  Detection and direct power conversion of high energy and high intensity
ionizing radiation could be a key element in next generation nuclear reactor
safety systems and space-born devices. For example, the Fukushima catastrophe
in 2011 could have been largely prevented if 1\% of the reactor's remnant
radiation ($\gamma$-rays of the nuclear fission) were directly converted within
the reactor to electricity to power the water cooling circuit. It is reported
here that the hybrid halide perovskite methylammonium lead triiodide could
perfectly play the role of a converter. Single crystals were irradiated by a
typical shut-down $\gamma$-spectrum of a nuclear reactor with 7.61E14 Bq
activity exhibit a high-efficiency of $\gamma$-ray to free charge carrier
conversion with radiation hardening. The power density of 0.3 mW/kg of
methylammonium lead triiodide at 50 Sv/h means a four times higher efficiency
than that for silicon-based cells. The material was stable to the limits of the
experiment without changing its performance up to 100 Sv/h dose rate and 57 Sv
H*(10) ambient total $\gamma$-dose. Moreover, the {\gamma}-shielding
performance of methylammonium lead triiodide was found to be superior to both
ordinary and barite concrete.
