Actually I don't think lithium will cause an explosion and lithium hypo is acceptable for use in a spa with a pH of about 8.0. It is more commonly used in Canada because dichlor is (or was) less available there. Cal hypo, which is exclusively used in pools, can cause an explosion if mixed with triclor or dichlor.
I would return the lithium and use dichlor because it is a better product for a spa.
