The X-10 semiworks operated as a plutonium production plant until January 1945, when it was turned over to research activities. By this time, 299 batches of irradiated slugs had been processed. A radioisotope building, a steam plant, and other structures were added in April 1946 to support the laboratory's peacetime educational and research missions. All work was completed by December 1946, adding another $1,009,000 to the cost of construction at X-10, and bringing the total cost to $13,041,000. Operational costs added another $22,250,000.