Neutron Capture reactions n+4X→[4+1X] A+1x+7 Neutron leakage Safety consideration
Neutron Capture Reactions Neutron leakage Safety consideration
Table C.l. Thermal neutron(2200 m s or 0.0253 eV) cross sections for some special isotopes at 300 K. Cross-section notation: ar for (n, m);os for elastic scattering; at for total; a for fission; aa for (n, a); and ap for(n, p) Abundance Isotope Half-life (atom % Reaction cross sections(b) 99.985 333mb s=30.5 t=30.9 H 0.015 0= 506 ub s=4.26 at=4.30 12.33y x=6 ub as=1.53 1.53 6 Li 92.5 aa=941 38.6mbat=943 7.42 ay=45.7mbas=1.04 t=1.09 10 B 19.6 3840 O=0.50 3847 80.4 ay=553mba:=5.08 5.08 12 C 8.8 as=4.74 ay =3.4 mb at=4.74 1.11 =137mbot=419 5736y g =1.0 ub 14 N 9964 rp=1.83 y= 75 mb t=12.2 0.36 24b 4.58 99756 d=190bas=4.03 at=4.03 17 0.039 =235mbay=384mbat=417 18 0.20 160ub
Spontaneous fission The fission produced in these cases is insignificant for energy production However the phenomenon is important since represents an uncontrollable source of neutrons in a reactor and it is furthermore possible to make use of it in the start-up stage an example of the use of this fission is the neutron source of 252 californium Fission prob Neutrons Nuclide Half-life a pr per decay (% per fission fis ssion 2331 U 1.59×10 1.3×10-10 1.76 7.6×1011 235 704 10y 2.0×10-7 1.86 50×10 238 U 4.47×109 5.4×10 2.07 1.9×106 237 Np214×106y2.1×10-12 2.05 47×101l P 285y 81×10-8 2.23 1.2×1039 238Pu 877 1.8×10-7 2.28 5.4×10 239Pu2.41×104y44×10-10 2.16 23×1011 240 Pu 6569 y 5.0×10-6 2.21 2.0×10 241Pu 1435y 57×10-13 2.25 4.3×109 252Cf2.638y 3.09 31
Spontaneous fission: The fission produced in these cases is insignificant for energy production However the phenomenon is important since represents an uncontrollable source of neutrons in a reactor and it is, furthermore, possible to make use of it in the start-up stage. An example of the use of this fission is the neutron source of 252 californium
Induced fission. Certain heavy nuclei can be induced to fission, as result of one neutron capture. Consequently, several high-energy neutrons are produced, which permit to maintain the chain reaction process. The nuclei 235U,233U, 239Pu and 241Pu experience fission with low-energy thermal neutrons and they are called fissile materials The nuclei 238U and 232Th fission with fast neutrons The radiative capture of neutrons by 238u and 232Th leads to the formation of the fissionable materials 239Pu and 233U, so they are called fertile materials
Induced fission: Certain heavy nuclei can be induced to fission, as result of one neutron capture. Consequently, several high-energy neutrons are produced, which permit to maintain the chain reaction process. The nuclei 235U,233U, 239Pu and 241Pu experience fission with low-energy thermal neutrons and they are called fissile materials. The nuclei 238U and 232Th fission with fast neutrons. The radiative capture of neutrons by 238U and 232Th leads to the formation of the fissionable materials 239Pu and 233U, so they are called fertile materials
Table C.l. Thermal neutron(2200 m s or 0.0253 eV) cross sections for some special isotopes at 300 K. Cross-section notation: ar for (n, m);os for elastic scattering; at for total; a for fission; aa for (n, a); and ap for(n, p) 232Th 100 1.405×101y as=2.5 ub 5.13 233Th 22.3m 15 1450 1478 233t 1592×100y f 46.0 t=588 0.0055 2.455 10y af=0.465 y=103 at=116 235U 0.7200 7.038×10°y 587 ay=99,3 t=700 236 U 2.342×10′yof=47mb y=5.14 14.1 238 U 992745 4468×10yaf=118bay=2.73 t=12.2 239 U 23.45m =14 y=22 239 24110y 749 271 ot=1028 240pu 6564y of=64 mb 241 Pu 14.35y 0f=1015 y=363 rt=1389 242 Pu 3.733×10°y of= 1.0 mb dy=19.3 t=27.0