Experimental Modeling of Hydrogen Evolution Rates from Surfaces with Exposed Aluminum in Contact with Containment Sprays in Pressurized Water Reactor Nuclear Power Plants

Containment spray solutions recommended for application by the Tennessee Valley Authority contain boric acid buffered with either sodium hydroxide or trisodium phosphate. These solutions react with aluminum to produce aluminum compounds and gaseous hydrogen. Rates of hydrogen evolution from aluminum surfaces immersed in (a) spray solution containing boric acid and sodium hydroxide (pH -9.8) and (b) solution containing boric acid, hydrazine, and trisodium phosphate (pH = 7.5) can be correlated within experimental error, respectively, by the equations:

	log10R =−3.4× 103T−1 + 9.2	(1)
and
	log10R = −4.2 × 103T−1 + 10.2 .	(2)

Significant reduction in hydrogen evolution rate is obtained if the sodium hydroxide buffered solution is modified by the addition of sodium silicate. Correlating equations for the modified solutions are, respectively:

	log10R=−1.9(103)T−1 + 2.0	(1a)
and
	log10R =−3.9(103)T−1 + 9.5 .	(2a)