Thermalhydraulic Assessment of the Pickering NGS ‘B’ Feed and Bleed System for the Hot Boiler Chemical Clean (Siemens Process)

Abstract

The Hot Boiler Chemical Clean (HBCC) process from Siemens, to be used in PNGS, requires that the Heat Transport System (HTS) temperature be maintained in the range160 to 170 oC for several days. To achieve these thermalhydraulic condition, the core decay power and the pump power of the main circulating pumps in a 3-3 configuration are employed to warm up the HTS from approximately 38 oC to 170 oC. At this point, high Bleed bias is applied to the signal of the HTS pressure controller to provide high Feed and Bleed flows, which are used to control the HTS temperature by means of the Bleed Cooler.To address any concern posed by these infrequently used HTS thermalhydraulic conditions, a detailed thermalhydraulic model of the Feed and Bleed System, that alsoincludes the Gland Supply, Gland Return and Purification systems, was developed for the TUF code to determine the suitability of the Feed and Bleed System to conduct theHBCC. The model was then used to estimate the parameters such as Feed and Bleed flows, valve openings, pressure and temperature distributions throughout the Feed and Bleed System required for the application of HBCC.