Automatic hydropneumatic actuation device

A nuclear reactor, comprising:

• a fuel assembly including a fuel assembly duct containing nuclear fuel;
• a pump in fluid communication with the fuel assembly duct of the fuel assembly, wherein the pump is configured to provide a coolant flow along a coolant flow path;
• and
• a control assembly including:
• a control assembly duct configured to conduct coolant along at least a portion of the coolant flow path;
• a plug fixed to the control assembly duct;
• a neutron modifying material coupled to a member;
• a first piston disposed within and slidably coupled to the control assembly duct, and coupled to the member;
• and
• a firing assembly disposed within the control assembly duct and coupled to the first piston and the member, and configured to release stored energy when the pressure of the coolant in the coolant flow path satisfies a firing condition;
• and
• wherein the release of the stored energy inserts the neutron modifying material into the nuclear fuel when the pressure of the coolant in the coolant flow path satisfies
• the firing condition;
• wherein the plug and the first piston define a pair of cooperating apertures that forms at least a portion of a converging-diverging passage.

A method of manufacturing a control assembly for a nuclear reactor, the method comprising:

• defining a coolant flow path within an inner volume of a duct;
• fixing a plug to the duct;
• disposing a loading assembly within the duct;
• slidably coupling a first piston to the duct, wherein the plug and the first piston define a pair of cooperating apertures that forms at least a portion of a converging-diverging passage;
• coupling a neutron modifying material to the first piston with a member;
• positioning the converging-diverging passage along the coolant flow path such that pressure variations within the converging-diverging passage secure the first piston, the member, and the neutron modifying material during normal operation of the nuclear reactor;
• and
• positioning a biasing member to apply a biasing force to the member and the first piston, the biasing force releasing the first piston, the member, and the neutron modifying material when the pressure of the coolant in the duct satisfies a firing condition.