An underground tunnel used to store abandoned railcars and filled with decades-old radioactive waste collapsed this week at the Washington state Hanford nuclear waste site, renowned as the most contaminated nuclear facility in the nation. Crews are investigating the cause of the collapse and responding to fears from residents of radioactive contamination. CBS News science and futurist contributor Dr. Michio Kaku joins from the ‘CBS This Morning’ newsroom to address the fallout. WATCH NOW!