Subchannel analysis of fuel temperature and departure of nucleate boiling of TRIGA Mark I

An evaluation of fuel temperature and departure of nucleate boiling as a function of bulk pool temperature was performed at the Texas A&M University Nuclear Science Center's TRIGA Mark I reactor. A subchannel analysis code was written with the support of experimentally determined correlations, including the development of a gap conductance model. The code was validated for predicting peak fuel temperature at all operational power levels. The peak fuel temperature was calculated using different correlations for forced and natural convection flows for pool temperatures of 30 °C and 60 °C. The forced convection correlation predicted a fuel temperature rise of 2 °C for the difference in pool temperatures, contrary to the predicted rise of 26 °C from natural convection relationships. Experimental data shows that the relationship of fuel temperature rise with increasing pool temperature is more accurately represented by the natural convection correlation. The peak fuel temperature, for the validated natural convection relationship, is predicted to be 441 °C and 457 °C at a pool temperature of 30 °C and 60 °C, respectively. The minimum departure of nucleate boiling ratio is calculated as 2.14 and 1.72 for a pool temperature of 30 °C and 60 °C, respectively, using the Bernath correlation.