Cockcroft Institute Postgraduate Lectures: Applications of Accelerators. Production of Radioisotopes

Transcription

1 Cockcroft Institute Postgraduate Lectures: Applications of Accelerators Production of Radioisotopes Hywel Owen Cockcroft Institute/University of Manchester

2 A Tale of Two Physicists Ernest O. Lawrence

3 Emilio Segrè and the 37-inch cyclotron deflector foil In February 1937 I received a letter from Lawrence containing more radioactive stuff. In particular, it contained a molybdenum foil that had been part of the cyclotron's deflector. I suspected at once that it might contain element 43. The simple reason was that deuteron bombardment of molybdenum should give isotopes of element 43 through well-established nuclear reactions. My sample, the molybdenum deflector lip, had certainly been intensely bombarded with deuterons, and I noted that one of its faces was much more radioactive than the other. I then dissolved only the material of the active face, in this way achieving a first important concentration of the activity.

4 60-inch Cyclotron, Berkeley

5 Isotope production today Three main areas: Conventional short-lived isotopes: F18, C11, N13 Hospital-based Commercial solutions widespread Compact low-cost accelerators Tc99m Reactor-based production mainly A number of accelerator methods exist PET Radionuclides Alpha-emitters, Ra223, At211, Bi213 Several methods exist CERN MEDICIS Nuclide Half-Life Positron (kev) F min 630 C m 960 N-13 10m 1200 O-15 2m 1730 Ge d 1900 Gammas (kev) 511(2)

6 Imaging

7

8 Mo-99/Tc-99m/Tc kev Tc-99m isomerism Seaborg and Segrè, Phys. Rev. 54(9), 772 Seaborg and Segrè, Phys. Rev. 55(9), 808 Tl-201 (made with a cyclotron, t1/2~3d) emits at 80 kev (through electron capture) which is not as good for imaging

9 Reactor and target

10 Mo99 Production and Use

11 Technetium Generators Eluent Needle Metal closure Glass column Lead shielding Eluate Sterile filter Hywel Owen IPAC14 THOAB02 19 June

12 Some facts about Tc-99m usage Hospital imaging: 1. Computed Tomography 2. Nuclear Medicine (85% Tc-99m) 3. MRI 35 M procedures/yr (global) Nuclear Medicine USA 29 M (44%) Europe 9 M (22%) Tc-99 Usage All Tc-99m 28 M Cardiac 12 M Primarily cardiac imaging e.g. post heart-attack World weekly supply: 2g of 235U used, 0.11g Mo-99 provided $140 M

13 All ways lead to Rome; many ways lead to 99m Tc 99 Mo production (for generator) direct 99m Tc production 235 U(n th,f) 238 U(n fast,f) 238 U(,f) 238 U(p,f) 98 Mo(n, ) nat Mo(n, ) 100 Mo(d,p) 100 Mo(p,2n) nat Mo(,x) 98 Mo(d,n) 99 Ru(n,p) 100 Mo(n,2n) 100 Mo(p,np) 96 Zr(,n) 102 Ru(n, ) 99m Tc production is not a physics problem!

14 Stability of Isotopes

15 Some reactions

16 Natural Molybdenum Abundance Isotope (atom %) Mo Mo Mo Mo Mo Mo Mo Each isotope can obviously undergo its own reactions.

17 235U fission

18 Fission Yields

19 Fission Cross-Sections in U/Pu

20 Segre Chart

21 Fission Beta Decay

22 A=98/99 Decay Chains Nuclide 99Y 99Zr 99Nb 99Mo 99Tc 99Ru Halflife 1.470(7) s 2.1(1) s 15.0(2) s (6) d 2.111(12)E+5 a Stable

23 Major producers of Mo-99

24 Reactor and target

25 Problems with the reactor method Reactors are all very old, with disrupted replacement plans: MAPLE-1/2 cancelled : 4 disruptions : 5 disruptions May 2009 & October 2009 are shortage months when 3 reactors are down. Uranium enrichment 5% for power, e.g. PWR 20% for research 95% for Mo-99 (or bombs) LEU < 20% HEU >20% 95% of global HEU use is for Mo-99 production USA does not like HEU being shipped around in boxes

26 Mo-99 Candidate Production Methods Accelerat ed Incident Reaction Comments Reference Deuteron Deuteron 98Mo(d,p)99Mo Segre and Lawrence Proton Neutron 100Mo(n,2n)99Mo Nagai & Hatsuwaka, JPSJ 78, (2009) Proton Proton 100Mo(p,2p)99,99mNb(β-)99Mo N/A Neutron 98Mo(n,γ)99Mo Reactor Mo W.Diamond, AECL Oct 2008 Ryabchikov et al., NIM B 213, 364 (2004) Proton Neutron 98Mo(n,γ)99Mo Be/Pb target Froment al., NIM A 493, 165 (2002) N/A Neutron 235U(n,f)99Mo Reactor method Proton Neutron 235U(n,f)99Mo ~1 GeV Proton Proton 238U(p,f)99Mo Lagunas-Solar, Trans.Amer.Nucl.Soc. 74, 134 (1996) Electron Gamma 100Mo(γ,n)99Mo 30 MeV Dikiy et al., Nuclear Physics Investigations (42), p (2004) Electron Gamma 235/238U(γ,f)99Mo Photofission/RIB Coceva et al., NIM 211, 459 (1983)

27 Mo-99 production R. Bennett et al., Nuclear Technology, 1999 vol. 126 (1) pp. 102 Based on development of high-current superconducting technology for energy-recovery linacs UK has significant expertise at Cockcroft/ALICE Typical parameters are 100 ma, 50 MeV electrons (for 15 MeV photons) Single target vs. multiple targets?

28 Haxby et al., Phys. Rev. 58(1), 92 (1940) Tungsten Target, Gamma Production, and Photofission 235U (also benefits from neutron reflection and fission cascade) 238U Berger and Seltzer, Phys Rev C 2, 621 (1970) Diamond, NIM A 432, 471 (1999)

29 Photofission Yields De Clerq et al., Phys Rev C 13 (4), 1536 (1976) P. Bricault, TRIUMF Diamond, NIM A 432, 471 (1999) A radioactive ion beam facility using photofission

30 Photofission Method P. Bricault, TRIUMF

31 Related target geometry (RIB) P. Bricault, TRIUMF

32 ALICE Accelerator Test Facility Nominal Gun Energy 350 kev Injector Energy 8.35 MeV Circulating Beam Energy 35 MeV Linac RF Frequency 1.3 GHz Bunch Repetition Rate MHz Max Bunch Charge 80 pc Max Average Current 13 µa Hz

33 Photonuclear Cross-Section in 100Mo W.Diamond, AECL, Oct 2008 Around 100 Ci/g with 100kW/50MeV electrons into W About 2 atoms in 10,000 (cf ~10% in fission products) - this requires a different (bigger?) generator - normal generator 60 in Target design is crucial Photofission is likely not practical Sabelnikov et al., Radiochemistry 48(2), 191 (2006) - report 390 mb with direct irradiation with 25 MeV electrons

34 ORNL ORELA Target design (Diamond/Beene)

35 Adiabatic Resonance Crossing (Rubbia) Rubbia, CERN/LHC/97-04 Arnould et al., Phys. Lett. B 458, 167 (1999)

36 Epithermal neutron capture in 98Mo Ryabchikov et al., NIM B 213, 364 (2004)

37 Resonant Neutron Capture Lethargy Isotope Abundance Abs (barn) Pb Pb Pb Pb Pb Froment al., NIM A 493, 165 (2002) Van Do et al., NIM B 267, 462 (2009)

38 65 MeV Protons into Be target (7 hour exposure) Froment et al., NIM A 493, 165 (2002) Abbas et al. 601, 223 (2009) About 1 neutron per 8 protons

39 Isotope Linac and Target Assembly 100Mo target (CLS) NRC INMS Proof-of-concept (Ottawa) Courtesy M. de Jong, CLS

40 Compact cyclotrons/ffags for conventional isotopes? Lower energy allows higher current E.g. Ionetix Isotron: 12.5 MeV/~6 T/35 kw 13 N SOLUTION in a compact Sc cyclotron Cryogen-free magnets Despite significant advantages over alternatives in SPECT and PET, 13 N h Cryocooler main tech, limits quite demanding to adoption: 1.5 W at 4.2 K Half-life is only 10 minutes so you have to make it where you will use it Still difficulty with fault recovery However, few medical facilities have on-site cyclotrons due to size and cost Isotron scale? Isotron N13 Demo Cyclotron- First beam Ultra-compact high field superconducting cyclotron system to provide supe flow imaging by enabling PET imaging agent 13 N availability directly in a cl PET Imaging Suite! Isotron' 2 October 2012 Courtesy T. Antaya, Ionetix

41 ined PET and SPECT radioisotope i set-up Dual use machine ling technology by CT T-P HTC Siemens Oniac IAC, a novel compact high h voltage electrostatic accelerator ers tor lead H IM Magnet free lthcare CTO / Strategy t iness Unit H IM MI Single stage only, perhaps up to 10 MV BiTech C-11 program (together th with CT T MHM MME) 5-stage Greinacher cascade, H - n, stripped to H+ at centre mber of the healthcare detector board CdTe Demonstrator installed at Corporate RAL results Technology to come!

42 Cyclotrons for 99mTc

43 Cyclotron Production of Tc-99m 98 Mo(p, ) 99m Tc 100 Mo(p,2n) 99m Tc 100 Mo(p,pn) 99 Mo -> 99m Tc ACeller et al Figure 3. Comparison of the 100 Mo(p,2n) 99m Tc excitation function to the six other technetium isotopes (isomeric and ground states) which are produced through the (p,n) reaction. The excitation function for 99m Tc is marked with red circles and stable isotopes are marked by an asterisk. Celler et al., PMB 56, 5469 (2011) Good purity is key to low dose to patient... licensing Hywel Owen IPAC14 THOAB02 19 June