Since X-rays are known to produce browning in some types of glass, that may eventually help to mask a previous bluish-green (complementary) coloration, which can possibly be imparted by a ferrous iron contribution. Eventually, a neutral coloration can be achieved, what can be understood as a kind of physical decolourization. You may find a few patents helpful with regards to this approach; e.g., John H, Connelly and George B. Hares (Corning Glass Works), "X-ray absorbing glass compositions", 3,464,932, Sept. 2, 1969.    

Have a look at this paper

https://www.researchgate.net/publication/233765864_Effects_of_X-rays_on_Crystal_Nucleation_in_Lithium_Disilicate

Article Effects of X-rays on Crystal Nucleation in Lithium Disilicate

Dear Prof Queiroz and Prof Martis

I really appreciated your suggestion, I will dig in more detail about it.

We have studied this effect in detail. You find many of our papers in researchgate.net.

With best regards

Doris Ehrt

Most glasses will discolor when exposed to significant doses of radiation. X-rays work just fine. There are hundreds of papers in the literature dealing with radiation induced coloration. The nature of the defect formed will depend on the composition of the glass. Many different colors can be formed this way in different glasses. Some vitreous silicas, for example, will turn purple due to the ALOHC. Titanium dioxide doped silica will turn black. Glasses containing PbO will also turn black. Many borosilicates will turn brown due to centers involving boron. Even just simple binary alkali silicate glasses will color under x-rays. It does depend on the dose and the overall glass composition. Most studies involve gamma rays, but x-rays do similar things. Even ultraviolet rays can cause color changes (see "desert glass"), changes in ferrous/ferric redox ratio, and some defects. Look at those papers by Doris Ehrt. And stuff by Dave Grissom. Oh, and some stuff from my group. 

Dear Prof Shelby

Thank for your contribution, how can I forget your work on glass since I do have your introduction of glass book when I was at Alfred.

Once again, thank you for your supports.

BR

Wirat

Dear All

After I have read papers from all of you. May I have conclusion as 'the discolouring (white colour or opaque) in glass after x-ray irradiation due to crystallization while discolouring (transparent) is caused by changing of absorption band'.

Please correct me if I am wrong.

Dear Wirat Lerdprom,

Yes, your last question is a good final question. Does the discolouration necessarily mean that nanometric crystals have formed? Or can the discolouration occur without crystallisation. The papers suggested by those who've replied here appear to suggest that this is the case.

I'd be interested to know the answer too. 

Cheers,

Fabian