Praise be to Allah.
There is no objection against one urinating while making ghusl. If the intention of ghusl was to purify oneself of janaba or major impurity, then he should complete his ghusl. If the intention was to purify himself of al-hadath al-asghar (minor impurity), he must renew his niyyah (intention) to cleanse himself of his state of impurity and it enough to make wudu' washing the body parts normally washed during wudu'.
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