Sanyo briefly closed the plant again after Monday's quake but reopened it after determining there was no damage. Any financial impact this time would be minimal, it said in a statement.
Of wider concern was an impending electricity crunch.
Tokyo-based TEPCO warned on Wednesday that the closure of its seven-reactor Kashiwazaka-Karima plant, which provides up to 13 percent of the utility's total electricity output, could trigger a power shortage for the busy capital.
TEPCO was considering bringing six retired thermal power generators into operation.
The utility has also asked six other Japanese power companies to sell it emergency electricity from late this month through the end of September.
In 2003, TEPCO was forced to temporarily halt all of its 17 nuclear reactors for several months after admitting it manipulated safety data in the late 1980s and early 1990s. The company managed to scrape through that summer by firing up retired thermal plants and buying emergency power.
TEPCO's shareholders have been anything but forgiving this time, driving the company's share price down 10.3 percent since its last close before the quake.
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