reactors was replaced with carbon dioxide, which conducted heat less efficiently. This allowed more heat to build up in the graphite. To reduce the incidence of cans jamming, their size was reduced from . More plutonium was produced by keeping the fuel elements in the reactor longer. Instead of pushing the entire tube out, half of it was, allowing elements to spend time in parts of the reactor where the neutron flux was less dense. The old reactors could now be run much longer. In December the AEC approved a scaled-back construction plan, with only one replacement reactor, at siteD (called DR), and one reactor at a new site (called H). The new reactors used the same designs as the wartime ones, although they had more pure graphite to allow them to be run at higher power levels, and smaller graphite blocks surrounding the process tubes to restrict expansion. Growth of Richland The population of Richland had already begun to increase again. In 1946 the Hanford Site had 4,479 operating employees and 141 construction workers. Two years later this had increased to 8,628 operating employees and 14,671 construction workers. Richland grew from 14,000 people in 1947 to 22,000 in 1950. To house the construction workers, a new construction camp was established called North Richland, which had a peak population of 13,000 in 1948. Many operating employees and construction workers also lived in Kennewick and Pasco. Shugg arranged for barracks to be brought by barge down the Columbia River from the old Naval Air Station Pasco. About 3,850 houses remained from the war; these were augmented by 800 houses and 64 apartments in 1947, and another 1,000 houses and apartments in 1948. Although the population stabilized, a housing shortage persisted into the 1950s. GE closed down the last of the dormitories in 1958. Richland had a newspaper, the Richland Villager, and every resident received a free copy. Commercial concession holders were pressured to buy adverting space. The villagers paid low rents for their houses, and Village Services was available to help with unpacking, laying carpets or babysitting. The adult population of Richland had an average education of 12.5 years, and 40 percent of the men had attended college, compared with 22 percent in the state of Washington as a whole, and the median annual family income in 1959 was compared with . In 1950 26 percent of American families had an