A system for controlling the power level of a natural circulation boiling water nuclear reactor (NCBWR) may include a heating subsystem for heating feedwater flowing into an annulus of the NCBWR to increase the temperature of recirculation water flowing through the core above a predetermined recirculation water operating temperature. Additionally the system may include a temperature sensor operable to sense the temperature of the feedwater flowing into the annulus. The temperature sensor is communicatively connected to a temperature controller operable to command the heating subsystem to increase the temperature of the feedwater flowing into the annulus to a requested temperature above a predetermined operating temperature of the feedwater flowing into the annulus. By increasing the temperature of the feedwater flowing into the annulus, the temperature of the recirculation water is increased above the predetermined recirculation water operating temperature causing a reduction in the power level generated by the NCBWR core.

The apparatus includes a flowmeter coupled a surface exposed to a flow channel. The flowmeter monitors a flow of coolant. The flowmeter includes a first temperature sensor that generates first temperature data based on measuring a first temperature of a first flowstream, a heating element coupled to the first temperature sensor where the heating element applies heat to the first temperature sensor through an interface, a second temperature sensor generates second temperature data based on measuring a second temperature of a second flowstream, the second temperature sensor being spaced apart from the heating element, and the second temperature sensor being at least partially insulated from the heating element so the second temperature data generated by the second temperature sensor is independent of heat generated by the heating element. A processor calculates a flowrate of the coolant based on the second temperature data and a temperature of the coolant fluid.

The apparatus includes a flowmeter coupled a surface exposed to a flow channel. The flowmeter monitors a flow of coolant. The flowmeter includes a first temperature sensor that generates first temperature data based on measuring a first temperature of a first flowstream, a heating element coupled to the first temperature sensor where the heating element applies heat to the first temperature sensor through an interface, a second temperature sensor generates second temperature data based on measuring a second temperature of a second flowstream, the second temperature sensor being spaced apart from the heating element, and the second temperature sensor being at least partially insulated from the heating element so the second temperature data generated by the second temperature sensor is independent of heat generated by the heating element. A processor calculates a flowrate of the coolant based on the second temperature data and a temperature of the coolant fluid.

In a sodium fast reactor, a bypass pipe is fluidly coupled to the primary sodium pump discharge and diverts a portion of the primary sodium coolant to an instrument assembly. The bypass pipe routes flowing sodium upward toward the reactor head where it fluidly couples to the instrument assembly. The instrument assembly includes an instrument tank and selectively swappable instrument modules. The instrument modules can be configured to measure flow, pressure, temperature, and fluid level, among other things. The instrument assembly is located relatively close to the reactor head and close to the sodium level in the sodium pool and is accessible from above the reactor head for quick and efficient removal and replacement of the entire instrument assembly or individual instruments.

A digital protection system includes a process protection system having at least two channels and a reactor protection system having at least two trains. The process protection system includes, in one channel, first and second comparative logic controllers of different types that are mutually independent of each other and that respectively receive process variables as inputs and each outputting comparison logic results. The reactor protection system includes, in one train, first and second concurrent logic controllers of different types that are mutually independent from each other and that respectively receive the comparison logic results as inputs and each outputting concurrent logic results. The reactor protection system includes initiation circuits, each circuit including a plurality of relays connected in series and a plurality of relays connected in parallel. One series-connected relay is controlled by one of the two different concurrent logic results, and one parallel-connected relay is controlled by the other.

A digital protection system includes a process protection system having at least two channels and a reactor protection system having at least two trains. The process protection system includes, in one channel, first and second comparative logic controllers of different types that are mutually independent of each other and that respectively receive process variables as inputs and each outputting comparison logic results. The reactor protection system includes, in one train, first and second concurrent logic controllers of different types that are mutually independent from each other and that respectively receive the comparison logic results as inputs and each outputting concurrent logic results. The reactor protection system includes initiation circuits, each circuit including a plurality of relays connected in series and a plurality of relays connected in parallel. One series-connected relay is controlled by one of the two different concurrent logic results, and one parallel-connected relay is controlled by the other.

Vibration-based flowmeters are useable in inaccessible nuclear reactor spaces. Flowmeters include an extension that blocks fluid flow in a path and a detector that detects vibrations caused by vortex shedding in the fluid flow around the extension. The detected frequency of the vibrations determines the flow rate. A Strouhal number may be used to calculate the flow speed using extension surface diameter and detected vortex shedding frequency. Several extensions may cover a range of frequencies and flow speeds. Pipe-organ-type flowmeters include a passage with an opening constricted, and subsequent widening section. An extension and outlet that create turbulence in the flow at the outlet create a standing wave and vibration in the extension and/or entire flowmeter. A flow rate of the fluid through the flowmeter can be calculated using length of the passage and/or known properties of the fluid. Multiple, flowmeters of customized physical properties and types are useable together.

Vibration-based flowmeters are useable in inaccessible nuclear reactor spaces. Flowmeters include an extension that blocks fluid flow in a path and a detector that detects vibrations caused by vortex shedding in the fluid flow around the extension. The detected frequency of the vibrations determines the flow rate. A Strouhal number may be used to calculate the flow speed using extension surface diameter and detected vortex shedding frequency. Several extensions may cover a range of frequencies and flow speeds. Pipe-organ-type flowmeters include a passage with an opening constricted, and subsequent widening section. An extension and outlet that create turbulence in the flow at the outlet create a standing wave and vibration in the extension and/or entire flowmeter. A flow rate of the fluid through the flowmeter can be calculated using length of the passage and/or known properties of the fluid. Multiple, flowmeters of customized physical properties and types are useable together.

The method includes generating first temperature data at a first temperature sensor based on a temperature of a first flowstream of a coolant fluid in a flow channel and heat transfer to the first temperature sensor from a heating element, the heating element being coupled to the first temperature sensor at an interface, the first temperature data indicating a first temperature measured by the first temperature sensor, generating second temperature data at a second temperature sensor based on a temperature of a second flowstream of the coolant fluid in the flow channel and independently of heat generated by the heating element, the first flowstream and the second flowstream running parallel to each other, the second temperature sensor being insulated from the heating element, the second temperature data indicating a second temperature measured by the second temperature sensor.

The method includes generating first temperature data at a first temperature sensor based on a temperature of a first flowstream of a coolant fluid in a flow channel and heat transfer to the first temperature sensor from a heating element, the heating element being coupled to the first temperature sensor at an interface, the first temperature data indicating a first temperature measured by the first temperature sensor, generating second temperature data at a second temperature sensor based on a temperature of a second flowstream of the coolant fluid in the flow channel and independently of heat generated by the heating element, the first flowstream and the second flowstream running parallel to each other, the second temperature sensor being insulated from the heating element, the second temperature data indicating a second temperature measured by the second temperature sensor.