Radioactivity Release Versus Probability for a Steam Generator Tube Rupture Accident

A calculation of the probability distributions for the radioactive releases of ¹³¹I and ¹³³Xe in a steam generator tube rupture accident is given; the effects of iodine spiking are included. The accident sequence considered involves loss of off-site power after the steam generator tube rupture. Two models are considered for iodine release, one of which yields upper bound releases, and the other of which is our best-estimate model. With the best-estimate model, the probability of a ¹³¹I release >2 Ci is 1 × 10⁻⁶ per reactor-year. With the upper bound model, the probability of a ¹³¹I release >66 Ci is 1 × 10⁻⁶ per reactor-year. The probability of a release exceeding 600 Ci of ¹³³Xe is 2 × 10⁻⁶ per reactor-year.