We report a Chandra observation of the z = 3.395 radio galaxy B2 0902+343 .
The unresolved X-ray source is centred on the active nucleus .
The spectrum is well fit by a flat power law of photon index of \Gamma \sim 1.1 with intrinsic absorption of 8 \times 10 ^ { 22 } { \thinspace cm } ^ { -2 } , and an intrinsic 2–10 keV luminosity of 3.3 \times 10 ^ { 45 } { \thinspace erg } { \thinspace s } ^ { -1 } .
More complex models which allow for a steeper spectral index cause the column density and intrinsic luminosity to increase .
The data limit any thermal luminosity of the hot magnetized medium , assumed responsible for high Faraday rotation measures seen in the radio source , to less than \sim 10 ^ { 45 } { \thinspace erg } { \thinspace s } ^ { -1 } .