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NexGen Announces Initiation of Maiden Preliminary Economic Assessment and Off-Scale Mineralization in the 180m Southwest Gap

Corporate Updates

NexGen Announces Initiation of Maiden Preliminary Economic

Assessment and Off-Scale Mineralization in the 180m Southwest Gap

Vancouver, BC, April 27, 2017 – NexGen Energy Ltd. (“NexGen” or the “Company”) (TSX:NXE,

OTCQX:NXGEF) is pleased to report commencement of an independen t maiden Preliminary Economic

Assessment (“PEA”) on the Arrow Deposit, and results from the on-going winter 2017 drilling program at our

100% owned, Rook I property, Athabasca Basin, Saskatchewan.

Initiation of Maiden PEA:

Advanced work has commenced on an independent maiden PEA which will incorporate the updated mineral

resource estimate released on March 6, 2017 (see News Release dated March 6, 2017) . The PEA is scheduled

to be completed late Q2/early Q3 2017 and will outline the following key aspects of Arrow:

• Annual production rate,

• Operating life,

• Mining method,

• Capital expenditures,

• Operating costs,

• Economic returns including: internal rate of return, net present value, payback period and sensitivity

analysis.

Roscoe Postle Associates Inc., a leading independen t consulting company with substantial experience in the

Athabasca Basin, and around the globe will be preparing the PEA.

Drilling Highlights:

Southwest Shallow Dravite A2

Drilling in a previously identified area of strong hydrothermal alteration within the A2 shear located

southwest of Arrow, has intersected mineralization including off-scale radioactivity for the first tim e. This

new area of mineralization begins 170 m below surface and is located 275 m up-dip and southwest of the A2

Mineral Resource domains . Highlighted holes include:

• Scissor hole AR-17-128 intersected 6.0 m of total composite mineralization including 1.1 m of total

composite off-scale radioactivity (>10,000 to 32,000 cps) within a 23.0 m section (195.0 to 218.0 m).

• Scissor hole AR-17-125 (50 m down-dip from AR-17-128) intersected 10.5 m of total composite

mineralization including 0.15 m of total composite off-scale radioactivity (>10,000 to 12,500 cps)

within a 13.0 m section (236.0 to 249.0 m).

Southwest A3 & A4 Gap Drilling

Strong off-scale radioactivity has been intersected in the ‘gap’ area located southwest of the Arrow resource

domains, and northeast of the 180 m Southwest Area Mineral Resource domains. The Southwest Gap Area

was not incorporated into the updated mineral resource estimate and represents a key resource expansion

opportunity , which has just begun to be targeted. Highlighted holes include:

• Hole AR-17-131c3 (85 m northeast and down-dip from AR-16-97) inters ected 64.5 m of total

composite mineralization including 6.6 m of total composite off-scale radioactivity (>10,000 to

>61,000 cps) within 337.0 m section (646.0 to 983.0 m) in the A 3 through A5 shears, and all of the

off-scale in this hole was encountered in the A3 shear.

• Hole AR-17-123c4 (30 m southwest from AR-16-97) intersected 75.5m of total composite

mineralization including 2.8 m of total composite off-scale radioactivity (>10,000 to >61,000 cps)

within 183.0 m section (660.0 to 843.0 m) in the A4 and A5 shears.

• Hole AR-17-123c3 (55 m southwest and down-dip from AR-16-97) inters ected 83.0m of total

composite mineralization including 1.3 m of total composite off-scale radioactivity (>10,000 to

14,000 cps) within 503.5 m section (442.0 to 945.5 m) in the A2 through A5 shears.

Arrow, Activities & Financial:

• The 2017 winter program comprising a minimum of 35, 000 m of drilling with seven drill rigs, will

continue into early May 2017.

• A maiden Preliminary Economic Assessment is scheduled to be completed in late Q2 / early Q3 2017.

• The Company has cash on hand of approximately $58 million.

A longitudinal section and a map showing drill hole locations are shown in Figures 1 and 2. Table 1 i s a

summary of the mineralized intervals.

Garrett Ainsworth, Vice-President, Exploration and Development, commented: “The Southwest Gap area is

showing extensive resource growth potential within the A3 and A4 shears. This area remains largely

untested at depth, which is encouraging given the o verall southwest plunge of the Arrow mineralization .

Targeted drill testing has paid off with the discov ery of off-scale radioactivity in a new area of the A2 shear

located 170 m below the surface. The strength and core lengths of alteration and radioactivity in thi s new

area reminds us of how large the overall Arrow mineralized system is, and how little it has been explored.”

Leigh Curyer, Chief Executive Officer, commented: “The drill results today paired with those previous ly

released from our ongoing winter 2017 program demonstrate how much material room there is for Arrow to

expand and optimize in terms of grade and tonnage. Commencement of an initial PEA is an important step in

providing guidance as to the economic power of Arrow relative to other sources of current and future mined

uranium worldwide. Noting, this initial PEA will be subsequently updated as the Arrow resource is furt her

defined.”

Figure 1: Arrow Deposit Schematic Long section

Figure 2: Arrow Deposit Drill Hole Locations

Table 1: Arrow Deposit Drill Hole Data

Drill Hole Athabasca

Group -

Basement

Unconformity

Depth (m)

Handheld Scintillometer Results (RS-120)

Hole ID Azimuth Dip

Total

Depth

(m)

From (m) To (m) Width (m) CPS Range

AR-17-122 147 -70 381.50 96.10 240.50 253.00 12.50 <500 - 8500

AR-17-123c1 147 -70 906.50 101.50 672.50 675.50 3.0 0 <500 - 1000

688.00 688.50 0.50 <500 - 560

708.00 708.50 0.50 <500 - 1050

725.00 727.00 2.00 <500 - 2340

730.50 733.50 3.00 <500 - 2100

830.00 831.00 1.00 <500 - 6400

AR-17-123c2 147 -70 864.50 101.50 651.00 655.00 4.0 0 <500 - 4600

657.50 658.00 0.50 <500 - 1140

668.50 670.00 1.50 <500 - 60000

675.00 676.00 1.00 <500 - 4100

680.50 684.00 3.50 <500 - 6600

687.00 688.00 1.00 <500 - 9800

707.00 720.50 13.50 <500 - 15000

725.50 742.00 16.50 <500 - 9700

753.50 754.00 0.50 <500 - 1710

761.00 761.50 0.50 <500 - 740

778.50 779.50 1.00 <500 - 530

784.50 791.00 6.50 <500 - 3900

825.00 825.50 0.50 <500 - 630

833.50 835.00 1.50 <500 - 1360

843.50 844.50 1.00 <500 - 560

847.50 850.00 2.50 <500 - 1350

AR-17-123c3 147 -70 984.50 101.50 442.00 443.00 1.0 0 <500 - 720

653.50 654.50 1.00 <500 - 13000

658.50 661.50 3.00 <500 - 8600

665.00 670.00 5.00 <500 - 11000

682.00 683.00 1.00 <500 - 1800

688.00 688.50 0.50 <500 - 630

697.50 736.50 39.00 <500 - 13000

739.00 761.00 22.00 <500 - 14000

783.00 784.00 1.00 <500 - 2300

794.00 797.00 3.00 <500 - 1150

800.00 800.50 0.50 <500 - 670

803.50 804.00 0.50 <500 - 620

817.00 818.00 1.00 <500 - 720

836.00 836.50 0.50 <500 - 885

848.00 848.50 0.50 <500 - 570

881.50 884.50 3.00 <500 - 1100

945.00 945.50 0.50 <500 - 550

AR-17-123c4 147 -70 864.50 101.50 660.00 667.50 7.5 0 <500 - 3900

672.50 673.50 1.00 700 - >61000

676.00 679.50 3.50 <500 - 13000

686.00 692.50 6.50 <500 - 7500

695.50 707.50 12.00 <500 - 29000

710.50 738.00 27.50 <500 - 30000

740.50 754.00 13.50 <500 - 54000

757.50 760.00 2.50 <500 - 5000

790.00 790.50 0.50 <500 - 760

829.00 829.50 0.50 <500 - 5000

842.50 843.00 0.50 <500 - 550

AR-17-124 147 -70 411.00 93.40 No Anomalous Radioac tivity

AR-17-125 327 -70 417.00 N/A 236.00 241.50 5.50 <50 0 - 3450

244.00 249.00 5.00 <500 - 12500

AR-17-128 327 -70 357.00 N/A 195.00 198.00 3.00 <500 - 18000

215.00 218.00 3.00 <500 - 32000

AR-17-130 327 -70 321.00 N/A 181.50 183.00 1.50 <500 - 19000

AR-17-131c1 147 -70 857.50 100.50 659.50 660.00 0.50 1600 - >61000

785.00 785.50 0.50 <500 - 3200

AR-17-131c2 147 -70 963.50 100.50 671.00 671.50 0.5 0 <500 - 1150

674.00 674.50 0.50 <500 - 1400

718.00 718.50 0.50 <500 - 520

749.00 749.50 0.50 <500 - 2000

752.50 753.50 1.00 520 - 8500

759.50 760.50 1.00 <500 - 2000

765.50 769.00 3.50 <500 - 14000

771.50 776.00 4.50 <500 - 4400

788.50 793.50 5.00 <500 - 55000

821.50 822.00 0.50 <500 - 1010

828.50 829.00 0.50 <500 - 14200

857.00 858.00 1.00 <500 - 3080

869.50 870.50 1.00 <500 - 8800

AR-17-131c3 147 -70 1029.50 100.50 646.00 667.50 21.50 <500 - >61000

671.00 678.50 7.50 <500 - 11000

724.50 725.00 0.50 <500 - 1100

756.00 757.50 1.50 <500 - 570

761.50 768.50 7.00 <500 - 2000

772.50 773.00 0.50 <500 - 1100

777.50 785.50 8.00 <500 - 1650

804.00 806.50 2.50 <500 - 4250

809.00 809.50 0.50 <500 - 530

816.50 819.00 2.50 <500 - 3000

881.00 881.50 0.50 <500 - 940

908.00 908.50 0.50 <500 - 770

913.50 914.50 1.00 <500 - 510

919.00 923.50 4.50 <500 - 2210

933.50 937.00 3.50 <500 - 1550

940.50 942.00 1.50 <500 - 680

952.00 952.50 0.50 <500 - 700

982.50 983.00 0.50 <500 - 525

AR-17-132 327 -70 232.00 N/A No Anomalous Radioacti vity

AR-17-134 327 -70 401.00 102.50 234.00 239.00 5.00 <500 - 5400

AR-17-135 327 -70 285.00 102.40 No Anomalous Radioa ctivity

AR-17-137 327 -70 366.00 N/A No Anomalous Radioacti vity

AR-17-139 327 -70 321.00 N/A No Anomalous Radioacti vity

AR-17-140 327 -70 477.00 108.60 262.00 263.50 1.50 <500 - 1240

AR-17-141 327 -70 330.00 N/A No Anomalous Radioacti vity

AR-17-142 327 -70 348.00 N/A No Anomalous Radioacti vity

AR-17-145 327 -70 315.00 N/A No Anomalous Radioacti vity

Parameters:

• Maximum internal dilution 2.00 m downhole

• All depths and intervals are meters downhole, true thicknesses are yet to be determined. Resource mode lling in

conjunction with an updated mineral resource estimate is required before true thicknesses can be estimated.

• “Anomalous” means >500 cps (counts per second) total count gamma readings by gamma scintillometer type RS-120

• “Off-scale” means >10,000 cps (counts per second) total count gamma readings by gamma scintillometer type RS-120

• Where “Min cps” is <500 cps, this refers to local low radiometric zones within the overall radioactive interval

Arrow Deposit Drilling

AR-17-122

Hole AR-17-122 was collared from surface at an angl ed orientation (-70°) to the southeast (147° Azimuth). It

was designed to test strong, shallow clay-breccia s tyle dravite alteration in the 180 m southwest area in the

A2 shear. The A2 shear was interested at an inclination of -71°.

The hole intersected silicified and hematized Athab asca Group sandstones between 95.9 m and the

unconformity at 96.1 m. Basement lithologies largely consisted of semi-pelitic gneiss and narrow intervals of

pelitic gneiss and mylonite. The hole successfully intersected anomalous radioactivity associated with

disseminated and fracture-hosted pitchblende minera lization. Continuous composite mineralization of 12 .5

m was intersected from 240.5 to 253.0 m in the A2 s hear. The hole was terminated at 381.5 m and