We are characterizing the corrosion behavior of the radioactive glass that was made with sludge from Tank 51 at the Defense Waste Processing Facility (DWPF) and a nonradioactive glass having the same composition, except for the absence of radionuclides. Static dissolution tests are being conducted in a tuff groundwater solution at glass surface area/solution volume ratios (S/V) of 2000 and 20,000 m−1. These tests are being conducted to assess the relationship between the behavior of this glass in a 7-day Product Consistency Test and in long-term tests, to assess the effects of radionuclides on the glass corrosion behavior, and to measure the disposition of radionuclides that are released as the radioactive glass corrodes. The radioactive glass reacts slower than the nonradioactive glass through the longest test durations completed to date, which are 140 days for tests at 2000 m−1 and about 400 days for tests at 20,000 m−1. This is probably because radiolysis results in lower solution pH values being maintained in tests with the radioactive glass. Rate-affecting alteration phases that had formed within one year in tests with other glasses having compositions similar to the Tank 51 glass have not yet formed in tests with either glass.