Washington Hospital Center spent about $6 million to hire 600 temporary nurses, beef up security and cover other costs during last week's nurses' strike and subsequent lockout at the region's largest hospital, hospital officials said. Janis Orlowski, the hospital's CMO, also said that more than 500 of the facility's 1,600 nurses crossed the picket line during Friday's strike. Ken Zinn, a spokesman for National Nurses United, which represents the nurses, said he could not confirm the hospital's figures but thought they were inflated. Union officials say more than 1,000 nurses took part in last week's job action. The nurses walked off the job for a one-day strike but were locked out by the hospital from Saturday until Wednesday, when they started returning about 5 a.m., hospital spokeswoman So Young Pak said. There was no drop in business between Friday and Wednesday.