Patent Number: 
Section: 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            E      →        12    =                    Gm        2                                                                  r              →                        12                                    2              ⁢                  r        ^            12      over a source fluid mass's entire geometry, calculating a gravity signal via at least one gravity meter due to a change in fluid levels using the equationdV=RdRdθdZ, andthe finite element mass (m2) being fluid density, ρ times the change in volume, dV: m2=ρdV. 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 comprisingdetecting 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, anddetecting 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.