PITZER is a PHREEQC version of the Yucca Mountain EQ3/6 thermodynamic database that includes 'Pitzer data' to parameterise the activity coefficients of aqueous species.

In 2008, Quintessa was commissioned by NWMO to convert the database format from its native EQ3/6 format into PHREEQC format. The associated work is documented in a Quintessa technical memorandum. The PHREEQC formatted version of the database can be obtained by contacting Steven Benbow. As noted in the Quintessa technical memorandum, there are known limitations with the database and any application must be undertaken with care to ensure that the database is used in an appropriate manner.