$[$Maximum mark:$11]$

$20\frac{N}{2}SL$

One possible fission reaction of uranium$-235(U-235)$ is

${?}_{92}^{235}U+{?}_0^{1}n{?}_{54}^{140}xe+{?}_{38}^{94}Sr+2_0^{l}n$

Mass of one atom of $U-235=235u$

Binding energy per nudeon for U$-235=7\mathrm{.}59$MeV

Binding energy per nucleon for $xe-140=8\mathrm{.}29$MeV

Binding energy per nucleon for Sr$-94=8\mathrm{.}59$MeV

$($a$($i$))$ State what is meant by binding energy of a nucleus:

$($a$($ii$)$ Outine why quantities such as atomic mass and nuclear binding energy are often expressed in non$-$sI units.

$($a$($iii$)$ Show that the energy released in the reaction is about $180$MeV.

A nuclear power station uses U$-23$S as fuel. Assume that evey fission reaction of U$\mathrm{.}235$ gives rise to $180$MeV of energy.

$($b$($i$)$ Estimate, in J kg ${?}^{-1},$ the specif eneroy of U$235.$

$($b$($ii$)$ The power station has a useful power output of $1\mathrm{.}2$ GW and an efficiency of $36\%.$ Determine the mass of U$-235$ that undergoes fisionin one day.

A sample of waste produced by the reactor contains $1.0kg$ of strontium$-94($Sr$94).5r-94$ is radioactive and undergoes beta minus $()$ decay into a daughter nucide $x.$ The reaction for this decay is

${?}_{38}^{4}Srx\frac{+}{b}ar(v{)}_e+e^{.}$

$($cii$)$ Write down the proton number of nuclide $x$