Neutron production

Pretzler G et al 1998 Neutron production by 200 mJ ultrashort laser pulses Rhys. Res. E 58 1165-8... 

Full advantage of the neutron production by plutonium requires a fast reactor, in which neutrons remain at high energy. Cooling is provided by a hquid metal such as molten sodium or NaK, an alloy of sodium and potassium. The need for pressurization is avoided, but special care is required to prevent leaks that might result in a fire. A commonly used terminology is Hquid-metal fast-breeder reactor (LMFBR). 

Nuclear reactions are excited when projectile energies are typically in the MeV range. Medium size ion-accelerators are, therefore, necessary to obtain these projectile energies. Protons and a projectiles, typical projectiles in other ion-beam analysis techniques as RBS or PIXE, have few useful nuclear reactions. Deuteron beams excite many more nuclear reactions, but the use of deuteron beams instead of standard beams is more hazardous, because of efficient neutron production. Strict safety rules are necessary when high-energy deuteron beams are used. 

The basic requirements of a reactor are 1) fissionable material in a geometry that inhibits the escape of neutrons, 2) a high likelihood that neutron capture causes fission, 3) control of the neutron production to prevent a runaway reaction, and 4) removal of the heat generated in operation and after shutdown. The inability to completely turnoff the heat evolution when the chain reaction stops is a safety problem that distinguishes a nuclear reactor from a fossil-fuel burning power plant. 

Other fusion reactions such as D plus "He" and D plus D (not to mention the II plus II of stars) require far more difficult physical conditions than D plus T, but offer potential advantages in reduced neutron production, and even larger reseiwes of potential energy in the case of D-D. 

The thermal neutron production product, 153Sm, is used in the formulation of Quadramet , a US FDA-approved radiopharmaceutical for pain palliation in metastatic bone disease. It is produced by an (n, 7) reaction on 152Sm ... 

Neutron production, plutonium, 77 585 Neutron radiation, high pressure, 13 431 Neutron-radiography (N-radiography), 77 418... 

While stellar evolution models describe neutron production, the calculations must be supplemented with nucleosynthesis calculations to determine what abundances of heavy elements the 13C or 22Ne neutron sources will produce. While analytic theory can approximate the production of heavy elements [3], numerical modelling of - 500 isotopes is used for detailed comparison of stellar evolution theory and observation. In general, the destruction of an isotope between Fe and Bi occurs due to that isotope capturing a neutron or f) decaying, while the creation of an isotope will be due to the neutron capture or f decay of lighter elements. 

A neutron production rate (not including the cosmogenic components) was calculated by Andrews et al. (1986) for a granitic rock as a function of U, Th contents,... 

As given in Equation (5.7), the neutron production rate can be expressed as a function of U content. From the production rate, we can calculate the neutron flux (X) with the relation fn = v x n, where v denotes the mean velocity of neutrons and n is an equilibrium concentration of neutrons. The latter quantity is related to the neutron production rate (pn) as n = (pjt) where T denotes the time constant for the neutron absorption in the medium (-2500 s1). Andrew et al. (1986) estimated the average neutron flux in the Stripa granite to be 5.5 x 10 4 neutrons cm 2s, which is in good agreement with the measured flux of 4.7 x 10 4 neutrons cm 2s 1 in the borehole in the granite. 

Fig. 12. Neutron resonance radiography absorption spectra for various angles of neutron production. Energy...

In source development, there is a need for more compact and reliable accelerator-based neutron systems. The advantage of accelerator-based technology (as distinguished from DD or DT systems) lies in the ability to both vary the energy of the neutrons and, with kinematic focusing, limit the angles of neutron production, i.e. produce neutrons in the forward direction rather than isotropically. However, sealed tube generators, both... 

Spontaneously fissioning radionuclides may be applied as neutron sources in those cases in which irradiation in a nuclear reactor is not possible, for example if manganese nodules at the bottom of the sea are to be analysed. For that purpose, Cf is a suitable neutron source. It has a half-life of 2.645 y and decays in 96.9% by emission of a particles and in 3.1% by spontaneous fission. It may be installed together with a shielded y-ray detector in the form of a mobile unit. The neutron production of Cf is 2.34 lO s g. The neutron flux density is only of the order of 10 cm s , but this is sufficient for applications in which high sensitivity is not needed. 

You are given all of the particles involved in an induced transmutation reaction, from which you must write the balanced nuclear equation. Because the alpha particle bombards the aluminum atom, they are reactants and must appear on the reactant side of the reaction arrow. Obtain the atomic number of aluminum and phosphorus from the periodic table. Write out the nuclear reaction, being sure to include the alpha particle (reactant) and the neutron (product). 

Nuclear and pion related 7-rays provide important information about the spectra of protons and ions accelerated in solar flares [e.g. Hua and Lingen-felter, 1987 Murphy et al., 1987 Lockwood et al., 1997 Hua et al., 2002], However, nuclear 7-ray lines probe the proton spectrum only up to 40 MeV, while 7-rays from pion decays are only observed in the most intense flares. In addition, any spectral break in the proton spectrum is likely to he below the pion production threshold. Neutrons produced at the solar surface over a wide range of energies may provide important information from the 50-300 MeV regime, complementing 7-ray observations. Due to the long neutron thermal-ization time ( 100 s) the 2.223 MeV neutron capture line is only a limited measure of neutron production. The spectrum of accelerated and interacting protons can be deduced more reliably from direct neutron measurements. 

Fig. 1 illustrates the importance of the various energy ranges of the energetic flare particles, in particular for the neutron production. A typical solar proton production spectrum d J/dE E 2-5 (A) is folded with the cross-sections for the neutron (B), 7-ray line (C and D) and pion production (E), and weighted by the elemental abundances of the target material [Lockwood et al., 1997],... 

That s-processing occurs in red giant AGB stars was clear from Merrill s discovery and Cameron s discussion of neutron production and capture. Full understanding of how the s-process operates in AGB stars may now be close - see Busso et al. (1999). Two neutron sources are recognized 22Ne(a,n)leO and 13C(a,n)lsO with ignition temperatures of... 

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