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SUMMARY:Plutonium solid solubility and radiation damage in xenotime (YPO4)
  - Katie Gunderson (Dept. Earth Sciences)
DTSTART:20110228T160000Z
DTEND:20110228T170000Z
UID:TALK29816@talks.cam.ac.uk
CONTACT:Ian Farnan
DESCRIPTION:\nPhosphates are known to exhibit superior resistance to radia
 tion\ndamage\, as evidenced by natural phosphate minerals that are minimal
 ly\ndamaged despite containing alpha-emitting actinides for hundreds of\nm
 illions of years.  This study looks to investigate radiation damage\nin xe
 notime (YPO4) and zircon (ZrSiO4). Radiation damage occurs by two\nprocess
 es: the recoil of the heavy nucleus (70-100 keV) and the alpha\nparticle i
 tself (4.5-5.5 MeV)\, which loses energy primarily by\nionizations but cau
 ses several hundred atomic displacements near the\nend of its path.  Here 
 we present results of Pu doping into xenotime\,\nwith insight into solid s
 olubility and response to radiation damage\ncompared to previous results f
 or zircon.  We also separate damage due\nto alpha particles from damage du
 e to the heavy nucleus recoil and\ncompare to Pu-doped studies.\n\nFor sol
 id solubility and accelerated ageing studies\, 239 and\n238Pu-doped xenoti
 me samples were prepared at the Institute for\nTransuranium Elements\, Kar
 lsruhe. At 4 mol% 238Pu\, xenotime is single\nphase\, and at 8 mol% 238Pu 
 a secondary PuP2O7 phase is present.\nPreliminary calculations using latti
 ce parameters indicate Pu solid\nsolubility of 7.4 mol% (9.4 wt%)\, which 
 is compared to Pu solid\nsolubility in zircon.  Radiation damage over time
  was monitored by\nX-ray diffraction in the 4 mol% sample.  Lattice parame
 ters of damaged\nxenotime over time are compared to initial xenotime latti
 ce parameters\nto observe swelling of the crystalline unit cell.\n\nTo sep
 arate the damage due to the α-particle from heavy recoil damage\,\nxenoti
 me and zircon were synthesized with natural boron (containing\n19.9 wt% 10
 B) and irradiated for 1\, 10\, and 28 days to achieve the\nreaction 10B + 
 n --> 7Li + α.  The dose for each irradiation was\ncalculated by 7Li MAS-
 NMR spin-counting\, and amorphous regions\nquantified by 31P and 29Si MAS-
 NMR. X-ray diffraction shows maximum\nunit cell volume swelling of 0.46% a
 t a dose of 6.72 x 1018 α-events/g\nfor xenotime\, and 1.7% at a dose of 
 20.43 x 1018 α-events/g for\nzircon.  Preferential swelling along the a- 
 or c-axis is discussed and\ncompared to Pu-doped samples.\n
LOCATION:Harker 2 lecture room\, Department of Earth Sciences\, Downing Si
 te
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