Photo taken by Tepco on June 10thNHK World public broadcasting in Japan has reported that a small work crew entered the Fukushima Daiichi Unit 4 secondary containment reactor building to inspect, and attempt to repair, the still dangerously overheating high-level radioactive waste storage pool. But, as reported at Daily Kos's Japan Nuclear Incident Live Blogs by FishOutOfWater, the work crew found severe damage and obstacles of fallen debris, including a water pipe crucial to restoring cooling circulation (see bent pipe in top center of photo at left). This will require a new approach to restoring cooling, that will take yet more time to figure out how to do, as the pool water hovers at 80 degrees Celsius -- close to the boiling point. If the water boils away, exposing the high-level radioactive waste to air, it could again catch fire, spewing deadly radioactive gases and particles directly onto the wind. Also, as reported by the Daily Kos blog, the Unit 4 pool is being shored up by steel support pillars, as it, and the building that houses it, leans precariously following a large-scale hydrogen explosion of still-indeterminate origin in the first days of the nuclear catastrophe in mid-March. The collapse of the pool could result in instant catastrophic loss of cooling, and large-scale radioactivity releases. Evidence also points to an ongoing nuclear chain reaction, due to the presence of high-levels of short-lived radioactive iodine-131 in the pool water. But the origin of the explosive hydrogen gas, and the location of the nuclear chain reaction -- whether from within the Unit 4 pool, or not -- remain a mystery.