrm{MeV}$). By employing an offline analysis, the $\ensuremath{\gamma}$-ray decay of the reaction product was investigated and reaction cross sections were calculated by means of the activation technique.Results: Individual reaction cross sections for the production channel of the metastable state ${\ensuremath{\sigma}}_{m}$ and the ground state ${\ensuremath{\sigma}}_{gs}$ as well as the branching of the $^{96m}\mathrm{Tc}\phantom{\rule{4pt}{0ex}}\ensuremath{\rightarrow}\phantom{\rule{4pt}{0ex}}^{96}\mathrm{Tc}$ decay were determined.Conclusion: The measured cross sections are in good agreement with previously measured cross sections as well as with recent Hauser-Feshbach calculations. The new branching ratio for the direct decay of $^{96m}\mathrm{Tc}$ into $^{96}\mathrm{Mo}$ amounts to $4.1{\phantom{\rule{0.16em}{0ex}}}_{\ensuremath{-}0.34}^{+0.39}\phantom{\rule{0.16em}{0ex}}%$ compared to previously reported $2\phantom{\rule{0.16em}{0ex}}\ifmmode\pm\else\textpm\fi{}0.5%$.

Purification and recovery of 100MoO3 in crystal production for AMoRE experiment

The AMoRE collaboration searches for the neutrinoless double-beta decay of 100Mo with ultra-radiopure molybdate crystals operated as low-temperature scintillating bolometers. For such a rare event search experiment, the techniques for investigating and reducing radioactive background contaminants in detector materials are extremely crucial. This paper discusses techniques for deep purification of enriched molybdenum for growing the crystals and the recovery of 100MoO3 from the residual melt left after growing lithium molybdate crystals. The purities of enriched molybdenum trioxide powders before and after the purification and that of the recovered powder were tested with ICP-MS; results of these tests are presented.

Total evaporation technique for high-accuracy isotopic analysis of isotopically enriched molybdenum by negative thermal ionization mass spectrometry

The isotopic composition of isotopically enriched materials is essential for isotope dilution mass spectrometry and calibrated mass spectrometry, which are considered to be potential primary methods/authority methods of the highest metrological quality for the analysis of elemental content or isotopic compositions. In this study, a total evaporation (TE) technique was developed for accurate determination of isotopic compositions for seven enriched molybdenum materials with the utilization of negative ion-thermal ionization mass spectrometry (NTIMS). By using La(NO3)3 as an activator, the sample was efficiently ionized into for NTIMS measurement. To achieve highly precise results, the oxygen isotope interference in on Mo isotopic analysis was corrected by using the IUPAC recommended isotopic compositions for atmospheric O2. Various sources of uncertainty to TE-NTIMS, such as measurement repeatability, oxide interference correction, and the ion loss before and after measurement were discussed with respect to the determination of their uncertainty contribution and their influence on the results. As a result, the major isotope abundance for each enriched Mo material were determined as (k = 2): x(92Mo) = 0.974 69 ± 11 for enriched Mo-92, x(94Mo) = 0.920 26 ± 11 for enriched Mo-94, x(95Mo) = 0.965 50 ± 20 for enriched Mo-95, x(96Mo) = 0.967 59 ± 12 for enriched Mo-96, x(97Mo) = 0.942 06 ± 13 for enriched Mo-97, x(98Mo) = 0.984 56 ± 11 for enriched Mo-98, and x(100Mo) = 0.993 655 ± 12 for enriched Mo-100, respectively. These measurement results have been compared to those determined by a multi-collector inductively coupled plasma mass spectrometry via the mathematical iteration method in our previous work. Identical major isotope-abundance values were achieved within their combined standard uncertainties, indicating that the TE technique is a powerful and alternative tool for accurate determination of the isotopic composition for isotopically enriched materials. The potential influence owing to the variations of O isotopic compositions during NTIMS measurements were also investigated by applying the ‘In-run O’ isotope-abundance values reported in recent literatures for O isotope interference correction. The corrected Mo isotope abundances of either the major or the minor isotopes were in good agreement with that corrected by using the IUPAC atmospheric O2 isotopic compositions.

Analysis of radioactive waste generated during the cyclotron production of 99mTc

Past and prospective shortages of medical radioisotopes have driven recent developments in the direct production of 99mTc via the 100Mo(p,2n)99mTc reaction. The cyclotron-based production method has been shown to successfully produce 99mTc, however trace impurities present in the enriched molybdenum target can also lead to the unintended creation of other radioisotopes which constitute waste. The isotopic composition of the waste has to be investigated in order to determine how it can be handled, transported and safely stored. In this article, we report which waste radioisotopes are created alongside 99mTc during target irradiation. Results are based on the gamma spectroscopy of waste produced. Significant complexities in the emission spectra made automated identification of radioisotopes inaccurate; complexities were resolved using a manual radioisotope identification procedure. The impact of target composition, integrated beam current and duration of target irradiation on the waste produced was studied. Results indicate that an average of 0.059 ± 0.003 GBq of waste is generated per 1 GBq of 99mTc produced. Two-thirds of the total waste activity produced was attributed to 99Mo (T1/2 = 66 h) alone, while a total of fifty radioisotopes were found in the waste. Long-lived isotopes (T1/2 > 2 months) constituted only 1% of the total waste activity at end of beam (EOB). In conclusion, it was determined that the waste generated during cyclotron-based 99mTc production was acceptably low for routine clinical production.

Economic evaluation of radiopharmaceutical Mo-99 production in reactor and accelerators in Iran

Introduction: Radioisotope 𝑇𝑐-99m is one of the most important in the field for thyroid imaging, intestinal or bladder appendages, blood vessel imaging, detecting blood clots, bone imaging, etc. This necessary radioisotope is the daughter of a nuclear-radioactive molybdenum-99 that is manufacturing in accelerators or research reactors. Our world now needs 12000 Ci. Given the growing trend in nuclear medicine imaging, the economic issue of producing the radioisotopes required for these images is going to be important. In this paper, using the TALYS code and the software SRIM, TRIM and MATLAB, we compared the accelerator gain with the reactor and provided an optimized method for Iran. Materials and Methods: Using the TALYS code, we find the dependence of the cross-sectional energy on energy and then, using the SRIM code, we consider the energy dependence of the protons in depth penetration. Using MATLAB, we obtain the mean value of the cross section using the equations from TALYS, and obtain yield for protons we guess demand Iran’s need. Results: So if we have two 30 Mev (and 300µA) accelerators in the two three-day sets in week with a one-day rest having irradiate, then Iran needs about 70-80 Ci will be satisfy, and the rest of the demand for Tehran will be from in direct way of Tc-99m production. In this case, for each accelerator per week, we need about 2 grams per week and for direct production of Tc, 40 mg of enriched molybdenum 100 per day is needed, which costs are calculated. Conclusion: Even without considering the cost of electricity and waste disposal and separation, and only by comparing the annual uranium cost with the total accelerator cost, we will find that the accelerator method is much more convenient and reasonable. In the accelerator method, regardless of the initial cost of the devices, we annually had the cost of electricity and enriched molybdenum and other costs that are shared with the reactor (employee salaries and separation, etc.). Perhaps these costs are higher in the reactor. In addition, we have a lot of problems with the acquisition of enriched uranium and we buy it at a great price from Argentina or Russia. Or the cost of molybdenum 99 at an annual price of $ 4 million from Russia, which can be produced at a lower cost at home and, in addition to economic optimization, also leads to entrepreneurship.

Impurities in Tc-99m radiopharmaceutical solution obtained from Mo-100 in cyclotron

The gamma emitting impurities in 99mTc solution obtained from enriched molybdenum 100Mo metallic target after its irradiation in a cyclotron were measured using a high-purity germanium (HPGe) detector. The radioactivity range of tested samples of 99mTc was rather low, in the range from 0.34 to 2.39 MBq, thus creating a challenge to investigate the standard measurement HPGe system for impurity detection and quantification. In the process of 99mTc separation from irradiated target the AnaLig® Tc-02 resin, Dionex H+ and Alumina A columns were used. Fractions of eluates from various steps of separation process were taken and measured for radionuclidic purity. The overall measurement sensitivity of gamma emitters in terms of minimum detectable activity (MDA) was found at the level of 14–70Bq with emission lines in range of 36 – 1836keV resulting in impurity content range of 6.7 × 10−4 to 3.4 × 10−3 % for 93Tc, 93mTc, 94Tc, 94mTc, 95Tc, 95mTc, 96Tc 96Nb, 97Nb, 99Mo contaminants and 9.4 × 10−3 % for 97mTc. The usefulness of the chosen measurement conditions and the method applied to testing the potential contaminators was proved by reaching satisfactory results of MDAs less than the criteria of impurity concentration of all nuclides specified in the European Pharmacopoeia.

Surface enriched molybdenum enhancing the corrosion resistance of 316L stainless steel

Surface enriched molybdenum 316L stainless steel was obtained by ball milling technique. The electrochemical tests showed surface enriched molybdenum improved the corrosion resistance of the 316L stainless steel. This was attributed to a fact that more molybdenum oxides improved the corrosion resistance of the 316L stainless steel in borate buffer solution. In addition, more chromium oxides in the passive film after ball milling also improved corrosion resistance of the 316L stainless steel.

Graphical user interface for yield and dose estimations for cyclotron-produced technetium

The cyclotron-based 100Mo(p,2n)99mTc reaction has been proposed as an alternative method for solving the shortage of 99mTc. With this production method, however, even if highly enriched molybdenum is used, various radioactive and stable isotopes will be produced simultaneously with 99mTc. In order to optimize reaction parameters and estimate potential patient doses from radiotracers labeled with cyclotron produced 99mTc, the yields for all reaction products must be estimated. Such calculations, however, are extremely complex and time consuming. Therefore, the objective of this study was to design a graphical user interface (GUI) that would automate these calculations, facilitate analysis of the experimental data, and predict dosimetry. The resulting GUI, named Cyclotron production Yields and Dosimetry (CYD), is based on Matlab®. It has three parts providing (a) reaction yield calculations, (b) predictions of gamma emissions and (c) dosimetry estimations. The paper presents the outline of the GUI, lists the parameters that must be provided by the user, discusses the details of calculations and provides examples of the results. Our initial experience shows that the proposed GUI allows the user to very efficiently calculate the yields of reaction products and analyze gamma spectroscopy data. However, it is expected that the main advantage of this GUI will be at the later clinical stage when entering reaction parameters will allow the user to predict production yields and estimate radiation doses to patients for each particular cyclotron run.

Cyclotron production of 99mTc: Recycling of enriched 100Mo metal targets

There is growing interest in the large scale cyclotron production of 99mTc via the 100Mo(p,2n)99mTc reaction. While the use and recycling of cyclotron-irradiated enriched molybdenum targets has been reported previously in the context of 94mTc production, to the best of our knowledge, previous recycling studies have been limited to the use of oxide targets. To facilitate reuse of high-power enriched 100Mo targets, this work presents and evaluates a strategy for recycling of enriched metallic molybdenum. For the irradiated 100Mo targets in this study, an overall metal to metal recovery of 87% is reported. Evaluation of “new” and “recycled” 100Mo revealed no changes in the molybdenum isotopic composition (as measured via ICP-MS). For similar irradiation conditions of “new” and “recycled” 100Mo, (i.e. target thicknesses, irradiation time, and energy), comparable levels of 94gTc, 95gTc, and 96gTc contaminants were observed. Comparable QC specifications (i.e. aluminum ion concentration, pH, and radiochemical purity) were also reported. We finally note that [99mTc]–MDP images obtained by comparing MDP labelled with generator-based 99mTc vs. 99mTc obtained following the irradiation of recycled 100Mo demonstrated comparable biodistribution. With the goal of producing large quantities of 99mTc, the proposed methodology demonstrates that efficient recycling of enriched metallic 100Mo targets is feasible and effective.

Theoretical dosimetry estimations for radioisotopes produced by proton-induced reactions on natural and enriched molybdenum targets

This study presents a summary of the dosimetry calculations performed for three technetium agents most commonly used in nuclear medicine diagnostic studies, namely sestamibi™, phosphonates and pertechnetate, labeled with cyclotron-produced technetium. Calculated patient doses were compared to those that would be delivered by the same radiotracers labeled with technetium obtained from a generator produced in a reactor. The main difference is that technetium from a generator is pure, i.e. contains only 99mTc and its decay product 99gTc, while in a cyclotron a large number of other stable and radioactive isotopes are created. In our calculations only technetium radioisotopes (ground and isomeric states) were considered as they will be included in the radiotracer labeling process and will contribute to the patient dose. Other elements should be removed by chemical purification. These dose estimates are based on our theoretical calculations of the proton-induced reaction cross sections and radioisotope production yields. Thick targets of enriched (three different compositions) and natural molybdenum, and three initial beam energies (16, 19 and 24 MeV) were considered for irradiation times of 3, 6 and 12 h with a beam current of 200 µA. The doses were calculated for injection times corresponding to 0, 2, 8, 12 and 24 h after the end of beam.

Investigation of activation cross-sections of deuteron induced nuclear reactions on natural Mo up to 50 MeV

Cross-sections of deuteron induced nuclear reactions on natural molybdenum have been studied in the frame of a systematic investigation of charged particle induced nuclear reactions on metals for different applications. The excitation functions of 93,94g,94m,95g,95m,96,99mTc, 90,93m,99Mo, 90,91m,92m,95m,95g,96Nb and 88,89Zr were measured up to 50MeV deuteron energy by using the stacked foil technique and activation method. The goal of this work was first of all to study the production possibility of the medically important 99mTc, and its 99Mo parent, to get experimental data useful in accelerator technology, and for testing nuclear reaction theories. The thick target yields and production possibilities of 99mTc and 99Mo were estimated up to 50MeV deuteron energy, and it is shown that besides the proton induced reactions, deuteron induced reactions on enriched molybdenum target seem to be promising. For most of the reaction products published experimental data for excitation functions are available only up to 20MeV, and our new values confirm and extend the dataset. The experimental data were compared with the results of model calculations obtained by using ALICE-IPPE-D, EMPIRE-II-D and two versions of the TALYS code resulting in moderate agreement.

Theoretical modeling of yields for proton-induced reactions on natural and enriched molybdenum targets

Recent acute shortage of medical radioisotopes prompted investigations into alternative methods of production and the use of a cyclotron and 100Mo(p,2n)99mTc reaction has been considered. In this context, the production yields of 99mTc and various other radioactive and stable isotopes which will be created in the process have to be investigated, as these may affect the diagnostic outcome and radiation dosimetry in human studies. Reaction conditions (beam and target characteristics, and irradiation and cooling times) need to be optimized in order to maximize the amount of 99mTc and minimize impurities. Although ultimately careful experimental verification of these conditions must be performed, theoretical calculations can provide the initial guidance allowing for extensive investigations at little cost. We report the results of theoretically determined reaction yields for 99mTc and other radioactive isotopes created when natural and enriched molybdenum targets are irradiated by protons. The cross-section calculations were performed using a computer program EMPIRE for the proton energy range 6–30 MeV. A computer graphical user interface for automatic calculation of production yields taking into account various reaction channels leading to the same final product has been created. The proposed approach allows us to theoretically estimate the amount of 99mTc and its ratio relative to 99gTc and other radioisotopes which must be considered reaction contaminants, potentially contributing to additional patient dose in diagnostic studies.

MO‐F‐110‐08: Yields and Dosimetry Estimates for Radioisotopes Produced in Proton‐Induced Reactions on Enriched Molybdenum Targets

Purpose: To investigate radiation dosimetry for 99mTc produced by medical cyclotrons, based on theoretical reaction cross‐sections and yields. Several other technetium isotopes produced in a cyclotron are chemically inseparable from 99mTc. This could increase patient absorbed dose. We compared the resulting doses to those from 99mTc produced by conventional 99Mo/99mTc generators. Methods: We simulated natural and enriched molybdenum thick targets irradiated by 10–30MeV protons. All reaction channels leading to any given reaction product were considered in final yields. The cross‐section calculations were performed using the EMPIRE code. A computer graphical user interface for automatic calculation of isotope yields and activities was created. The pertechnetate, phosphonate as well as MIBI radiation absorbed doses were calculated by OLINDA/EXM 1.1 using the adult male reference. Generator produced 99mTc was assumed to have 100% radionuclide purity. Results: The thick target yields for 99mTc, 99gTc and other isotopes were determined for 16‐ 10MeV, 19‐10MeV and 24‐10MeV energy protons. The difference of radiation doses between pure‐Tc (reactor produced) and mixture‐Tc (cyclotron produced) in main organs were estimated. In highly enriched targets (99.5% 100Mo), the mixture‐Tc doses are about 0.5% larger than the pure‐Tc doses. These differences decreased in the first few hours from the end of beam (EOB) and then increased to 1 % after 24 hours from EOB. In targets with lower enrichment (97.4% 100Mo), the 0–8 hours after EOB doses from the mixture‐Tc isotopes exceeded the pure‐99mTc dose by ∼1% or less. For radiopharmaceuticals injected in patients 24 hours after EOB, this difference increased to 2–5%. Conclusion: Other radioisotopes, which will be produced in the cyclotron together with 99mTc must be considered for their potential to increase patient dose exposure. The differences between the radiation absorbed doses from technetium produced by cyclotrons and nuclear reactors are minimal at EOB, and increase slightly after 24 hours.

The mechanism of order-induced intrinsic embrittlement in a stoichiometric Ni 4Mo alloy by TEM and 3DAP characterization

To illustrate the mechanism of order-induced intrinsic embrittlement in a stoichiometric Ni 4Mo alloy, TEM and 3DAP were employed to investigate the phase separation during ordering in this paper. It showed that the atomic ordering initiated homogeneously, but some oriented ordered domains can grow preferentially later. Therefore, with atomic ordering, the average ordered domain size continues to increase, which improves the yield strength and ultimate strength due to increasing the critical shear stresses. However, except the growth of ordered phase, different phases with enriched molybdenum and depleted molybdenum were formed after ordering. The depleted molybdenum phase gradually reduces the Mo composition, which deteriorates the ultimate strength, and meantime the strength of grain boundary does not enhance, or even weakens. Hence, the atomic ordering induces embrittlement.

Two-neutrino double- beta decay measurement of 100Mo.

From data accumulated over 6140 h with 172 g of enriched molybdenum (1.18 mol yr of Mo100) with the NEMO 2 detector in the Fréjus Underground Laboratory, a clear ββ2ν signal (1433 events) is observed, leading to a half-life T1/2=0.95±0.04(stat)±0.09(syst) 1019 yr. The experimental two-electron energy spectrum and the two-electron angular distribution are in agreement with the expected ones. Limits for ββ0ν decays to the ground state, excited states (21+ and 01+), and also with Majoron emission are given.Received 29 June 1994DOI:https://doi.org/10.1103/PhysRevD.51.2090©1995 American Physical Society

Thermochromatographic Separation of 94mTc from Enriched Molybdenum Targets and its Large Scale Production for Nuclear Medical Application

The thermochromatographic behaviour of 'carrier-free' technetium species TcO[sub x] (x probably 3) and HTcO[sub 4] was studied in dry and moist air atmospheres. Temperatures of adsorption on quartz surfaces (T[sub a]) were measured to be 400[+-]40 C and 300[+-]30 C, respectively, for the two technetium species for 20 min experimental periods. Two alternative routes for fast and quantitative thermochromatogrphic separation of the short-lived positron emitting technetium isotope [sup 94m]Tc from highly enriched molybdenum targets ([sup 94]MoO[sub 3]) were tested. The optimum conditions to separate [sup 94m]Tc within 25 min, with overall radiochemical yields of about 80-85% (non-decay-corrected 40-45%) and in high radiochemical purity of >99% as pertechnetate, were developed. The radionuclidic purity at EOB was covery and cyclic use of the enriched target material. (orig.)

Gamma radiation from the decay of the95Tc ground state and from the93Tc isomeric pair

The γ-ray spectra, following the decay of the 20 h95Tc ground state and of the 2.7 h93Tc ground state and its 43 min isomeric state, were studied by means of scintillation techniques. The sources were produced from enriched molybdenum targets. The energies (and relative intensities in per cent per decay) of the γ-rays from (20±1) h95Tc are: (205±5) (1.0%), (680±20) (2.0%), (765±5) (82±10%), (840±10) (10.5%), (930±10) (1.7%) and (1060±10) keV (4.0%) of which the first, second and fourth have not been reported before. The decay of the (43±2) min93Tc isomer only shows γ-rays of (390±5) (I.T., 82% per decay) and (2660±40) keV (18% per decay), that of the (2.7±0.1) h ground state shows 2 new transitions of (860±20) (2.6% per decay) and (2440±30) keV (0.3% per decay) in addition to the already known ones of (1350±10) (60%), (1490±10) (30%) and (2030±30) (0.35%) keV. A slightly revised decay scheme is proposed for93Tc.

Technetium of Mass Number 98

By (p, n) reactions on enriched molybdenum isotopes, it has been found that Tc 98 does not have a half-life in the neighborhood of either 42 minutes or 2.8 days as had been variously claimed.