Physical design of photo-neutron source based on 15 MeV Electron Linac accelerator and Its Application

Transcription

1 TMSR Physical design of photo-neutron source based on 15 MeV Electron Linac accelerator and Its Application WANG Hongwei 10/2012 on behalf of Reactor Physics Division of TMSR Nuclear Physics Division Shanghai INstitute of Applied Physics(SINAP), Chinese Acaedy of Science(CAS) 钍基核能系统 Reactor Physics Division

2 TMSR Contents 1. The requirement of nuclear data for TMSR 2. Monte Carlo Calculation 3. Neutron target 4. Detection system 5. Summary Reactor Physics Division

3 RPD 1 The Requirement of Nuclear Data For TMSR High accuracy fission cross section data for some 232Th and U isotopes(233,234,236u) are important for the development of the Th-U fuel cycle for energy production. High accuracy neutron capture cross section data are needed to address some still-open questions in fundamental, Reactor Physics and nuclear astrophysics. Precise measurements of neutron cross section are of great importance for the safety design and for the evaluation of neutron flux density and energy spectrum around a reactor Reactor Physics Division Thorium-Based Molten Salt Reactor System

4 RPD Scheme of Thorium-Uranium cycle Reactor Physics Division Thorium-Based Molten Salt Reactor System

5 RPD Learn from the Scheme the most impotant decay channels in this cycle are β - and decay in the last decay chains the cross section related with the most important reactions must be located in a good precision of an order of few percent(5-10%),but many data shows large discrepances or large uncertainty Reactor Physics Division Thorium-Based Molten Salt Reactor System

6 RPD For example: For 232 Th(n,γ) capture reaction, it shows that discrepancy among data published is around 20-30%, sometimes for neutron energies above 50keV, some new data have been corrected by accurately measured recently. The nucleus 233 Pa(protactinium) plays a key role in Th cycle and acts as a precursor to the long lived fissile nucleus 233 U, the half life of 233 Pa(27d) is rather long,it open a possibility to capture neutron in the reactor. So far no reliable data exist (was available) for the cross section of this reaction, moreover those data at some energies differ by almost a factor two. Reactor Physics Division Thorium-Based Molten Salt Reactor System

7 RPD Other related nuclei Fuel salt Th, Pa, 233 U,Be,F,Na, 7 Li Reactor poison 135 Xe, Sm, 133 Cd, 6 Li,Te Control rod Gd, 10 B, O,Al Alloy Fe,Cr,Ni,Mo Reactor Physics Division Thorium-Based Molten Salt Reactor System

8 RPD Status of the Key Nuclear Data in TMSR The lack of nuclear data Differences of nuclear data Updated nuclear data Full set of data: 234 Pa. Fission yield data: 233 Pa 233 Th 232 U Full set of data: 232 Pa 234 U. Fission yield data: 131 I 135 I 135 Xe Full set of data: 232 Th 233 U 155 Gd Fission yield data: 233 U 232 Th.. Activation data: 233 Pa 233 Th.. Decay data: 231 Th 232 U 233 Pa Resolved Methods Improved evaluation method Improved equipment performance Improved measuring method Measurement system and the method of measurement development!!! Reactor Physics Division Thorium-Based Molten Salt Reactor System

9 RPD The summary of status U-233(n,f) U-233(n,g) XS Energy range Evaluation data Exp data Note eV Above 500eV 5-50eV Above 500eV JENDL-4.0 more wide in Resonance energy area JENDL-4.0 more wide in Resonance energy area Differences of evaluation data Larger error Differences of evaluation data Th-232(n,g) 10eV-5KeV fewer experimental data Th-232(n,f) Below 60KeV JEFF-3.1 without evaluation data 1-500KeV Larger error Pa-233 (n,g) Thermal neutrons and several fast neutron Better agreement Y No other energy experimental data Pa-233 (n,f) Below 1MeV The lack of JEFF-3.1 N Th-233(n,g) Only thermal neutrons Better agreement Y Th-233(n,f) 1eV-10keV Differences of ENDF/B and JEFF Only eV Pa-234 Only TENDL N Xe-135 (n,g) Above 50eV Differences of all data librarys Only eV and 318eV experimental data 9 Reactor Physics Division No other energy experimental data No other energy experimental data No other energy Thorium-Based Molten Salt Reactor System

10 The Way to Produce Neutron

11 RPD TOF facility in the world From this table, we find the photo-neutron source is a powerful tool to produce intense pulsed neutrons, it are effective for measuring energy dependent XS with TOF technics, the energy range from thermal neutrons to a few tens of MeV. Until now, No photo-neutron source be build in China. Reactor Physics Division Thorium-Based Molten Salt Reactor System

12 Principle of photo-neutron source Electron bombs the target which made by heavy elements, γ rays produced through bremsstrahlung reaction, then neutrons emit from target by (γ, n) reaction. Empirical formula W. P. Swanson, Radiological Safety Aspects of the operation of Electron Linear Accelerators, IAEA Tech. Rep. 188 (1979) 12

13 RPD Neutron yield as a function of electron energy for different element Candidates : U,W,Pb,Ta,Au Electron energy above 30 MeV, neutron yield approaches a saturated value, and neutron yield of W higher than Ta target. taken from Reference Reactor Physics Division Thorium-Based Molten Salt Reactor System

14 RPD Our consideration of nuclear data measurement priority 14 Reactor Physics Division Thorium-Based Molten Salt Reactor System

15 Plan for nuclear cross section measurement Measurement for total and resonance cross section from thermal to slow neutron, dividing two steps: First step 15 MeV electron LINAC produces neutron, located at Jiading campus, SINAP Neutron yield ~10 11 n/s TOF path ~ 5m Second step for fast neutron 100 MeV electron LINAC, in Future Neutron yield ~10 12 n/s TOF path ~ 10-50m 15

16 Why choose 15MeV electron linac as driving facility? Produce white light neutron, for the required neutron cross section related with TMSR at thermal and slow neutron energy Preparing technique for building high energy electron linac accelerator based photo-neutron source Study Irradiation effect of neutron and gamma on TMSR material, organism and detectors The advantage: Build up a 15MeV accerelator in a short time based on our prior electron linac technique, will be easy to extend to high energy. Exist a suitable neutron experimental hall, Save time, but space limited!

17 RPD Comparison with other neutron source facility based on the electron LINAC Reactor Physics Division Thorium-Based Molten Salt Reactor System

18 2 Monte Carlo Calculation Neutron source streng calculated by MCNP 15 MeV electron + target Tungsten target Tantalum target Neutron Yield(n/e) E E-4 Photon Yield (photon/e) Neutron yield calculated by MCNP for beam power 2kW and 7.5kW 15 MeV electron /Tantalum 2 kw(normal) 7.5 kw(max) Neutron yield(n/s) 5.53E E+12 Photon yield(p/s) 7.76E E MeV electron/tungsten 2 kw(normal) 7.5 kw(max) Neutron yield(n/s) 5.04E E+12 Photon yield(p/s) 6.30E E+15

19 Neutron & photon flux(n/s/cm 2 ) at 90 direction relative to electron beam 15MeV Electron(2kW )+W 0.5m/(n/s/cm2) 5m/(n/s/cm2) Neutron 1.51E E+05 Photon 1.81E E+08

20 The neutron spectra with different moderator(water) size After moderated, Neutron Energy spectra extend from about 1MeV to thermal neutron.

21 3 Neutron target selection In the region of 15-20MeV, no significant difference between W and Ta target W and Ta is one of good candidates, respectively

22 The parameters of electron linac accelerator Item working Region (1% TOF time resolution) Thermal slow Fast Electron energy 15 MeV 15 MeV 15 MeV Pulse width 3 s- 0.5 us 30 ns-15 ns ~3 ns Pulse frequency 10 Hz 200 Hz 266 Hz 266 Hz Average current 18 ua 100 ua 2.5 ua-5 ua 0.5 ua Average power W W 7.5 W Neutron energy ~0.025 ev- 8 ev 8 ev-5 kev 5 kev- 60 kev Diameter of e beam 3-4 cm 3-4 cm 3-4 cm TOF of neutron 4m 3m 2m Source strenght( n/s) ( ) (0.2-2) Neutron flux (n/s/cm 2 ) Time/Statistics error 1 day/ 1% 4 day/ 1% -5 % 7 day/ 1% -5 %

23 Element density g/cm 3 Melting point / C Young Modulus /GPa thermal conductance W/m/K Tungsten-74(W) Tantalum-73(Ta) From: (1) The W has very high melting point and high Young Modulus, (2) thermal conductance of W is three times higher then Ta, easy be cooled So, we will choose the W as the target of photo neutron source for 15 MeV electron Linac

24 The design of W target Thickness at 4 6 cm, the neutron yield approaches a saturated value Diameter at 5 7 cm, the neutron yield approaches a saturated value The W target size with 5 cm length and 6 cm diameter is selected

25 Selection of target model Plate-shaped Target for high power beam Whole Target for low power beam

26 The W target can work on normal cooling condition 7.5kW Power Cooling water speed 3m/s Target : W Cooling water speed 3m/s Target : Ta Reach Boiling Target Reach Target Max temperature point of Cooling Temperature melting point Cooling Water Water (1atm) ~1150 C No ~70 C No ~3300 C Yes ~70 C No When water speed 3m/s,Ta target not reach boiling point of Cooling water, but target temperature reach the melting point (Melting point: W 3422 C, Ta 3017 C.) When water speed 3m/s,W target not reach boiling point of Cooling water, not reach the melting point of W. So the W target is a good choice at cooling water speed 3m/s,original temperature 25

27 Outline of W target for 2kW Power Condition:electron 15 MeV,power 2 kw Beam size 3σ=2cm(99.7% electron focus in diameter 4 cm Simulation with purity W target + copper cooling base + Al shell by ANSYS code W target:φ6 cm x4.8 cm cylinder shape; Copper base:thickness 4 cm; Al Shell :thickness 2 mm; Inner Pipe:like heat sink, each rib length 8mm, thick 3mm, interval 2 mm Water Pipe: by diameter 3cm pipe Condition of cooling water:inlet water temperature 25 C, speed 1m/s,about 42.4L/min

28 Results 15MeV, 2kW electron+w target model,at 25 C; Water speed at 1m/s(42.4L/min),the temperature of water and copper surface is 61 C, Temperature difference in entrance and exit water is less then 1 C. So we can cooling W target safely at 2kW and 7.5kW 28

29 Layout of experimental setup of photo-neutron SINAP

30 4 Detection system Neutron energy measured by TOF technique E E t 2 t t L m sec E ev

31 TOF measurement:start signal (1)record the recoil particle by neutron(6lif/pe foil + recoil particle detector); (2)related particle:for example gamma ray with the neutron; (3)pulse electron:rf signal from linac

32 Neutron and Gamma ray detectors for primary measurement

33 Experimental plan Test and calibration for neutron source(first stage) Measure Flux of neutron and gamma rays. Energy spectra of Neutron and Gamma Determine parameters of neutron source Calibration of detector, efficiency measurement Neutron data measurement(second stage) Check Neutron source with Gold target, For example Au(n,tot), (n, ) Measure 232Th (n,tot), (n,γ) XS at resonant energy region Measure 233U (n,tot), (n,γ) XS at resonant energy region Measure neutron elastic scattering cross section Other XS study The main purpose of data measurement be focused on the total XS and capture reaction in 15MeV photonneutron source

34 Experimental setup for(n, tot)reaction Transmission method:measure neutron emitted at zero degree by neutron detector Neutron detectors: Liquid scintillator detector (thermal and slow neutron) 6LiI: ZnS neutron detector(thermal neutron) 34

35 Experimental setup for (n, )reaction Liquid scintillator Det target LiI/ZnS Detector Detector(C 6 D 6 ) 35

36 5 Summary W target is the best choice for our first phase 15 MeV photo-neotron source. We can cooling W target safely at 2kW and 7.5kW(max) beam power. Main purpose of data measurement be focused on the total cross section and capture reaction in 15MeV photon-neutron source

37 Collabration Members: Nuclear physics Division:WANG Hongwei,LI Chen,ZHANG Song, ZHANG Guoqiang,CAO Xiguang,ZHONG Chen et al., And some master students Reactor Physics Division:CAI Xiangzhou,CHEN Jingeng, WANG Naxiu,HUAN Jiangping,LIN Zuokang,HU Jifeng et al., Electron linac accelerator:gu Qiang,LIN GuoQiang et al., Reactor Safety Division:WANG Jianghua,CAI Junet al., Reactor Engineering Division:CAO Yun,HU Ruirong et al., Common office:he zhanjun,fang Guoping et al., Many thanks to our Consultant Prof ZHANG Guilin for useful discusstion. Thanks for your helps

38 谢谢!Thinks

39 Backup

40 加速器束流脉冲对中子能谱测量的限制 脉冲频率是对测量能区最低能量限制 脉冲宽度是对测量能区最高能量限制 脉冲频率 Hz 脉冲宽度 3us-0.5us 飞行路径 4m 脉冲频率 266Hz 脉冲宽度 30ns-15ns 飞行路径 3m 脉冲频率 266Hz 脉冲宽度 3ns 飞行路径 2m 10% 分辨区 0.025eV 可以测量的中子能区 15MeV

41 中子反应截面测量 数据需求 几个关键问题及其对核数据的需求 (Th-U 燃料循环 ) 232 Th/ 233 U 转化 235 U 的生成 全套中子数据 : 232,233,234 Th 232,233,234 Pa 232,233,234 U 活化截面 : 233 Pa (n,γ) 234g Pa 233 Pa (n,γ) 234m Pa 233 Th(n, γ) 衰变数据 : 233,234 Th 233,234,234m Pa 233 Th β-, T 1/2 = 22.3m, ENDSF 21.83m, Nucl.Wallet Card 41

42 电子能量 15MeV, 功率 2kW/0.133mA, 重复频率 266Hz,90 方向 : 15MeV 电子 +W 靶 0.5 米 /(n/s/cm2) 5 米 /(n/s/cm2) 中子 2kW/0.133mA 1.51E E+05 光子 2kW/0.133mA 1.81E E+08

43 Th-U 与 U-Pu 链比较 钍铀循环比铀钚循环在 Z 上低 2 个 台阶, 从而决定了前者在核能利用上相比后者有一个先天性优越条件 : 后处理较简单 反应堆物理报告人 43