Passive safety systems cool reactors using surrounding ground as a heat sink. A coolant flow channel may loop around the reactor and then pass outside, potentially through a containment building, into surrounding ground. No active components need be used in example embodiment safety systems, which may be driven entirely by gravity-based natural circulation. The coolant loop may be air-tight and seismically-hardened and filled with any coolant such as water, air, nitrogen, a noble gas, a refrigerant, etc. The ground may include a soil of grey limestone, soft grey fine sandy clay, grey slightly silty sandy gravel, etc. or any other fill with desired heat-transfer characteristics. Coolant fins and/or jackets with secondary coolants may be used on the coolant loop. The coolant loop may be buried at any constant or variable depth, and the reactor and containment may also be buried in the ground.

Sodium-cesium detection systems and methods for the simultaneous detection of both sodium (Na) and cesium (Cs) in gas are provided. The detection systems include two non-identical ionization chambers each having an anode and a cathode that ionize Na and Cs in gas. Each ionization chamber generates a current proportional to the Na and Cs concentration and based on the current, Na concentration and Cs concentration in the gas is determined.

Sodium-cesium detection systems and methods for the simultaneous detection of both sodium (Na) and cesium (Cs) in gas are provided. The detection systems include two non-identical ionization chambers each having an anode and a cathode that ionize Na and Cs in gas. Each ionization chamber generates a current proportional to the Na and Cs concentration and based on the current, Na concentration and Cs concentration in the gas is determined.

A potentiometric oxygen sensor for measuring the oxygen concentration of a liquid metal, including: a metal tube forming at least one sensor body part; an electrochemical subassembly containing an electrolyte, intended to be in contact with the liquid metal, and a reference electrode contained in the electrolyte, the electrolyte being made of yttrium-doped or calcium-doped hafnia (HfO.sub.2), or of thoria (ThO.sub.2), which is optionally yttrium-doped or calcium-doped, or of yttrium-doped or calcium-doped zirconia (ZrO.sub.2), the reference electrode containing at least one metal and its oxide form at the operating temperature of the sensor, an insert made of a transition metal from group 4 of the Periodic Table or an alloy thereof, arranged between the sensor body part and the electrolyte, the insert being attached to the sensor body part and brazed onto the electrolyte by a brazing joint.

A potentiometric oxygen sensor for measuring the oxygen concentration of a liquid metal, including: a metal tube forming at least one sensor body part; an electrochemical subassembly containing an electrolyte, intended to be in contact with the liquid metal, and a reference electrode contained in the electrolyte, the electrolyte being made of yttrium-doped or calcium-doped hafnia (HfO.sub.2), or of thoria (ThO.sub.2), which is optionally yttrium-doped or calcium-doped, or of yttrium-doped or calcium-doped zirconia (ZrO.sub.2), the reference electrode containing at least one metal and its oxide form at the operating temperature of the sensor, an insert made of a transition metal from group 4 of the Periodic Table or an alloy thereof, arranged between the sensor body part and the electrolyte, the insert being attached to the sensor body part and brazed onto the electrolyte by a brazing joint.

System for detecting, in a space being monitored, for example a gap, obstacles to rotation of the rotating plugs during refueling operations. The system includes an ultrasound reflector configured in the form of a ring on which at least one row of vertical cylindrical rods is arranged. The ring is attached to one of the thermal screens surrounding the reactor core, preferably one proximate to the nuclear reactor vessel. The spacing at which the cylindrical rods are arranged in the row is less than the spacing between the assemblies.

Apparatus, systems, and methods for identifying and quantifying chemical components in a high-melting-point liquid. One such method includes: receiving, into a nebulizer assembly, a high-melting-point liquid from a molten liquid conduit; aerosolizing, using the nebulizer assembly, at least a portion of the received high-melting-point liquid; delivering, into one or more instruments, the aerosolized high-melting-point liquid from the nebulizer; and chemically analyzing, using the one or more instruments, the aerosolized high-melting-point liquid.

The method and system for control of oxygen concentration in the coolant of a reactor plant including a reactor, coolant in the reactor, gas system, mass-exchange apparatus, disperser and an oxygen sensor in the coolant have been disclosed. The method includes the following steps implemented by the system: estimation of the oxygen concentration; comparison of the oxygen concentration with the permissible value; if the oxygen concentration is reduced, comparison of the reduction value and\or rate with the corresponding threshold value; if the reduction value and\or rate of oxygen concentration is below the threshold value, activation of the mass-exchange apparatus; if the reduction value and/or rate of oxygen concentration is above the corresponding threshold value, supply of oxygen-containing gas from the gas system to the near-coolant space and/or activation of the disperser. Technical result: improvement of controllability of oxygen concentration in coolant, enhancement of safety and extension of reactor plant operating life.

The method and system for control of oxygen concentration in the coolant of a reactor plant including a reactor, coolant in the reactor, gas system, mass-exchange apparatus, disperser and an oxygen sensor in the coolant have been disclosed. The method includes the following steps implemented by the system: estimation of the oxygen concentration; comparison of the oxygen concentration with the permissible value; if the oxygen concentration is reduced, comparison of the reduction value and\or rate with the corresponding threshold value; if the reduction value and\or rate of oxygen concentration is below the threshold value, activation of the mass-exchange apparatus; if the reduction value and/or rate of oxygen concentration is above the corresponding threshold value, supply of oxygen-containing gas from the gas system to the near-coolant space and/or activation of the disperser. Technical result: improvement of controllability of oxygen concentration in coolant, enhancement of safety and extension of reactor plant operating life.

Passive safety systems cool reactors using surrounding ground as a heat sink. A coolant flow channel may loop around the reactor and then pass outside, potentially through a containment building, into surrounding ground. No active components need be used in example embodiment safety systems, which may be driven entirely by gravity-based natural circulation. The coolant loop may be air-tight and seismically-hardened and filled with any coolant such as water, air, nitrogen, a noble gas, a refrigerant, etc. The ground may include a soil of grey limestone, soft grey fine sandy clay, grey slightly silty sandy gravel, etc. or any other fill with desired heat-transfer characteristics. Coolant fins and/or jackets with secondary coolants may be used on the coolant loop. The coolant loop may be buried at any constant or variable depth, and the reactor and containment may also be buried in the ground.