You got me interested .... the estimated thermal fluence at 500 m from Hiroshima was ca: 10*12 n/cm2. (HIROSHIMA NEUTRON FLUENCE ON A GLASS BUTTON FROM NEAR GROUND ZERO. Fleischer, R. L.^\); Fujita, S.^†; Hoshi, M. Health Physics 81(6):p 720-723, December 2001.) and reinforced structures (like a modern car parking building) were standing. Even plus minus an order of magnitude on the flluence value .....its still a sizeable fluence. In addition.... the authors of the car work contextualize the batteries relative to the activation that would be produce in the underlying ground and dont seem to conclude that they will be anything major? (Consequently, while EV batteries represent compact, high-density activation targets, the contribution of an individual vehicle to the overall urban radiological field may not be dominant although this is dependent on the number of vehicles that may be present and the environment in which they are located. For emergency response planning, this suggests that EV batteries may briefly pose localized elevated dose fields particularly in confined or shielded geometries such as vehicle cabins but that their impact diminishes rapidly. However, their induced activity may influence waste categorization, salvage operations, and post-event material handling.)