starboard nuclear reactor's cooling system dropped to zero. The reactor department crew found a major leak in the reactor coolant system, causing the coolant pumps to fail. The boat could not contact Moscow and request assistance because a separate accident had damaged the long-range radio system. The control rods were automatically inserted by the emergency SCRAM system, but the reactor temperature rose uncontrollably. Decay heat from fission products produced during normal operation eventually heated the reactor to . Making a drastic decision, Zateyev ordered the engineering section to fabricate a new coolant system by cutting off an air vent valve and welding a water-supply pipe to it. This required men to work in high radiation for extended periods. The jury-rigged cooling water system successfully reduced the temperature in the reactor. The accident released radioactive steam containing fission products that were drawn into the ship's ventilation system and spread to other compartments of the ship. The entire crew was irradiated as was most of the ship and some of the ballistic missiles on board. All seven members of the engineering crew and their divisional officer died of radiation exposure within the next month. Fifteen more sailors died within the next two years. Instead of continuing on the mission's planned route, the captain decided to head south to meet diesel-powered submarines expected to be there. Worries about a potential crew mutiny prompted Zateyev to have all small arms thrown overboard except for five pistols distributed to his most trusted officers. A diesel submarine, , picked up K-19s low-power distress transmissions and joined up with it. American warships nearby had also heard the transmission and offered to help, but Zateyev, afraid of giving away Soviet military secrets to the West, refused and sailed to meet S-270. He evacuated the crew and had the boat towed to its home base. Over the next two years, repair crews removed and replaced the damaged reactors. The repair process contaminated the nearby environment, in a zone within , and the repair crew. The Soviet Navy dumped the original radioactive compartment into the Kara Sea. K-19 returned to the fleet with the nickname "Hiroshima". According to the government's official explanation of the disaster, the repair crews discovered that the catastrophe had been caused by a faulty welding incident during initial construction. They discovered that during installation of the primary cooling system piping, a welder had failed to cover