Denison Mines Corp.? announced the initial results of a highly successful In-Situ Recovery ("ISR") field test program ("2021 ISR Field Test") completed within the commercial-scale ISR test pattern installed in the Phase 1 area of the high-grade Phoenix uranium deposit ("Phoenix") at the Company's 95% owned Wheeler River Uranium Project ("Wheeler River" or the "Project") in northern Saskatchewan.? The 2021 ISR Field Test program was designed to further increase confidence and reduce risk in the application of the ISR mining method at Phoenix ? with the detailed results providing the necessary datasets for the permitting and preparation of a planned lixiviant test in 2022, which is expected to support the completion of the recently announced Feasibility Study (or "FS") for the Project. Test Pattern Installation: A test pattern consisting of five commercial-scale wells ("CSWs"), including GWR-038 to GWR-042, and 10 additional small diameter monitoring wells ("MWs") (together described as the "Test Pattern"), was successfully installed within the Phase 1 area of the Phoenix deposit during the summer months. Three methods of permeability enhancement were successfully evaluated on the five CSWs, with post permeability enhancement testing resulting in observed improvement in hydraulic responses and inter-well connectivity within the Test Pattern.? These results exhibit and confirm the ability to engineer additional access to the natural permeability within the deposit.? Permeability enhancement methods included the use of the MaxPERF drilling tool as well as wireline-conveyed tools designed to perforate and stimulate well production using a controlled propellant. The wireline tools can effectively "clean out" restricted pathways within the well screen, well bore, and the geological formation and provide increased flow rates in the wells by intersecting and connecting to the naturally occurring fractures within the ore zone. Twenty single-well injection tests were completed on the Test Pattern to evaluate natural permeability and the efficiency of permeability enhancement methods deployed in the CSWs. ?Nine single-well pump tests were completed amongst the five CSWs and four of the MWs to evaluate permeability, sustainable pumping rates, hydraulic connectivity, and baseline groundwater conditions. Importantly, testing showed good hydraulic connection between the CSWs in the ore zone horizon and no significant responses in any of the MWs in overlying or underlying horizons. One step-rate injection test was conducted on the center CSW (GWR-040) to evaluate hydraulic connectivity, maximum injection rates and injection pressures. Full-Scale Well Pattern Pump and Injection Test: A full-scale well pattern injection and pumping test was conducted to determine hydraulic connectivity for the Test Pattern as a whole, and to evaluate potential production rates for the pattern. The test was run as a modified 4-spot pattern as there was an unanticipated failure of the submersible pump in GWR-042. During the test, injection rates were matched to pumping extraction rates for balanced flow in the Test Pattern. Pumped groundwater from each of the outer wells (GWR-038, GWR-039, and GWR-041) was recycled for injection in the center well (GWR-040) to create a closed system. Production rates for the Test Pattern achieved a sustainable rate of 45.3 litres per minute ("L/min") injection in GWR-040 with minimal pressure on surface balanced with 15.1 L/min extraction at each GWR-038, GWR-039 and GWR-041. This test fundamentally achieved the 50 L/min flow rate assumed in the PFS for an operating well pattern.? Hydraulic control of the Test Pattern was confirmed by no significant hydrologic responses observed in any of the overlying or underlying monitoring wells. Ion Tracer Test: Following the full-scale injection and pumping test, an ion tracer test was completed using the 4 functional CSWs in the Test Pattern.? Flow rates were run at the same levels as the full-scale well pattern test with 45.3 L/min injection at the center well and a balanced extraction flow of 15.1 L/min at each of the three outer wells. The ion tracer, consisting of a 15% concentration of potassium chloride (KCl) by weight, was injected as an initial slug into the Test Pattern at GWR-040, followed by a chase phase involving the recirculation of water extracted from the three outer wells (closed system). The chase phase continued until peak concentrations of the ion tracer, measured in total dissolved solids ("TDS"), were observed at the three extraction wells (GWR-038, GWR-039 and GWR-041), followed by a decline in TDS prior to commencement of a remediation test. Breakthrough of the ion tracer, as observed by an increase in the TDS, occurred at the three extraction wells within 9 hours (GWR-039), 12 hours (GWR-041), and 14 hours (GWR-038). These breakthrough times observed during the field test are consistent with previous hydrogeological modelling conducted by Petrotek. Remediation Test: After completion of the ion tracer test, a "clean-up" remediation test was conducted to simulate the ability to remove injected fluid from the Test Pattern. For this test, injection was halted at the center well (GWR-040) and the three extraction wells were pumped to remove the remaining injected ion tracer.? Tracer concentrations measured during the eight-day clean-up simulation, as observed by field TDS measurements, declined to as low as 13% of the peak TDS value in GWR-038, 11% of the peak TDS value in GWR-041, and 4% of the peak TDS value in GWR-039. Hydrogeological Monitoring: Monitoring during the ion tracer test and subsequent clean-up test included: 376 field measurements of TDS from the CSW extraction wells to identify tracer concentrations; logging of water levels in each of the CSWs along with all of the surrounding MWs at five-minute intervals; logging of TDS values at five-minute intervals in the three overlying MWs to confirm the absence of any tracer concentrations in the overlying horizons; and daily groundwater sampling to send for lab analysis to confirm TDS values measured in the field and the exact concentration of the KCl tracer. The ability to maintain hydraulic control was established by sampling the three overlying MWs for TDS values before and after the ion tracer test.? No elevated values in TDS were observed during the test, thus confirming there was no migration of the tracer to overlying horizons. Data collected as part of the 2021 field program will be utilized to update the Phoenix hydrogeological model, and will provide the necessary data for the permitting and preparation of a lixiviant test planned for the Test Pattern in 2022.