Cell: Structure and Functions
Consider the fission of 92238U by fast neutrons. In one fission event, no neutrons are emitted and the final end products, after the beta decay of the primary fragments, are 58140Ce and 4499Ru. Calculate Q for this fission process. The relevant atomic and particle masses are:
Under certain circumstances, a nucleus can decay by emitting a particle more massive than an α-particle. Consider the following decay processes:
Calculate the Q-values for these decays and determine that both are energetically allowed.
A piece of wood from the ruins of an ancient building was found to have a C14 activity of 12 disintegration per minute per gram of its carbon content. The C14 activity of the living wood is 16 disintegration per minute per gram. How long ago did the tree, from which the wooden sample came, di? Given half-life of C14 is 5760 years.
A 1000 MW fission reactor consumes half of its fuel in 5.00 y. How much 92235U did it contain initially? Assume that the reactor operates 80% of the time, that all the energy generated arises from the fission of 92235U and that this nuclide is consumed only by the fission process.
The fission properties of 94239Pu are very similar to those of 92235U. The average energy released per fission is 180 MeV. How much energy, in MeV, is released if all the atoms in 1 kg of pure 94239Pu undergo fission?
When charcoal is prepared from a living tree, it shows a disintegration rate of 15.3 disintegration of 14C per gram per minute. A sample from an ancient piece of charcoal shows . 14C activity to be 12.3 disintegration per gram per minute . how old is this sample? half-life of 14C is 5730 y.
The radio nuclide 11C decays according to
611C→511B+e++ν: T1/2 =20.3 min
The maximum energy of the emitted positron is 0.960 MeV.
Given the mass values:
m(611C)=11.011434u and m(611B)=11.009305u
Calculate Q and compare it with the maximum energy of the positron emitted.
The normal activity of living carbon-containing matter is found to be about 15 decays per minute for every gram of carbon. This activity arises from the small proportion of radioactive 614C present with the stable carbon isotope 612C. When the organism is dead, its interaction with the atmosphere (which maintains the above equilibrium activity) ceases and its activity begins to drop. From the known half-life ( 5730 years) of 614C, and the measured activity, the age of the specimen can be approximately estimated. This is the principle of 614C dating used in archaeology. Suppose a specimen from Mohenjodaro gives an activity of 9 decays per minute per gram of carbon. Estimate the approximate age of the Indus-Valley civilisation.