Who are the clients of this SLSB? How do they get access to the bean?
Looks like you need StrictMaxPool to cap the maximum number of beans in a pool. See the guide here http://www.jboss.org/file-access/default/members/jbossejb3/freezone/docs/reference/1.0.7/html/SessionBean_and_MDB_configuration.html
Also see this similar discussion http://community.jboss.org/message/364033#364033