GRAPHITE-MODERATED SYSTEM

H. L. Reynolds,"Critical Measurements and Calculations for Enrtched-Uranium j Graphite-Moderated Systems, HCRL-5175 (1958), k>. 2-7. 

The DOE N-Reactor is one of the plutonium production reactors located on the Hanford Reservation near Richland, Washington. It is graphite moderated, pressurized water reactors that in addition to production of special nuclear materials also provided steam to turbine generators owned by the Washington Public Power Supply System for electric power production. It began op ition in 1 is put into standby status in 1988 and closed because of similarities to Chernobyl. 

A typical example of chemical transport reaction in a nuclear reactor system is the reaction between graphite moderator and COj (or oxygen) gas in a gas-cooled reactor ... 

An RBMK is a graphite-moderated, water-cooled system. The Chernobyl reactor that exploded in 1986 was an RBMK. Fourteen RBMKs are in operation. Several problems are inherent in RBMKs. If several pressure tubes rupture simultaneously, the force will raise the reactor lid, releasing radioactive fission products. An RBMK is susceptible to power instabilities. Increased boiling can boost power levels, creating an uncontrolled reaction. The emergency core-cooling, fire protection, and electronic control-and-protection systems in the older RBMKs do not meet international standards. 

A production reactor is a complex of systems and equipment designed to sustain, control, cool and replenish a nuclear chain reaction over relatively long operating periods for the purpose of converting uranium to plutonium, Hanford production reactors are graphite moderated, horizontal tube, water-cooled reactors. 

In this concept there is no annulus gas, garter spring and calandria tube unifies with pressure tube. The main reason for this simplification is that the operating pressure of this system is atmospheric pressure and it has graphite moderator, which in case of leakage, there in no negative effect in the neutronic point of view and besides that the solubility of lead in the graphite is very low. 

General It is necessary to identify materials for coolant, moderator, and fuel, and for the structure and components of the reactor and reactor systems, which are compatible under all operating conditions. Basic compatibility was established for the combination of lead coolant, graphite moderator, and TRKO fuel, and for lead and the reactor and reactor systems, structures and components. Specifics are discussed below. 

In the event that all normal reactivity control systems fail, the negative temperature coefficients of the graphite moderator and fuel (Figures 8 and 9) shut the reactor down well before the integrity of the fuel is threatened. 

On failure of both electrical power sources, the rods are supplied with cooling water from the same system as used for the last-ditch graphite moderator backup cooling and the fog spray systems. 

Xhe N-Reaotor core at Initial startup vlU be coaprlBed of ICX) lattice units as described previously (Figure 2.1 1) Provisions have been made to Increase this nuniber of 1072 If future operating trends Justify additional Irradiation volume l bls core Is pierced by three systems of openings In addition to the process channels and steam vents horizontal control rod channels the ball 3X safety system channels and the graphite moderator cooling tubes ... 

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