Assessment of the Radiation Dose Level of the PAL-XFEL Hard X-ray Beamlines under Accident Conditions

• Published in: Journal of the Korean Physical Society Vol. 73; no. 8; pp. 1061 - 1067
• Main Authors: Jung, Nam-Suk, Kim, Min Ho, Bae, Oryun, Kim, Hee Hoon, Lee, Hyeon Jae, Lee, Hee-Seock
• Format: Journal Article
• Language: English
• Published: Seoul The Korean Physical Society 01.10.2018; Springer Nature B.V; 한국물리학회
• Subjects: Accident conditions; Accidents; Electron beams; Free electron lasers; Laser beams; Mathematical and Computational Physics; Particle and Nuclear Physics; Particle beams; Physics; Physics and Astronomy; Radiation dosage; Radiation shielding; Safety; Theoretical; 물리학; PAL-XFEL; Shielding; FLUKA; Accident; X-ray free electron laser; Radiation dose level
• ISSN: 0374-4884; 1976-8524
• DOI: 10.3938/jkps.73.1061

A PAL-XFEL is a free electron laser using 10-GeV, 0.2-nC electron beams. The failure of the main dump magnet can cause a serious radiation risk because electron beams go straight to the experimental area of the hard X-ray beamlines and high-energy radiation is produced in the forward direction. This type of accident should be prevented through a suitable shielding design and a Personal Safety and Interlock System. A proper safety design based on a reliable method for estimating the radiation dose level is as important as anything else. In this study, the leakage dose rate was estimated under predictable accident conditions, and the suitable radiation shielding of the hard X-ray beamlines was designed using a well-known Monte Carlo code, FLUKA, in preparation for an accident. The result was verified by measurements of the radiation dose rate during commissioning period and was compared with the result obtained by using a semi-empirical code, SHIELD11. The measured radiation dose rates in the lateral direction under failure of the main dump magnet were agreed to the radiation dose rates calculated by using the SHIELD11 well, and the FLUKA results were relatively overestimated. In addition, the assessment error of the neutron dose rate depending on the type of neutron rem-counter was verified for high-energy neutrons. The effect of an accidental loss is negligible compared to the annual dose received by beamline users.