Let $R$ be an integral domain and $\bar R$ be its integral closure in the fraction field. If $b \in R$ is an irreducible element in $R$, then does $b$ remain irreducible in $\bar R$ also ?
I can see that $b$ is still a non-unit in $\bar R$, but I am unable to say anything about its factorization.
This may be related When prime element in an integral domain stays prime in integral extension
A counterexample . . .
Let $K$ be a field, and let $R=K[x^2,x^3]$.
Then $x^2$ is irreducible in $R$, but $x^2$ is not irreducible in $\bar R$, since $\bar R = K[x]$.