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Gadolinium Gadolinium I 3500Synthesis and Characterization of Gadolinium Phosphate Neutron Absorber. -GdPO 4 ·H 2 O is synthesized from aqueous solutions of GdCl 3 or Gd(NO 3 ) 3 and H 3 PO 4 . The samples are characterized by XRD and DTA. The powders are extremely insoluble in water. Calcination at 800-1000°C results in the formation of GdPO4 in a monazite (monoclinic) crystal structure. GdPO4 is an excellent candidate for a chemically stable, water-insoluble neutron absorber for inclusion in spent nuclear fuel canisters. -(LESSING*, P. A.; ERICKSON, A. W.; J.

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An equation was developed to predict fracture toughness of green powder compacts. The model combines crack tip toughness predicted by Kendall's model with crack tip shielding due to bridging of moisture meniscuses across the crack.The model predicts that crack tip shielding due to moisture should be dominant. Fracture tests on ceria green pellets verified that storing pellets at a high relative humidity (98% RH) for an extended period of time led to fracture strength more than double those stored at lower RH. However, at lower RH there is no significant increase in fracture strength with increased RH as predicted by the model.The lower strength at low RH is due to insufficient capillary and surface forces but may also be related to the lack of sufficient adsorbed moisture to form bridging meniscuses. The high green strengths achieved by storing pellets at a high RH suggest a method of strengthening green parts without adding binder. K E Y W O R D Sabsorption/absorbents, green body, pressing, strength, toughness