Modeling The Temperature of a Calorimeter at Clab : Considering a Thermodynamic Model of The Temperature Evolution of The Calorimeter System 251

• Main Author: Ekman, Johannes
• Format: Others
• Language: English
• Published: Uppsala universitet, Tillämpad kärnfysik 2021
• Subjects: calorimetry; calorimeter; System 251; temperature evolution; spent nuclear fuel; SNF; MATLAB; SERPENT2; Clab; nuclear decay heat; calibration measurements; thermodynamic model; gamma escape fraction; mass correction; electric heater; three component system; system of ordinary differential equations; eigenvalues; eigenvalue estimation; temperature increase method; polynomial approximation of mass correction; sensitivity of mass correction; calorimeter heat capacity; mass correction uncertainty; calorimeter calibration curve; monoenergetic gamma spectrum; curve fitting of temperature as function of time; Subatomic Physics; Subatomär fysik; Other Physics Topics; Annan fysik
• Online Access: http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-461926

It is important to know the heat generated due to nuclear decay in the final repository for spent nuclear fuel. In Sweden, the heating powers generated in spent nuclear fuels are currently measured in the calorimeter System 251 at the Clab facility, Oskarshamn. In order to better measure, and increase understanding, of the temperature measurements in the calorimeter, a simple thermodynamic model of its temperature evolution was developed. The model was described as a system of ordinary differential equations, which were solved, and the solution was applied to calibration measurements of the calorimeter. How precise the model is, how its parameters affect the model, et cetera, are addressed. How the temperature evolution of the system changes as the values of parameters in the model are changed is addressed. The mass correction of the calorimeter could be estimated from this model, which validated the established mass correction of the calorimeter. How the measurement results from the calorimeter would be affected if the volume of the calorimeter was changed was also considered. Additionally, gamma radiation escape from the calorimeter without being detected as heat in the calorimeter. The gamma escape energy fraction was estimated by SERPENT simulations of the calorimeter, as a function of the initial photon energy. The gamma escape was also estimated for different values of the radius of System 251.