1. The Trouble With Technetium
Hywel Owen
School of Physics and Astronomy
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. Natural Molybdenum
Each isotope can obviously undergo its own reactions, either from neutrons or otherwise.
Isotope
Abundance (atom %)
Mo-92
15.84
Mo-94
9.04
Mo-95
15.72
Mo-96
16.53
Mo-97
9.46
Mo-98
23.78
Mo-100
9.63

5. Mo-99/Tc-99m/Tc-99 143 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

6. 235U fission

7. Fission Yields

8. Fission Cross-Sections in U/Pu

9. Segre Chart

10. Fission Beta Decay

11. A=98/99 Decay Chains Nuclide Halflife 99Y 1.470(7) s 99Zr 2.1(1) s
99Nb
15.0(2) s
99Mo
2.7489(6) d
99Tc
2.111(12)E+5 a
99Ru
Stable

12. Research and Power Reactors
Research reactors
Better neutronics, but need high power (>20 MW)
Easier fuel cycle: can extract targets out quickly and process them, needed to obtain Mo-99
Only 5 reactors meet these requirements

13. Major producers of Mo-99

14. Reactor and target

15. Technetium Generators
Typical Mo-99 specific activity 3000 Ci/gm (0.6%)
Typical price UKP , gives ~100 doses (depending on modality), GBq (3-7 Ci)
92,000 sold in USA in 2005
Total market around 600 MEuro, but this is artificially cheap because of cross-subsidy from nuclear research
Only few companies worldwide doing either processing or packaging:
General Electric (50%), MDS Nordion, Covidien (25%), Mallinckrodt, NTP
‘Demand is 200% of supply’ (Alan Perkins, BNMS)

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

17. 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

18. Switching to LEU targets
LEU target issues
25 times more 239Pu generated (due to 238U n capture)
but alpha contamination is about the same (due to 234U concentration during enrichment)
Switching to LEU targets
Use LEU (around 20% 235U)
Needs about 5 times as much Uranium as a (95%) HEU target, since the 238U doesn’t do anything.
No-one is using LEU and associated processing – yet
Mo-99 purity will be about the same
Target is not bigger, since you use different U density
Use U foil target (8g/cm3) rather than UO2 (1.6 g/cm3) or extruded U/Al rods
Use Cintichem process for extraction
Still 50 Ci of waste per 1 Ci of Mo (c.f. 30:1 with 235U)
(Vandegrift et al., Industrial & Engineering Chemistry Research 39(9), 3140 (2000))
Mushtaq et al., NIM B 267, 1109 (2009)

19. Mo-99 Candidate Production Methods
Accelerated
Incident
Reaction
Comments
Reference
Deuteron
98Mo(d,p)99Mo
Segre and Lawrence
Proton
Neutron
100Mo(n,2n)99Mo
Nagai & Hatsuwaka, JPSJ 78, (2009)
100Mo(p,2p)99,99mNb(β-)99Mo
N/A
98Mo(n,γ)99Mo
Reactor Mo
W.Diamond, AECL Oct 2008
Ryabchikov et al., NIM B 213, 364 (2004)
Be/Pb target
Froment al., NIM A 493, 165 (2002)
235U(n,f)99Mo
Reactor method
~1 GeV
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)
235/238U(γ,f)99Mo
Photofission/RIB
Coceva et al., NIM 211, 459 (1983)

20. 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?

21. Tungsten Target, Gamma Production, and Photofission
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)

22. 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’

23. Photofission Method
P. Bricault, TRIUMF

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

25. ALICE Accelerator Test FacilityHz

26. ALICE Cavities high current cavity under construction;
to be evaluated in 2010

27. Liquid (Solution)/Solid Target for Photonuclear Mo (Kharkov)
Dikiy et al., Nuclear Physics Investigations (42), p (2004)
Dikiy et al., EPAC’98
Either solid or aqueous solution target (Na2MoO4/K2MoO4)
Yield in solution is very low, but yield in target is ok (e.g. ~1 Ci from 24h at 1mA
Target should be enriched 100Mo to avoid production of other isotopes (expensive)

28. 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 10000
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

29. ORNL ORELA Target design (Diamond/Beene)

30. Direct Proton Reactions
100Mo(p,pn)99Mo
100Mo(p,2n)99mTc
98Mo(p,γ)99mTc
Kim et al., IEEE Nuclear Science Symposium Conference Record, NSS'07, N15-307
Scholten et al., Applied Radiation and Isotopes 51, 69 (1999)
Uddin et al., Applied Radiation and Isotopes 60, 911 (2004)
M. Challan et al., J. Nucl.Rad.Phys. 2(1), 1 (2007)

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

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

33. Resonant Neutron Capture
Isotope
Abundance
Abs (barn) Pb
---
0.171
204Pb
1.4
0.65
206Pb
24.1
0.03
207Pb
22.1
0.699
208Pb
52.4
Resonant Neutron Capture
Lethargy
Froment al., NIM A 493, 165 (2002)
Van Do et al., NIM B 267, 462 (2009)

34. 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

35. Which is the best method?
Questions to answer
Which is the best method?
238U Photofission
100Mo Photonuclear
100Mo Direct Proton
98Mo Epithermal Capture
Probably photofission, but targets need comparison and optimisation
Modelling software
MCNPX
GEANT
FLUKA
(EMPIRE-II)
Nuclear reaction data
Some discrepancies

36. Carlo Rubbia patent
Patent 2005/ (2005)
Resonant neutron capture in Mo, possibly Na2MoO4 solution

37. Cockcroft would like to develop a demonstrator Mo-99 facility
UK Plans and Elsewhere
Cockcroft would like to develop a demonstrator Mo-99 facility
10mA, 50 MeV electrons as demo machine
Full facility with hot cells probably on nuclear site, e.g. Sellafield
Target design needs to be done as part of demo design
TRIUMF have collaboration with MDS-Nordion
Non-disclosure agreement!
ORNL have done target work – in contact with them