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Title: Alpha decay self-damage in cubic and monoclinic zirconolite

Abstract

Samples of primarily-monoclinic /sup 238/Pu-doped zirconolite were stored at ambient temperature to allow accumulation of alpha decay self-damage to a dose of 1 x 10/sup 24/ ..cap alpha../m/sup 3/ (equivalent to a SYNROC age of approx. 10/sup 3/y). Bulk swelling reached 2.3 vol% with no tendency toward saturation, a damage response similar to that observed for cubic Pu-doped zirconolite. X-ray volumetric swelling at 4 x 10/sup 24/ ..cap alpha../m/sup 3/ was 1 vol%, considerably less than that for the cubic material. Changes in cell dimensions differed significantly from those reported by others for a monoclinic natural mineral. Extensive microcracking was observed, and is attributed at least partially to swelling differences between the matrix and minor phases.

Authors:
; ; ; ;
Publication Date:
Research Org.:
Los Alamos National Lab., NM (USA)
OSTI Identifier:
5913566
Report Number(s):
LA-UR-81-2954; CONF-811122-7
ON: DE82002400; TRN: 82-000203
DOE Contract Number:
W-7405-ENG-36
Resource Type:
Conference
Resource Relation:
Conference: Annual meeting of the Materials Research Society, Boston, MA, USA, 16 Nov 1981
Country of Publication:
United States
Language:
English
Subject:
12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES; 36 MATERIALS SCIENCE; ZIRCONOLITE; CRYSTAL DOPING; CUBIC LATTICES; LATTICE PARAMETERS; MONOCLINIC LATTICES; PHYSICAL RADIATION EFFECTS; ALPHA DECAY; AMBIENT TEMPERATURE; CRACKS; EXPERIMENTAL DATA; PLUTONIUM 238; RADIOACTIVE WASTE PROCESSING; SWELLING; SYNROC PROCESS; X-RAY DIFFRACTION; ACTINIDE ISOTOPES; ACTINIDE NUCLEI; ALKALINE EARTH METAL COMPOUNDS; ALPHA DECAY RADIOISOTOPES; CALCIUM COMPOUNDS; CALCIUM OXIDES; CHALCOGENIDES; COHERENT SCATTERING; CRYSTAL LATTICES; CRYSTAL STRUCTURE; DATA; DECAY; DIFFRACTION; EVEN-EVEN NUCLEI; HEAVY NUCLEI; IMPLANTS; INFORMATION; ISOTOPES; MANAGEMENT; MINERALS; NUCLEI; NUMERICAL DATA; OXIDES; OXYGEN COMPOUNDS; PLUTONIUM ISOTOPES; PROCESSING; RADIATION EFFECTS; RADIOISOTOPES; SCATTERING; TITANIUM COMPOUNDS; TITANIUM OXIDES; TRANSITION ELEMENT COMPOUNDS; WASTE MANAGEMENT; WASTE PROCESSING; YEARS LIVING RADIOISOTOPES; ZIRCONIUM COMPOUNDS; ZIRCONIUM OXIDES; 052001* - Nuclear Fuels- Waste Processing; 360605 - Materials- Radiation Effects

Citation Formats

Clinard, F.W. Jr., Land, C.C., Peterson, D.E., Rohr, D.L., and Roof, R.B. Alpha decay self-damage in cubic and monoclinic zirconolite. United States: N. p., 1981. Web.
Clinard, F.W. Jr., Land, C.C., Peterson, D.E., Rohr, D.L., & Roof, R.B. Alpha decay self-damage in cubic and monoclinic zirconolite. United States.
Clinard, F.W. Jr., Land, C.C., Peterson, D.E., Rohr, D.L., and Roof, R.B. Thu . "Alpha decay self-damage in cubic and monoclinic zirconolite". United States. doi:. https://www.osti.gov/servlets/purl/5913566.
@article{osti_5913566,
title = {Alpha decay self-damage in cubic and monoclinic zirconolite},
author = {Clinard, F.W. Jr. and Land, C.C. and Peterson, D.E. and Rohr, D.L. and Roof, R.B.},
abstractNote = {Samples of primarily-monoclinic /sup 238/Pu-doped zirconolite were stored at ambient temperature to allow accumulation of alpha decay self-damage to a dose of 1 x 10/sup 24/ ..cap alpha../m/sup 3/ (equivalent to a SYNROC age of approx. 10/sup 3/y). Bulk swelling reached 2.3 vol% with no tendency toward saturation, a damage response similar to that observed for cubic Pu-doped zirconolite. X-ray volumetric swelling at 4 x 10/sup 24/ ..cap alpha../m/sup 3/ was 1 vol%, considerably less than that for the cubic material. Changes in cell dimensions differed significantly from those reported by others for a monoclinic natural mineral. Extensive microcracking was observed, and is attributed at least partially to swelling differences between the matrix and minor phases.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Thu Jan 01 00:00:00 EST 1981},
month = {Thu Jan 01 00:00:00 EST 1981}
}

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  • /sup 238/Pu-substituted cubic zirconolite (CaPuTi/sub 2/O/sub 7/) was stored at ambient temperature, 575/sup 0/ K, and 875/sup 0/ K until alpha decay doses of 2.4 to 3.6 x 10/sup 25//m/sup 3/ had been accumulated. The ambient temperature material swelled to a saturation value of 5.5 vol %, and the originally crystalline structure was transformed to one with an amorphous matrix and small domains that had retained their crystallinity. At 575/sup 0/ K, lesser amounts of swelling (4.1 vol %) and transformation were observed, reflecting concurrent partial recovery. The material held at 875/sup 0/ K remained crystalline, swelled only 0.4 volmore » %, and exhibited formation of isolated defect clusters. 5 figures.« less
  • The zirconolite phase of SYNROC nuclear waste was fabricated with 5 mol % /sup 238/PuO/sub 2/ substituted for a like amount of ZrO/sub 2/, in order to induce self-irradiation damage. The resulting product exhibited a matrix of monoclinic zirconolite containing approx. 3.8 mol % PuO/sub 2/ along with roughly 20 vol % of the cubic polymorph with approximately twice the PuO/sub 2/ content of the matrix. After a dose of 2.1 x 10/sup 25/ ..cap alpha.. decays/m/sup 3/ at room temperature (800 days' storage), swelling reached 5.5 vol % and neared saturation. The monoclinic phase became x-ray metamict at approx.more » 1.0 x 10/sup 25/ ..cap alpha../m/sup 3/ after slight atomic rearrangement within the crystalline material. Periodic TEM examination revealed a gradual evolution from the crystalline state to an amorphous condition with residual crystallites, consistent with a model involving conversion by alpha recoil tracks. Optical metallography showed extensive microcracking, attributed to differences in swelling rates of the two zirconolite polymorphs. 7 figures.« less
  • Neutron irradiation was used to simulate alpha-decay damage in zirconolite, resulting in a transformation from the crystalline to the amorphous state at doses of 4--25 {times} 10{sup 19} n/cm{sup 2} (E {ge} 1 MeV). With increasing dose, the radiation damage microstructures resemble damage caused by: (1) alpha-decay of {sup 232}Th and {sup 238}U in natural zirconolites, (2) alpha-decay of {sup 238}Pu or {sup 244}Cm in synthetic samples, and (3) collision cascades in samples irradiated with heavy ions. Heavily damaged zirconolite recovers to a defect fluorite phase on annealing at temperatures up to 1,000 C. The main stage of structural recoverymore » was found to occur at temperatures of 600--800 C. The microstructures after heating depend on the initial level of damage: zirconolite grains with low to moderate levels of damage anneal to imperfect single crystals, whereas heavily damaged grains recrystallize to a polycrystalline microstructure. Complications encountered in this work include the production of fission tracks (due to trace amounts of U) and a non-uniform distribution of damage at higher dose levels (possibly due to electron beam heating).« less
  • Zirconolite (CaZrTi{sub 2}O{sub 7}) is the major host phase for actinides in Synroc, a promising waste form for the immobilization of high-level radioactive waste. The effect of radiation damage on the structure and durability of zirconolite are important to predictive modeling of zirconolite`s behavior in the repository environment and risk assessment. In this study, radiation damage effects in zirconolite were investigated by irradiating samples with 1.5 MeV Kr{sup +} ions using the HVEM-Tandem at Argonne National Laboratory (ANL) and energy loss electron spectroscopy (EELS). The HVEM-Tandem consists of a modified AEI high voltage transmission electron microscope interfaced to a 2more » MV tandem ion accelerator. EELS spectra were collected using a Philips 420 TEM, operated at 120 kV, fitted with a Gatan Model 607 Serial EELS. EELS data were recorded at resolutions of {approximately} 1.0 eV and at a dispersion of about {approximately} 0.25 eV. Selected area diffraction patterns (SADs) of individual grains of various zirconolites were monitored as a function of dose to establish the critical dose for amorphization (D{sub c}). The authors found that (1) D{sub c}(zirconolite) is independent of the atomic weight of dopants in zirconolite and the mean atomic weight of the sample and that (2) the Bragg reflections in SAD patterns which persist to the highest doses are firstly those resulting from the fluorite sublattice and secondly the four (110)-type reflections which lie on the innermost of the two diffuse rings representative of amorphous zirconolite.« less
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