Among the many fission products that may be extracted chemically from the spent fuel of a nuclear power reactor is . It is produced in typical large reactors at the rate of . By its radioactivity it generates thermal energy at the rate of . (a) We have to calculate the effective disintegration energy associated with the decay of a nucleus. ( includes contributions from the decay of daughter products in its decay chain but not from neutrinos, which escape totally from the sample.) (b) It is desired to construct a power source generating 150 W (electric) to use in operating electronic equipment in an underwater acoustic beacon. If the source is based on the thermal energy generated by and if the efficiency of the thermal-electric conversion process is 5.0% , we have to calculate the amount of that will be needed. The atomic mass of is 89.9 u.

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(a)

The atomic mass of is 89.9 u. Therefore, number of atoms contained in 1.0 g of will be

As the half-life of disintegration of is , its disintegration constant will be

One gram of will decay at the rate

By its radioactivity 1.0 g of generates thermal energy at the rate of 2.3 J per second. Therefore, the effective disintegration energy associated with the decay of a nucleus will be

(b)

It is desired to construct using a power source generating 150 W (electric) to use in operating electronic equipment in an underwater acoustic beacon. It is given that the efficiency of the thermal-electric conversion process is 5.0%. Therefore, the amount of required will be