Northwest ratepayers will save $23.8 million in interest costs because of a bond refinancing sale approved Thursday by operators of the commercial nuclear plant at Hanford.

The Washington Public Power Supply System's Executive Board approved the sale of $481 million in bonds.

The new bonds, sold at 5.1 percent interest, will replace others with interest rates ranging from 6 to 7.5 percent.

In the past 15 months, WPPSS has had six such refinancing bond sales, resulting in a savings to Northwest ratepayers of about $100 million.

The Bonneville Power Administration buys all WPPSS electricity and pays all costs of the bonds issued to build three nuclear plants BPA ordered in the 1970s. Only one was completed.

Lower debt cost for WPPSS will mean lower payments from Bonneville, which markets about half the region's electricity.