QuoteIt doesn't matter if the primary spectrum is gamma because by the time it gets to the outside of the reactor it will be gamma. That would be enough to excite the characteristic x-ray of the tungsten.
Maybe, but looking for second order effects -- gammas from bremsstrahlung in light metals producing characteristic x-rays from tungsten -- would be far down in intensity. But if the tungsten is present in comparable amount with other metals, then the characteristic x-rays will have intensity similar to the bremsstrahlung gammas, or in any case, much higher than the 2nd order x-rays.