Absence of (n,2n) reactions on Zr90


I am using the Hadr03 example with the QGSP_BIC_AllHP physicslist to simulate the irradiation of a 1 cm thick Zr target by neutrons with 19 MeV energy.

At 19 MeV the Zr90(n,2n)Zr89 reaction has a cross section of 1.2 barns. Considering a density of natural zirconium of 6.52 g/cm^3, and isotopic fraction of Zr90 of 51.45%, I should get about 265 Zr89 nuclei with 10^4 incident 14MeV neutrons.

Yet when I run the example I have no Zr89 at all ! I don’t understand this result, hopefully someone can help.

Thank you in advance,

_Geant4 Version:_11.2.0
_Operating System:_Red Hat 8.5.0-18
_CMake Version:_3.20.2

HP not; but QGSP_BIC or FTFP_BERT yes.