BERKELEY, Calif. (AP) - More change is on the way for the national labs managed by the University of California, with the head of the Lawrence Berkeley facility announcing plans Monday to step down after 15 years.

"I feel I've accomplished what I've come here to do," Charles Shank said in a telephone interview Monday. "Any institution needs new leadership after 15 years."

UC has managed Lawrence Berkeley, which conducts unclassified research, since it was founded by pioneering physicist Ernest O. Lawrence in 1931. The university has managed the Los Alamos and Lawrence Livermore nuclear weapons labs since they were formed in 1943 and 1952 respectively.

But challenges to UC's stewardship role have been raised in recent years, especially at the Los Alamos facility in New Mexico, where there have been a series of embarrassing business and security lapses.

Last year, the Energy Department announced it would seek competitive bids for a lab manager when the Los Alamos contract expires in 2005. And Congress has since passed legislation requiring competitive bids for a number of facilities, including the Berkeley and Livermore labs.

The Lawrence Berkeley management contract expired Jan. 31, but the Energy Department extended the date to January 2005. That means the contract will go up for bid at the same time as the Los Alamos contract. It is unclear when the Livermore contract will be bid.

UC regents haven't decided yet whether they will submit bids. If they do the 60-year-old Shank, who will be returning to the Berkeley faculty as a professor, will play an important role, said UC President Robert C. Dynes.

"I believe Chuck's effective leadership, the tremendous accomplishments of the scientists at Berkeley Lab and our own efforts to renew and reinforce management practices throughout the UC laboratory system have created a very strong competitive position for the University of California," Dynes said in a statement.

Dynes said he'll begin looking immediately for a new lab director.

Shank said it's hard to imagine who could compete against UC to run the Berkeley lab, so closely connected with the UC Berkeley campus for so long, but he is ready to work with lab leadership on a proposal if regents decide to bid.

"There is a need to go through the whole process," Shank said. "We intend to take it very seriously."