Abstract: A method to determine a global core reactivity bias and the corresponding estimated critical conditions of a nuclear reactor core prior to achieving reactor criticality. The method first requires collection and evaluation of the inverse count rate ratio (ICRR) data; specifically, fitting measured ICRR vs. predicted ICRR data. The global core reactivity bias is then determined as the amount of uniform reactivity adjustment to the prediction that produces an ideal comparison between the measurement and the prediction.

Abstract: A method to determine a global core reactivity bias and the corresponding estimated critical conditions of a nuclear reactor core prior to achieving reactor criticality. The method first requires collection and evaluation of the inverse count rate ratio (ICRR) data; specifically, fitting measured ICRR vs. predicted ICRR data. The global core reactivity bias is then determined as the amount of uniform reactivity adjustment to the prediction that produces an ideal comparison between the measurement and the prediction.

Abstract: A solid state semiconductor neutron detector that automatically varies its sensitivity to provide a pulsed output over the entire range of operation of a nuclear reactor. The sensitivity is varied by changing the thickness or makeup of a converter layer that emits charged particles to the active region of the semiconductor surface.

Abstract: A solid state semiconductor neutron detector that automatically varies its sensitivity to provide a pulsed output over the entire range of operation of a nuclear reactor. The sensitivity is varied by changing the thickness or makeup of a converter layer that emits charged particles to the active region of the semiconductor surface.

Abstract: The present invention is a detector assembly for a nuclear reactor which includes platinum detector segments (30-40) axially distributed end to end within a reactor assembly and vanadium detector segments (42-52) spatially congruent in the same assembly. The vanadium detectors calibrate the platinum detector signals to remove the flux contributions of fission products. A full length vanadium detector (62) and a full length platinum detector (90) can be substituted and used to determine the compensation for the platinum detector segments (30-40). The compensated platinum detector signals, wherein compensation consists of isolating that portion of the total platinum detector signal that is directly proportional to the current local heat deposition rate in the reactor fuel, can be used for reactor core protection purposes.

Abstract: The present invention is a system which determines nuclear reactor control rod axial position using a deviation signature database generated from a current or reference signal pattern produced by one or more strings of axially dispersed fixed incore detector sections in the reactor core. The deviation signature database is produced by assuming deviant axial positions for the control rods in the core, calculating expected detector signals for the assumed positions and storing the deviation of expected signals from a calibration reference along with corresponding assumed rod positions. The signature database is periodically updated to take into account changed core conditions. When a change in detector responses is detected the system performs a signature analysis of the deviations in the signature database using the current deviation from the reference to search for the closest match.

Abstract: The present invention is a system that updates a pressurized water reactor core model, or data file describing the core, periodically using measured values determinable from core instrumentation. The system starts with a calibrated model calibrated from a flux map and a boron concentration measurement both determined monthly. Reactor system measurements are performed and the model is updated from the measurements using a standard depletion calculation. Some of the measured values are also used to determine measured actual values of axial offset and pinch. Standard neutronics equations are used to calculate analytical values of axial offset and pinch from the model, and the measured and calculated values are compared. If a deviation beyond a certain magnitude is detected, buckling coefficients in the model are adjusted to compensate for model drift. The updated model is stored and a time-out period is entered until it is time for another drift compensation cycle to start.

Abstract: The present invention obtains enthalpy rise deviations in core power distribution using core exit thermocouples 18 and an inlet temperature detector 20. The enthalpy rise deviations are used to determine control rod position change relative a rod reference position. Because rod position change is linear with respect to enthalpy deviation, the change can be determined from the slope using the deviation. By adding the change to a reference rod position the actual rod position can be determined.

Abstract: A smart reactivity computer is disclosed that processes signals from multiple neutron detectors to generate values of regional core reactivity that are output to a strip chart recorder. The computer compares the regional reactivity values and, when the values are coincident for a period sufficient to satisfy a statistical fit test to a straight line, indicates to the operator that true core reactivity can be determined. The computer determines control rod worth by first fitting a straight line to the coincident portion of the reactivity values. The computer then determines intersections between the straight line and the reactivity value lines produced when the control rods are moved on both ends of the straight line. The difference between intersections for a single control rod movement line determines control rod worth for that movement.

Abstract: The present invention provides a power distribution synthesis system that uses a small number of local axial power distributions determined from less than a full complement of fixed incore neutron detectors and a power sharing map produced from a full complement of core exit thermocouple temperature signals to synthesize the full core power distribution. The localized tilt of the core is determined from the power sharing map and used to remove the tilt from the local distribution. The tilt adjusted local distribution is assigned to symmetric core locations where uninstrumented core power values are determined by interpolation. The interpolated, assigned and tilt corrected local distribution power values are transformed into the three dimensional power distribution using the tilt.

Abstract: A method and apparatus for monitoring and generating on-line, real time displays of two and three dimensional nuclear reactor core power distributions and off-line, periodically updated summaries of three dimensional nuclear reactor core power and burnup distributions is disclosed. The method and apparatus makes use of information obtained from inlet sensors and core-exit thermocouples to produce enthalpy rise values. Flux measurements are combined with enthalpy to produce power values. In one aspect of the invention, deviations from reference values are classified and displayed on a two-dimensional color graphics terminal where the various classifications are displayed according to a color code which enables a rapid and convenient method of analysis of the dynamics of the reactor operation.

Abstract: A calibrator for a pressurized water reactor (PWR) core predictor utilizing a distribution expression for the transverse buckling factor, in a one dimensional diffusion model, which has coefficients correlated with overall neutron balance and with a set of power distribution characterization parameters including axial offset, axial pinch, axial quarters and axial fifths. The coefficients are periodically adjusted incrementally one at a time to produce criticality with the model at measured values of rod position, reactor power level, cold leg temperature and boron concentration until the power distribution characterization parameters calculated from a power distribution generated by the model are within preset tolerances of those from a power distribution measurement generated by movable, or if provided, fixed, incore detectors.