Ecological aspects of 99Mo/99mTc production at an electron accelerator

The present report deals with experimental investigations into possible processes of accumulation of radioactive by-products (RBPs) during 99Mo/99mTc production at an electron linac. Foils from natural molybdenum (a target) and a number of typical target setup materials (Al, Ti, Cu, Ta, Ni and sta...

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Автори: Dikiy, N.P., Lyashko, Yu.V., Uvarov, V.L., Shlyakhov, I.N., Malets, Eu.B.
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Опубліковано: Національний науковий центр «Харківський фізико-технічний інститут» НАН України 2004
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Цитувати:Ecological aspects of 99Mo/99mTc production at an electron accelerator / N.P. Dikiy, Yu.V. Lyashko, V.L. Uvarov, I.N. Shlyakhov, Eu.B. Malets // Вопросы атомной науки и техники. — 2004. — № 1. — С. 191-193. — Бібліогр.: 6 назв. — англ.

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spelling nasplib_isofts_kiev_ua-123456789-790702025-02-09T18:14:10Z Ecological aspects of 99Mo/99mTc production at an electron accelerator Екологічні аспекти виробництва 99Мо/99mТс на прискорювачі електронів Экологические аспекты производства 99Мо/99mТс на ускорителе электронов Dikiy, N.P. Lyashko, Yu.V. Uvarov, V.L. Shlyakhov, I.N. Malets, Eu.B. Применение ускоренных пучков The present report deals with experimental investigations into possible processes of accumulation of radioactive by-products (RBPs) during 99Mo/99mTc production at an electron linac. Foils from natural molybdenum (a target) and a number of typical target setup materials (Al, Ti, Cu, Ta, Ni and stainless steel) were chosen as an object of investigations. The generation of radionuclides in the samples was performed in identical conditions under secondary radiation (bremsstrahlung + photoneutrons) of the linac LU-20 in a typical range of electron energies from 24 to 34 MeV. Викладені результати експериментального дослідження можливих процесів наробітку побічних радіонуклідов при виробництві 99Мо/99mТс на прискорювачі електронів. Як об'єкт дослідження відібрані фольги з природного молібдену (мішень) і набору характерних конструкційних матеріалів (Al, Ti, Cu, Ta, Ni, а також нержавіюча сталь). Генерація радіонуклідів у зразках виконувалося в ідентичних умовах у полі вторинного випромінювання (гальмівне+фотонейтрони) прискорювача ЛП-20 у характерному діапазоні значень енергії електронів 24...34 МеВ. Изложены результаты экспериментального исследования возможных процессов наработки побочных радионуклидов при производстве 99Мо/99mТс на ускорителе электронов. В качестве объекта исследования отобраны фольги из природного молибдена (мишень) и набора характерных конструкционных материалов (Al, Ti, Cu, Ta, Ni, а также нержавеющая сталь). Генерация радионуклидов в образцах производилась в идентичных условиях в поле вторичного излучения (тормозное+фотонейтроны) ускорителя ЛУ-20 в характерном диапазоне значений энергии электронов 24...34 МэВ. Робота виконана за підтримкою НТЦУ, контракт № 2185 2004 Article Ecological aspects of 99Mo/99mTc production at an electron accelerator / N.P. Dikiy, Yu.V. Lyashko, V.L. Uvarov, I.N. Shlyakhov, Eu.B. Malets // Вопросы атомной науки и техники. — 2004. — № 1. — С. 191-193. — Бібліогр.: 6 назв. — англ. 1562-6016 PACS: 06.60.Mr, 07.85.-m, 07.88+y, 81.30.Hd, 81.70.Jb https://nasplib.isofts.kiev.ua/handle/123456789/79070 en Вопросы атомной науки и техники application/pdf Національний науковий центр «Харківський фізико-технічний інститут» НАН України
institution Digital Library of Periodicals of National Academy of Sciences of Ukraine
collection DSpace DC
language English
topic Применение ускоренных пучков
Применение ускоренных пучков
spellingShingle Применение ускоренных пучков
Применение ускоренных пучков
Dikiy, N.P.
Lyashko, Yu.V.
Uvarov, V.L.
Shlyakhov, I.N.
Malets, Eu.B.
Ecological aspects of 99Mo/99mTc production at an electron accelerator
Вопросы атомной науки и техники
description The present report deals with experimental investigations into possible processes of accumulation of radioactive by-products (RBPs) during 99Mo/99mTc production at an electron linac. Foils from natural molybdenum (a target) and a number of typical target setup materials (Al, Ti, Cu, Ta, Ni and stainless steel) were chosen as an object of investigations. The generation of radionuclides in the samples was performed in identical conditions under secondary radiation (bremsstrahlung + photoneutrons) of the linac LU-20 in a typical range of electron energies from 24 to 34 MeV.
format Article
author Dikiy, N.P.
Lyashko, Yu.V.
Uvarov, V.L.
Shlyakhov, I.N.
Malets, Eu.B.
author_facet Dikiy, N.P.
Lyashko, Yu.V.
Uvarov, V.L.
Shlyakhov, I.N.
Malets, Eu.B.
author_sort Dikiy, N.P.
title Ecological aspects of 99Mo/99mTc production at an electron accelerator
title_short Ecological aspects of 99Mo/99mTc production at an electron accelerator
title_full Ecological aspects of 99Mo/99mTc production at an electron accelerator
title_fullStr Ecological aspects of 99Mo/99mTc production at an electron accelerator
title_full_unstemmed Ecological aspects of 99Mo/99mTc production at an electron accelerator
title_sort ecological aspects of 99mo/99mtc production at an electron accelerator
publisher Національний науковий центр «Харківський фізико-технічний інститут» НАН України
publishDate 2004
topic_facet Применение ускоренных пучков
url https://nasplib.isofts.kiev.ua/handle/123456789/79070
citation_txt Ecological aspects of 99Mo/99mTc production at an electron accelerator / N.P. Dikiy, Yu.V. Lyashko, V.L. Uvarov, I.N. Shlyakhov, Eu.B. Malets // Вопросы атомной науки и техники. — 2004. — № 1. — С. 191-193. — Бібліогр.: 6 назв. — англ.
series Вопросы атомной науки и техники
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fulltext ECOLOGICAL ASPECTS OF 99Mo/99mTc PRODUCTION AT AN ELECTRON ACCELERATOR N.P. Dikiy, Yu.V. Lyashko, V.L. Uvarov, I.N. Shlyakhov National Science Center “Kharkov Institute of Physics and Technology”, 61108, Kharkov, Ukraine; E-mail: uvarov@kipt.kharkov.ua; Eu.B. Malets Kharkov State Pedagogical University The present report deals with experimental investigations into possible processes of accumulation of radioactive by-products (RBPs) during 99Mo/99mTc production at an electron linac. Foils from natural molybdenum (a target) and a number of typical target setup materials (Al, Ti, Cu, Ta, Ni and stainless steel) were chosen as an object of investi- gations. The generation of radionuclides in the samples was performed in identical conditions under secondary radi- ation (bremsstrahlung + photoneutrons) of the linac LU-20 in a typical range of electron energies from 24 to 34 MeV. PACS: 06.60.Mr, 07.85.-m, 07.88+y, 81.30.Hd, 81.70.Jb 1. INTRODUCTION In modern practice, more than 8500 medical institu- tions throughout the world are exploiting up to 20 000 gamma-chambers for diagnostics of diseases by the scintigraphy method. More than 70% of the procedures are carried out with the use of 99mTc (daughter product of the 99Mo isotope) as a radioactive tracer. The main body of 99Mo (up to 200 000 Ci per year with a steady tendency to increase) is produced in nuclear reactors with the use of 235U fission reactions. In this case, only 6% of the reactions are accompanied by the production of 99Mo. As a result, this method gives up to 50 Ci of ra- dioactive waste (RAW) per 1 Ci of 99mTc, including long-lived RBPs [2]. In view of the annual growth of 99Mo production and the absence of immediate prospect of replacing 99mTc by another diagnostic radionuclide, there arises the necessity of creating a new process of 99Mo/99mTc production with a less ecological load. This technology based on the use of a high-current electron accelerator has been developed (see ref. [3]) and is now being promoted at KIPT. 2. SOURCES OF RBPs By new technology, the converter, the target sub- stance comprising 100Mo, and also the devices which ac- commodate them serve as RBPs sources. The composi- tion of RBPs and the rate of their generation are deter- mined by the energy and value of the electron flow, by the isotopic composition of the mentioned structures, and also by their geometry with respect to the secondary radiation field. In this case, only those active products that are not retrapped into the production cycle can be considered as RAW. These are the waste resulting from the process of target treatment, 99mTc discharges (for the most part, liquid), and also the spent constructives (sol- id-state RAW). The technology developed here provides for applica- tion of different-type solid targets (metallic Mo or MoO3 oxide) or liquid targets based on water solutions of molybdenum acid salts, with molybdenum being of both natural composition and enriched in the 100Mo iso- tope. In view of relatively low total (up to 3 Ci) and spe- cific (≤0.1 Ci/g) activities of the irradiated target, the methyl ethyl ketone extraction of 99mTc (e.g., see refs. [4,5]) has appeared the most acceptable method for ex- traction of 99mTc. In the natural molybdenum case as a target, the spent water phase (at the end of the week- term technological cycle) is the main type of waste. 3. LIQUID TARGET As it has become obvious from the studies, the liq- uid target variant is most easily producible [6]. To in- vestigate regularities in the liquid-phase generation of 99Mo and RBPs, a target device prototype was devel- oped (Fig.1). V2 V3 V4 e- H2O V1 γ γ γ n n n n n Mo C Fig. 1. Schematic of experiment to investigate the pro- duction of 99Mo and RBPs in a liquid target It includes a flowing water-cooled bremsstrahlung converter C. Immediately behind the converter there is a cylindrical vessel (V1), 80 mm in diameter and 40 mm in height, which is axially symmetric to the electron beam. Then sequentially follow a vessel, 32 mm in di- ameter and 60 mm high (V2), and two vessels (V3 and V4), 100 mm in height. After irradiation of the target at given conditions, 1 to 2 ml samples of solution were taken from the vessels and were directed for the analysis of induced activity by means of the Ge(Li) detector. Tables 1 and 2 give the results of the analysis of partial activity of targets based on water solutions of Na2MoO4 salts (comprising 142 mg/ml of natural Mo) and K2MoO4 (208 mg/ml). ___________________________________________________________ PROBLEMS OF ATOMIC SIENCE AND TECHNOLOGY. 2004. № 1. Series: Nuclear Physics Investigations (42), p.191-193. 191 4. SOLID TARGET AND CONSTRUCTIVES To investigate the processes of RBPs generation in structural materials of the target facility, samples of most typical materials (Al, Ti, Cu, Ta, Ni, Mo and stain- less steel) were chosen in the form of foils. The foils were assembled as a sandwich and placed directly be- hind the bremsstrahlung converter. Table 1. Volumic activity (A) of isotopes in liquid target vessels (Na2MoO4, 1 hour, 10 µA) Е0, MeV № v. A, nCi/ml 90Mo 96Nb 99Mo 22Na 24Na 24 1 1.58 6.67 156.12 2.46 44.05 2 3.52 11.78 183.59 3.32 9.71 3 1.60 5.23 77.30 2.11 1.57 4 0.75 2.45 30.42 1.94 0.86 28 1 8.84 30.96 264.43 3.19 88.12 2 20.47 46.76 371.45 4.87 23.44 3 9.58 17.66 141.35 1.23 3.07 4 4.59 6.84 57.49 0.29 1.51 34 1 48.72 52.52 452.56 4.44 106.66 2 76.16 54.72 404.72 6.74 18.61 3 38.36 30.49 173.37 3.68 5.54 4 16.13 13.85 62.61 1.45 3.11 Table 2. Volumic activity of isotopes in target vessels (K2MoO4) E0, MeV № v. A, nCi/ml 90Mo 96Nb 99Mo 24 1 - 13,18 293,93 2 - 23,66 386,40 3 - 9,80 139,43 4 - 4,25 61,22 28 1 - 40,89 458,00 2 - 79,30 659,74 3 - 26,32 246,68 4 - 10,68 91,64 34 1 86,19 93,18 623,81 2 211,33 119,15 947,52 3 98,33 62,40 346,71 4 92,67 24,70 134,55 The accelerator LU-20 was operated in the mode of direct (unscanned) beam, the parameters of which are similar to the parameters described above. After irradia- tion the foils were forwarded for the measurement of their partial activity by means of the Ge(Li) spectrome- ter. Table 3 lists the measured values of RBPs genera- tion in the chosen set of structural materials and in natu- ral Mo. The columns of the table contain the following in- formation: 1 - modes of target irradiation at accelerated electron energies of 24 MeV (mode I), 28 MeV (mode II) and 34 (mode III), the average accelerator current be- ing 10 µA, 2 - basic reaction, 3 - half-life T1/2 of the ra- dionuclide produced (days), 4 - specific partial activity of radionuclide in the sample, 5 - iAmax is the estimated maximum activity of the i- radionuclide in the techno- logical cycle (300 µA, 24 hours), 6 - iAmax/ Mo-99Amax is the ratio of iAmax to the maximum activity of generated Mo-99. The maximum activity of RBPs in the technological cycle, iAmax, was estimated in the assumption that the given material is concentrated in the infinite layer of thickness (µρ)-1, where µ is the attenuation coefficient of braking photons in the material, the photon energy being in the region of photonuclear reaction, ρ is the density of material. For mode III (its conditions in the electron energy are the closest to the ones realized in the technological process), Table 4 gives both the calculated values of RBPs activity accounted for by 5 Ci of the generated 99Mo immediately after completion of target irradiation, and the data obtained from RBPs residual activity (total Ai and gamma Ai γ) at the end of the 5-day technological cycle. Table 3. Generation of basic radionuclides in structural elements of the target facility 1 2 3 4(kBq /g) 5(Ci) 6(Ci/ /Ci) I 100Mo(γ,n) →99Mo 2.75 54,4 3,24 1 48Ti(γ,p) 47Sc 3.35 19,5 1,27 0,39 58Ni(γ,n)57Ni 58Ni(γ,p) →57Co 270.9 102,3 7,48 2,3 181Ta(n,γ) →182Ta 115.0 0,260 0,00586 0,0018 65Cu(γ,n) →64Cu 0.53 644 38,7 11,9 II 100Mo(γ,n) →99Mo 2.75 80,8 4,53 1 48Ti(γ,p) →47Sc 3.35 54,8 3,68 0,81 58Ni(γ,n)57Ni 58Ni(γ,p) →57Co 270.9 204,7 14,5 3,28 181Ta(n,γ) →182Ta 115.0 0,357 0,00838 0,00184 65Cu(γ,n) →64Cu 0.53 1195 75,5 16,65 III 100Mo(γ,n) →99Mo 2.75 103,0 5,87 1 48Ti(γ,p) →47Sc 3.35 103,6 7,04 1,2 58Ni(γ,n)57Ni 58Ni(γ,p) →57Co 270.9 298,3 21,4 3,65 181Ta(n,γ) →182Ta 115.0 0,457 0,01089 0,00185 65Cu(γ,n) →64Cu 0.53 1545 94,5 16,1 5. DISCUSSION The analysis of the present data shows that the equivalent dose rate (EDR) at the maximum of its distri- bution on the surface of the samples under study is ap- proximately proportional to the activity of radionuclides produced in them as a result of irradiation, and increases with electron energy in all cases. The data make it pos- sible to make the proper choice for the target facility components. The last ones should give the minimum contribution to the total EDR of the radiated target setup as compared with the radiation of the Mo target itself, and also to produce mainly short-lived radionuclides. The identical yield ratios of the 99Mo, 57Ni and 47Sc isotopes in the samples from natural Mo, Ni and Ti for different modes of irradiation have appeared the same as in the stainless steel samples comprising similar ele- ments. 57Ni is found to be the main source of induced activity in stainless steel. 192 Table 4. Activity of basic RBPs in the technological cy- cle Iso- top Ai/5CiMo-99, mCi Аi after 5 days,mСi Аγ i after5 days,mСi 95mNb 2600 651 635 95Nb 3.1 26.9 26.9 88Zr 3.15 2.97 2.88 92mNb 8.0 4.9 4.9 96Nb 730 4.2 ∼4.2 91mNb 160 148 4.5 The data on the radionuclide yields in different ma- terials (iAmax) at a target thickness equal to the mean path of photons having the energy in the excitation re- gion of the corresponding photonuclear reaction should be considered as certain ultimate estimates. In particu- lar, at a material thickness d << (µρ)-1 the produced ac- tivity is Ai ~di⋅µ⋅ρ⋅ iAmax << iAmax. Besides, if the given material is located in the target facility behind the Mo target of thickness (µρ)-1, then the maximum yield of side radionuclides is reduced by a factor of about e. The measurement of surface activity distribution of foils by the collimated radiometry method makes it pos- sible to determine geometrical characteristics of the re- gion of generation of different radionuclides and thus to characterize the beam quality for the isotope production process, and also to optimize the geometry and the ele- mental composition of the target facility. 6. CONCLUSION Methods have been developed and studies have been made into the generation of radionuclides in targets and structural materials at production of 99Mo/99mTc on the electron accelerator. The photonuclear channel was the main channel of radionuclide generation. The effect of photoneutrons may manifest itself only in the reactions 98Mo(n,γ)99Mo, 92Mo(n,p)92mNb, 181Ta(n,γ)182Ta and 23Na(n,γ)24Na. Among the structural elements under study, 54Mn has the longest half-life (312.3 days). As regards the ac- tivity produced, the use of such materials as Ni, Cu and stainless steel is found to be the least desirable. The data obtained on the yields of side radionuclides with respect to the yield of 99Mo in the case of natural Mo-based target are independent of the phase composi- tion of the target (metal, solution or trioxide). These data are required for the calculation of biological shield of the “hot” chamber, which accommodates the extrac- tion generator of 99mTc, and also, the vessel-collector for liquid radioactive waste. The results of determining the radionuclide compo- sition of irradiated materials and their activity with due regard for possible optimization of target facility materi- als and geometry give evidence for considerable advan- tages of the proposed technology of 99Mo/99mTc produc- tion in relation to the ecology load. REFERENCES 1. Isotopes for Medicine and Life Sciences. Editors S.G. Adelsten and F.G. Wanning. // Nat. Acad. Press, Washington, D.C., 1995, p.1, 4, 36, 40. 2. W.Z. Villiers. The Management of Radioactive Waste from Fission Mo-99 Production. // Int. Top. Meet. Nucl. and Hazardous Waste Management. Atlanta, USA, Aug. 1994. 3. N.P. Dikiy, A.N. Dovbnya, V.L. Uvarov. Funda- mentals of Technological Cycle of 99mTc Produc- tion at Electron Accelerator // Problems of Atomic Science and Technology. Series: “Nuclear Phys- ics Investigations” (42). 2004, № 1, р. 168-171. 4. V.S. Skuridin et al. Method of Technetium-99m Production by Extraction and Device for Realiza- tion of Method // Patent USSR N 2118858, 10.09.1998. Bull. N25 (in Russian). 5. A.V. Yegorov, M.P. Zykov, G.V. Korpusov et al. Production of 99mTc on the Centralized Generator in St. Petersburg // J. Nucl. Biol. Med. 1994, v. 38, № 3, p. 399-402. 6. N.P. Dikiy, A.N. Dovbnya, V.L.Uvarov. Electron Accelerator-Based Soft Technology for Medical Imaging Isotopes Production // Proc. of the 8-th European Particle Conference EPAC 2002 (Par- is, 3-7 June, 2002), p. 2760-2762. ЭКОЛОГИЧЕСКИЕ АСПЕКТЫ ПРОИЗВОДСТВА 99Мо/99mТс НА УСКОРИТЕЛЕ ЭЛЕКТРОНОВ Н.П. Дикий, Ю.В. Ляшко, В.Л. Уваров, И.Н. Шляхов, Е.Б. Малец Изложены результаты экспериментального исследования возможных процессов наработки побочных ра- дионуклидов при производстве 99Мо/99mТс на ускорителе электронов. В качестве объекта исследования ото- браны фольги из природного молибдена (мишень) и набора характерных конструкционных материалов (Al, Ti, Cu, Ta, Ni, а также нержавеющая сталь). Генерация радионуклидов в образцах производилась в идентич- ных условиях в поле вторичного излучения (тормозное+фотонейтроны) ускорителя ЛУ-20 в характерном диапазоне значений энергии электронов 24...34 МэВ. Работа выполнена при поддержке НТЦУ, контракт № 2185 ЕКОЛОГІЧНІ АСПЕКТИ ВИРОБНИЦТВА 99Мо/99mТс НА ПРИСКОРЮВАЧІ ЕЛЕКТРОНІВ М.П. Дикий, Ю.В. Ляшко, В.Л. Уваров, І.М. Шляхов, Є.Б. Малец Викладені результати експериментального дослідження можливих процесів наробітку побічних радіону- клідов при виробництві 99Мо/99mТс на прискорювачі електронів. Як об'єкт дослідження відібрані фольги з природного молібдену (мішень) і набору характерних конструкційних матеріалів (Al, Ti, Cu, Ta, Ni, а також нержавіюча сталь). Генерація радіонуклідів у зразках виконувалося в ідентичних умовах у полі вторинного випромінювання (гальмівне+фотонейтрони) прискорювача ЛП-20 у характерному діапазоні значень енергії електронів 24...34 МеВ. ___________________________________________________________ PROBLEMS OF ATOMIC SIENCE AND TECHNOLOGY. 2004. № 1. Series: Nuclear Physics Investigations (42), p.191-193. 193 Робота виконана за підтримкою НТЦУ, контракт № 2185 194 N.P. Dikiy, Yu.V. Lyashko, V.L. Uvarov, I.N. Shlyakhov National Science Center “Kharkov Institute of Physics and Technology”, 61108, Kharkov, Ukraine; E-mail: uvarov@kipt.kharkov.ua; 1. INTRODUCTION 3. LIQUID TARGET 4. SOLID TARGET AND CONSTRUCTIVES A, nCi/ml Isotop REFERENCES