RE: G Value

["King, Michael S." <MICHAEL.S.KING@saic.com>]

For the radiolytic decomposition of water (Farooq et al, 1993)

H2O -> [2.7] ·OH + [2.6] eaq- + [0.6] ·H + [0.7]H2O2 + [2.6] H3O+ + [0.45]
H2.

In the above reaction, the values in the brackets are the G-values for the
specific species in the reaction.  A G-value is defined as the number of a
given species produced per 100 eV of energy loss by the original charged
particle and its secondaries, on the average, when it stops in water
(Turner, 1986). H3O+ is the hydronium ion, eaq- is the aqueous electron, and
·OH is the hydroxyl radical, 

First of all, I have never calculated the pressurization inside a sealed
quartz ampoule.  
But, this is how I would "try"...

First, I would "look-up" the reaction rate constants, k (change in
concentration per unit time) for Ni and the various radiolytic products.

Example,
Ni + ·OH  -> NiOH  , k1 = ? (where k1 is the reaction rate constant)