The ''Nile Valley Parliament,'' set up under last year's integration pact between Egypt and Sudan, held its first session. The parliament has no legislative powers but can issue recommendations for joint action. At the session, Egyptian President Hosni Mubarak urged Arab countries to take a more active role in solving their problems. Meanwhile, a Nile River steamer carrying 627 passengers and crew caught fire and sank in waters behind the Aswan Dam. Police said the accident killed at least 48 people and left 269 passengers missing.