GRAVITY-BASED, NON-INVASIVE REACTOR SYSTEM AND METHOD FOR COOLANT INVENTORY MONITORING

• US 20170206987A1
• Filed: 01/17/2017
• Published: 07/20/2017
• Est. Priority Date: 01/19/2016
• Status: Active Grant

• Current Assignee: Information Systems Laboratories, Inc.
• Original Assignee: Information Systems Laboratories, Inc.
• Inventors: Prelewicz, Daniel Adam, Bloom, Scott Harris, Ridgway, Jeffrey Richard
• Granted Patent: US 10,460,847 B2
• Time in Patent Office: Days
• CPC Class Codes: G01F 23/00 Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm
• CPC Class Codes: G01F 23/20 by measurement of weight, e.g. to determine the level of stored liquefied gas
• CPC Class Codes: G01F 23/22 by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water involving the use of floats G01F23/30
• CPC Class Codes: G21C 17/002 Detection of leaks by testing the coolant or the moderator G21C17/04
• CPC Class Codes: G21C 17/035 Moderator- or coolant-level detecting devices indicating or measuring liquid level in general G01F23/00
• CPC Class Codes: G21D 3/001 Computer implemented control
• CPC Class Codes: Y02E 30/30 Nuclear fission reactors

Abstract

A gravity-based, non-invasive method of measuring a level of fluid in a container comprises use of at least one gravity meter located as proximate a center of mass of the fluid as possible. In a nuclear reactor system a method for monitoring the level of fluid in a nuclear reactor module, a report of a loss or gain of fluid within a cylindrical module may be generated from capturing a time series of gravity data from a first gravity meter mounted as an upper gravity meter and a second gravity meter mounted as a lower gravity meter, for example, proximate a cylindrical nuclear reactor module so as not to require any invasive conduit through, for example, a containment pressure vessel (CPV) or a reactor pressure vessel (RPV). In one embodiment, the upper and lower gravity meters are mounted on stable mounts as close to the fluid in the module as possible within a coolant pool or a structure containing cooled air. If a coolant pool of water surrounds a nuclear reactor module, the meters may be housed within a dry housing in the coolant pool such that the meters may be accessed from above the coolant pool and are located as close as possible to the reactor module and its contained mass of fluid.

Claims

1. Apparatus for non-invasive monitoring of a fluid level in a module comprising a first platform mounted proximate a substantially cylindrical module containing a volume of fluid having a center of mass, the substantially cylindrical module being vertically oriented and substantially in line with the gravitational field of the earth, a first gravimeter mounted on the first platform such that that gravimeter is stable and proximate the center of mass of the fluid contained within the cylindrical module, first data leads from the gravimeter for communication of a first time series of gravitational data to a computer processor for processing the gravitational data to determine the location of the center of mass of the fluid in the module over time, and the computer processor for computing the volume of fluid in the substantially cylindrical module over time and one of outputting a signal to allow control of the fluid level by a system that adds and removes fluid and of providing an alert signal when the computed volume of fluid compared with a prior computed volume of fluid over time or an estimated volume of fluid in the module exceeding a predetermined value indicates a significant gain or loss of fluid from the substantially cylindrical module.

2. Apparatus as recited in claim 1 further comprising a second platform mounted below the first platform and proximate the substantially cylindrical module and a second gravimeter mounted on the second platform proximate the bottom of the substantially cylindrical module, and second data leads from the second gravimeter for communication of a second time series of gravitational data to the computer processor for processing the gravitational data, the computer processor for computing the volume of fluid respecting the difference between the first and second time series of gravitational data received from the first and second gravimeters and outputting one of a normal fluid regulation signal and the alert signal when the computed column of fluid when compared with a prior computed volume of fluid indicates one of a gain or loss of fluid and one of a normal and an abnormal flow of fluid from the substantially cylindrical module.

3. Apparatus as recited in claim 1 wherein the first gravimeter and the first platform are located in one of a coolant pool and an air filled building comprising one of air or water proximate to a nuclear reactor module, the coolant pool for cooling a volume of coolant within the nuclear reactor module.

4. Apparatus as recited in claim 1 wherein the gain or loss of fluid comprises a gain of fluid or a loss of coolant fluid from a nuclear reactor pressure vessel (RPV) into a containment pressure vessel (CPV) of a nuclear reactor module.

5. Apparatus as recited in claim 2, the computer processor for outputting an occurrence of a loss of coolant fluid accident via an output device when an amount of coolant lost exceeds a predetermined value over a short period of time or the fluid level falls below a lower limit of a fluid regulation band.

6. Apparatus as recited in claim 5, the computer processor for further calculating a quantity of fluid loss over time for output to the output device.

7. Apparatus as recited in claim 2, the computer processor further having a memory containing computer code for distinguishing a scenario where the reactor pressure vessel loses fluid into a containment pressure vessel and a scenario where the reactor pressure vessel loses fluid (either accidentally in a leak or deliberately in a regulating action) in a CVCS line connected to the reactor module but bypassing the containment vessel, and outputting a result as to which scenario occurs via an output device.

8. Apparatus as recited in claim 7, the apparatus further comprising a fluid temperature sensor for measuring the temperature of fluid in the reactor, a pressure sensor for measuring the pressure of steam in the reactor and line in-flow and out-flow rate sensors for assisting in outputting the results of which scenario occurs.

9. A method of determining a loss or gain of fluid from a container module comprising mounting a first gravity meter proximate to the fluid container module for measuring a first time series of gravity signals, eliminating noise effects of recurring events comprising changes in tides, atmosphere or groundwater levels, calculating a first center of mass of the fluid in the container module at a first point in time and calculating a second center of mass of the fluid in the container module at a second point in time responsive to the first time series of gravity signals, subtracting the value of the two centers of mass of fluid in the container module, and if the difference signal resulting from the subtraction exceeds predetermined values of a regulation band comprising an upper and a lower fluid level for determining a significant loss or gain of fluid, alerting of the significant loss or gain of fluid from the container module.

10. The method of claim 9 further comprising measuring reactor fluid temperature, pressure, in-flow rates and out-flow rates.

11. A method of determining a loss or gain of fluid from a container module of claim 9 further comprising low-pass filtering the first time series of gravity signals to remove high-frequency noise to aid in improving accuracy.

12. A method of determining a loss or gain of fluid from a container module as recited in claim 11 further comprising mounting a second gravity meter proximate to the fluid container module and one of above or below the first gravity meter for measuring a second time series of gravity signals, and eliminating noise effects of recurring events such as changes in groundwater levels by differentiating the first and second time series of gravity data.

13. A method of determining a loss or gain of fluid from a container module as recited in claim 9 further comprising defining m₂ as a point mass of a source mass of fluid and integrating the equation

14. A method of determining a loss or gain of fluid from a container module as recited in claim 12 further comprising mounting a third gravity meter vertically or horizontally distant from the first and second gravity meters for removal of common-mode noise.

15. A method of determining a loss or gain of fluid from a container module as recited in claim 11 further comprising differentiating among an internal loss of fluid from the container module, an external loss of fluid from the container module, and a normal or abnormal gain of loss of fluid occurring during normal regulation of fluid level of the containment module.

16. A method of determining a loss or gain of fluid from a container module as recited in claim 12 wherein the container module comprises a nuclear reactor container module containing fluid.

17. A method of determining a loss or gain of fluid from a container module as recited in claim 16 wherein the container module comprises concentric cylinders, an inner cylinder having a nuclear reactor core at its bottom.

18. A method of determining a loss or gain of fluid from a container module as recited in claim 16 further comprising detecting a variation from a predetermined expected range of fluid level of a pressurizer of the nuclear reactor.

19. A method of determining a loss or gain of fluid from a container module as recited in claim 10 further comprising detecting a difference between a rate of inflow of water to a containment pressure vessel of a nuclear reactor and a rate of outflow of water to the containment pressure vessel, the flow of water regulated by a chemical volume and control system of the nuclear reactor within a level regulation band comprising an upper level and a lower level limit.

20. A method of determining a loss or gain of fluid from a container module as recited in claim 14 further comprising comparing the location of the center of mass of the fluid in the containment vessel with an estimated location of the center of mass of the fluid in the containment vessel as determined by a computer processor.