\section*{Problem 9}
\subsection*{Part A}

The boron concentration must be less than 1200ppm.

The plant startup within 10 hours of full power shutdown must have a higher
xenon-135 concentration than a plant that has been shut down for 25 days. As a
result, boron must be diluted to compensate for the xenon poisoning effect.

\subsection*{Part B}

At first boron must be concentrated to reduce power. At this point, xenon will
increase in the core as xenon burnup reduces. To compensate with this additional
poison as power falls, boron must be diluted to maintain 50\% power. Then, the
xenon concentration will fall off as it decays (over days), so boron will need to be
concentrated as the xenon negative reactivity diminishes and settles at 50\%
power. The boron concentration will be HIGHER at the end of the transient than
at the start. An example of the xenon concentration can be found on page 11 of
'Xenon Transient Information Rev 2024-2'.

Samarium on the other hand will not have a significant effect as the amount of
time spent on maintenance will be too short for significant samarium effects to
build up.
