Journal of Radiation Protection and Research

The Korean Association for Radiation Protection (대한방사선방어학회)
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Study on Concrete Activation Reduction in a PET Cyclotron Vault

  • Bakhtiari, Mahdi (Division of Advanced Nuclear Engineering, Pohang University of Science and Technology (POSTECH)) ;
  • Oranj, Leila Mokhtari (Pohang Accelerator Laboratory, Pohang University of Science and Technology (POSTECH)) ;
  • Jung, Nam-Suk (Pohang Accelerator Laboratory, Pohang University of Science and Technology (POSTECH)) ;
  • Lee, Arim (Pohang Accelerator Laboratory, Pohang University of Science and Technology (POSTECH)) ;
  • Lee, Hee-Seock (Division of Advanced Nuclear Engineering, Pohang University of Science and Technology (POSTECH))
  • Received : 2020.06.07
  • Accepted : 2020.09.05
  • Published : 2020.09.30
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Abstract

Background: Concrete activation in cyclotron vaults is a major concern associated with their decommissioning because a considerable amount of activated concrete is generated by secondary neutrons during the operation of cyclotrons. Reducing the amount of activated concrete is important because of the high cost associated with radioactive waste management. This study aims to investigate the capability of the neutron absorbing materials to reduce concrete activation. Materials and Methods: The Particle and Heavy Ion Transport code System (PHITS) code was used to simulate a cyclotron target and room. The dimensions of the room were 457 cm (length), 470 cm (width), and 320 cm (height). Gd2O3, B4C, polyethylene (PE), and borated (5 wt% natB) PE with thicknesses of 5, 10, and 15 cm and their different combinations were selected as neutron absorbing materials. They were placed on the concrete walls to determine their effects on thermal neutrons. Thin B4C and Gd2O3 were placed between the concrete wall and additional PE shield separately to decrease the required thickness of the additional shield, and the thermal neutron flux at certain depths inside the concrete was calculated for each condition. Subsequently, the optimum combination was determined with respect to radioactive waste reduction, price, and availability, and the total reduced radioactive concrete waste was estimated. Results and Discussion: In the specific conditions considered in this study, the front wall with respect to the proton beam contained radioactive waste with a depth of up to 64 cm without any additional shield. A single layer of additional shield was inefficient because a thick shield was required. Two-layer combinations comprising 0.1- or 0.4-cm-thick B4C or Gd2O3 behind 10 cm-thick PE were studied to verify whether the appropriate thickness of the additional shield could be maintained. The number of transmitted thermal neutrons reduced to 30% in case of 0.1 cm-thick Gd2O3+10 cm-thick PE or 0.1 cm-thick B4C+10 cm-thick PE. Thus, the thickness of the radioactive waste in the front wall was reduced from 64 to 48 cm. Conclusion: Based on price and availability, the combination of the 10 cm-thick PE+0.1 cmthick B4C was reasonable and could effectively reduce the number of thermal neutrons. The amount of radioactive concrete waste was reduced by factor of two when considering whole concrete walls of the PET cyclotron vault.

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References

  1. Kumagai M, Sodeyama K, Sakamoto Y, Toyoda A, Matsumura H, Ebara T, et al. Activation reduction method for a concrete wall in a cyclotron vault. J Radiat Prot Res. 2017;42:141-145. https://doi.org/10.14407/jrpr.2017.42.3.141
  2. Wang Q, Masumoto K, Bessho K, Matsumura H, Miura T, Shibata T. Evaluation of the radioactivity in concrete from accelerator facilities. J Radioanal Nucl Chem. 2007;273:55-58. https://doi.org/10.1007/s10967-007-0710-3
  3. Dodd AC, Shackelton RJ, Carr DA, Ismail A. Activation of air and concrete in medical isotope production facilities. AIP Conf Proc. 2017;1845:020006.
  4. International Atomic Energy Agency. Application of the concepts of exclusion, exemption and clearance: safety guide (RS-G-1.7). Vienna, Austria: International Atomic Energy Agency; 2004.
  5. Sato S, Morioka A, Kinno M, Ochiai K, Hori J, Nishitani T. Experimental study on induced radioactivity in boron-doped low activation concrete for DT fusion reactors. J Nucl Sci Technol. 2004;41(sup4):66-69.
  6. Sato S, Maegawa T, Yoshimatsu K, Sato K, Nonaka A, Takakura K, et al. Development of a low activation concrete shielding wall by multi-layered structure for a fusion reactor. J Nucl Mater. 2011;417:1131-1134. https://doi.org/10.1016/j.jnucmat.2010.12.302
  7. Ehrlicher U, Pauli H. Waste reduction by re-use of low activated material. Proceedings of the International Conference on Radioactive Waste Management and Environmental Remediation; 2009 Oct 11-15; Liverpool, UK. p. 423-430.
  8. Wang P, Tang X, Chen F, Chen D. The design, fabrication and safety evaluation of a novel spent fuel storage basket material. Nucl Eng Des. 2015;284:91-96. https://doi.org/10.1016/j.nucengdes.2014.12.010
  9. Major B. PET cyclotron design for decommissioning and waste inventory reduction. Proceedings of the International Conference on Radioactive Waste Management and Environmental Remediation; 2009 Oct 11-15; Liverpool, UK. p. 19-24.
  10. Sato T, Iwamoto Y, Hashimoto S, Ogawa T, Furuta T, Abe SI, et al. Features of particle and heavy ion transport code system (PHITS) version 3.02. J Nucl Sci Technol. 2018;55:684-690. https://doi.org/10.1080/00223131.2017.1419890
  11. Bakhtiari M, Oranj LM, Jung NS, Lee A, Lee HS. Estimation of neutron production yields from H2 18O as the 18F-production target bombarded by 18-MeV protons. Radiat Phys Chem. 2020;177:109120. https://doi.org/10.1016/j.radphyschem.2020.109120
  12. Fujibuchi T, Horitsugi G, Yamaguchi I, Eto A, Iwamoto Y, Obara S, et al. Comparison of neutron fluxes in an 18-MeV unshielded cyclotron room and a 16.5-MeV self-shielded cyclotron room. Radiol Phys Technol. 2012;5:156-165. https://doi.org/10.1007/s12194-012-0149-2
  13. Masumoto K, Miura T, Bessho K, Matsumura H, Toyoda A, Wang Q, et al. Evaluation of radioactivity in concrete samples obtained from various accelerator facilities. Proceedings of the 2nd Asian and Oceanic Congress for Radiation Protection (AOCRP); 2006 Oct 9-13; Beijing, China.
  14. Masumoto K, Toyoda A, Eda K, Izumi Y, Shibata T. Evaluation of radioactivity induced in the accelerator building and its application to decontamination work. J Radioanal Nucl Chem. 2003;255:465-469. https://doi.org/10.1023/A:1022511811356
  15. Boudard A, Cugnon J, David JC, Leray S, Mancusi D. New potentialities of the Liege intranuclear cascade model for reactions induced by nucleons and light charged particles. Phys Rev C. 2013;87:014606. https://doi.org/10.1103/physrevc.87.014606
  16. Furihata S. Statistical analysis of light fragment production from medium energy proton-induced reactions. Nucl Instrum Methods Phys Res B. 2000;171:251-258. https://doi.org/10.1016/S0168-583X(00)00332-3
  17. Shibata K, Iwamoto O, Nakagawa T, Iwamoto N, Ichihara A, Kunieda S, et al. JENDL-4.0: a new library for nuclear science and engineering. J Nucl Sci Technol. 2011;48:1-30. https://doi.org/10.3327/jnst.48.1
  18. Lee A, Jung NS, Lee HS. Composition analysis of ordinary concrete to estimate residual isotopes in the decommissioning of particle accelerator. Proceedings of the 14th Workshop on Shielding Aspects of Accelerators, Targets and Irradiation Facilities (SATIF-14); 2018 Oct 30-Nov 2; Gyeongju, Korea.
  19. Gwon DY, Kim Y, Jeong KY, Jung NS, Lee HS. Regulation improvement of cyclotrons in the Republic of Korea through analysis of radioactivation and questionnaire on operation status. Indian J Public Health Res Dev. 2018;9:675-680. https://doi.org/10.5958/0976-5506.2018.00811.2
  20. Jung NS, Lee A, Oranj LM, Lee HS, Gwon DY, Kim Y, et al. Activation assessment of self-shielded and non-self-shielded PET cyclotrons. Proceedings of the 14th Workshop on Shielding Aspects of Accelerators, Targets and Irradiation Facilities (SATIF-14); 2018 Oct 30-Nov 2; Gyeongju, Korea.
  21. Vichi S, Infantino A, Zagni F, Cicoria G, Braccini S, Mostacci D, et al. Activation studies for the decommissioning of PET cyclotron bunkers by means of Monte Carlo simulations. Radiat Phys Chem. 2020;174:108966. https://doi.org/10.1016/j.radphyschem.2020.108966
  22. Martinez-Serrano JJ, Diez de los Rios A. Prediction of neutron induced radioactivity in the concrete walls of a PET cyclotron vault room with MCNPX. Med Phys. 2010;37:6015-6021. https://doi.org/10.1118/1.3505919
  23. Mughabghab SF. Neutron cross sections: neutron resonance parameters and thermal cross sections (Part B, Z=61-100). Orlando, FL: Academic Press; 1984.