Neutron life cycle

For the following neutron life cycle, calculate the fast fission factor, fast non-leakage probability, resonance escape probability, thermal non-leakage probability, thermal utilization factor, reproduction factor, Keff and core reactivity. 

A neutron life cycle in a thermal reactor moderator or reflector may be divided on an energy basis into two main categories thermal and epithermal. The distance a neutron travels while its energy is in the thermal portion of this cycle is of prime importance. The thermal-neutron diffusion length is proportional to this distance. 

Plutonium-239 is a fissile element, and vvill split into fragments when struck by a neutron in the nuclear reactor. This makes Pu-239 similar to U-235, able to produce heat and sustain a controlled nuclear reaction inside the nuclear reactor. Nuclear power plants derive over one-third of their power output from the fission of Pu-239. Most of the uranium inside nuclear fuel is U-238. Only a small fraction is the fissile U-235. Over the life cycle of the nuclear fuel, the U-238 changes into Pu-239, which continues to provide nuclear energy to generate electricity. 

The neutron-physical characteristics and the efficiency of the reactivity control system are such that at any moment in the reactor life cycle, cold subcriticality, with no dissolved boron is assured, even in the case of the most effective rod being stuck in its upper position. The liquid absorber injection system is used only in beyond design accidents. 

The life cycle of a neutron in a thermal reactor, moderator, or reflector can be considered to be divided on an energy scale into thermal and epithermal regions. The Argonaut experiment "Measurement of Thermal Neutron Diffusion Length in H2O" concerns itself with the fate of the neutron in the thermal portion of such a cycle this experiment completes the picture by considering the neutron behavior during its epithermal career. 

Neutron cycle is die average life history of a neutron m a nuclear reactor. The gain in the number of neutrons in a reactor during any individual neutron cycle ts given by n(k-1). where n is the number of neutrons in the reactor of the beginning of the cycle and k is the multiplication factor. 

Plutonium-239. Plutonium-239 represents a fortuitous phenomenon. Whereas U-235 is the only significant fissile nuclide in nature, its major isotope, U-238, captures a neutron to produce another fissile nuclide, plutonium-239. A substantial amount of the energy produced during the life of uranium fuel is produced by the conversion of U-238 to Pu-239 which subsequently fissions. This process provides the basis for the nuclear breeding cycle. 

The neutron activation production cycle requires only neutron irradiation without chemical separation. The target and the product are the same chemical element but have different nuclide compositions. The specific radioactivity of the product is a function of the nuclide composition of the target, the neutron flux environment, the irradiation time, and the half-life of the product nuclide, along with the nuclear cross-sections of target and product nuclides. 

C is produced continuously in the upper atmosphere by the bombardment of N with neutrons of cosmic radiation. The reaction is aN +on - 6C + iH . As a result, all carbon-containing compounds currently being biosyn-tliesized on the earth contain sufficient C to yield 13 DPM/g carbon. After death of an organism the C decays with a half-life of 5700 years. Calculate (a) the abundance of c in the carbon that is participating in the carbon cycle on the surface of the earth today and (b) the age of a sample of biological material that contains 3 DPM/g carbon. 

The reaction between atmospheric nuclei and cosmic rays (neutrons) produces the radionuclide accompanied by the emission of a proton. produced in this manner enters the Earth s carbon cycle from which some carbon may be trapped in a form that ceases to exchange with atmospheric carbon (e.g., as rocks or plant material). As has a half-life of 5 730 years, the determination of the to ( C- - C) ratio has become a useful technique for estimating the age of objects from 1000 to 10 000 years timescale. The ratio of the at-... 

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