Neutronics calculations

Neutronic calculations show that fast neutron fluxes at fusion reactor magnet locations are rather high and the energy deposited by neutrons compares to or exceeds that by y-rays [2]. It is therefore important to establish the characteristics of radiation damage due to fast neutrons in comparison with those due to y-rays. 

If a sulfur ion, S , has 16 protons and 16 neutrons. Calculate its a) Number of electrons b) Atomic mass number... 

The Li nucleus can absorb a fast (above 3 MeV) neutron to produce a tritium nucleus, an alpha particle, and a slower neutron. A moderated neutron can be absorbed by a Li nucleus to produce a tritium and an alpha. Neutronic calculations indicate that a thick sphere of natural lithium could breed about 1.8 tritium atoms for each tritium atom burned in a fusion reaction (1 ). Structure and portions of the volume left open for fueling or driver beams reduce the 1.8 tritium breeding ratio. If the ratio falls below 1.0, it may be increased by addition of a neutron multiplier such as Be or Pb, and by isotopically enriching the Li in °Li. 

In this calculation you will determine the order of magnitude of nuclear energies. Assume that a nucleus can be represented as a cubic box of side 10 m. The particles in this box are the nucleons (protons and neutrons). Calculate the lowest allowed energy of a nucleon. Express your result in MeV (1 Me V = lO eV = 1.602 X 10-13J.)... 

In a neutron star, gravity causes the electrons to combine with protons to form neutrons. A typical neutron star has a mass half that of the sun, compressed into a sphere of radius 20 km. If such a neutron star contains 6.0 X 10 neutrons, calculate its density in grams per cubic centimeter. Compare this with the density inside a Th nucleus, in which 142 neutrons and 90 protons occupy a sphere of radius 9.1 X 10 cm. Take the mass of a neutron to be 1.675 X 10... 

Figure 4. Yatsevich and Honda (1997) calcnlate the energy spectrum of neutrons produced from U and Th (a,n) reactions in an homogenous mantle over 4.5 Ga. They calculate a lower energy spread than the simplified calculation of Rison (1980) because of the inclusion of the effect of elastic and, to a lesser extent, inelastic scattering of the neutrons. Calculated yields for fast neutron reactions, such as with that have a 2-4...

Neutronic calculations have shown that the consequences of such a test are symmetrical to those of a control-rod withdrawal. 

A series of neutronics calculations were conducted to evaluate the coolant void coefficient and to understand its sensitivity to various core parameters. Both ORNL and SNL participated in the physics analysis using slightly different models and assumptions. The results are in good agreement, however. 

Steady state neutronics calculation of a nearly-zero void reactivity core design project of the Russian BN-800 fast reactor... 

Critical facility A critical facility has been built and will be operated during 1994/95, for adjusting the core neutronic calculations. 

Detailed neutronics calculations were performed in spherical geometry using the transport code DTF-IV in the P1-S4 approximation with 27 broad energy groups. A space-independent perturbation cross section was also computed at the center of the system for comparison with measured results. The first-order transport perturbation theory program GAPER was used in evaluating central material worths as well as Doppler and sodium-void reactivity coefficients. 

These methods have been tested by neutronics calculations for a group of simple spherical assemblies consisting of a central core of Pu and reflected by 93.2% U, U(nat), W, and BeO. Independent calculations for these evaluated assemblies have been made at tee Los Alamos Scientific Laboratory and AWRE, Aldermaston. The results and conclusions of this study are presented. 

Considerable effort has been expended at Los Alamos toward. the establishment of a consistent set of uranium and plutonium cross sections that can be used to yield accurate neutronics calculations for a wide range of fast-neutron assemblies. This work has been documented in detail in Refs. 1 through 3, and includes extensive evaluations of U, U, Pu, and Pu. The purpose of this paper is to compare neutronics calculations made with data from this LASL library and with data fromT the EiroF/B Version II file. Significant differences exist between the microscopic data in these two files, and this motivated the comparisons-reported in this paper. 

In such situations, it the literature reporting criticality data or calculations does not provide suffitient guitomce to establish critically safe operati procedures, detailed neutronics calculations are performed to investigate toe possibility that a critical system could be formed when a container of scrap of known volume is placed into the counting geometry. the results of these calculations provide the criteria by which standard operating procedures are developed. 

Thus, NDA instrumentation often can be used to increase the number of individual units that can be safely batched for more efficient and economical processing. Operating procedures for toe critically safe assay of Itiidlvidual units can be established by means of careful neutronics calculations and appropriate screening procedures. 

The most useful information in the prevention of criticality is knowledge of the conditions required to produce criticality for fissile materials. Experiment and validated, detailed neutronic calculations are the best source of useful basic information. Translation of these data into terms familiar to engineers and operators is... 

What is the mass number of an iron atom that has 28 neutrons Calculate the number of neutrons of Pu. 

The RA-8 critical facility has been designed and constmcted to measure neutronic parameters typical of the CAREM core. It provides a reactor shielding block and a reactor tank that can be adapted to contain custom designed reactor cores. Experiments were performed using fuel rods of the same radial geometry and pitch as in the CAREM-25 fuel element. Components of the neutronic calculation lines were validated with the use of data for VVER type reactors obtained in the experiments at ZR-6 Research Reactor (Central Research Institute for Physics, Academy of Sciences, Hungary) and data for PWR critical experiments. 

PRODUCTION OF NUCLEAR DATA FOR REACTOR NEUTRONICS CALCULATIONS... 

For neutron calculations, core parameters have been modified on the following features only ... 

Neutron stars are composed of sohd nuclear matter, primarily neutrons. Assume the radius of a neutron is approximately 1.0 X 10 cm. Calculate the density of a neutron. [Hint. For a sphere V = (4/3)77 . ] Assuming that a neutron star has the same density as a neutron, calculate the mass (in kg) of a small piece of a neutron star the size of a spherical pebble with a radius of 0.10 mm. 

The ZrHi.6-10 wt% plutonium fuel form was considered in this study, but neutronic calculations indicate that it would have a positive fuel temperature coefficient of reactivity. Consequently, the addition of burnable poisons mu.st be explored if this fuel form is considered. 

To facilitate modeling of the metal fuel used in KALIMER, several reactivity models are modified in SSC-K code. For neutronic calculations, SSC-K uses point kinetic equations with detailed reactivity feedback from each channel. Reactivity effects are required both for transient safety analysis and for control requirements during normal operation. Reactivity changes are calculated for control rod scram, the Doppler effect in the fuel, sodium voiding or density changes, fuel thermal expansion, core radial expansion, thermal expansion of control rod drives, and vessel wall thermal expansion. Figure 5 shows the components of reactivity feedback considered in the KALIMER core. The effect of fuel expansion becomes more significant when metallic fuel is used. 

The high temperatore core without the critical heat flux criterion (i.e. the MDHFR) was designed in 1998 [12]. The two-dimensiraial R-Z model of the core cannot accurately predict bum-up of fuel rods. The three-dimensional coupled neutro-nic-thermal-hydraulic core calculation was developed in 2003 [18]. It is shown in Fig. 1.9. This calculation considered the control rod pattern and fuel loading pattern [19, 20] and was similar to the core calculation for BWRs. But the finite difference code SRAC [21] was used for the three-dimensional neutronic calculation instead of a nodal code. The core design of the Super FR also adopted the three dimensional neutronic and thermal hydraulic coupled core bum-up calculation. 

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