NOVELTY - Concentric fusion reactor comprises: a target predisposed to provide an impact location; an envelope shell of material enclosing a space; a rarefied fusion reactive gas (38) contained within the envelope shell; an insulating and cooling medium; a thermally and electrically insulated enclosure; a radiation absorbing and cooling medium; a heat absorbent container; and a high voltage alternating current (AC) power supply and electrical interconnections for connecting the high voltage AC power supply between the concentric fusion reactor and earth ground.    USE - The concentric fusion reactor is useful to provide controllable hot fusion of heavy and/or light hydrogen.    ADVANTAGE - The concentric fusion reactor provides controllable hot fusion of fusion reactive gases: without magnetic or electrostatic confinement of ionized gases; using cylindrical, spherical and other electrode shapes; without control grids, a cathode and thermionic emission; with cylindrical, spherical, toroidal and other reactor shapes; within an oscillating electrical field; without ion guns; within a reactor shape promoting greater energy transfer efficiency; in a phase two reactor without internal electrodes, this results in greater reliability since vital structures can be distant from the reaction and thus they are much less exposed to the extreme heat generated by the reaction therefore having greater reliability; and utilizing ACs. The concentric fusion reactor provides energy from fusion in a fashion in which this energy: is efficiently harnessed; can be throttled via electrical current amplitude variation; can be throttled via electrical current frequency variation; can be throttled via electrical current waveform shape; can be throttled via electrical current duty cycle variation; can be throttled via electrical current focus voltage amplitude variation; can be throttled via electrical current frequency variation with respect to reaction chamber resonance phenomena; can be throttled via a combination of at least two electrical current characteristics of amplitude, frequency, waveform shape, duty cycle, focus voltage amplitude, and/or resonance, where the control parameters of the reaction are within a feedback loop, where the disruption of the reactor vessel integrity results in internal pressure changes resulting in immediate termination of the reaction.    DETAILED DESCRIPTION - Concentric fusion reactor comprises: a target predisposed to provide an impact location for fusion reactions of ions impacting with fusion reactive energies; an envelope shell of material enclosing a space coaxially centered upon a centrally located target; a rarefied fusion reactive gas (38) contained within the envelope shell; an insulating and cooling medium within which the envelope shell is suspended; a thermally and electrically insulated enclosure whose partial radius is concentrically centered on the central target and enclosing envelope shell containing the insulating and cooling medium; a radiation absorbing and cooling medium within which the thermally and electrically insulated enclosure is suspended; a heat absorbent container for containing the radiation absorbing and cooling medium; and a high voltage alternating current (AC) power supply and electrical interconnections for connecting the high voltage AC power supply between the concentric fusion reactor and earth ground. An INDEPENDENT CLAIM is also included for a light hydrogen gas production plant comprising: an inlet water conditioning plumbing system; a sequential series of heavy water separation unit(s); a water electrolysis unit; a light hydrogen gas collection unit; a light hydrogen gas storage unit; a plumbing system; and electrical and electronic apparatus.    DESCRIPTION OF DRAWING(S) - The figure shows a basic process schematic of a side view through cross-section of a cylindrical phase one reactor with associated sub-systems, and alternating current power supply.    Target rod (12)    Wire conductor (13)    Non-conducting spherical reactor vessel (21)    Insulated support (22)    Fusion reactive gas (38)