2018·213·fall within the results of other different participating organizations,especially being in good agreement with FZK, IPPE and RIT,which average relevant differences are0.03%,−0.22%and−0.18%respectively.It can be found that burnup code has lower relevant differences,which proves that the burnup code has acceptable accuracy in fast spectrum burnup system.
Fig.1R-Z geometry sketch for ADS benchmark.Fig.2The evolution of effective eigenvalue as function
of time.
6-19Scheme and Progress on Thermal-hydraulic Experiment of a 19-pin Wire-wrapped Hexagonal Fuel Bundle
Fan Dajun,Gu Long,Peng Tianji,Tang Yanze,Tian Wangsheng,Liu Daxiao and Fan Xukai The Lead-cooled Fast Reactor(LFR)is a nuclear reactor using molten lead or lead-bismuth eutectic as the coolan
t.Features of LFR are fast neutron spectrum,closed fuel cycle,operating in high temperature and low-pressure.For its outstanding safety and design simplification,LFR was regarded as one of the Generation IV reactors by the Generation IV International Forum(GIF)and was selected as the reactor type of China Initiative Accelerator Driven System(CiADS)as well.The national major science and technology infrastructure CiADS was approved by the National Development and Reform Commission(NDRC)at the end of2015,and it will be built by2024[1−3].
The fuel assembly is the“heart”of a nuclear reactor.Fission energy is released herein,and leads to high temperature and high-level radioactive of the environment inside.One of the critical tasks of reactor thermal analysis is to investigate theflow characteristics of the coolant,especially the transverseflow in the subchannels. However,conducting an experiment with LBE is very difficult due to its high operating temperature.Moreover,the LBE is opaque.Therefore,it’s impossible to investigate theflow characteristic by optical measurement techniques. Whereas,based to the dimensional analysis and similarity theory,by selecting reasonable model and working liquid, the results from experiment with the scaled model can be transferred to its prototype phenomenon,if the similarity conditions are fulfilled[4].
A test section made from PMMA was designed to study the velocityfield and pressurefield,especially the transverseflow of the fuel assembly.PMMA is a high-quality plastic,with the advantage of high trans
parency,easy to manufacture and acceptable price.
As showed in Fig.1,fuel pins are helically wrapped with wire spacers,ranged in a triangular lattice,and closed in a hexagonal duct.The function of the wire spacer is to maintain the certain space of adjacent fuel pins,reduce vibration,and enhance heat transfer.To meet the condition of geometry similarity,the fuel pins and wire wraps in the test section was designed have the same size with the real fuel assembly.36differential pressure transducers were used to obtain the pressurefield.In addition,a particle image velocimetry(PIV)was employed to obtain the velocity vector of the test section,including x-y plane and x-z plane.
As we can see in the Fig.2,the experimental loop including four parts,namely the test section,measuring and controlling system,pipeline system,and supporting system.In the window of the measuring and controlling system,there have buttons for us to startup and shut down the pump,turn the value opening by PID regulator, and monitor and save the data in real time.
·214·2018
Fig.1(color online)Schematic of fast reactor fuel assem-
bly model.Fig.2(color online)Photograph of the experimental loop.
In 2018,we had finished the building of the experimental loop and had conducted some test work.This year,we will pay attention to get the data in some certain cases,and compare the experimental data with the simulation results.
References
[1]
C.Rubbia,R.J.A.,S.Buono,et al.,Conceptual design of a fast neutron operated high power energy amplifier.Cern/At/95-44(Et)[J],(1995).[2]
W.Zhan,A.X.H.,Advanced Fission Energy Program -ADS Transmutation System.Bulletin of the Chinese Academy of Sciences,2012.27(03):p.375-381.[3]reactor technology
T.J.Peng,et al.,Conceptual Design of Subcritical Reactor for China Initiative Accelerator Driven System.Atomic Energy Science &Technology,2017.[4]Sedov,L.I.,Similarity and Dimensional Methods in Mechanics.10th ed.1993,Boca Raton:CRC Press.
6-20A Refractive Index Matching Liquid Employed in the Flow Visualization Experiment of Fast Reactor Fuel Assembly Model
Fan Dajun,Gu Long,Peng Tianji,Tang Yanze,Tian Wangsheng,Liu Daxiao and Fan Xukai
The LBE is opaque,therefore,it is impossible to investigate the flow characteristic of fuel assembly in LFR by optical measurement techniques.Whereas,based on the dimensional analysis and similarity theory,by selecting reasonable model and working liquid,the results from experiment with the scaled model can be transferred to its prototype phenomenon,if the similarity conditions are fulfilled.The test section made from polymethyl methacrylate (PMMA)was designed to study the velocity field and pressure field.Many researchers have employed the refractive index matching (RIM)technique to match the RI of PMMA to obtain accurate,undistorted flow characteristics.However,many solutions in t
he literatures [1,2]can meet RIM purpose,but have the disadvantages of high viscosity,low stability,high toxicity and/or high cost for our experiment.
After reading lots of papers and conducting the necessary tests,we present a new RIM fluid to match RI of the fuel assembly model and tracer particles.The main properties of these two colorless,transparent and miscible liquids are listed in Table 1.
Table 1
Main properties of these two liquids.Material
Melting point/◦C Boiling point/(◦C)Density/(kg/m 3)Dynamic viscosity/(Pa ·s)Tetralin
−35.8207.69800.214at 20◦C Ethyl alcohol −114.178.3789.3at 20◦C 0.120at 20◦C
Solutions of various tetralin volume fraction were prepared by micropipettes.We employed a 2WAJ Abbe refractometer with a manufacturer’s uncertainty of 0.0002to measure the refractive index of the mixture.Since the laser sheet wavelength of particle image velocimetry (PIV)is 532nm,a filter to get the wavelength of 532nm only was set in front of the light portal of the Abbe refractometer.A DC0506N thermostatic water bath with the tolerance of 0.1◦C was connected to the three equipment mentioned a
bove to maintain a constant temperature.In addition,insulating pipes were utilized to reduce heat diffusion between the emulsion tube and environment.Moreover,we took the mean value of six measurements to reduce error.

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