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Denison Announces 22.5% Owned Mcclean Lake Operations Granted 10-YEAR Licence Renewal BY Cnsc

Permits & Approvals

Denison Mines Corp.

1100 – 40 University Ave

Toronto, ON M5J 1T1

www.denisonmines.com

@DenisonMinesCo

PRESS RELEASE

DENISON ANNOUNCES 22.5% OWNED MCCLEAN LAKE OPERATIONS

GRANTED 10-YEAR LICENCE RENEWAL BY CNSC

Toronto, ON – July 5, 2017 Denison Mines Corp. (“Denison” or the “Company”) (DML: TSX, DNN: NYSE

MKT) is pleased to announce that its 22.5% owned McClean Lake operations have been granted a 10-year

Uranium Mine Operating Licence from the Canadian Nuclear Safety Commission (“CNSC”), which is valid

as of July 1, 2017 and will expire on June 30, 2027.

The McClean Lake operations are located in the infrastructure rich eastern portion of the Athabasca Basin

region in northern Saskatchewan and are owned by the McClean Lake Joint Venture ("MLJV"), a joint

venture between AREVA Resources Canada Inc. ("AREVA") (70%), Denison (22.5%) and OURD (Canada)

Co. Ltd. (7.5%). The McClean Lake operations incl ude several uranium deposits as well as the McClean

Lake mill, which is currently operating and processi ng ore from the Cigar Lake mine under a toll milling

agreement. The MLJV is operated by AREVA.

Denison’s President and CEO, David Cates, commented, “We are quite familiar with the CNSC’s rigorous

processes, having worked closely with the CNSC for many years in regards to our own reclaimed mine

sites in Elliot Lake, and we are very pleased with t he outcome of the McClean Lake renewal process.

AREVA continues to be a tremendous par tner at McClean Lake and we ar e very appreciative of not only

AREVA’s commitment to the licence renewal process, but also their commitment to operating the McClean

Lake operations with the utmost respect for em ployee safety, the environment, and the neighbouring

northern communities.”

McClean Lake Mill

The McClean Lake mill is one of the most technologica lly advanced uranium mills in operation and is the

only facility in the world designed to process high grade uranium ore with out dilution. In 2016, the MLJV

obtained regulatory approval from the CNSC to increase its annual production capacity of uranium (U3O8)

to 24 million pounds per year. With the Cigar Lak e mine expected to produce approximately 18 million

pounds U3O8 annually, the McClean Lake mill currently has excess licenced processing capacity of up to

six million pounds U3O8 per year.

Denison’s Preliminary Economic Assessment (“PEA”) for the Wheeler River Project, completed in 2016

(see press releases dated April 4, 2016 and May 12, 2016), contemplates the use of the McClean Lake

mill, on a toll milling basis, for the processing of mine production from Wheeler River’s Gryphon and Phoenix

uranium deposits. The Wheeler River project is a joint venture between Deni son (60%), Cameco Corp.

(30%), and JCU (Canada) Exploration Company Limited (10%).

Further details regarding the Gryphon and Phoenix deposits are provided in the NI 43-101 Technical Report

for the Wheeler River project titled "Preliminary Ec onomic Assessment for the Wheeler River Uranium

Project, Saskatchewan, Canada" dated April 8, 2016 wi th an effective date of March 31, 2016. A copy of

this report is available on Denison's website a nd under its profile on SEDAR at www.sedar.com and on

EDGAR at www.sec.gov/edgar.shtml.

On July 19th, 2016, Denison announced the initiation of a Pre-Feasibility Study ("PFS") for the Wheeler

River project and the complimentary commencement of an infill drilling program at the Gryphon deposit to

bring the inferred resources to an indicated level of confidence. This work continues at present, and an

updated mineral resource estimate for Wheeler River is planned to be completed once summer assay

results are received, and is then expected to be incorporated into the completion of a PFS planned for 2018.

McClean Lake Uranium Deposits

McClean Lake is also host to the Caribou, Sue D, Sue E and McClean North uranium deposits. Together

the deposits are currently estimated to contain indicated mineral resources of 18 million pounds U3O8, plus

inferred mineral resources of 7.6 million pounds U3O8, as outlined below.

Indicated Mineral Resource Estimates (1)(2)(3)

100% Basis

Denison

Share

(22.5%)

Project/Deposit

Tonnes

(,000)

Grade

% U3O8

Pounds of

U3O8

(,000)

Pounds of

U3O8

(,000)

McClean - Caribou 47.8 2.62 2,800 600

McClean - Sue D 122.8 1.05 2,800 600

McClean - McClean North 205.8 2.75 12,400 2,800

Total Indicated Mineral Resources 18,000 4,000

Inferred Mineral Resource Estimates (1)(2)(3)

100% Basis

Denison

Share

(22.5%)

Project/Deposit

Tonnes

(,000)

Grade

% U3O8

Pounds of

U3O8

(,000)

Pounds of

U3O8

(,000)

McClean - Sue D 24.2 0.39 200 0

McClean – Sue E(4) 483.4 0.69 7,300 1,600

McClean - McClean North 3.3 0.74 100 0

Total Inferred Mineral Resources 7,600 1,600

Notes:

(1) Mineral resources are not mineral reserves and do not have demonstrated economic viability. No mineral reserves

have as yet been defined.

(2) The mineral resources were estimated at a cut-off grade of 0.10% U 3O8.

(3) The Company received a technical report from Scott Wils on RPA (now RPA Inc.) dated November 21, 2005, as revised

February 16, 2006, on its mineral reserves and mineral resources at certain of the deposits (Sue A, B, E and McClean

North and Caribou) at McClean Lake ent itled “Technical Report on the Denis on Mines Inc. Uranium Properties,

Saskatchewan, Canada”. Further revised reports were obtained for the mineral resources at Sue D and McClean North

deposits entitled “Technical Report on the Sue D Uranium Deposit Mineral Resource Estimate, Saskatchewan,

Canada” dated March 31, 2006, and "Technical Report on the McClean North Uranium Deposit Mineral Resource

Estimate, Saskatchewan, Canada" dated January 31, 2007 respectively. Copies of all Technical Reports are available

on the Company’s profile on the SEDAR website at www.sedar.com.

(4) The operator conducted confirmatory drilling on a porti on of these mineral resource s outside the designated pit and

late in 2006 submitted a preliminary analysis detailing an inferred mineral resource of approximately 2 million pounds

on a 100% basis in this area, as compared to the 7.3 milli on pounds that Scott Wilson Roscoe Postle Associates Inc.

(now RPA Inc.) has estimated in its February 2006 technical report. RPA Inc. has not re-estimated the mineral resource

using the new drill information.

Qualified Persons

Dale Verran, MSc, Pr.Sci.Nat., Deni son's Vice President, Exploration, who is a Qualified Person in

accordance with the requirements of NI 43-101, has reviewed and approved the technical information

contained in this release.

About Denison

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

region of northern Saskatchewan. Including its 60% owned Wheeler Ri ver project, which hosts the high

grade Phoenix and Gryphon uranium deposits, Denison' s exploration portfolio consists of numerous

projects covering over 330,000 hectares in the infr astructure rich eastern Athabasca Basin. Denison's

interests in Saskatchewan also include a 22.5% ownership interest in the McClean Lake joint venture, which

includes several uranium deposits and the McClean Lake uranium mill, which is currently processing ore

from the Cigar Lake mine under a toll milling agreement, plus a 25.17% interest in the Midwest deposit and

a 63.63% interest in the J-Zone deposit on the Wa terbury Lake property. Both the Midwest and J Zone

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

Denison is also engaged in mine decommissioning and environmental services through its Denison

Environmental Services division and is the manager of Uranium Participation Corp., a publicly traded

company which invests in uranium oxide and uranium hexafluoride.

For more information, please contact

David Cates (416) 979-1991 ext. 362

President and Chief Executive Officer

Sophia Shane (604) 689-7842

Investor Relations

Follow Denison on Twitter @DenisonMinesCo

Cautionary Statement Regarding Forward-Looking Statements

Certain information contained in this press release constitutes “forward-looking information”, within the meaning of the United States

Private Securities Litigation Reform Act of 1995 and similar Canadian legislation concerning the business, operations and finan cial

performance and condition of Denison. Genera lly, these forward-looking statements can be identified by the use of forward-looki ng

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 press release containsforward-looking information

pertaining to the following: the potential use of the McClean Lak e mill, on a toll milling basis, for the processing of mine pr oduction

from Wheeler River’s Gryphon and Phoenix uranium deposits as contemplated by the PEA; the anticipated timing for an updated

resource estimate at Wheeler River; the anticipated completi on and timing of a PFS on the Wheel er River Project; exploration

(including drilling) and evaluati on activities, plans and objectives; potential mi neralization of drill targets; the estimates of Denison's

mineral resources and the results of its PEA.

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. Denison believes that the expec tations reflected in this forward-looki ng information are reasonable but there can b e no

assurance that such statements will prove to be accurate and may differ materially from those ant icipated in this forward looki ng

information. For a discussion in respect of risks and other factors that could influence forward-looking events, please refer to the “Risk

Factors” in Denison’s Annual Information Form dated March 24, 2016 available under its profile at www.sedar.com and in its Form

40-F available at www.sec.gov/edgar.shtml. These factors are not, and should not be construed as being, exhaustive.

Accordingly, readers should not place undue re liance on forward-looking statements. The forward-looking information contained i n

this press release is expressly qualified by this cautionary statement. Denison does not undertake any obligation to publicly update or

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

in its expectations except as otherwise required by applicable legislation.

Cautionary Note to United States Investors Concerning Estimates of Measured, Indicated and Inferred Mineral Resources: This

press release may use the terms “measured”, “indicated” and “inferred” mineral resources. United States investors are advised that while

such terms are recognized and required by Canadian regulations, the United States Securities and Exchange Commission does not

recognize them. “Inferred mineral resources” have a great amount of uncertainty as to their existence, and as to their economic and legal

feasibility. It cannot be assumed that all or any part of an inferred mineral resource will ever be upgraded to a higher category. Under

Canadian rules, estimates of inferred mineral resources may not form the basis of feasibility or other economic studies. United States

investors are cautioned not to assume that all or any part of measured or indicated mineral resources will ever be converted into mineral

reserves. United States investors are also cautioned not to assume that all or any part of an inferred mineral resource exists, or is

economically or legally mineable.