Would it be possible for an intelligent item to detonate a rune with the Read Magic Sp? and if they can how would the item then take the damage?
Yes, and it depends.
Intelligent items wouldn't even need the Read Magic special ability to read an explosive runes spell. Explosive runes detonates as soon as anything reads it, regardless of how they do so. Since all intelligent items can see and hear out to a distance of 30 feet, they can read an explosive runes just like any other character could.
The explosive runes spell description says that it damages any creature near the runes when they go off. According to the text on carried or worn items,
Unless the descriptive text for a spell (or attack) specifies otherwise, all items carried or worn by a creature are assumed to survive a magical attack.
Since explosive runes mentions nothing about damaging held objects, the intelligent item is totally safe if it is worn or carried by another creature.
However, if the intelligent item is unattended, and reads the explosive runes while away from another creature, it takes damage exactly as the spell describes. Its Reflex save is 2 + the caster level of the item. Since explosive runes does force damage, it counts as an energy attack, so divide the damage by 2 before applying hardness. The above rules and all of the other rules you're likely to need to determine how damaged your item will get are here.