Jun Nishiyama Research Laboratory for Nuclear Reactors, Tokyo Institute of Technology

Transcription

1 Nuclear and Emerging Technologies for Space 2015 Albuquerque Marriott in Albuquerque, NM on February 23-26, Feasibility Study on Polonium Isotopes as Radioisotope Fuel for Space Nuclear Power Jun Nishiyama Research Laboratory for Nuclear Reactors, Tokyo Institute of Technology 1

2 Contents 1. Introduction 2. Alternative isotope of 238 Pu 3. Production efficiency 4. Other option 5. Summary and Future work 2

3 1. Introduction Curiosity rover and RTG Landed on Mars on August 6, 2012 Power source: Radioisotope thermoelectric generator(rtg) Advantages Electricity Warming system NASA's Curiosity rover Pu-238 about 4 kg 3

4 1. Introduction Plutonium-238 Pu-238 is the best radioisotope High power density (540 W/kg) Enough half-life (87.7 years) Low radiation levels Stable fuel form at high temperature PuO 2 pellet 4

5 1. Introduction Pu-238 Short supply 1. Irradiate U fuel 2. Separate 237 Np 3. Irradiate 237 Np 4. Separate 238 Pu Z U 0.72% 238 Pu 87.7y 237 Np 2.1e6y 236 U 2.34e7y 238 Np 2.1d 237 U 6.75d 238 U 99.3% 239 U 23.5m N Nuclear arms reduction Shout down Irradiation reactors Processing facilities No large-scale production of 238 Pu in the World 5

6 1. Introduction Situation of Japanese space development Safeguards and Safety issue Non-nuclear weapon states RTG using 238 Pu Space exploration of Japan is limited to the inside of Mars s orbit Hayabusa and Itokawa Itokawa's orbit I: Itokawa S: Sun E: Earth M: Mars 6

7 1. Introduction Motivation RTG is good power source Short supply of Pu-238 Restriction in Japan Increase the need to explore Alternative isotope of 238 Pu for space nuclear power applications 7

8 1. Introduction Objectives 1. To investigate alternative isotope of 238 Pu 2. To evaluate production efficiency Independent of nuclear weapons manufacturing technology Special irradiation reactors Nuclear reprocessing facilities No Safeguards issue Not include fissile material for nuclear weapon 8

9 2. Alternative isotope 1 st Key factor: Power density and specific power q α = λn AQ α b α M q α : Specific power by α decay [W/kg] M:Molar mass [kg/mole] λ:decay constant [1/s] N A :Avogadro constant [1/mole] Q α :Decay heat by α decay [J] b α :Branching ratio of α decay 9

10 2. Alternative isotope Specific Power Long half-life (> 10 years) High specific power (> 100 W/kg) Nuclide Specific Power [W/kg] Half-life [y] 238 Pu Gd Po U Am Cm Cm Cf Cf

11 2. Alternative isotope Polonium Po-209: Decay: α 99.52%, EC 0.48% Specific power: 490 W/kg Half-life: years Some prototype RTGs, first built in 1958 by the US Atomic Energy Commission, have used Po-210. But it has limited use because of its very short half-life of 138 days. Po-209 has the possibility to be an alternative isotope of Pu

12 2. Alternative isotope Production method of 209 Po Z 85 (α,n) (α,γ) Po 5.80h 206 Bi 6.243d 205 Pb 1.73e7y 208 Po 2.898y 207 Bi 32.9y 206 Pb 24.1% 205 Tl 70.5% 209 Po 102y 208 Bi 3.68e5y 207 Pb 22.1% 206 Tl 4.202m 210 Po 138.4d 209 Bi 100% 208 Pb 52.4% 210 Bi 5.012d N (p,n) β (p,γ) (h,p) (γ,n) A Z (n,γ) (d,α) (γ,p) Β +,EC (n,p) α (n,α) 209 Bi(p,n) 209 Po Reaction 209 Bi(Natural abundance 100%)

13 2. Alternative isotope Cross section of 209 Bi(p,n) 209 Po Cross section [mb] JENDL/HE ENDF/B-VII.1 JEFF-3.1 TENDL-2012 PADF-2007 C. G. Andre (1956) J. Wing (1961) K. Miyano (1973) K. Miyano (1978) B.V.Zhuravlev(2010) Incident Proton Energy [MeV]

14 Po Production efficiency Calculation code: PHITS* with INCL model Calculation condition Target: Natural Bi, thick target, without transmutation Projectile: p + beam Energy: > 5 MeV (Threshold of 209 Bi(p,n) is 2.69 MeV ) Proton beam 100% 209 Bi * T. Sato et al., Particle and Heavy Ion Transport Code System PHITS, Version 2.52, J. Nucl. Sci. Technol. 50, pp (2013). 14

15 3. Production efficiency Production rate 10 0 Production rate [1/proton] Po-207 Po-208 Po-209 Po-210 (p, 3n) E th =18.1 MeV (p, 2n) E th =9.69 MeV (p, n) E th =2.69 MeV (p, γ) Incident Proton Eneryg [MeV] 15

16 3. Production efficiency Isotope ratio of 209 Po Po-209/(Po ) Nuclide Power density [W/kg] Specific Power [W/kg] Half life [y] 208 Po Po Po Po-208 Po Po Incident Proton Energy [MeV] Operation time [year] 16

17 3. Production efficiency Requirement - Beam Current - Beam current [A/kg(Po-209)/y] Po-209 Po-208 Po-209: 1kg/year Po-208: 0.027kg/year Incident Proton Eneryg [MeV] 17

18 3. Production efficiency Requirement - Beam Power - Beam Power [MW/kg/y] 10 5 Po-209 Po Po MeV 14 A 560 MW Po MeV 0.13 A 3.3 MW Incident Proton Eneryg [MeV] 18

19 3. Production efficiency Accelerator capability Active R&D in the medical field Cyclotrons 1. For BNCT: Boron Neutron Capture Therapy Subject: High current 30 MeV, 10 ma 2. For PET: Positron emission tomography Subject: Downsizing ~20 MeV, 100 µm Over 100 facilities in Japan Only 1 hour operation/day 7 Li(p,n) 7 Be reaction 18 O(p,n) 18 F reaction 19

20 4. Other option Using a proton accelerator Requirement for accelerator is quite large in comparison with the current accelerator technology 1. Other production path of 209 Po 2. Utilization of 208 Po 20

21 4. Other option Production path of 209 Po 209 Bi(n,γ) 210g Bi 210 Po(n,2n) 209 Po Z Po 5.80h 208 Po 2.898y 209 Po 102y 210 Po 138.4d Fast reactor(fr) or Bi 6.243d 205 Pb 1.73e7y 207 Bi 32.9y 206 Pb 24.1% 208 Bi 3.68e5y 207 Pb 22.1% 209 Bi 100% 208 Pb 52.4% 210 Bi 5.012d Accelerator Driven System(ADS) Tl 70.5% 206 Tl 4.202m N Pb-Bi Eutectic(LBE) as coolant or beam target

22 4. Other option Utilization of 208 Po Specific power [W/kg] 10 6 Po-208 Po Po Nuclide Specific Power [W/kg] Half life [y] 208 Po Po Po Operation time [year] 22

23 Summary Po-209 has the possibility to be an alternative radioisotope of Pu-238 for physical property. The requirement for accelerator is quite large in comparison with the current accelerator technology. It is possible to use Po-208 as a radioisotope fuel since it has a large power density (18300 W/kg). 23

24 Future work To validate calculation results by experiment for Po isotope production with accelerator To evaluate the efficiency of methods with nuclear reactors Foreground Background Counts/Channel/s Gamma-ray energy [kev] 24

25 25

26 Decay gamma of 238 Pu 43 kev: 30% 26

27 Decay gamma of 209 Po 260 kev: 1%, 900 kev: 0.5% 27

28 KUCA Pb-Bi 照射実験 測定条件 Pb-Bi 板のサイズ : 直径 50mm 厚さ 6mm (3mm 2 枚 ) 照射では陽子の飛程を考慮して厚さ 18mm(3mm 6 枚 ) を使用 ガンマ線の測定にはビーム側の 3mm 2 枚の板を使用 サンプル : 未照射の Pb-Bi 板と照射後の Pb-Bi 板を測定 検出器 :HPGe 検出器 測定位置 : 検出器表面とサンプルの距離 10cm( 添付の写真を参照 ) 照射条件 照射日時 :2014/1/ /3/5( 照射条件は日々異なる ) 電流値 :0.2-1 na 照射時間 : 合計約 35 時間 ( 電流値を 1nA に規格化して積算した照射時間 ) 例 )0.5 na x 1 時間 1nA x 0.5 時間 陽子のエネルギー :100MeV 周期 :20Hz

29 Gamma-ray spectra Foreground Background Counts/Channel/s Gamma-ray energy [kev]

30 Average Proton Flux 0.02 Incident proton energy 15 MeV 40 MeV Flux [1/cm 2 /source] Proton Energy [MeV] 30

31 Po isotopes Gamma rays >200 kev Po d E [kev] Intensity [%] Po h E [kev] Intensity [%] Po y E [kev] Intensity [%] Po y E [kev] Intensity [%] Po d E [kev] Intensity [%]

32 Bi isotopes Gamma rays Bi d E [kev] Intensity [%] Bi d E [kev] Intensity [%]

33 Gd