* Study faulted for not looking at absolute reactor numbers
* Nuclear proportion at 22-29 pct could still mean more reactors
* More than half of nuclear reactors face life-span expiry by 2035
By Meeyoung Cho and Jane Chung
SEOUL, Nov 7 (Reuters) - South Korea should reduce its reliance on nuclear power as advised by a working group last month but should clarify how many new reactors will be added in absolute terms, participants at a public congressional hearing said on Thursday.
A working group in October recommended that South Korea reduce nuclear power's share of overall generating capacity, but participants at the hearing said that might still mean a rise in the number of reactors as power demand grows.
The study group said nuclear power should be reduced to between 22 percent and 29 percent of overall capacity by 2035, compared with a government plan for 41 percent by 2030, due to safety concerns triggered by its own corruption scandal and Japan's Fukushima crisis.
"This suggested proportion looks like reduction but if nuclear capacity is calculated based upon electricity demand growth, this could mean completing on-going and planned reactors and adding 12-18 units," Yun Sun-jin, a professor at Seoul National University, told the hearing.
That will considerably hike the risk from nuclear power generation, she said.
Asia's fourth-largest economy faces severe power shortages this winter and next summer due to nuclear plants that have been shut amid the safety scandal that started late last year.
Authorities have indicted 100 people, including a former top state utility official, for corruption after the discovery of the fake safety certificates.
A shift away from nuclear, which generates a third of South Korea's electricity, could cost tens of billions of dollars a year by boosting imports of liquefied natural gas, oil or coal.
The congressional energy committee's first public hearing ahead of a possible revision of Seoul's energy policy next month was attended by scores of representatives from the government, industry, civic group and academic sectors.
Lee Heon-seok, representative of civic group Energy Justice Actions, said the working group's suggestion should have also considered that the life-spans of 14 nuclear reactors, more than half of the country's 23 reactors, will expire by 2035.
Kim Jun-dong, deputy minister of energy & resources policy, confirmed that a target number of nuclear reactors has yet to be considered.
South Korea also has to decide at "a high level" if in the ranges recommended for nuclear power it is possible to reduce carbon emissions and ensure stable power supply, Kim said.
Of the country's total 23 reactors, six are offline. That includes three shut since May to replace cables supplied with fake documents, one awaiting approval for an extension on its 30-year life-span, and another shut for maintenance, according to Korea Hydro & Nuclear Power (KHNP). (www.khnp.co.kr)
A sixth reactor closed last week to check welding work related to the safety of a steam generator.
KHNP, owned by state-run utility Korea Electric Power Corp (KEPCO), operates South Korea's nuclear reactors.
The International Atomic Energy Agency (IAEA) last week said South Korea may struggle to cut its reliance on nuclear power, as the study group suggested it do, as the country has no natural resources to meet its huge energy requirements. (Editing by Tom Hogue)