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Title: High power ring methods and accelerator driven subcritical reactor application

Abstract

High power proton accelerators allow providing, by spallation reaction, the neutron fluxes necessary in the synthesis of fissile material, starting from Uranium 238 or Thorium 232. This is the basis of the concept of sub-critical operation of a reactor, for energy production or nuclear waste transmutation, with the objective of achieving cleaner, safer and more efficient process than today’s technologies allow. Designing, building and operating a proton accelerator in the 500-1000 MeV energy range, CW regime, MW power class still remains a challenge nowadays. There is a limited number of installations at present achieving beam characteristics in that class, e.g., PSI in Villigen, 590 MeV CW beam from a cyclotron, SNS in Oakland, 1 GeV pulsed beam from a linear accelerator, in addition to projects as the ESS in Europe, a 5 MW beam from a linear accelerator. Furthermore, coupling an accelerator to a sub-critical nuclear reactor is a challenging proposition: some of the key issues/requirements are the design of a spallation target to withstand high power densities as well as ensure the safety of the installation. These two domains are the grounds of the PhD work: the focus is on the high power ring methods in the frame ofmore » the KURRI FFAG collaboration in Japan: upgrade of the installation towards high intensity is crucial to demonstrate the high beam power capability of FFAG. Thus, modeling of the beam dynamics and benchmarking of different codes was undertaken to validate the simulation results. Experimental results revealed some major losses that need to be understood and eventually overcome. By developing analytical models that account for the field defects, one identified major sources of imperfection in the design of scaling FFAG that explain the important tune variations resulting in the crossing of several betatron resonances. A new formula is derived to compute the tunes and properties established that characterize the effect of the field imperfections on the transverse beam dynamics. The results obtained allow to develop a correction scheme to minimize the tune variations of the FFAG. This is the cornerstone of a new fixed tune non-scaling FFAG that represents a potential candidate for high power applications. As part of the developments towards high power at the KURRI FFAG, beam dynamics studies have to account for space charge effects. In that framework, models have been installed in the tracking code ZGOUBI to account for the self-interaction of the particles in the accelerator. Application to the FFAG studies is shown. Finally, one focused on the ADSR concept as a candidate to solve the problem of nuclear waste. In order to establish the accelerator requirements, one compared the performance of ADSR with other conventional critical reactors by means of the levelized cost of energy. A general comparison between the different accelerator technologies that can satisfy these requirements is finally presented. In summary, the main drawback of the ADSR technology is the high Levelized Cost Of Energy compared to other advanced reactor concepts that do not employ an accelerator. Nowadays, this is a show-stopper for any industrial application aiming at producing energy (without dealing with the waste problem). Besides, the reactor is not intrinsically safer than critical reactor concepts, given the complexity of managing the target interface between the accelerator and the reactor core.« less

Authors:
 [1]
  1. Univ. of Grenoble (France)
Publication Date:
Research Org.:
Brookhaven National Laboratory (BNL), Upton, NY (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Nuclear Physics (NP) (SC-26)
OSTI Identifier:
1351800
Report Number(s):
BNL-113766-2017-TH
R&D Project: KBCH139; KB0202011
DOE Contract Number:
SC00112704
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
43 PARTICLE ACCELERATORS

Citation Formats

Tahar, Malek Haj. High power ring methods and accelerator driven subcritical reactor application. United States: N. p., 2016. Web. doi:10.2172/1351800.
Tahar, Malek Haj. High power ring methods and accelerator driven subcritical reactor application. United States. doi:10.2172/1351800.
Tahar, Malek Haj. Sun . "High power ring methods and accelerator driven subcritical reactor application". United States. doi:10.2172/1351800. https://www.osti.gov/servlets/purl/1351800.
@article{osti_1351800,
title = {High power ring methods and accelerator driven subcritical reactor application},
author = {Tahar, Malek Haj},
abstractNote = {High power proton accelerators allow providing, by spallation reaction, the neutron fluxes necessary in the synthesis of fissile material, starting from Uranium 238 or Thorium 232. This is the basis of the concept of sub-critical operation of a reactor, for energy production or nuclear waste transmutation, with the objective of achieving cleaner, safer and more efficient process than today’s technologies allow. Designing, building and operating a proton accelerator in the 500-1000 MeV energy range, CW regime, MW power class still remains a challenge nowadays. There is a limited number of installations at present achieving beam characteristics in that class, e.g., PSI in Villigen, 590 MeV CW beam from a cyclotron, SNS in Oakland, 1 GeV pulsed beam from a linear accelerator, in addition to projects as the ESS in Europe, a 5 MW beam from a linear accelerator. Furthermore, coupling an accelerator to a sub-critical nuclear reactor is a challenging proposition: some of the key issues/requirements are the design of a spallation target to withstand high power densities as well as ensure the safety of the installation. These two domains are the grounds of the PhD work: the focus is on the high power ring methods in the frame of the KURRI FFAG collaboration in Japan: upgrade of the installation towards high intensity is crucial to demonstrate the high beam power capability of FFAG. Thus, modeling of the beam dynamics and benchmarking of different codes was undertaken to validate the simulation results. Experimental results revealed some major losses that need to be understood and eventually overcome. By developing analytical models that account for the field defects, one identified major sources of imperfection in the design of scaling FFAG that explain the important tune variations resulting in the crossing of several betatron resonances. A new formula is derived to compute the tunes and properties established that characterize the effect of the field imperfections on the transverse beam dynamics. The results obtained allow to develop a correction scheme to minimize the tune variations of the FFAG. This is the cornerstone of a new fixed tune non-scaling FFAG that represents a potential candidate for high power applications. As part of the developments towards high power at the KURRI FFAG, beam dynamics studies have to account for space charge effects. In that framework, models have been installed in the tracking code ZGOUBI to account for the self-interaction of the particles in the accelerator. Application to the FFAG studies is shown. Finally, one focused on the ADSR concept as a candidate to solve the problem of nuclear waste. In order to establish the accelerator requirements, one compared the performance of ADSR with other conventional critical reactors by means of the levelized cost of energy. A general comparison between the different accelerator technologies that can satisfy these requirements is finally presented. In summary, the main drawback of the ADSR technology is the high Levelized Cost Of Energy compared to other advanced reactor concepts that do not employ an accelerator. Nowadays, this is a show-stopper for any industrial application aiming at producing energy (without dealing with the waste problem). Besides, the reactor is not intrinsically safer than critical reactor concepts, given the complexity of managing the target interface between the accelerator and the reactor core.},
doi = {10.2172/1351800},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Sun Aug 07 00:00:00 EDT 2016},
month = {Sun Aug 07 00:00:00 EDT 2016}
}

Technical Report:

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  • A summary of the activities and of the scientific production of the “NSTD/C-AD ADS-Reactor Think-Tank” collaboration, over the period May 2013 - May 2015.
  • A lead-bismuth eutectic (LBE) target design concept has been developed to drive the subcritical multiplier (SCM) of the accelerator-driven test facility (ADTF). This report gives the target design description, the results from the parametric studies, and the design analyses including physics, heat-transfer, hydraulics, structural, radiological, and safety analyses. The design is based on a coaxial geometrical configuration to minimize the target footprint and to maximize the utilization of the spallation neutrons. The target is installed vertically along the SCM axis. LBE is the target material and the target coolant. Ferritic steel (HT-9 alloy) is the selected structural material based onmore » the current database and the design analyses. Austenitic steel (Type 316 stainless steel) is the backup choice. A uniform proton beam is employed to perform the spallation process. The proton beam has 8.33-mA current and 8.14-cm radius resulting in a current density of 40 {micro}A/cm{sup 2}. The beam power is 5 MW and the proton energy is 600 MeV. The beam tube has 10-cm radius to accommodate the halo current. A hemi-spherical geometry is used for the target window, which is connected to the beam tube. A conical target window with a rounded tip is also considered since it has a lower average temperature relative to the spherical geometry. The beam tube is enclosed inside two coaxial tubes to provide inlet and outlet manifolds for the LBE coolant. The inlet and the outlet coolant manifolds and the proton beam are entered from the top above the SCM. Several design constraints are developed and utilized for the target design process to satisfy different engineering requirements and to minimize the design development time and cost.« less
  • Highly Compact Accelerator-Driven Subcritical Assembly for Medical and Industrial Applications
  • A subcritical facility driven by an electron accelerator is planned at the Kharkov Institute of Physics and Technology (KIPT) in Ukraine for medical isotope production, materials research, training, and education. The conceptual design of the facility is being pursued through collaborations between ANL and KIPT. As part of the design effort, the high-fidelity analyses of various target options are performed with formulations to reflect the realistic configuration and the three dimensional geometry of each design. This report summarizes the results of target design optimization studies for electron beams with two different beam profiles. The target design optimization is performed viamore » the sequential neutronic, thermal-hydraulic, and structural analyses for a comprehensive assessment of each configuration. First, a target CAD model is developed with proper emphasis on manufacturability to provide a basis for separate but consistent models for subsequent neutronic, thermal-hydraulic, and structural analyses. The optimizations are pursued for maximizing the neutron yield, streamlining the flow field to avoid hotspots, and minimizing the thermal stresses to increase the durability. In addition to general geometric modifications, the inlet/outlet channel configurations, target plate partitioning schemes, flow manipulations and rates, electron beam diameter/width options, and cladding material choices are included in the design optimizations. The electron beam interactions with the target assembly and the neutronic response of the subcritical facility are evaluated using the MCNPX code. the results for the electron beam energy deposition, neutron generation, and utilization in the subcritical pile are then used to characterize the axisymmetric heat generation profiles in the target assembly with explicit simulations of the beam tube, the coolant, the clad, and the target materials. Both tungsten and uranium are considered as target materials. Neutron spectra from tungsten and uranium are very similar allowing the use of either material in the subcritical assembly without changing its characteristics. However, the uranium target has a higher neutron yield, which increases the neutron flux of the subcritical assembly. Based on the considered dimensions and heat generation profiles, the commercial CFD software Star-CD is used for the thermal-hydraulic analysis of each target design to satisfy a set of thermal criteria, the most limiting of which being to maintain the water temperature 50 below the boiling point. It is found that the turbulence in the inlet channels dissipates quickly in narrow gaps between the target plates and, as a result, the heat transfer is limited by the laminar flow conditions. On average, 3-D CFD analyses of target assemblies agree well with 1-D calculations using RELAP (performed by KIPT). However, the recirculation and stagnation zones predicted with the CFD models prove the importance of a 3-D analysis to avoid the resulting hotspots. The calculated temperatures are subsequently used for the structural analysis of each target configuration to satisfy the other engineering design requirements. The thermo-structural calculations are performed mostly with NASTRAN and the results occasionally compared with the results from MARC. Both, NASTRAN and MARC are commercially available structural-mechanics analysis software. Although, a significant thermal gradient forms in target elements along the beam direction, the high thermal stresses are generally observed peripherally around the edge of thin target disks/plates. Due to its high thermal conductivity, temperatures and thermal stresses in tungsten target are estimated to be significantly lower than in uranium target. The deformations of the target disks/plates are found to be insignificant, which eliminate concerns for flow blockages in narrow coolant channels. Consistent with the specifications of the KIPT accelerator to be used in this facility, the electron beam power is 100-kW with electron energy in the range of 100 to 200 MeV. As expected, the 100 MeV electrons deposit their energy faster while the 200-MeV electrons spread their energy deposition further along the beam direction. However in that electron energy range, the energy deposition profiles near the beam window require very thin target plates/disks to limit the temperatures and thermal stresses.« less