Gaseous reactor control system

A nuclear reactor control system for controlling the reactivity of the core of a nuclear reactor comprising:

• a control gas having a high neutron cross-section;
• a first tank containing a first supply of the control gas;
• a first conduit providing a first fluid passage extending into the core, the first conduit being operatively connected to communicate with the first tank;
• a first valve operatively connected to regulate the flow of the control gas between the first tank and the first conduit;
• a second conduit concentrically disposed around the first conduit such that a second fluid passage is defined between the outer surface of the first conduit and the inner surface of the second conduit;
• a second tank containing a second supply of the control gas, the second tank being operatively connected to communicate with the second fluid passage;
• a second supply valve operatively connected to regulate the flow of the control gas between the second tank and the second fluid passage;
• a first exhaust tank and a first exhaust valve, the first exhaust valve operatively connected to control the flow of the control gas between the first fluid passage and the first exhaust tank, and, hence, the gas pressure in the first fluid passage;
• and
• a second exhaust tank and a second exhaust valve, the second exhaust valve operatively connected to control the flow of the control gas between the second fluid passage and the second exhaust tank.