def irradiation_chronology(name, allow_null=False):
    p = os.path.join(paths.meta_root, name, 'chronology.txt')
    return Chronology(p, allow_null=allow_null)
def irradiation_chronology(name, allow_null=False):
    p = os.path.join(paths.meta_root, name, 'chronology.txt')
    return Chronology(p, allow_null=allow_null)