Delayed-neutron groups fuels

TWINKLE is a multidimensional spatial neutron kinetics code, whieh is patterned after steady-state codes currently used for reactor core design. The code uses an implicit finite-difference method to solve the two-group transient neutron diffusion equations in one, two, and three dimensions. The code uses six delayed neutron groups and contains a detailed multi-region fuel-clad-coolant heat transfer model for calculating point-wise Doppler and moderator feedback effects. The code handles up to 2000 spatial points and performs its own steady-state initialisation. Aside from basic cross-section data and thermal-hydraulic parameters, the code accepts as input basic driving functions, such as inlet temperature, pressure, flow, boron concentration, control rod motion, and others. Various edits are provided (for example, channel-wise power, axial offset, enthalpy, volumetric surge, point-wise power, and fuel temperatures). 

The neutron kinetics was described with due regard for six groups of delayed neutrons. The core reactivity changes were determined by temperature effects of reactivity of fuel elements and the alloy as well as by water penetration into the core. 

J. A. Fleck, Jr., Theory of Low-power Kinetics of Circulating Fuel Reactors with Several Groups of Delayed Neutrons, Brookhaven National Laboratory, BNL 334 (T-57), April, 1955 The Theory of Circulating Reactor Kinetics at Low Power, BNL 1933, Apr. 13, 1954 also, Kinetics of Circulating Reactors at Low Power, Nucleonics, 12, 11 (1954). 

Failedfuel detection Failed fuel is detected by sampling the cover gas and the sodium coolant. Sodium samples are taken from 4 locations in the hot pool. As this method cannot identify the failed fuel subassembly, 3 localization modules are provided and housed in the control plug. Samples of sodium from the top of the subassemblies are taken one by one by means of a selector valve and measured for delayed neutrons. The subassemblies are divided into three groups and each group has a localization module. 

Fli ck, Jr., Theory of Low Power Kinetics of Circulating Fuel Reactors with Several Groups of Delayed Neutrons, US. UC Report RNL-334, Hrookhaven National Lahoi atory, April 1955. 

The TF ACE nuclear model uses built-in point kinetics calculations linked to the six fuel powered heat structures. A neutron lifetime of 1. OE-6 seconds is used along with a six group delayed neutron fraction. The code allows both axial and radial power profiles to be defined in the fuel region. A parabolic axial power profile has been applied with a peak power of 1.23 (consistent with the Reference 12-1 concept selection report Table 2.2-1). Currently, no radial power profile is modeled... 

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