"His oversight of the crew's performance did not identify these issues" on his own, Navy Lt. Alli Myrick, a public affairs officer, told The Associated Press. Portland's commanders identified the problems during a routine review, she said.
It appears from a preliminary investigation on the Hampton that sailors in Submarine Squadron 11 had skipped the required analysis of the chemical and radiological properties of the submarine's reactor for more than a month, even though a daily check is required.
The Hampton, a Los Angeles Class submarine assigned to Submarine Squadron Eleven, is the most advanced nuclear attack submarine in the world, carrying a torpedo, cruise missile, and mine-laying arsenal, according to information on the Navy's Web site. The submarine is docked in San Diego.
Portland's dismissal as commander is effective immediately. Myrick said Portland will be temporarily assigned to squadron duty and the Hampton will not conduct operations until the Navy can confirm the operational standards have been met. Myrick said at no time was the submarine conducting unsafe operations.
"He has not been charged with any offense nor has he received non-judicial punishment," Myrick said.
There was no phone listing for Portland in San Diego, and the Navy did not immediately respond to an AP interview request.
Portland's removal comes after officials also discovered that logs on the Hampton had been filled out to make it appear the daily checks of the reactor water had actually been done.
Other members of the squadron discovered the lapse during a routine examination required as part of the redundancy built into the system so problems are caught. The examination was done as the submarine was nearing the end of a West Pacific deployment that concluded Sept. 17.
The investigation was first reported in Monday's edition of Navy Times newspaper, which quoted an unidentified source as saying that failing to measure and maintain the correct water chemistry in the reactor over the long-term could cause corrosion in the propulsion system.
The reported problems with procedures and record keeping in the Navy squadron follows an incident in August when a B-52 bomber was mistakenly armed with six nuclear-tipped cruise missiles and flown to a Louisiana base.
The mission from Minot Air Force Base in North Dakota was to ferry cruise missiles that had been slated for decommissioning but the warheads were supposed to have been removed beforehand.
The Air Force disciplined some 70 airmen.
Portland is the fourth commanding officer of a submarine to be relieved of duty this year. The other three, who were relieved for various unrelated actions, were: Cmdr. Edwin Ruff of the USS Minneapolis St. Paul, Cmdr. Matthew Weingart of the USS Newport News and Cmdr. William Schwalm of the USS Helena.
Portland will be replaced by Cmdr. William J. Houston, who previously was assigned as a special assistant to the Director of the Naval Reactors.