MTR-type fuel elements

In order to have a definite chemical system to study, we have chosen a reactor which is probably not very realistic as a power producer, but one which has the advantage that we know both the design details of the fuel element and the cost and design data for the chemical processing plant in which this fuel element is presently handled. We have adopted an MTR type fuel element which is composed of enriched uranium aluminium alloy, but we have assumed that the is replaced by Since any thermal reactor power economy... 

In summary, we can say that we are deeply convinced that it is possible to reprocess enriched fuel elements for about 1 per gram by being realistic in the plant design. We do not think that oiu choice of the MTR type fuel element... 

The RP-0 reactor is located at IPEN headquarters in the San Boija district, close to downtown Lima. It is a critical facility that reached criticality for the first time in July 1978 using extruded rod type fuel elements made with 20.09% enriched UO2 mixed with graphite and aluminium cladding. In 1991 the core was converted to 19.75% enriched fuel. In June of that year the reactor reached criticality using MTR type fuel elements supplied by the Argentinian National Commission of Atomic Energy (Comision Nacional de Energia Atomica — CNEA). 

Wigner s second contribution to the MTR was the curved plate fuel element. A curved plate is stiffer and its thermal expansion more predictable, than is a flat plate this suggestion was incorporated into the design of MTR fuel, and has been used in many other pool-type reactors. 

FIG. 1.1. Typical MTR type spent nuclear fuel element. 

Several experimental nuclear reactors have been put into service in Argentina since the early 1960s. All of them use aluminium clad fuel, most of the MTR type. RA3, located at the Ezeiza Atomic Centre (near Buenos Aires) is the most powerful of these experimental reactors. It started up burning 90% enriched uranium, and the fuel plates were made of pure (99.7%) aluminium It was converted to use 20% enriched uranium at the end of the 1980s, and at that time the fuel plates started to be manufactured with 6061 alloy. Some of the earliest irradiated fuel elements were inserted into RA6 in Bariloche (some 1700 km south-west of Buenos Aires), a zero power reactor, where they have been in service for almost 20 years. 

The reactor is a typical MTR pool type reactor, using standard LEU plate type fuel assemblies. The core has a rectangular shape formed by a 5 x 6 lattice. It has 24 standard fuel assemblies, five control assemblies, and one irradiation position at the centre of the lattice. The standard fuel assemblies have 16 plates containing LEU in the form of UsOg dispersed in aluminium the control fuel assemblies have 12 plates. The core is surrounded with eight beryllium elements and 13 graphite elements that work as reflector for the fission neutrons. Demineralized light water is used as moderator and coolant. 

A detailed report on the CP-5 reactor is given in the Atomic Energy Commission document Research Reactors a few of its principal characteristics are summarized here. The reactor core proper is an upright cylinder of D2O 2 ft high and 2 ft in diameter in which are immersed MTR-type aluminum fuel elements (see Fig. 5.28). The sides and bottom of the core are reflected by 2 ft of D2O, and this region in turn is surrounded by 2 ft of graphite. The top of the core is reflected by 2J ft of D2O alone. The fuel elements, of which there are 16, consist of boxlike arrays of fuel plates fabricated of a uranium-aluminum alloy, composed of 17.5 per cent aluminum and 82.5 per cent uranium. For computational purposes we will assume that the volume fraction of aluminum in the core is Vax = 0.0688 and that of D2O, Vdio = 0.914. The reactor was designed to produce 1,000 kw of heat, and at this power level the temperature of the D2O is 49 C. 

Fuel element MTR-type curved plates 46% enriched uranium alloyed with aluminium clad in aluminium... 

Fuel element Aluminium MTR type 14 fuel plates per element... 

After completing experimental verification of the HEATHYD model, it was applied to calculate the thermohydraulics of a plate type MTR. It was assumed that the core consists of 48 fuel elements generating a total power of 30 MW. The coolant flow and heat transfer for the hot channel was analyzed. In the hot channel case, the saturation temperature has been partly exceeded by the clad surface temperature with the result of subcooled boiling. In the case of the average channel, the clad temperature does not reach the saturation temperature. 

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