NEW METHODS FOR THE CALCULATION OF BURN-UP IN REACTORS

Journal Article · Fri Sep 01 04:00:00 EDT 1961 · Atomkernenergie (West Germany) Merged with Kerntechnik to form Atomkernenerg./Kerntech. Acta Radiol. Changed to Acta Radiol.: Oncol., Radiat. Phys.

OSTI ID:4823630

Kern, E

When calculating the burn-up one generally applies rough approximations, e.g., by calculating the time-dependent decrease of the reactivity of a fuel system under the provision of a neutron flux constant with regard to space and time and a space constant fuel distribution, disregarding the criticality conditions for the reactor. In the present artlcle the burn-up is calculated in another way than in the above method, i.e., the calculation of burn-up under consideration of the flux dependence and the variation of the distribution of concentration of the fuel components by solving at any time the boundary problem, which represents the criticality of the reactor. To simplify the formalism, the fuel charging is assumed in such a way that the fresh fuel is continually piled up from the top on a (vertical) cylindrical core (with reflector). The core height thus increases monotonously with time. The burn-up can be calculated in a relatively simple way by representing the fuel charging as above in a simplified manner. This method of treating the problem can be taken as a simplified model for the complicated case of burn-up control by control rods. Apart from the quantitative values of fuel required, the calculation of burn-up gives the concentration of the individual fuel components in dependence of height z within the core (depending upon the method of solution whether the radial dependence is taken into account or not) and of time t and the flux distribution over z in dependence of t. It gives especially the direct or indirect valuesn burn-up of the uranium, quantity of bred fission materials (conversion), and poisoning by fission products. ln connection with a perturbation calculation, the temperature coefficient of the reactor can be calculated in dependence of the operating time t. In view of a practical application of the formalism, formulas are derived to treat this problem with an analog computer. The problem is characterized by solving a partial differential equation (with integral additional condition) representing a boundary problem with nonconstant boundaries. The formalism is applied to the example of the BBC-Krupp pebble-bed reactor. The charging with fuel balls in this reactor corresponds to the above described simplified charging mechanism. Apart from this kind of charging, in which case the core height increases with time, another method of fuel charging at a given constant core height is treated, where simultaneously with the charging of fresh fuel from the top the same quantity of burned-up fuel is discharged at the bottom of the core. This case is analogous to that of a reactor with flxed fuel elements, where at one side of the core fresh elements are inserted and burned-up elements are removed correspondingly at the other side of the core. Similar modifications of the formalism as to other specific methods of fuel charging are possible without difficulties. (auth)

• Research Organization: BBC-Krupp, Mannheim, Ger.
• NSA Number: NSA-16-004991
• OSTI ID: 4823630
• Journal Information: Atomkernenergie (West Germany) Merged with Kerntechnik to form Atomkernenerg./Kerntech. Acta Radiol. Changed to Acta Radiol.: Oncol., Radiat. Phys., Journal Name: Atomkernenergie (West Germany) Merged with Kerntechnik to form Atomkernenerg./Kerntech. Acta Radiol. Changed to Acta Radiol.: Oncol., Radiat. Phys. Vol. Vol: 6; ISSN ATKEA
• Country of Publication: Country unknown/Code not available
• Language: German

Related Subjects

ANALOG SYSTEMS
BUCKLING
BURNUP
COMPUTERS
CONFIGURATION
CONTROL
CONTROL ELEMENTS
CONVERSION
CRITICALITY
CYLINDERS
DENSITY
DIFFERENTIAL EQUATIONS
DIFFUSION
DISTRIBUTION
EQUATIONS
ERRORS
FERTILE MATERIALS
FISSIONABLE MATERIALS
MASS
NEUTRON FLUX
NEUTRONS
NUMERICALS
PEBBLE BED
PELLETS
PERTURBATION THEORY
POISONING
PRODUCTION
PROGRAMMING
REACTIVITY
REACTOR CORE
REACTOR FUELING
REACTOR TECHNOLOGY
REACTORS
REFLECTORS
RODS
SPHERES
TEMPERATURE
URANIUM
VARIATIONS