On the evening of December 18, 2007, a night shift process operator cleaned and dried the reactor in
preparation for a new MCMT batch. At about 7:30 am on December 19, the day shift process operator
began manufacturing Batch 175 from the control room adjacent to the process line. He likely followed
the routine batch procedures, loading the reactor with the specified quantities of raw materials using an
automated process control system (Section 3.2). An outside operator hand-loaded the reactor with blocks
of sodium metal, then sealed the reactor. At about 11:00 am, the process operator began heating the batch
to melt the sodium and initiate the chemical reaction, while monitoring the temperature and pressure on
the process control screen.
Once the sodium melted, at 210°F (98.9°C), the process operator likely started the mixer (agitator).
Mixing the raw materials increased the reaction rate, creating heat. Heat from the reaction and the
heating system continued raising the temperature in the reactor. At a reaction temperature of about 300°F
(148.9°C), the process operator likely turned off the heating system as specified in the procedure, but heat
from the reaction continued increasing the mixture temperature