* Staff seeks commission action in March
* Proposed orders follow task force recommendations
* Timeline calls for full compliance in 2016
Feb 22 (Reuters) - The staff of the U.S. Nuclear Regulatory Commission has proposed the first three rules to address safety issues raised by Japan's Fukushima nuclear disaster, changes the staff said could be implemented by the end of 2016.
"Each of the orders is focused on enhancing defense in depth at nuclear power plants through increased capabilities to minimize the potential for core damage following a beyond design basis external event," the NRC said in a memo detailing the proposal.
March 11 will mark the first anniversary of the world's worst nuclear disaster in 25 years when an earthquake and tsunami overwhelmed the Fukushima Daiichi plant on Japan's northeast coast, knocking out power and resulting in a nuclear meltdown and the release of radiation.
The first orders, subject to lengthy review and commission approval, call for all U.S. nuclear operators to develop plans to deal with extreme situations, such as earthquakes, floods and other natural disasters that could affect multiple reactors operating at a single site.
The NRC staff also proposed that all plants improve instrumentation in the pools used to store spent nuclear fuel.
A third proposal would address containment "vent" structures at plants similar in design to the crippled Daiichi nuclear plants, according to the NRC memo from R.W. Borchardt, the NRC's executive director of operations.
Modifications and operating changes based on lessons from the Fukushima disaster are expected to add millions of dollars in costs for nuclear operators, including Exelon Corp, Entergy Corp, Southern Co and others.
Earlier this week, the Nuclear Energy Institute, a U.S. nuclear industry trade group, said plant owners had committed to purchase additional equipment to respond to emergencies that interrupt off-site power to reactors.
The NRC staff said the industry initiative, called FLEX, may satisfy the proposed order to mitigate certain safety challenges.
The staff recommended that the commission issue the orders early next month before the first Fukushima anniversary.
An implementation timeline proposed by the staff calls for all plants to submit a compliance plan to the agency by Feb. 28, 2013, and to incorporate all changes by Dec 31, 2016, at the latest.
The proposed rules were among the most important changes identified by the NRC's Fukushima task force last year and viewed as upgrades that could move forward without significant delay.
The task force made numerous other recommendations, but many will require more study of the Fukushima disaster and industry review. It will take years for the agency to modify its regulations and implement changes outlined by the task force.
NRC chairman Gregory Jaczko has called for the work to be completed in five years which would be an accelerated time line for the NRC.
The staff said the proposed Fukushima rules would affect the recently approved two-unit expansion at Southern Co's Vogtle plant the same as any existing reactor.
On Feb. 9, the NRC approved Southern's construction and operating license to build an advanced nuclear design over the objections of Jaczko.
Southern officials have said the AP1000 reactor design they are building will meet most Fukushima-related safety upgrades to be ordered by the NRC.
The U.S. has 104 operating nuclear reactors in 31 states.