The increase in intensity of a 252Cf neutron source surrounded by uranium depleted in the 235U isotope has been measured, and the results of this experiment were used to determine of238U for 252Cf spontaneous-fission neutrons. The measurement was performed in the TRIGA Mark III reactor, using the multiplication property of a subcritical TRIGA core. A Monte Carlo calculation was performed, which employed ENDF/B-III data, to provide analytical results for comparison with the measurements. The source enhancement obtained using a depleted uranium cylinder surrounding the 252Cf source was measured to be (7.35 ± 0.20)% compared with a calculated value of (7.11 ± 0.15)%. The calculated results, using ENDF/B-III data, agree with the measurement within the uncertainty of the evaluated values of v and σƒ.