US Patent No. 10,406,847

The U.S. Patent and Trademark Office granted a patent to ISL for its Gravisense technology, which uses gravimeters to measure liquid levels inside vessels non-invasively. Gravisense can measure liquid levels in a doubled-walled vessel in both the internal vessel and in the region between the inside and outside vessel, thus detecting any potential leakage from the inside to the outside vessel, as well as any potential leakage from the outside vessel. Gravisense uses commercial off-the-shelf (COTS) superconducting gravity sensors to measure accurately fluid level in vessels by locating gravimeters at strategic points outside the vessel. Depending on vessel size and sensor placement, Gravisense can measure the fluid level to single centimeter or better accuracy.

Co-Inventor Dr Jeff Ridgeway, ISL’s Research Scientist in Geophysics, noted that “Gravisense is an innovative method that leverages the unprecedented accuracy of modern superconducting, commercially available gravimeters to accurately monitor vessels non-invasively.”
A key innovation of Gravisense is that it measures the liquid levels non-invasively without requiring any penetration of the vessel for measuring or sensing devices. The elimination of these penetrations into the vessel significantly reduces the probability of vessel leakage and simplifies maintenance of level measurement equipment, which can be located and serviced without disturbing the vessels.

Gravisense is specifically applicable to double-walled vessels, such as the pressure vessels and containments used for small modular nuclear plants and for tanks containing hazardous materials. In the nuclear power industry, Gravisense solves the problem of having to penetrate pressurized nuclear vessels or hardened waste vessels, which weakens the vessels and increases the odds of a containment breach. It also solves the problem of routinely extracting sensors from inside the vessels for maintenance or replacement.
Co-Inventor Dan Prelewicz, ISL’s Principal Scientist in Nuclear, summed up Gravisense’s utility and observed that the “invention will facilitate the process of safely isolating hazardous materials in aging waste storage tanks, in enhancing the attractiveness of small modular reactors, and in any other application where multiple wall tanks are utilized.”