5th International Workshop on Accelerator Radiation Induced Activation (ARIA19)

23 Sept 2019, 08:30 → 25 Sept 2019, 12:00 Asia/Seoul

Science Culture Center (Institute for Basic Science)

The fifth International Workshop on Accelerator Radiation Induced Activation(ARIA19) is being organized by the Institute for Basic Science (IBS) and will be hosted by a team of Rare Isotope Science Project(RISP) on Sep 23-25, 2019 in Daejeon, Korea focusing for the international discussion on Radionuclide transmutation issues arising from various applications of accelerator facilities.

Important Dates

Abstract submission deadline	July 31, 2019
Registration deadline	August 15, 2019
Conference dates	September 23-25, 2019

Monday, 23 September

08:30 Reception

09:30 Welcome address (IBS-RISP Director: Myeun KWON)

09:45 Workshop Schedule and Notices (Shinwoo NAM)

Session 1

Convener: Stefan ROESLER

1 An Update on CINDER2008 and AARE V1.0

The software package AARE V1.0: Activation in Accelerator Radiation Environments V1.0 was developed over several years by a collaboration between Oak Ridge National Laboratory, Paul Scherrer Institut, and Argonne National Laboratory. The core of this package is the CINDER2008 transmutation code, the latest release in the CINDER data and code series, which begun with the work of Tal England at Bettis Atomic Power Laboratory in the early 1960s. CINDER2008 is a modern implementation of the CINDER’90 software package. The most notable improvements include (1) modern programming language and methods, (2) new algorithms to more accurately solve the underlying differential equations, (3) new extended data libraries developed using fission, fusion and constant weighting functions, (4) new data library development tool, (5) automatic post-processing capabilities, (6) accident analysis tools, (7) NAMELIST input option, (8) constant power approximation and (9) high-fidelity β-delayed gamma spectra. Also included in AARE are the “Activation Script Version 2.0” and “Gamma Source Script 2.0.” The Activation Script reads a compact user-prepared input file, which specifies selected MCNPX cells and the irradiation history to be used in activation calculations, parses the MCNPX output file, prepares inputs, and runs activation calculations. The results provide a wealth of information, including but not limited to nuclide inventories, activities, decay powers, and multi-group gamma-ray spectra, at the selected time steps during irradiation or at the selected decay times after the end of irradiation. The Activation Script is not limited to the CINDER2008 but supports also the SP-FISPACT and the ORIHET3 activation codes. For planning of maintenance, shipment, or disposal of irradiated structures not only their isotopic inventories but also the radiation fields surrounding them need to be known. To facilitate such calculations the Gamma Source Script was developed. The Gamma Source Script reads the gamma-ray intensities and spectra produced by the activation calculations by either the CINDER2008 or the SP-FISPAC code and prepares gamma-ray source definition cards than can be used directly in subsequent MCNPX calculation of the radiation fields. Large number of cells can be processed in a single run, resulting in a complex gamma source. AARE V1.0 was submitted to the Radiation Safety Information Computational Center in the spring of 2019 and is expected to become available soon as RSICC Code Package CCC-846. Some of the new capabilities of the CINDER2008, Activation Script, and Gamma Source Script, which we hope will be of interest to the ARIA19 participants, will be described and illustrated with examples.

Speaker: Igor REMEC

Slides 1.Igor_REMEC.pdf

2 Activation Studies at a Medical Cyclotron using ActiWiz and RAW

The European Organization for Nuclear Research CERN in Geneva and the Institute of Radiation Physics IRA in Lausanne develop in collaboration new tools and methods for the characterization of activated materials at accelerators. These materials can be the components of the accelerators, auxiliary devices, architectural infrastructure and/or any object exposed to primary and secondary radiation fields. In this context, new tools (ActiWiz and RAW) were developed which allow for a very time and cost efficient characterization. The latter becomes necessary because of the enormous quantities of materials being concerned. They have to cover activation processes in a wide range from sub electron volt (thermal neutrons) to TeV. These tools together with FLUKA have been applied to materials from a medical cyclotron at the University Hospital HUG in Geneva. In this presentation, a short description of these tools will be given followed by a discussion of the first results.

Speaker: Valentin BONVIN

Slides 2.Valentin_BONVIN.pdf

3 Development of the platform to calculate the cross section induced by the proton beam

The cross section of a nucleus is defined as the probability that a nuclear reaction will occur and the cross section measurements of the nuclear reaction interested are very important stage to understand the production yield of the radioactive isotopes. In general, the targets induced by the proton beam are measured using the HPGe in order to measure the amount of the radioactivity of the target material produced. However, the procedure to calculate the cross section from the measurement data collected using HPGe is the time-consuming task to involve analyzing results using a lot of raw measurement data. If this procedure has been performed by the platform consisting of the data analysis programs such as the ROOT data analysis language, the working time and mistakes to occur during this work process can have been reduced. These measurement data can also have been analyzed using the data-fitting method included in the platform. In this research, the algorithm to calculate the cross section from the raw measurement data and the procedure to analysis the data using the data-fitting method would be described.

Speaker: Sung-kyun PARK

Slides 3.Sungkyun_PARK.pdf

11:30 Lunch

Session 2

Convener: Kazuyoshi MASUMOTO

4 A fundamental study on the distribution of contents for the dominant activation nuclides in concrete materials

Concrete is one of the useful materials for radiation shielding in the points of its flexibility and inexpensively. The activation, however, is important problem at the decommissioning stage. For the above problem, we have been developing Low-Activation concrete, in order to reduce concrete radioactive waste, and establishment of activation data base for concrete and concrete raw materials. Quite few activation data were obtained for concrete raw materials (such as aggregates, cements, additive and son on) gathered throughout Japan during the past dozens of years ago, and the distribution figure between Europium and Cobalt were shown based those data. On the other hand, concrete raw materials were gradually changed because of decrement of natural gravel and sand and/or the supply and demand turn of events. These changes affect the concrete activation performance, so new data are gathered again, and analyses data are shown in this study.

Speaker: Kenichi KIMURA

5 Prediction of specific activity in concrete of accelerator facilities for long-term operation using the Na-24 measurement method

Na-24 measurement method Content The advanced zoning of activated/non-activated concrete in accelerator facilities is very important for planning the decommissioning of an accelerator. In a previous study, we found that long-half-life radionuclides, such as Eu-152 and Co-60, should be considered when decommissioning concrete. However, a method that directly measures Eu-152 and Co-60 has some difficulties. Therefore, in a previous work, we proposed a method to nondestructively predict the specific activity of Eu-152 + Co-60 in concrete for long-term operation. This method is based on the specific activity determination of a short-half-life radionuclide, Na-24, instead of Eu-152 and Co-60. In this study, this method was applied to predict the Eu-152 + Co-60 specific activity in the concrete floor at various facilities of electrostatic accelerators and synchrotron radiation sources. The concrete in the investigated facilities was found to be non-activated because the predicted specific activities of Eu-152 + Co-60 were much lower than the Japanese clearance limit.

Speaker: Hiroshi MATSUMURA

6 Study on Concrete Activation Reduction

PETtrace cyclotron is one the medical cyclotrons in Korea which is used to generate 18F by impinging 16.5 MeV protons (60 μA) on a water target with enriched 18O via 18O(p, n)18F reaction. The secondary neutrons can activate the surrounding materials that result in radiological hazards. A huge amount of radioactive waste will be generated which is one the main issues due to high cost of radioactive waste management. It is important to decrease the activation level of the concrete. PHITS-3.02 Monte Carlo code was used to simulate a simplified PETtrace cyclotron target and enclosure. In this work, neutron absorbing materials such as Gd2O3, B4C, polyethylene (PE) and borated (wt.5%) polyethylene (BPE) were considered to reduce the thermal neutrons at 20 cm depth in concrete. Results showed that 23 cm of Gd2O3, 7 cm B4C, 14 cm of PE and 12 cm of BPE (wt.5%) would be effective to decrease the activation level of concrete at depth of 20 cm by a factor of three. B4C and Gd2O3 would be costly to cover whole walls. On the other hand, PE and BPE (wt.5%) showed an acceptable ability of reducing thermal neutrons. These materials are much more cost-effective as well.

Speaker: Mahdi BAKHTIARI

Slides 3.Mahdi_BAKHTIARI.pdf

7 Radiological Assessment of the Beam Dump Facility at CERN

The Beam Dump Facility (BDF) working group has recently submitted a Comprehensive Design Study of a new general-purpose fixed-target facility at CERN. In its initial phase, it will be dedicated to the Search for Hidden Particles (SHiP) experiment. A dense target/dump is located at the core of the facility, approximately 10 m underground. It has the aim of fully absorbing the high intensity 400 GeV/c Super Proton Synchrotron (SPS) beam, while maximizing the production of charmed and beauty mesons. Due to the high beam intensity delivered on the target, the high density and high-Z composition of the target/dump, significant activation of materials is expected. Additional radiation protection (RP) challenges arise from the proximity to the surface, other experimental facilities, and the CERN fence. The design of the facility was therefore heavily influenced by the evaluation of the RP risks. In particular, high prompt and residual dose rates require considerable shielding and remote interventions in the target area. Air, water and soil activation were carefully addressed and minimized in order to respect the applicable CERN RP regulations and objectives. To assess the above-mentioned aspects, extensive simulations were performed with the FLUKA Monte Carlo particle transport code.

Speakers: Claudia AHDIDA, Heinz VINCKE, Mirkoantonio CASOLINO

Slides 4.Claudia_AHDIDA.pdf

15:00 Coffee break

Session 3

Convener: Igor REMEC

8 Investigation of the Activated Areas in the Electrostatic Accelerator Facilities

To identify activated areas in electrostatic accelerator facilities and to develop strategies for safety decommissioning them, four accelerator facilities were selected and the induced activity caused by charged particles and secondary neutrons on the accelerator and its surrounding areas before and after performing experiments was measured. We also measure neutron flux during experiments. Moreover, we compared the monitored neutron flux with the calculated value derived using the Monte Carlo particle and heavy ion transport code system (PHITS) simulation. It was confirmed that the results between calculated data and measured data showed the good agreement with each other. Finally, it was determined that beam line and target area are radioactive and have to be decontaminated. However, it is not necessary to treat the accelerator tank, the surrounding materials, and the building concrete as radioactive materials when decommissioning the facility.

Speaker: Kazuyoshi MASUMOTO

Slides 1.Kazuyoshi_MASUMOTO1.pdf

9 Investigation of the activated areas in various synchrotron radiation facilities

We are working on the research for establishment of more reasonable decommissioning process of accelerator facilities with the aid of Japan Nuclear Regulation Authority. In this research, there are three important issues: (1) clarification of the target facilities and accelerators for assessment of activation, (2) development of novel technique for assessment of activation, and (3) provide a guideline for decommissioning as a manual book. This research has been progressed since September 2017. To achieve the aim of theme (1) and (2), we have investigated various type of facilities such as synchrotron, cyclotrons, and electrostatic accelerators. In this presentation, we will discuss the result of radiation measurement experiment at some typical synchrotron radiation facilities in Japan. The investigated facilities and maximum acceleration energy are follows: Spring-8 (8 GeV), KEK PF (2.5 GeV), UVSOR (750 MeV), HiSOR (700 MeV), and SR-center (575 MeV). These accelerators not only differ in the maximum energy but also differ in the type of pre-accelerator up to the storage ring. First, we set the solid track detectors (CR-39) and the thermo-luminescent dosimeters (TLD) at principal places that were expected the beam-loss level was high, and mapped the thermal and epithermal neutron flux for the whole facility. And, after the accelerator operation was stopped, contact dose-rate measurement with a NaI survey meter and gamma-ray spectrometry with a LaBr3 scintillation detector was conducted for the beam line components such as magnets, beam profile-monitors, gate-valves and beam-pipes. In all facilities, activation level was quite low. Whole beam-line tunnels made of concrete were not activated and no radionuclides were detected except natural nuclides. Also, almost beam-line components were not and/or low activated. Especially, no places exceeded the background level with dose-rate measurement in SR-center. Whereas, some components such as RF-cavity, beam-profile monitor, and flexible tube joint were strongly activated, and nuclides made by (γ, n) reaction such as 51Cr, 54Mn, and 57Ni were identified. 57Co which is a daughter nuclide of 57Ni was also detected in the same place. 57Ni could be considered to reflect the beam-loss during the just previous operation, due to short life of 36 h. Actually, we found the count rate (cps) of 57Ni and the contact dose rate of an accelerator component showed good correlation in all facilities. This result indicates the beam losses in the synchrotron radiation facilities could be normalized regardless of the acceleration energy. Details and other results will be discussed in the presentation.

Speaker: Go YOSHIDA

Slides 2.Go_YOSHIDA1.pdf

10 Evaluation of Activated Areas in the Particle Radiotherapy Facilities

Recently, number of particle radiotherapy hospitals is increasing in Japan. Accelerators for several hundred MeV proton and/or carbon beam irradiation are used. In case of decommissioning these facilities, it is important to estimate the radioactivity induced in the accelerator room. Three types of accelerator facilities, such as proton acceleration by cyclotron, proton acceleration by synchrotron and carbon acceleration by synchrotron acceleration, were selected for the survey of activation under their routine operation conditions. Then, the induced activity caused by charged particles and secondary neutrons was measured on the accelerator and its surrounding areas in order to evaluate the activated/non-activated area. First of all, we set the three types of neutron monitors, such as track detector CR-39, TLD and Au foils, inside the accelerator room and on the beam line during operation. Then, surface dose rate and induced activity were measured in order to confirm the activated area on accelerator, beam line, surrounding materials, and floor and wall of accelerator room. Moreover, we compared the monitored neutron flux with the calculated value derived using the Monte Carlo simulation using PHITS code. In case of carbon acceleration, neutron fluxes obtained by the measurement of 24Na activity in floor concrete of accelerator room were the order of 10 cm-2·s-1, and induced activity of beam lines were very low. In case of proton acceleration by synchrotron, several parts of accelerators were activated. Neutron fluxes inside the accelerator room during operation were almost 1 × 10 cm-2·s-1 and maximum flux of 1.1 × 102 cm-2·s-1 was observed under the electrostatic degrader. In case of proton acceleration by cyclotron, beam loss was mainly occurred at the deflector for beam extraction and the energy degrader outside of cyclotron. Then the maximum neutron flux of 1.1 × 105 cm-2·s-1 was obtained around the degrader. Then, residual activity in the cyclotron and the degrader was high. In this irradiation condition, we have to consider the activation of floor concrete under the degrader. Recently, beam current for treatment was reduced, because the spot scanning method was developed for irradiation. In order to reduce activation of accelerator room, a neutron shield surrounding of the degrader and an improvement of beam transport technique are also important.

Speaker: Kazuyoshi MASUMOTO

Slides 3.Kazuyoshi_MASUMOTO2.pdf

17:00 Dinner (Banquet)

Move to Korean Restaurant

Tuesday, 24 September

Session 4

Convener: Heinz VINCKE

11 Measurements and FLUKA simulations of aluminium, bismuth and indium activation by stray radiation from the annihilation of low energy antiprotons

The Antiproton Decelerator at the CERN Proton Synchrotron complex provides antiprotons at a kinetic energy of 5.3 MeV to several experiments where the antiprotons finally annihilate. The stray radiation from these annihilations is the most important radiation field with respect to radiation protection in the Antiproton Decelerator experimental areas. In August 2018, aluminium, bismuth and indium samples were exposed to the annihilation stray radiation. The activation experiment was performed with antiprotons being directed onto a closed vacuum valve, that acts as beam stopper. The average beam intensity amounted to 2.59E+7 antiprotons per pulse with one pulse every ∼100 seconds. The samples, placed upstream of the vacuum valve, were irradiated for ∼3 hours by the secondary radiation field. The resulting induced radioactivity of Na-24, Bi-201, Bi-202, Bi-204 and In-115m was measured by γ-ray spectrometry and compared to the predictions of FLUKA Monte Carlo simulations. In addition, dedicated FLUKA simulations were performed to assess the contribution of neutrons in the activation process. The observed agreement between the FLUKA predictions and the measured values is better than a factor of 2. This agreement demonstrates that FLUKA is a very suitable tool for describing the stray radiation from the annihilation of low–energy antiprotons.

Speakers: Angelo INFANTINO, Claudia AHDIDA, Elpida ILIOPOULOU, Robert FROESCHL, Simon JENSEN

Slides 1.Angelo_INFANTINO.pdf

12 An Update on SNS STS with Emphasis on the Target Activation

The Spallation Neutron Source (SNS) in operation since 2006 at the Oak Ridge National Laboratory was designed from the beginning to accommodate two upgrades: the accelerator proton power upgrade (PPU), and a second target station (STS). The PPU project is currently funded and underway, while the STS project is preparing for the US Department of Energy Critical Decision 1 review. The PPU will double the proton beam power from 1.4 MW to 2.8 MW. Both targets, the existing first target station (FTS) and added STS will operate in pulsed mode, receiving short (< 1 µs long) proton pulses with the energy of ~46 kJ per pulse. The FTS currently operates at up to 1.4 MW power, with pulse frequency of 60 Hz. After the completion of the PPU and the construction of the STS, the FTS will receive 2 MW at 45 Hz, and the STS will get 700 kW of the proton beam power at 15 Hz. High proton beam power and pulsed operation create challenges and constrains for the target design due to high local heating rates, high stresses, high activation, and decay heat. The FTS operates with liquid mercury target. The initial STS concept was based on stationary tungsten target, with small proton beam footprint of only 30 cm2. However, target activation simulations and subsequent accident analyses found that high residual heat from activation products, concentrated in a small target volume, could lead to the target meltdown in case of the most severe loss-of-cooling accident. This moved the current conceptual design of the STS to the rotating target. The rotating target consists of a segmented tungsten disk with diameter of ~ 1.1m, with tungsten plates clad with tantalum, cooled with water and covered with stainless-steel shroud. The target disk will contain twenty-one segments, will perform one turn in 1.4 s, and will be synchronized with the proton pulses so that the consecutive proton pulses will hit adjacent target segments. In the rotating target the proton beam heating, radiation damage, activation, and decay heat are spread over much larger volume compared to the stationary target, thus greatly reducing the consequences of accidents. The present status of the STS target design will be presented with emphasis on the activation analysis and results.

Speaker: Igor REMEC

Slides 2.Igor_REMEC2.pdf

10:00 Coffee break

13 Induced radioactivity of metal samples in the radiation field by 9.6 GeV electrons at PAL-XFEL

The precise evaluation of the induced radioactivity is very important for the design and the waste management of the high-energy electron accelerator. However, a few experimental data and benchmarking studies are available for high-energy electrons with energies of 2.5 GeV[1,2] and 28.5 GeV[3]. This study is an extension of previous studies. Samples of copper, stainless steel, low carbon steel and aluminum were irradiated in the radiation field by 9.6 GeV electrons hit thick copper target at PAL-XFEL HX main beam dump bunker. The induced specific activity was measured by the gamma spectroscopy, and the irradiation experiment was simulated by the Monte Carlo code, FLUKA[4]. The measured activity and the comparison results will be discussed. References [1] A. Fasso et al., Journal of Nuclear Science and Technology 37:sup1 (2000) 827-834 [2] M. Brugger et al., Progress in Nuclear Science and Technology 4 (2014) 363-366 [3] S.H. Rokni et al., Nuclear Instruments and Methods A 484 (2002) 680-689 [4] A. Fasso et al., FLUKA: A Multi-Particle Transport Code, CERN-2005-10 (2005)

Speaker: Nam-suk JUNG

Slides 3.Nam-Suk_JUNG.pdf

14 Radiological characterization of radioactive magnets at CERN

The radiological characterization is an essential requirement for the disposal of radioactive waste in national repositories. At the same time, such characterization can be particularly challenging in the case of radioactive waste produced in particle accelerators like the ones operated at the European Organization for Nuclear Research (CERN) – where most of the accelerator components are unique prototypes and the radiation environment includes neutrons, protons, photons and pions with a wide range of energies and fluences. More specifically, accelerator components can also include electromagnets, which are used to guide and focus charged particle beams. As a consequence of the accelerator complex operation, those electromagnets become radiologically activated and hence referred to as radioactive magnets. After the decommissioning of a particular accelerator, the electromagnets are temporarily stored at CERN awaiting radioactive decay and characterization for an adequate definition of a waste elimination pathway. The characterization of CERN radioactive magnets is particularly challenging. Firstly, their dimensions can be several meters in length and their masses are typically above one ton. Secondly, they are composed of different types of metals (e.g. cast iron and copper) in different proportions. Thirdly, they present heterogeneous activity distribution. Finally, the magnets' physical geometry does not lend itself easily to radiation dose profile measurements due to hardly accessible surfaces (e.g. inside the vacuum chambers). In this paper, we present a characterization method which is based on a prior extensive study using the analytical code ActiWiz [1], in order to define the expected radionuclide inventory and activity levels over hundreds of possible activation scenarios. By normalizing the activity levels of all the radionuclides to the activity level of the dominant gamma emitter, one can infer the so-called “fingerprints”: a list of radionuclides with the associated activity ratios. We then performed a series of Monte Carlo simulations with Fluka [2,3] and In-Situ HPGe (High Purity Germanium) gamma spectroscopy measurements, in order to define the ratio between a contact dose-rate measurement and the specific activity of the dominant gamma emitter. By combining the fingerprints with the dose-to-activity ratios, we obtained the so-called “conversion factors”, which provide the radiological characterization of the magnet from the dose rate map. The French National Radioactive Waste Management Agency (ANDRA) approved the proposed based on the conversion factors and dose rate map. A pilot phase was successfully carried out using this method, which has now reached an operational phase at CERN. In addition, we performed an experimental validation by comparing results from this characterization method with those from In-Situ HPGe gamma spectroscopy measurements. Thanks to this study and to the experience gained in the pilot elimination campaigns, we could identify the number of dose-rate measurements and how to choose representative measurement points in order to obtain the most accurate activity evaluation. The conversion factors method can be applied to radioactive waste from other particle accelerators, in particular to large accelerator components with a non-homogeneous activity distribution. The propose method has a clear advantage over the In-Situ HPGe gamma-spectrometry and sampling techniques. It can be performed with a hand-held radiation detector, and does not require destructive analyses. [1] C. Theis, H. Vincke, ActiWiz – optimizing your nuclide inventory at proton accelerators with a computer code, Progress in Nuclear Science and Technology (2013). [2] T.T. Böhlen, F. Cerutti, M.P.W. Chin, A. Fassò, A. Ferrari, P.G. Ortega, A. Mairani, P.R. Sala, G. Smirnov and V. Vlachoudis, The FLUKA Code: Developments and Challenges for High Energy and Medical Applications, Nuclear Data Sheets 120, 211-214 (2014). [3] A. Ferrari, P.R. Sala, A. Fasso`, and J. Ranft, FLUKA: a multi-particle transport code, CERN-2005-10 (2005), INFN/TC_05/11, SLAC-R-773

Speaker: Stefan ROESLER

Slides 4.Stefan_ROESLER.pdf

11:30 Lunch

Session 5

Convener: Hiroshi MATSUMURA

15 Risk Considerations of Large Accelerator Facility

Speaker: Hee-Seock LEE

16 RP aspects of the BDF/SHiP prototype tests in 2018

The Beam Dump Facility (BDF) is a proposed general-purpose fixed target facility at CERN. In the beginning, it will be exploited by the Search for Hidden Particles (SHiP) experiment, whose aim is to absorb the vast majority of the particle cascade produced by the high intensity 400 GeV/c SPS proton beam. Two BDF/SHiP target prototypes were tested in the SPS North Area at CERN in 2018. One test was performed to measure the flux of muons leaving the target, which forms the main background of the SHiP experiment. The second test had the objective to validate the target design in terms of thermal and mechanical stability. Due to the high beam load, density and Z-composition of the target, considerable prompt radiation and material activation was expected for both tests and was therefore assessed with the FLUKA Monte Carlo code. Furthermore, the second test allowed to irradiate different material samples, being located at the target’s surface, with the purpose of conducting tritium out-diffusion experiments. The tritium out-diffusion is relevant for estimating its contribution to the total amount of tritium released from BDF. The effect of the obtained results on the environmental impact assessment of the BDF facility will be presented.

Speakers: Claudia AHDIDA, Heinz VINCKE, Mirkoantonio CASOLINO

Slides 2.Mirkoantonio_CASOLINO.pdf

17 Verification of applying the current gamma-ray imaging techniques for discrimination of accelerator magnet activation

Gamma-ray imaging technique that rapidly prevailed in Japan after Fukushima Dai-ichi Nuclear Power Plant accident is expected to be powerful tool for detection of activated area and generated nuclides on an accelerator magnet. Although, Co-60 which emits high energy (1173, and 1333 keV) photons is principal nuclides for activated magnet, most of current techniques aim detection of 137Cs which emits 662 keV photon. Moreover, strong radiations from beam lines disturb to identify the source location. In this study, we experimentally investigated the effectiveness of current imaging technique for the identification of activated areas and generated nuclides in the accelerator magnet, with representative commercially available devices. Fundamental studies by using the magnet moved from the beamline to the low-background environment were conducted, then measurements at the actual beamline were conducted to investigate the effects under high background environment. In the presentation, we will report on the series of experimental results, particularly focusing on "Detection of gamma rays of Co-60", and "Identification of the radiation source location (activated area)".

Speaker: Go YOSHIDA

Slides 3.Go_YOSHIDA2.pdf

14:30 Coffee break

Session 6

Convener: Hee-Seock LEE

18 Introduction to RAON project

Speaker: Youngkwan KWON

Slides 1.Youngkwan_Kwon.pdf

19 Radiation Dose Assessment in RAON ISOL building Due to Production of Rare-Isotope Beams

A Korean heavy-ion accelerator complex called RAON is currently under development. Isotope Separation On-Line (ISOL) system can produce rare isotope (RI) beams of high purity and intensity by shooting 70 MeV proton beam from cyclotron driver onto a Uranium Carbide (UCx) target to induce nuclear fission reaction process and it is preferentially considered in order to produce RI beam in RAON. The RI beams are transported into Superconducting Linac 3 (SCL3) for acceleration through pre-separator room and RIB separation and transportation room (RIB-STR). Normally, the pre-separator room is considered to be extremely high-level radiation zone. Because most of the unwanted contaminants from UCx is removed in pre-separator room besides desired isotopes for ISOL system. During the transport of RI beams, those are likely to be deposited in pre-separator room. Therefore, RI beams are important radiation source to be protected as well as prompt neutrons from UCx target on operation. In addition, RIB-STR has several components that help to prepare acceleration of RI beams such as RF cooler buncher, EBIS charge breeder, and A/q separator. The RI beams can be either leaked in the beamline or deposited in the several main components in the middle of transportation. For safe operation of ISOL, radiation safety by accumulation of RI beams should be carefully reviewed in pre-separator room, RIB-STR, and near the RI beam line. However, it is not easy to evaluate the residual dose occurred from accumulation of RI beams due to absense of an established analytical method in RI production and transportation system like both ISOL and IF. So, we have developed the analytical method and evaluated the radiation dose in ISOL building due to RI beams transporation and accumulation.

Speaker: Jae Cheon KIM

Slides 2.JaeCheon_KIM.pdf

20 Shielding analysis for the In-Flight Fragment target facility of the RAON complex in Korea

The In-Flight Fragment (IFF) target facility of the heavy-ion accelerator facility complex, named RAON, is under a construction in Korea. It is planned that various rare isotope beams will be produced using by the IFF target. In this study, the radiation shielding analysis for the IFF target facility was performed. At first, conservative neutron source term was evaluated with the candidate beam-target conditions and as a result, the neurons produced from the nuclear reaction of the oxygen beam and graphite target was applied as the source term for the prompt shielding calculation. In the shielding calculation, design optimization of the shield and facility walls was performed while the design satisfies the domestic regulations about the exposure for the radiation workers and public. The combination of the iron and concrete was used as the high energetic neutron with a few hundred of MeV. In the activation analyses, induced activities for the air, coolant, equipment (target and beam line), iron shield and concrete walls were estimated and finally and decay gamma dose distribution was calculated. To reduce tha activation concentration in the air, additional shield was installed around the IFF target. Additionally, skyshine dose, soil activation and ground water migration were analyzed to evaluate the public exposure level around the facility. The PHITS ver.2.64 and MCNPX ver.2.7 were used in the particle transport calculations. DCHAIN/SP-2011 and Advantg ver.3.1 were used in the activation calculation and weigh window generation, respectively. As a result, the radiation shielding design was determined for the IFF target facility of the RAON complex, being expected the exposure level under 10 mSv/yr and 0.5 mSv/yr for the radiation workers and public, respectively.

Speaker: Cheol-woo LEE

Slides 3.CheolWoo_LEE.pdf

Session 7: Discussion for the next workshop and etc. (Stefan ROESLER and Kazuyoshi MASUMOTO)

Conveners: Kazuyoshi MASUMOTO, Stefan ROESLER

21 Discussion for the next workshop and etc.

Slides ARIA-summary.pdf

Wednesday, 25 September

09:00 Move to RAON Construction Site

09:30 Briefing on RAON Construction

10:00 RAON Site Tour