Speaker
Description
In pressurized water reactors (PWRs), including VVER-type reactors, slow changes in reactivity are controlled using boric acid dissolved in the coolant of the primary circuit. Dissolved boric acid is also one of the solutions used by the nuclear industry to prevent any criticality events in spent fuel pools.
Framatome's Continuous Measurement of Boron Concentration (COMBO) allows the early detection of disturbances on an almost real-time basis. The measuring principle is based on the absorption of neutrons by the isotope B-10, which depends on the boron content of the coolant. Neutrons from an Am-Be source diffuse through the coolant and a portion of these neutrons is absorbed by the B10 content. The remaining neutron radiation is then detected by suitably positioned counter tubes. For signal acquisition and processing TELEPERM XS – Framatome’s instrumentation and control platform for safety-related applications – is used.
Today it is still standard to use Polyethylen (PE) as a moderator in the Boronmeter devices which limits the temperature range due to the softening temperature of PE to 0 - 100°C.
Post-Fukushima requirements for VVERs include the new request to enable a boron concentration measurement of the primary coolant during station black out and / or a seismic event at higher temperatures. Also calculation algorithms in current nuclear power plant design can be replaced with an online measurement, directly at the location of interest on the circuit, where the temperature range is not limited to 0-100°C, giving the relevant value online to the processing systems.
In this talk Framatome's safety related qualified Hot COMBO is presented, a measurement device using Graphite as moderator and covering the total temperature range of NPP coolants, while still keeping the strong performance requirements (accuracy, response time, seismic events etc.) for this kind of safety related applications.
