15.1. Comparisons between theory and experiments

Although as we have seen, modern HTR calculations do not make use of any experimental correlation, many experiments have been performed in order to test the accuracy of the calculational methods and data used for HTR design.

Zenith I

These experiments started in 1959 with the zero energy Zenith I reactor in Winfrith which reached temperatures up to 800°C.(1 3) The experiments included criticality, temperature coefficient, flux distributions, integral and differential (time of flight) spectrum measurements, fine structure, etc. These experiments have been performed on the U-Th systems, while later the Zenith reactor has been used for measurements on Pu-Th systems.

Dragon

Although not designed for physics experiments the Dragon reactor experiment provided, and still provides, a considerable amount of valuable data, first on U-Th systems and later on low enriched U systems.

Calculations on the Dragon reactor are difficult because of the small size and irregular nature of the core, but in spite of that it has been possible to analyse some zero energy experiments with a good accuracy. Reactivity was predicted to within 200mNile.<4)

Measurements of fast neutron damage have been performed and compared with the fast flux obtained from routine core calculations (see § 8.12). Physics measurements on highly irradiated fuel are under way.’5’