Some methods described in the literature for the determination of α in the 1/E1+α epithermal neutron spectrum are critically reviewed with respect to their accuracy. The multi resonance—detector method with
Cd-covered irradiations, as used by SCHUMANN and ALBERT, is generalized by subtracting the epithermal 1/v-tail and by introducing
the effective resonance energy, as defined by RYVES. The two-detector method of RYVES is modified by using Cd-ratio measurements,
thus eliminating the introduction of systematic errors due to the inaccuracy of absolute nuclear data. The adapted methods
are applied in channel 15 of the Thetis reactor (Gent).