Denison Announces Discovery of High-Grade Uranium Mineralization At 24.68% Owned Waterfound JV

Denison Mines Corp. 

1100 – 40 University Ave 

Toronto, ON  M5J 1T1 

www.denisonmines.com 

PRESS RELEASE

Denison Announces Discovery of High-Grade Uranium Mineralization

At 24.68% Owned Waterfound JV

Toronto, ON – March 29, 2022. Denison Mines Corp. (“Denison” or the “Company”) (DML: TSX, DNN:

NYSE American) is pleased to report the discovery of multiple new high-grade intercepts of unconformity-

hosted uranium mineralization in the final three drill holes completed during the winter 2022 exploration

program on the Waterfound River property (“Waterfound” ). The results were highlighted by drill hole

WF-68, which returned a broad zone of uranium mineralization, including a peak interval of 5.91% eU3O8

over 3.9 metres (0.05% eU 3O8 cut-off) with a sub-interval grading 25.30% eU3O8 over 0.7 m , located

approximately 800 metres west, along the La Rocque Conductive Corridor, of the previously discovered

high-grade mineralization (including 4.49% U3O8 over 10.53 metres) at the Alligator Zone.

Denison has an effective 24.68% ownership interest in the Waterfound River Joint Venture (“Waterfound

JV”) to which each of Orano Canada Inc. (“Orano Canada”), Denison, and JC U (Canada) Exploration

Company, Limited (“JCU”) are participants. Orano Canada has a 62.42% interest in the Waterfound JV

and is the project operator.

Andy Yackulic, P. Geo., Denison’s Director, Exploration, commented, “We are excited to see additional

high-grade mineralization discovered within the La Rocque corridor, which also hosts Cameco’s La

Rocque Lake Zone and IsoEnergy’s Hurricane Zone. Not only has the drilling at Waterfound

intersected high-grade uranium, but the mineralization remains open along strike in both

directions.”

David Cates, Denison’s President & CEO, added, “Denison is appreciative of the efforts of Orano

Canada to breathe new life into Waterfound. Denison has a unique partnership with Orano – as

joint owners of the McClean Lake mill and the nearby Midwest project. This discovery at Waterfound

is well situated relative to the McClean Lake mill and has the potential to translate into a further

important source of future mill feed for the McClean Lake joint venture. Waterfound is also a good

example of the significant, but often underapp reciated, discovery potential associated with

Denison's well situated and prospective exploration property portfolio.”

2022 Waterfound River Winter Exploration Program Highlights

Drill holes WF-67, WF-68, and WF-68-1 were all drilled on line 4000E, approximately 800 m along strike to

the west of the Alligator Zone, to test the potential for uranium mineralization along the up-dip projection of

a graphitic structure inters ected at depth in historical drill hole WF -50. All three drill holes successfully

identified high-grade uranium mineralization, highlighted by hole WF-68, which returned 5.91% eU3O8 over

3.9 metres. The mineralized intersections are illustrated in Figure 1 and summarized in Table 1 below.

Table 1 – 2022 Waterfound River Winter Exploration Drilling Highlights

Drill Hole From (m) To (m) Length (m) (1) eU 3O8 (%)(2)

WF-67(3,4) 474.1 488.3 14.2 0.73

WF-68(3,4) 459.7 462.0 2.3 0.66

WF-68(3,4) 467.1 470.3 3.2 0.97

WF-68(3,4) 473.7 477.6 3.9 5.91

including(5) 476.2 476.9 0.7 25.3

WF-68-1(3,4) 464.2 472.2 8.0 0.87

WF-68-1(3,4) 474.0 476.4 2.4 0.31

WF-68-1(3,4) 480.3 482.7 2.4 2.20

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Notes: (1) Lengths indicated represent the down-hole length of mineralized intersections.

(2) Radiometric equivalent U3O8 ("eU3O8") derived from a calibrated gamma downhole probe

(3) WF-67 was drilled at an azimuth of 154° and a dip of -70.0°, WF-68, was drilled at an azimuth of

154° and a dip of -71.5°, and WF-68-1 was drilled at an azimuth of 154° and a dip of -73.5°.

(4) Mineralized interval is composited above a cut-off grade of 0.05% eU3O8

(5) Mineralized interval is composited above a cut-off grade of 10.0% eU3O8

The 2022 exploration program was designed to test for the potential expansion of previously discovered

mineralization in the Alligator Zone, as well as to test for new mineralization in the surrounding area along

the La Rocque conductive corridor (see Figure 2). The program was planned to occur during both the

winter and summer drilling seasons with approximately 7,400 metres of diamond drilling in an estimated 12

drill holes. Six diamond drill holes, totalling 3,175.4 metr es, were completed as part of the winter drill

program.

The first two drill holes of the winter program (WF- 64 and WF-65) were completed on the eastern end of

the property to test the D-1 conductor, located with in the La Rocque conductive corridor. While each of

these holes encountered elevated radioactivity at the unconformity, no mineralization above a 0.05% eU3O8

cut-off was identified. WF-66, the third drill hole of the winter program, was drilled to test the D-1 conductor

approximately 500 metres west of the Alligator Zone. WF-66 failed to intersect significantly elevated

radioactivity. The final three drill holes (WF-67, WF-68, and WF-68-1), as described above, were successful

in intersecting significant uranium mineralization associ ated with the D-1 conductor, which lies within the

La Rocque conductive corridor. This newly identifie d mineralization remains open along strike in both

directions. Additional drilling to test the extent of mineralization is expected to be completed during the

planned summer exploration drilling program.

Radiometric Equivalent Grades, Sampling, Analysis and Data Verification

Following the completion of a drill hole, the hole is radiometrically logged using a downhole slimline gamma

probe, which collects continuous readings of radioact ivity along the length of the drill hole. Probe results

are then calibrated using an algorithm calculated from the comparison of probe results against geochemical

analyses in the area. The gamma-log results provid e an immediate radiometric equivalent uranium value

(eU%, then converted to eU 3O8%) for the hole, which, except in very high-grade zones, is reasonably

accurate. The Company typically reports eU3O8, as a preliminary result and subsequently reports definitive

assay grades following sampling and chemical analysis of the mineralized drill core.

Assay sample intervals are generally 50 centimet res long, except where higher or lower grade

mineralization boundaries fall within the interval. In that case, two 25 centimetre samples are collected.

Flank samples of 1.0 metre are always collected where mineralization is located. Systematic geochemistry

samples are collected every 10 metres down the hole.

All assayed core is split in half, with one half reta ined and the other sent to the SRC Geoanalytical

Laboratory in Saskatoon for analysis. Control sample s are routinely assayed with each batch of core

samples analyzed.

About Waterfound River

The Waterfound River property is located within t he eastern portion of the Athabasca Basin region of

northern Saskatchewan, approximately 40 kilometres northwest of Denison’s 22.5% owned McClean Lake

mill. The Waterfound JV is an unincorporated contractual arrangement between Orano Canada

(62.4223%), Denison Mines Inc. (11.7767%), and JCU (25.8010%). Denison holds an effective 24.6772%

ownership interest in the Waterfound JV through its direct interest in the joint venture and its 50% ownership

of JCU.

About Denison

Denison is a uranium exploration and development company with interests focused in the Athabasca Basin

region of northern Saskatchewan, C anada. The Company has an effective 95% interest in its flagship

Wheeler River Uranium Project, which is the largest undeveloped uranium project in the infrastructure rich

eastern portion of the Athabasca Basin region of northern Saskatchewan.

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Denison's interests in the Athabasca Basin also incl ude a 22.5% ownership interest in the McClean Lake

joint venture, which includes several uranium deposits and the McClean Lake uranium mill that is contracted

to process the ore from the Cigar Lake mine under a toll milling agreement, plus a 25.17% interest in the

Midwest Main and Midwest A deposits, and a 66.90% intere st in the Tthe Heldeth Túé ("THT," formerly J

Zone) and Huskie deposits on the Waterbury Lake pr operty. The Midwest Main, Midwest A, THT and

Huskie deposits are each located within 20 kilometres of the McClean Lake mill.

Through its 50% ownership of JCU, Denison holds additional interests in various uranium project joint

ventures in Canada, including the Millennium project (JCU 30.099%), the Kiggavik project (JCU 33.8123%)

and Christie Lake (JCU 34.4508%). Denison's exploration portfolio includes further interests in properties

covering ~300,000 hectares in the Athabasca Basin region.

Denison is also engaged in post-closure mine care and maintenance services through its Closed Mines

group (formerly Denison Environmental Services), wh ich manages Denison’s reclaimed mine sites in the

Elliot Lake region and provides related services to certain third-party projects.

For more information, please contact

David Cates (416) 979-1991 ext 362

President and Chief Executive Officer

Mac McDonald (416) 979-1991 ext 242

Exec. Vice President & Chief Financial Officer

Follow Denison on Twitter @DenisonMinesCo

Qualified Persons

The technical information contained in this rele ase has been reviewed and approved by Mr. Andrew

Yackulic, P. Geo., Denison's Director, Exploration, who is a Qualified Person in accordance with the

requirements of NI 43-101.

Cautionary Statement Regarding Forward-Looking Statements

Certain information contained in this news release constitutes ‘forward-looking information’, within the meaning of the applicable United

States and Canadian legislation, concerning the business, operations and financial performance and condition of Denison.

Generally, these forward-looking statements c an be identified by the use of forward-look ing terminology such as ‘plans’, ‘expects’,

‘budget’, ‘scheduled’, ‘estimates’, ‘forecasts’, ‘intends’, ‘anticipates’, or ‘believes’, or the negatives and/or variations of such words and

phrases, or state that certain actions, events or results ‘may’, ‘could’, ‘would’, ‘might’ or ‘will be taken’, ‘occur’, ‘be achieved’ or ‘has

the potential to’.

In particular, this news release contains forward-looking information pertaining to the following: the interpretation of exploration results

and expectations with respect thereto, incl uding the interpretation of the results from the Waterfound River exploration progra m

undertaken by Orano Canada, underlying assumptions and the Waterfound JV’s intentions with respect thereto; exploration plans and

objectives; and expectations regarding its joint venture ownership interests and the continuity of its agreements with its partners.

Forward looking statements are based on the opinions and estimates of management as of the date such statements are made, and

they are subject to known and unknown risks, uncertainties and other factors that may c ause the actual results, level of activi ty,

performance or achievements of Denison to be materially different from those expre ssed or implied by such forward-looking

statements. For example, the modelling and assumptions upon whic h the interpretation of results are based may not be maintaine d

after further testing or be representative of actual conditions. Denison believes that the expectations reflected in this forward-looking

information are reasonable but no assurance can be given that these expectations will pr ove to be accurate and results may diff er

materially from those anticipated in this forward-looking information. For a discussion in respect of risks and other factors that could

influence forward-looking events, please refer to the factors discussed in Denis on’s Annual Information Form dated March 26, 2021

or subsequent quarterly financial reports under the heading ‘Risk Factors’. These factors are not, and should not be construed as

being exhaustive.

Accordingly, readers should not place undue re liance on forward-looking statements. T he forward-looking information contained in

this news release is expressly qualified by this cautionary statement. Any forward-looking information and the assumptions made with

respect thereto speaks only as of the date of this news releas e. Denison does not undertake any obligation to publicly update or

revise any forward-looking information after the date of this news release to conform such information to actual results or to changes

in Denison's expectations except as otherwise required by applicable legislation.

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Figure 1 – Location – Waterfound River JV

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Figure 2 – 2022 Winter Exploration Drilling – Alligator Extension