Lessons in solid-state kinetics from nuclear energy research

ABSTRACTThis paper presents radiocarbon (14C) variations in the atmosphere from Ramnicu Valcea, Romania. The samples were collected in the vicinity of the Experimental Pilot Plant for Tritium and Deuterium Separation (PESTD) from the Institute of the Cryogenics and Isotopic Technologies (ICSI) placed about 10 km south from the Ramnicu Valcea city (Romania), in the Govora industrial area. This facility is an experimental project in the national nuclear energy research program, which has the aim of developing technologies for tritium separation from heavy water. It should be noted that in the Govora industrial area operates a 315 MW coal-fired thermoelectric power plant and two chemical plants. In order to determine radiocarbon activity in the atmosphere, samples were collected monthly by absorption of CO2 into sodium hydroxide (NaOH) at Ramnicu Valcea. In addition, control materials (tree leaves, wild vegetation, and grapes), known activity standards, and process blanks (marble) were analyzed. Radiocarbon measurements were performed using the direct absorption method and liquid scintillation counting. The measured Δ14C levels varied between –57‰ and 61‰. The results have a decreasing trend, but due to local influence caused by the continuous production of fossil CO2, we cannot observe Δ14C seasonal variations.

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3rd Int. Symp. on Advanced Nuclear Energy Research

Journal of Nuclear Science and Technology ◽

10.1080/18811248.1990.9731279 ◽

1990 ◽

Vol 27 (10) ◽

pp. 984-984

Keyword(s):

Nuclear Energy ◽

Energy Research

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The Prout-Tompkins rate equation in solid-state kinetics

Thermochimica Acta ◽

10.1016/s0040-6031(96)03119-x ◽

1997 ◽

Vol 300 (1-2) ◽

pp. 93-106 ◽

Cited By ~ 84

Author(s):

Michael E. Brown

Keyword(s):

Solid State ◽

Rate Equation ◽

Solid State Kinetics

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Kinetic analysis of solid-state processes

Journal of Materials Research ◽

10.1557/jmr.2001.0255 ◽

2001 ◽

Vol 16 (6) ◽

pp. 1862-1871 ◽

Cited By ~ 73

Author(s):

Jiří Málek ◽

Takefumi Mitsuhashi ◽

José Manuel Criado

Keyword(s):

Solid State ◽

Kinetic Analysis ◽

Crystallization Process ◽

Good Description ◽

Simple Method ◽

Solid State Kinetics ◽

Kinetics Of ◽

Nonisothermal Conditions ◽

Two Parameter

A simple method for kinetic analysis of solid-state processes has been developed. A criteria capable of classifying different processes is explored here with a view toward visualizing the complexity of solid-state kinetics. They provide a useful tool for the determination of the most suitable kinetic model. The method has been applied to the analysis of crystallization processes in amorphous ZrO2 and RuO2. It is found that the crystallization kinetics of as-prepared sample exhibits a complex behavior under nonisothermal conditions. This is probably due to an overlapping of the nucleation- and crystal-growth processes at the beginning of crystallization. As a consequence, the Johnson–Mehl–Avrami nucleation-growth model cannot be applied. A two-parameter autocatalytic model provides a good description of the crystallization process under isothermal and nonisothermal conditions.

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