Technical Report with an Updated Mineral Resource Estimate for the Waterbury Lake Property, Northern Saskatchewan, Canada Report Prepared by Denison Mines Corp. Effective date: December 21, 2018 Signature date: December 21, 2018 With Audited Mineral Resource Statement for the Huskie deposit by SRK Consulting (Canada) Inc. Authors and Qualified Persons Serdar Donmez, P.Geo.,E.I.T., Denison Mines Corp. Dale Verran, Pr.Sci.Nat., P.Geo., Denison Mines Corp. Paul Burry, P.Geo., Denison Mines Corp. Oy Leuangthong, P.Eng, SRK Consulting (Canada) Inc. Cliff Revering, P.Eng, SRK Consulting (Canada) Inc. Allan Armitage, P.Geo, SGS Geostat Alan Sexton, P.Geo, GeoVector Management Inc. www.denisonmines.com Technical Report with an Updated Mineral Resource Estimate for the Waterbury Lake Property, Northern Saskatchewan, Canada Denison Mines Corp. 230-22nd Street East, Suite 200 Saskatoon, Saskatchewan, Canada S7K 0E9 Website: www.denisonmines.com Tel: +1 306 652 8200 Fax: +1 306 652 8202 SRK Consulting (Canada) Inc. SGS Geostat GeoVector Management Inc. 155 University Avenue 10 Boul. de la Seigneurie 10 Green St Suite 312 Toronto, Ontario, Canada Est, Suite 203 Nepean ON, Canada M5H 3B7 Blainville, QC, Canada K2J 3Z6 Tel: +1 416 601 1445 J7C 3V5 Tel: +1 613 843 8109 Fax: +1 416 601 9046 Tel: +1 450 433 1050 Fax: +1 613 843 8110 E-mail: [email protected] Fax: +1 450 433 1048 Email: [email protected] Email: [email protected] Effective date: December 21, 2018 Signature date: December 21, 2018 Authors and Qualified Persons: Serdar Donmez, P.Geo., E.I.T. Dale Verran, P.Geo. Pr.Sci.Nat. Paul Burry, P.Geo. Denison Mines Corp. Denison Mines Corp. Denison Mines Corp. Oy Leuangthong, P.Eng. Cliff Revering, P.Eng. SRK Consulting (Canada) Inc. SRK Consulting (Canada) Inc. Allan Armitage, P.Geo. Alan Sexton, P.Geo SGS Geostat GeoVector Management Inc . Technical Report with an Updated Mineral Resource Estimate for the Waterbury Lake Property www.denisonmines.com TABLE OF CONTENTS TABLE OF CONTENTS ................................................................................................................ I LIST OF FIGURES .................................................................................................................... VII LIST OF TABLES ....................................................................................................................... IX 1 SUMMARY ............................................................................................................................ 1 1.1 Executive Summary ........................................................................................................ 1 1.2 Technical Summary ........................................................................................................ 2 1.2.1 Property Description and Location .......................................................................... 2 1.2.2 Ownership ............................................................................................................... 2 1.2.3 Geology and Mineralization ..................................................................................... 3 1.2.4 History ..................................................................................................................... 5 1.2.5 Mineral Resource Estimates and Methodologies .................................................... 6 1.2.5.1 J Zone .............................................................................................................. 6 1.2.5.2 Huskie .............................................................................................................. 7 1.2.6 Conclusions and Recommendations ....................................................................... 9 1.2.7 Work Program and Budget for 2019 ........................................................................ 9 2 INTRODUCTION ................................................................................................................. 1 1 2.1 Denison Mines Corp. .................................................................................................... 11 2.2 Terms of Reference ...................................................................................................... 12 2.3 Purpose of the Report .................................................................................................. 12 2.4 Sources of Information ................................................................................................. 12 2.5 Inspection on Property .................................................................................................. 13 2.6 Abbreviations and Definitions ....................................................................................... 13 3 RELIANCE ON OTHER EXPERTS ..................................................................................... 16 4 PROPERTY DESCRIPTION AND LOCATION ................................................................... 17 4.1 Location ........................................................................................................................ 17 4.2 Mineral Disposition and Tenure .................................................................................... 17 4.3 Ownership .................................................................................................................... 2 1 4.4 Nature and Extent of Title ............................................................................................. 21 4.5 Royalties, Agreements and Encumbrances ................................................................. 22 4.6 Environmental Liabilities ............................................................................................... 23 4.7 Work Permits ................................................................................................................ 23 4.8 Other Significant Factors and Risks ............................................................................. 24 Technical Report with an Updated Mineral Resource Estimate for the Waterbury Lake Property Page i www.denisonmines.com 5 ACCESSIBILTY, CLIMATE, LOCAL RESOURCES, INFRASTRUCTURE AND PHYSIOGRAPHY ....................................................................................................................... 25 5.1 Access to Property ....................................................................................................... 25 5.2 Climate ......................................................................................................................... 25 5.3 Local Resources and Infrastructure .............................................................................. 25 5.4 Physiography ................................................................................................................ 26 6 HISTORY ............................................................................................................................. 27 6.1 Prior Ownership ............................................................................................................ 27 6.2 Discovery ...................................................................................................................... 29 6.2.1 Fission Energy Corp. 2007 - 2012 ......................................................................... 29 6.2.2 Denison Mines Corp. 2013 - Present .................................................................... 30 6.3 Historical Resource and Reserve Estimations ............................................................. 30 6.3.1 J Zone ................................................................................................................... 30 6.3.2 Huskie ................................................................................................................... 32 7 GEOLOGICAL SETTING .................................................................................................... 33 7.1 Regional Geology ......................................................................................................... 33 7.1.1 Sub-Athabasca Crystalline Metamorphic Basement ............................................. 34 7.1.2 Hudsonian Granites/pegmatites ............................................................................ 37 7.1.3 Paleoweathering .................................................................................................... 42 7.1.4 Athabasca Group Sandstone ................................................................................ 43 7.1.5 Quaternary Geology .............................................................................................. 44 7.1.6 Uranium Mineralization .......................................................................................... 46 7.2 Local Geology ............................................................................................................... 47 7.2.1 J Zone ................................................................................................................... 47 7.2.2 Huskie Zone .......................................................................................................... 48 7.2.3 Sub-Athabasca Crystalline Metamorphic Basement ............................................. 48 7.2.4 Athabasca Group Sandstone ................................................................................ 50 7.2.5 Quaternary Geology .............................................................................................. 50 7.3 Uranium Mineralization ................................................................................................