[Peter]

Your problem isn't Hibernate, but the definition of the tables:
Check this:
Here, you define the primary key of the nuser and it is 2 columns

notification_id and nuser_id

Code:

 CREATE TABLE `nuser` (
  [...]

   PRIMARY KEY  (`notification_id`,`nuser_id`),

 )

But, here you tell it, to does a reference to a nuser table, only with the column notification_id

Code:

 CREATE TABLE `nuseractions` (

   CONSTRAINT `nuseractions_fk` FOREIGN KEY (`notification_id`)
 REFERENCES `nuser` (`notification_id`) ON DELETE CASCADE ON UPDATE CASCADE,

But nuser has a primary key with 2 columns, so it's incorrect.
check it, and fix it