25 October 2011 at the Energy Department's Pantex Plant. An April 2014 GAO report notes that the National Nuclear Security Administration (NNSA) is retaining canned sub-assemblies (CSAs) "associated with a certain warhead indicated as excess in the 2012 Production and Planning Directive are being retained in an indeterminate state pending a senior-level government evaluation of their use in planetary defense against earthbound asteroids." In its FY2015 budget request, the NNSA noted that the B53 component disassembly was "delayed", leading some observers to conclude they might be the warhead CSAs being retained for potential planetary defense purposes. W-53 The W-53 nuclear warhead of the Titan II ICBM used the same physics package as the B53, without the air drop-specific components like the parachute system and crushable structures in the nose and sides needed for lay-down delivery, reducing its mass to about . The Mark-6 re-entry vehicle containing the W53 warhead was about long, in diameter and was mounted atop a spacer which was in diameter at the missile interface (compared to the missile's core diameter of ). With a yield of 9 megatons, it was the highest yield warhead ever deployed on a US missile. About 65 W53 warheads were constructed between December 1962 and December 1963. On 19 September 1980 a fuel leak caused a Titan II to explode within its silo in Arkansas, throwing the W53 warhead some distance away. Due to the safety measures built into the weapon, it did not explode or release any radioactive material. Fifty-two active missiles were deployed in silos prior to the beginning of the retirement program in October 1982. Effects Assuming a detonation at optimum height, a 9 megaton blast would result in a fireball with an approximate diameter. The radiated heat would be sufficient to cause lethal burns to any unprotected person within a radius (). Blast effects would be sufficient to collapse most residential and industrial structures within a radius (); within () virtually all above-ground structures would be destroyed and blast effects would inflict near 100% fatalities. Within a 500 rem (5 Sievert) dose of ionizing radiation would be received by the average person, sufficient to cause a 50% to 90% casualty rate independent of thermal or blast effects at this distance. Artifacts B53 on display in the free introduction exhibit room at the Atomic Testing Museum, Las Vegas, Nevada B53 on display at the Wings Over the Rockies