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Author Topic: Dysprosium (Z=66)  (Read 6256 times)

Offline Astronuc

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Dysprosium (Z=66)
« on: June 06, 2004, 09:48:48 AM »
Dysprosium has a good thermal neutron absorbtion cross-section and an even better resonance absorption cross-section.  The Russians have developed a material for control rods - dysprosium titanate - as opposed to Ag-In-Cd (which has lower melting point and swells with irradiation) or B4C which preduces helium due to an (n,alpha) reaction.  Hf has been used by its dense, and during operation, it absorbs hydrogen and swells.

Dysprosium titanate as an absorber material for control rods

Risovany, V.D.a; Varlashova, E.E.a; Suslov, D.N.a
a. State Scientific Center of Research Institute of Atomic Reactors, 433510 Dimitrivgrad-Ulyanovsk region, Russian Federation

Disprosium titanate is an attractive control rod material for the thermal neutron reactors. Its main advantages are: insignificant swelling, no out-gassing under neutron irradiation, rather high neutron efficiency, a high melting point (1870°C), non-interaction with the cladding at temperatures above 1000°C, simple fabrication and easily reprocessed non-radioactive waste. It can be used in control rods as pellets and powder. The disprosium titanate control rods have worked off in the MIR reactor for 17 years, in VVER-1000 – for 4 years without any operating problems. After post-irradiation examinations this type of control rod having high lifetime was recommended for the VVER and RBMK. The paper presents the examination results of absorber element dummies containing dysprosium titanate, irradiated in the SM reactor to the neutron fluence of 3.4×1022 cm-2 (E>0.1 MeV) and, also, the data on structure, thermal–physical properties of dysprosium titanate, efficiency of dysprosium titanate control rods.

Journal of Nuclear Materials 
Vol: 281, Issue: 1, September 2, 2000 pp.84-89

==================================

and if that's not enough -

Dysprosium titanate and holmium titanate have interesting magnetic properties, which are being investigated in the field of "frustrated magnets".

When "frustrated" by their arrangement, magnetic atoms surrender their individuality, stop competing with their neighbors and then practice a group version of spin control—acting collectively to achieve local magnetic order—according to scientists from the Commerce Department's National Institute of Standards and Technology, Johns Hopkins University and Rutgers University writing in the Aug. 22, 2002, issue of the journal Nature. (Source - http://www.nist.gov/public_affairs/releases/n02-13.htm)


http://www.grenoble.cnrs.fr/hfm2003/program/program.html

Ordering and partial ordering in holmium titanate and related systems (http://arxiv.org/abs/cond-mat/0009265)
Authors: R. Siddharthan, B. S. Shastry, A. P. Ramirez
Comments: 10 pages, latex, 16 eps figures
Subj-class: Statistical Mechanics

We take another look at two compounds which have been discussed as possible realizations of ``spin ice'', namely holmium titanate and dysprosium titanate.  As we have earlier observed, holmium titanate does not display ice-like behaviour at low temperatures because the long ranged dipolar interactions between spins are strong compared to the nearest neighbour interactions. We show, analytically, that the true ground state of this system must be fully ordered, but simulations only reach partially ordered states because there are infinite energy barriers separating these from the true ground state.  We also show that the true ground state of our model of dysprosium titanate is also fully ordered, and offer some explanations as to why simulations and experiments show ice-like behaviour.  We discuss the effect on these systems of an applied magnetic field.  Finally, we discuss several other models which show similar partial or full ordering in their ground states, including the well known Ising model on the fcc lattice.
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