Gravity-based, non-invasive reactor system and method for coolant inventory monitoring

• US 10,460,847 B2
• Filed: 01/17/2017
• Issued: 10/29/2019
• Est. Priority Date: 01/19/2016
• Status: Active Grant

• Current Assignee: Information Systems Laboratories, Inc.
• Original Assignee: Information Systems Laboratories, Inc.
• Inventors: Bloom, Scott Harris, Prelewicz, Daniel Adam, Ridgway, Jeffrey Richard
• Primary Examiner(s): Gibson, Randy W
• Assistant Examiner(s): Kidanu, Gedeon M
• Application Number:
  US15/407,509
• Publication Number:
  US 20170206987A1
• Time in Patent Office: 1,015 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. A method of determining a loss or gain of fluid from a first and second concentric container module, the method comprising:

mounting a first gravity meter proximate to one of a vertical side and a top of the second concentric container module, the second concentric container module being external to the first concentric container module, the first concentric container module normally containing a mass of fluid, the first gravity meter being mounted above the mass of fluid normally contained in the first concentric container module, the first gravity meter for measuring a first time series of gravity signals, the first time series of gravity signals measuring a change in null of the mass of fluid normally contained in the first concentric container module,

mounting a second gravity meter proximate to one of the vertical side and at the bottom of the second concentric container module, the second gravity meter mounted below the mass of fluid normally contained by the first concentric container module, the second gravity meter for measuring a second time series of gravity signals comprising a different change in pull of the mass of fluid normally contained in the first concentric container module responsive to a vertical distance between the first and second gravity meters,

determining by a computer processor a change in gravimetric pull of the mass of fluid normally contained by the first concentric container module, the change in gravitational pull of the mass of fluid comprising;

subtracting the second timer series of gravity signals from the first time series of gravity signals;

result of the subtraction representing excludable changes in pull of the mass of fluid normally contained in the first concentric module measured over time due to expected changes in at least one of tides, atmosphere, a value of drift of one of the first gravity meter and the second gravity meter and groundwater levels, the subtraction eliminating noise effects of recurring events comprising at least one of the changes in tides, changes in atmosphere, changes in drift of one of the first gravity meter and the second gravity meter and changes in groundwater levels,

calculating, responsive to the subtraction, a first center of mass of the fluid in a combination of the first and second concentric container modules at a first point in time via the gravity signals output by the first and second gravity meters and calculating a second center of mass of the fluid in the first and second concentric container modules at a second point in time later in time than the first point in time,

responsive to a difference between calculations of the first center of mass and the later in time second center of mass, evaluating, responsive to the subtractions, the gravity signals over time measured by the first and second gravity meters to determine an occurrence of one of a leak from the first concentric container module to the second concentric container module and a leak to outside the second concentric container module via a value or center of mass over time falling below one or another of first and second predetermined values.

2. The method of determining a loss or gain of fluid from first and the second concentric container modules of claim 1 further comprising:

low-pass filtering the first and second time series of gravity signals of the first and second gravity meters to remove high-frequency noise to aid in improving accuracy.

3. The method of determining a loss or gain of fluid from the first and the second concentric container modules as recited in claim 1 further comprising:

mounting a third gravity meter proximate to one of the first concentric container module and the second concentric container module and horizontal to and at a predetermined distance from the first and second gravity meters, one of the first, second and third gravity meters for measuring a third time series of gravity signals, and eliminating noise effects of recurring events responsive to changes in groundwater levels by differentiating the first, second and third time series of gravity signals.

4. The method of determining a loss or gain of fluid from the first and the second concentric container modules as recited in claim 1, further comprising:

defining m₂ as a point mass of a source mass of fluid and integrating the equation

5. The method of determining a loss or gain of fluid from the first and the second concentric container modules as recited in claim 1 further comprising:

mounting a third gravity meter one of vertically and horizontally distant from the first and second gravity meters for removal of common-mode noise.

6. The method of determining a loss or gain of fluid from the first and the second concentric container modules as recited in claim 1 further comprising:

differentiating among an internal loss of fluid from the first concentric container module, an external loss of fluid from the second concentric container module, and a normal or abnormal gain or loss of fluid occurring during normal regulation of fluid level of the first concentric contain module.

7. The method of determining a loss or gain of fluid from the first and the second concentric container modules of claim 1 further comprising:

measuring one of fluid temperature of fluid normally contained in the first concentric container module, pressure, and in-flow rates and out-flow rates of fluid flow to or from thirst concentric container module via at least one sensor of at least one of the first and second gravity meters at a given point in time.

8. The method of determining a loss or gain of fluid from one of fluid from the first and the second concentric container modules as recited in claim 7 further comprising:

calculating first and second gravity signal values by the first and second gravity meters at the given point in time responsive to measuring one of fluid temperature of fluid normally contained in the first concentric container module, pressure, and in-flow rates and out-flow rates of fluid flow to or from the first concentric container module.

9. The method of determining a loss or gain of fluid from the first and the second concentric container module as recited in claim 1 wherein the first concentric container module comprises a nuclear reactor container module containing fluid.

10. The method of determining a loss or gain of fluid from at first and the second concentric container modules as recited in claim 9 wherein the nuclear reactor container module comprises a nuclear reactor core at its bottom.

11. The method of determining a loss or gain of fluid from the first and the second concentric container modules as recited in claim 9 further comprising:

detecting a variation from a predetermined expected range of fluid level of a pressurizer of a nuclear reactor comprising the nuclear reactor container module containing fluid.

12. The method of determining a loss or gain of fluid from the first and the second concentric container modules as recited in claim 9 further comprising

detecting a difference between a rate of inflow of water to the nuclear reactor container module, the nuclear reactor container module comprising a containment pressure vessel of the nuclear reactor container module, and

detecting 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 container module within a level regulation band comprising an upper level and a lower level limit.

13. The method of determining a loss or gain of fluid from the first and the second concentric container modules as recited in claim 9 further comprising:

comparing the location of the center of mass of the fluid in the nuclear reactor container module with an estimated location of a center of mass of the fluid in the nuclear reactor module as determined by the computer processor from gravity signal data received from sensors of the first and second gravity meters.