Fast neutron reactors thermal power

Those fast neutrons that have energies greater than about 1 MeV may cause a limited amount of fission of fertile material. To account for this, the reactor designer usually specifies a quantity e, called the fast-fission factor, which is defined as the ratio of the net rate of production of fast neutrons to the rate of production of fast neutrons by thermal fission. The fraction e — 1 of the fast neutrons comes from fission of fertile material with fast neutrons e — 1 may be of the order of a few hundredths in a thermal power reactor. The net production rate of fast neutrons from fission is er N a 4>-... 

Far and away the development of nuclear power in Russia with fast neutron reactors is connected with the use in a closed fuel cycle primarily of power plutonium, produced in thermal reactors. However, availability of successfully operated BN-600 reactor and the construction in sight of BN-800 reactors permits to consider the... 

The moderator absorbs 4.5% of reactor thermal power. The largest portion of this heat is from gamma radiation. Additional heat is generated by moderation (slowing down) of the fast neutrons produced by fission in the fuel and a small amount of heat is transferred to the moderator from the hot pressure tubes. For reactivity control, gadolinium, and occasionally boron, can be added or removed from the moderator fluid. 

The Rapsodie experimental sodium cooled reactor was the first French fast neutron reactor. The construction was started in 1962 within an association of CEA and EURATOM. The reactor went critical on 28 January 1967, reaching 20 MW (th) power on 17 March 1967. The core and equipment were modified in 1970 to increase the thermal power level to 40 MW (th). The operating parameters were similar to those in large commercial size reactors. During 16 yets of operation 30 000 fill pins of the driver core were irradiated, of which -10 000 reached a bumup beyond 10% 300 irradiation experiments and more than 1 000 tests have been performed. The maximum bumup of the test fuel pins was 27% (173 displacement per atom). In 1971, the irradiations performed in the core revealed a phenomenon of irradiation swelling in the stainless steel of the wrapper and the fuel cladding in the high neutron flux. The R sodie results have been extrapolated in the Phenix reactor. 

Fig. 5. Radioactivity after shutdown per watt of thermal power for A, a Hquid-metal fast breeder reactor, and for a D—T fusion reactor made of various stmctural materials B, HT-9 ferritic steel C, V-15Cr-5Ti vanadium—chromium—titanium alloy and D, siUcon carbide, SiC, showing the million-fold advantage of SiC over steel a day after shutdown. The radioactivity level after shutdown is also given for E, a SiC fusion reactor using the neutron reduced...

Nuclear and magneto-hydrodynamic electric power generation systems have been produced on a scale which could lead to industrial production, but to-date technical problems, mainly connected with corrosion of the containing materials, has hampered full-scale development. In the case of nuclear power, the proposed fast reactor, which uses fast neutron fission in a small nuclear fuel element, by comparison with fuel rods in thermal neutron reactors, requires a more rapid heat removal than is possible by water cooling, and a liquid sodium-potassium alloy has been used in the development of a near-industrial generator. The fuel container is a vanadium sheath with a niobium outer cladding, since this has a low fast neutron capture cross-section and a low rate of corrosion by the liquid metal coolant. The liquid metal coolant is transported from the fuel to the turbine generating the electric power in stainless steel... 

Shortages of oil and coal will be followed by one of uranium. The nuclear industry knows that the fuel of today s thermal nuclear reactors (U235) is exhaustible and therefore in a few decades they plan to shift to breeder reactors. They say little to the public, except that this conversion would make nuclear power inexhaustible. This is true, because the conventional "slow neutron" thermal reactors are "once through" (in the sense that they consume their uranium fuel), while fast neutron breeder reactors make more fuel than they use. 

The thermal and nuclear properties of sodium (it scatters neutrons without absorbing them) made it the heat exchange fluid of choice for fast-flux reactors in spite of its nasty chemical properties when exposed to air or water. The French Superphenix, a commercial-scale sodium cooled reactor, was beset with technical problems, but demonstrated that fast-flux reactors can produce electric power at the 1000 MW level. 

A thermal reactor is one in which the neutrons have been slowed down until they are in thermal equilibrium with reactor materials in a typical power reactor, thermal neutrons have speeds around 3000 m/s. At these lower speeds, the neutron-absorption cross sections are much larger than for fast neutrons. 

However, gram and kilogram amounts can be obtained by fission of U with thermal neutrons in the high, cumulative fission yield of 6.13 atom% [12]. This fission yield results in the production of about 1 kg of Tc from 1 ton of uranium ( 3 % enriched in after burnup in a nuclear reactor [13. Reactors with a power of 100 MW produce about 2.5 g of - Tc per day [14], Tc is also formed in high yield (atom%) from thermal neutron fission of-- U (4.8), (5.9), and fast neutron fission of Pu (5.9), (6.3) and -" Th (2.7) [15]. (Compared to the high fission yield... 

In January 1959, BR-5 reactor having 5 MW rated power was put into operation at the IPPE. There are three heat removal circuits in the BR-10 facility (sodium in the primary circuit, originally sodium-potassium and then sodium — in the secondary circuit, and air in the third circuit) with two parallel loops. Initial parameters of the primary and secondary coolants were respectively 430/500°C and 380/450°C, i.e. close to those of power FR. Now sodium temperatures in the primary and secondary circuits are respectively equal to 330/450°C and 270/370°C. There is a wide range of experimental devices in the reactor, namely test channels and irradiation devices and beams of thermal and fast neutrons. There are 5 dry instrumented channels in the reactor. Fast neutron flux in the central loop channel is up to 8.4x lO " n/cm -s. 

Abstract The chapter is devoted to the practical application of the fission process, mainly in nuclear reactors. After a historical discussion covering the natural reactors at Oklo and the first attempts to build artificial reactors, the fimdamental principles of chain reactions are discussed. In this context chain reactions with fast and thermal neutrons are covered as well as the process of neutron moderation. Criticality concepts (fission factor 77, criticality factor k) are discussed as well as reactor kinetics and the role of delayed neutrons. Examples of specific nuclear reactor types are presented briefly research reactors (TRIGA and ILL High Flux Reactor), and some reactor types used to drive nuclear power stations (pressurized water reactor [PWR], boiling water reactor [BWR], Reaktor Bolshoi Moshchnosti Kanalny [RBMK], fast breeder reactor [FBR]). The new concept of the accelerator-driven systems (ADS) is presented. The principle of fission weapons is outlined. Finally, the nuclear fuel cycle is briefly covered from mining, chemical isolation of the fuel and preparation of the fuel elements to reprocessing the spent fuel and conditioning for deposit in a final repository. 

The balance-of-plant design (Figure 9.3) utilizes a relatively simple direct cycle power conversion system. The reference design for this concept is a 1700-MWe reactor operating at a pressure of 25 MPa with a reactor outlet temperature between 510°C and 550 C. This reactor can be designed as a fast neutron spectrum or thermal neutron spectrum reactor. The relatively simple design also allows for the incorporation of passive safety features. However, unlike the previously discussed concepts, the lower reactor outlet temperature... 

Flux traps are useful for reactors of all power levels and a variety of irradiation facilities is desirable (e.g., pneumatic transfer, hydraulic transfer, irradiating baskets in core, or in beam tubes). Similarly, capabilities for thermal interactions and fast neutron irradiations should be available. 

FAST NEUTRON BATTERY-TYPE GAS COOLED POWER REACTOR OF 300 MW THERMAL (BGR-300)... 

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