Systematic analysis of the transport critical current densities J_c at 77 K for ^235U-oxide (UO_2·2H_2O) doped Ag-sheathed (Bi,Pb)_2Sr_2Ca_2Cu_3O_x tapes (Bi2223) irradiated with thermal neutrons is presented. Within the explored range of U-oxide concentrations (c £ 2 wt%) and neutron fluences (ϕ £ 6·10_19 n/m^2), the pinning of vortices in irradiated tapes increases approximately linearly with fission track density (proportional to cϕ), as evidenced by progressively weaker magnetic field dependence of Jc on increasing cf. Accordingly, the crossover field B* at which the pinning force density F_p reaches its maximum value F_pmax = J_cB* and the irreversibility field B_irr(F_p → 0) increase approximately linearly with cϕ. Therefore, J_c-B and F_p-B variations for all tapes with vortex pinning dominated by fission tracks show universal scaling behaviour with the scaling parameter B* (proportional to cϕ). Taking into account the adverse effects of c and f on Jc of our tapes, we estimate a maximum B* and B_irr that can be reached in ^235U-oxide doped Bi2223 tapes at 77 K
