Consequences of Steam Generator Tube Failures at the Pickering "B" Nuclear Generating Station

Abstract

It has been shown that postulated steam generator tube failure accidents at the Pickering 'B' nuclear generating station have only minor radiological consequences. The accidents can be safely terminated by the automatic actions of reactor safety systems and by manual actions of plant operators.

Using analytical and numerical techniques, accidents involving the rupture of a single tube and multiple tubes have been studied. Thermal hydraulic characteristics of the events were used to model the transport of 1-131 and tritium from the primary heat transport system to the damaged steam generator and thence to the steam piping outside containment. Individual and population whole body doses were calculated based upon a maximum expected tritium concentration in the reactor coolant. Thyroid doses were calculated assuming a typical 1-131 concentration in the coolant at the time of the accident.

Exposures following the considered failures were within the single failure limit set by the Atomic Energy Control Board. The work was done as a licensing analysis and thus pessimistic assumptions were used to ensure that the most severe radiological consequences were obtained for the cases studied.