The nuclear isomer ^229mTh, with its ~8 eV excitation energy, is a prime candidate for a nuclear clock that will revolutionize precision measurement and fundamental physics. Recent breakthroughs in the observation of ^229mTh radioactive decay and the direct nuclear laser excitation in ²²⁹Th-doped crystals have inspired a series of foundational works towards the realization of a solid-state nuclear clock. However, the global scarcity of ²²⁹Th, extracted mainly from ²³³U decay, along with material science challenges in fabricating highly doped ²²⁹Th crystalline targets, present a severe bottleneck of nuclear clock developments. Here, we present a solution to these challenges by demonstrating in situ conversion of ²³²Th-doped crystals into ²²⁹Th-doped variants. Utilizing the naturally abundant ²³²Th isotope as a precursor enables safe and scalable production of SrF₂ crystals for solid-state nuclear clocks. Through photonuclear reactions induced by bremsstrahlung from an electron beam, we experimentally verify this photonuclear conversion technique in ²³²Th:SrF₂ and ²³²Th:CaF₂ crystals while preserving their VUV transparency. This process generates ^229m,gTh along with parent isotopes ²²⁹Ac and ²²⁹Ra via (gamma, 3n), (gamma, 2np), and (gamma, 2pn) reactions. Off-line gamma-ray spectroscopy reveals ²²⁹Th concentrations of order 10⁹ cm^-3. Using a high-flux broadband gamma ray sources, ²²⁹Th concentrations at 10¹⁵ cm^-3 can potentially be achieved within several hours, comparable to crystals used in direct laser excitation experiments. Moreover, while VUV spectroscopy of irradiated SrF₂ and CaF₂ crystals shows evidence of direct photon decay from ^229mTh, the VUV transparency of SrF₂ crystal basically recovered without any annealing, which is of great importance for long-term irradiation production of ²²⁹Th. This approach overcomes critical limitations in isotope availability and radioactives handling, paving the way for the exploration of various solid-state host crystals and scalable production of nuclear clocks.

nuclear clock,,photonuclear,229Th