Thermoionic Fuel Elements
Development of the System for Ex-reactor Heating of Multy-cell Thermoionic Fuel Assemblies and for Obtaining their J-V Characteristics
Tech Area / Field
- NNE-MEC/Miscellaneous Energy Conversion/Non-Nuclear Energy
3 Approved without Funding
Kurchatov Research Center, Russia, Moscow
Project summaryIn I.N. Vekua Sukhumi Institute of Physics and Technology there were developed the technique and equipment for ex-reactor investigations of multicell thermionic fuel elements.
Ex-reactor testing of multicell thermionic fuel elements (TFE) allows performing the following operations on thermal testbeds with the minimum costs:
(a) TFE thermal and vacuum treatment, preliminary checking of their serviceability prior to their installation into the loop channel of converter-reactor;
(b) monitoring of TFE electrical parameters after certain technological operations, such as vibration testing;
(c) monitoring of resistance in the TFE collector stack in the course of lifetime testing;
(d) examination of fuel composites in the TFE cells (their interaction with emitter cladding at high temperatures, studies on the effect of fission gas products on the TFE J-V characteristic and mass transport from the cathode to the anode);
(e) testing in experimental conditions (temperature drops, thermal cycling, various vacuum conditions, operation at high power density etc.);
(f) further improvement of the TFE design (optimum geometry, selection of electrode materials etc.).
During the TFE reactor testing the method of heating with backward currents combined with nuclear heating allows to heat the TFE emitter up to 2300 К and above when the reactor power is not sufficient. The method of the TFE backward heating includes the thermionic converter collector heating with the help of an external heater, filling of the interelectrode gap with cesium vapor and supply of the accelerating voltage to the TFE electrodes.
The emitter is heated up due to the kinetic energy of the electron flux from the arc-discharge plasma.
The TFE emitter heating with backward currents is carried out in the pulsed mode, and between the pulses J-V characteristic is recorded by the pulsed method as well.
The feasibility of the concept used in the proposed method, which has no analogs in the world practice, has been demonstrated in Sukhumi Institute of Physics and Technology.
The major stages in the development of this method are as follows:
1. Development of a high-current electronic circuit with the automatic control over temperature conditions on the electrodes of a multicell thermionic fuel element.
2. Development of an optimum design heat exchanger for the control over the temperature field on the multicell TFE collector stack.
3. Investigations of the TC model with the backward currents heating system.
4. Multicell TFE full-scale testing by the method of backward heating with optimization of the output electrical parameters.
5. Reporting to the Center on each of the above stages of development.
As a result of the effort to be carried out by a team of the RRC "Kurchatov Institute" and Sukhumi Institute of Physics and Technology personnel there will be built in RRC "Kurchatov Institute" a unique test facility allowing to perform ex-reactor investigations of actual multicell TFEs of any design and to determine their quality.
The proposed method generated interest among a number of the US firms (General Atomic, Rasor Corp., Space Exploration Assoc.), that are interested in the development of this proposal.
The effort will involve minimum costs because, on the one hand, for the TFE testing there will be utilized state of the art test facilities (irradiation), located in RRC "Kurchatov Institute", which will be only slightly modernized. On the other hand, in Sukhumi Institute of Physics and Technology all of the physics and engineering principles, underlying this method, has been developed and the concept feasibility has been demonstrated.
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