Identification of radionuclides in cooling circuit of Cyclone 18/9-HC

In the present work the patterns of relationship of photonic radiation dose rate from Cyclone 18/9HC water cooling system were studied at production of positron-emitting nuclides. Reaction (n, p) was shown to be the main source of activation nuclides in cyclotron cooling water at 18F production, resulting in formation of 16N (T1/2 = 7 s) from 16О. In water targets with high accumulated dose, when beam partially irradiates a target body, proton-induced reactions: 16О(p, α)11С and 18О(p, n)18F take place. Fluoride 18F–, carbonate 11СО32– and hydrocarbonate Н11СО3– anions, formed in proton-induced activation reactions, efficiently precipitate on anion-exchanging resin during water circulation resulting in circuit purification from the named radionuclides. Activation of cooling water does not occur at irradiation of gas targets. Projected annual dose for cyclotron operator from cooling water activation is less than 1 % of annual dose limit for personnel from technogeneous radioactive sources. In order to minimize operator`s accumulated doses it is recommended to decrease the duration of personnel activities at the distance less than 1 meter from heat exchanger during 18F production. At operation of water targets with absorbed dose higher than 2500 μA·h it is desirable to conduct the preventive maintenance of water cooling system not earlier than in half an hour after the end of irradiation and with mandatory dosimetry control. To decrease the activation of impurities it is essential to use only deionized water in cooling circuit. In case of its specific conductivity increase due to corrosion the coolant should be replaced promptly.

cyclotron, water cooling system, 18F, radionuclides, activation, positron emission tomography (PET), radiation safety

1. Bowden L., Vintró L. L., Mitchell P. I., O’Donnell R. G., Seymour A. M., Duffy G. J. Radionuclide impurities in proton-irradiated [18O]H2O for the production of 18F−: Activities and distribution in the [18F]FDG synthesis process. Applied Radiation and Isotopes, 2009, vol. 67, no. 2, pp. 248–255. https://doi.org/10.1016/j.apradiso.2008.10.015

2. Brinkevich S. D., Sukonko O. G., Chizh G. V., Naumovich A. S. Positron emission tomography. Part 1: Method description. Production of radiopharmaceuticals. Mediko-biologicheskie problemy zhiznedeyatel’nosti [Medical and Biological Problems of Life Activity], 2013, no. 2 (10), pp. 129–137 (in Russian).

3. Remetti R., Burgio N. T., Arcese M., Filannino M. A. Monte Carlo simulation and radiometric characterization of proton irradiated [18F]H2O for the treatment of the waste streams originated from [18F]FDG synthesis process. Applied Radiation and Isotopes, 2011, vol. 69, no. 7, pp. 1046–1051. https://doi.org/10.1016/j.apradiso.2011.02.008

4. Wilson J. S., Avila-Rodriguez M. A., Johnson R. R., Zyuzin A., McQuarrie S. A. Niobium sputtered Havar foils for the high-power production of reactive [18F]fluoride by proton irradiation of [18F]H2O targets. Applied Radiation and Isotopes, 2008, vol. 66, no. 5, pp. 565–570. https://doi.org/10.1016/j.apradiso.2007.12.004

5. Cyclotron produced radionuclides: Operation and maintenance of gas and liquid targets. IAEA radioisotopes and radiopharmaceuticals Series No. 4. Vienna, International atomic energy agency, 2012. 103 p.

6. Chu S. Y. F., Ekström L. P., Firestone R. B. The Lund /LBNL Nuclear Data Search. 1999. Available at: http://nucleardata.nuclear.lu.se/toi/ (accessed 18 December 2018).

7. Kohler M., Degering D., Zessin J., Fuchtner F., Konheiser J. Radionuclide impurities in [18F]F-and [18F]FDG for positron emission tomography. Applied Radiation and Isotopes, 2013, vol. 81, pp. 268–271. https://doi.org/10.1016/j.apradiso.2013.03.044

8. Marshall C., Talboys M. A., Bukhari S., Evans W. D. Quantification of the activity of tritium produced the routine synthesis of 18F fluorodeoxyglucose for positron emission tomography. Journal of Radiological Protection, 2014, vol. 34, no. 2, pp. 435-444. https://doi.org/10.1088/0952-4746/34/2/435

9. Evaluated Nuclear Data File. Available at: https://www-nds.iaea.org/exfor/endf.htm (accessed 09 October 2018).

10. Tylets P. V., Tugay О. V., Krot V. О., Ivaniykovich А. А., Soroka S. A., Brinkevich D. I., Brinkevich S. D., Baranovski О. А., Chizh G. V. Long-lived radionuclides in the production of [18F]fluorocholine for PET-diagnosis. Vestsi Natsyyanal’nai akademii navuk Belarusi. Seryya khimichnykh navuk = Proceedings of the NationalAcademy of Sciences of Belarus. Chemical series, 2018, vol. 54, no. 3, pp. 359–368 (in Russian). https://doi.org/10.29235/1561-8331-2018-54-3-359-368

11. Krot V. O., Tugay O. V., Brinkevich D. I., Brinkevich S. D., Chizh G. V., Vabishchevich S. A. Management of aueous radioactive wastes in the production of 18F-labeled radiopharmaceuticals. Vestnik Polotskogo gosudarstvennogo universiteta. Seriya C. Fundamental’nyye nauki. Fizika = Vestnik of Polotsk State University. Series С. Fundamental sciences. Physic, 2018, no. 4, pp.128–134 (in Rusian).