Analysis of Wolsong-1 Reactor Power Pulses with Boron in Moderator at Plutonium Peak

The restart of the Wolsong-1 CANDU 6 reactor (W- 1) after the major refurbishment project including replacement of the pressure tube is scheduled for spring 2011. After the refurbishment, the reactor is due to be operated based upon the Improved Technical Specifications (ITS) that are in the finalization phase for the regulatory approval. During the course of preparing ITS, it is felt that the operation of the W-1 reactor during the time period with boron and/or gadolinium in the moderator system should be supported with the detailed analysis results of power pulses so that the Limiting Condition of Operation (LCO) selection base, which corresponds to Criterion 2 (Design Basis Accident/Transient Safety Analysis. Initial Conditions) of Article 2008-10, as applied to the design of ITS is satisfactorily met. Thus, a study is conducted in the present paper as a preliminary step to the accomplishment of the comprehensive compilation of power pulse analyses for various scenarios related to the situations with boron in the moderator system that are expected to be encountered during reactor operations. In consideration of LCO selections for ITS, this paper specifically deals with a case when the boron concentration in the moderator system would reach the maximum value at plutonium peak of initial core as it will be the case for the W-1 reactor. In the following, the technical background of consequences resulting from the presence of boron in the moderator system in the context of safety aspects is briefly described with respect to the power pulse during a transient accompanied by the insertion of positive reactivity worth into the core. Then, the model used for simulations is described followed by the discussion of results and some conclusions