ML25255A019

January 9, 2025, Wy State Engineer Final Opinion, Terrapower, LLC, Kemmerer Unit 1

ML25255A019
Person / Time
Site:	Kemmerer File:TerraPower icon.png
Issue date:	01/08/2025
From:	Gebhart B State of WY, Engineer's Office
To:	Office of Nuclear Material Safety and Safeguards
References
Download: ML25255A019 (1)

Text

State Engineers Office HERSCHLER BUILDING, 2W CHEYENNE, WYOMING 82002 (307) 777-6150 MARK GORDON GOVERNOR BRANDON GEBHART, P.E.

STATE ENGINEER Surface Water Ground Water Board of Control (307) 777-6475 (307) 777-6163 (307) 777-6178 FINAL OPINION of NATRIUM DEMONSTRATION REACTOR WATER SUPPLY AND WATER YIELD ANALYSIS LINCOLN COUNTY, WYOMING Prepared By:

Wyoming State Engineers Office Surface Water Division January 2025

State Engineers Office HERSCHLER BUILDING, 2W CHEYENNE, WYOMING 82002 (307) 777-6150 MARK GORDON GOVERNOR BRANDON GEBHART, P.E.

STATE ENGINEER Surface Water Ground Water Board of Control (307) 777-6475 (307) 777-6163 (307) 777-6178 THE STATE ENGINEERS ROLE IN INDUSTRIAL DEVELOPMENT AND SITING The State Engineers role in industrial development and siting is outlined under Wyoming Statute (W.S. § 35-12-108). If an applicant for an industrial siting permit plans to construct a facility which will use 800 or more acre-feet of water per year, the applicant must submit a water supply and water yield analysis to the State Engineer. The State Engineer will then review the analysis and render a preliminary opinion as to the quantity of water available for the proposed facility (W.S. § 35-12-108(c)). This preliminary opinion will be made available for public comment and the State Engineer will consider submitted comments in preparing a final opinion. The State Engineers final opinion will be binding on the Industrial Siting Council for the purpose of issuing an industrial siting permit.

The State Engineers review is limited to questions of water supply and water yield. Industrial siting and development statutes specifically provide that the State Engineers preliminary and final opinion shall not create a presumption concerning injury or noninjury to water rights (W.S. § 35-12-108(g)).

INTRODUCTION As part of the application process for an industrial siting permit, Wright Water Engineers, Inc.

(WWE) prepared and submitted to the State Engineers Office (SEO) the Natrium Demonstration Reactor Water Supply and Yield Analysis (Report), on behalf of the project owner, US SFR Owner, LLC (USO), which is a wholly owned subsidiary of TerraPower, LLC (TerraPower). The initial Report was received on June 10th, 2024. At TerraPowers request, review of the initial Report was placed on hold on September 5th, 2024. The final revised report was received on November 18, 2024 and formed the basis for the preliminary opinion. The SEOs preliminary opinion was published once a week for three consecutive weeks in the Kemmerer Gazette (i.e.,

November 26th, and December 3rd & 10th, 2024). Before rendering this final opinion as to the quantity of water available for the proposed Natrium Demonstration Reactor Project (Project), the State Engineer provided a 20-day period after the last date of publication which ended on December 30th, 2024, for the submission of written comments. No comments were received.

USO plans to build and operate the Project, a commercial nuclear power plant with an expected power output capacity of 345 Megawatts electric (MWe) and the ability to boost the power output to 500 MWe. The Project will use Natrium reactor technology, which is a combination of a sodium fast-cooled reactor and a molten salt energy storage subsystem. The planned project site is on 44 acres of land, with 16 acres designated as the primary nuclear island, located approximately four miles southeast of the existing Naughton Power Plant, near the City of Kemmerer in Lincoln County, Wyoming. The Naughton Power Plant is owned by PacifiCorp, Inc. (PacifiCorp). The Projects main source of water will be from Lake Viva Naughton Reservoir (VNR), through an

3 Natrium Demonstration Reactor Water Supply and Yield Analysis - SEO Final Opinion, 01/08/2025 agreement with PacifiCorp. The current source of supply for the Naughton Power Plant is VNR, which is supplied from the Hams Fork River, and located in Section 14, Township 23 North, Range 117 West. Construction activities for non-safety related aspects of the Project are expected to begin in March 2025. Construction of the Project is expected to be completed in Spring 2030 with commercial operations beginning in Fall 2031. The duration of the Project, including construction, operations, and decommissioning is anticipated to be 60 years.

WATER SUPPLY NEEDS WWE estimated the water supply needs for three different phases of the Project (construction, operations, and decommissioning):

During the construction phase, the Project will produce up to 120 acre-feet of groundwater as a result of construction site dewatering activities. A portion of this water will be used for construction purposes. Any water produced as a result of dewatering activities that is not needed for construction purposes will be discharged to North Fork Little Muddy Creek. In addition to and separate from the groundwater use, the Project is estimated to use a total 25.3 million gallons of water, or approximately 77.7 acre-feet, during the construction phase. The majority of water used during the construction phase will be for dust suppression purposes.

During the operations phase, the facility is currently estimated to use a total of 5,950 acre-feet of water per year, which is based on a continuous diversion at 3,689 gpm or approximately 8.21 cfs. However, the water supply and yield analysis is conservative, based on the maximum diversion allowed under the contract with PacifiCorp, which is 6,323 acre-feet of water per year.

Diverting continuously at 8.73 cfs generates 6,323 acre-feet of water per year. Equivalently, diverting at an average operating demand of 3,375 gpm (7.52 cfs) for 18.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> each day and a peak operation demand of 5,750 gpm (12.81 cfs) for 5.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> each day generates the same 6,323-acre-foot volume of water each year. The majority of the water used during this phase of the Project is to supply makeup water to the Projects cooling towers. During the operations phase of the project, TerraPower stated that the annual water demand could be reduced to accommodate shortages in water supply by reducing or making adjustments to operations. Adjustments to operations could include increasing cycles of concentration for cooling tower makeup or using some version of a dry or wet-dry hybrid cooling system. Based on TerraPowers preliminary engineering considerations and supporting data from EPRI TR2011, a hybrid wet-dry cooling system can be designed to reduce the cooling tower water usage by 30%.

Cooling tower use accounts for an estimated 79% of the water use at the facility during operations. Once the operations phase of the project is complete, water will no longer be needed for cooling tower purposes. Based on this change, the annual water demand during the decommissioning phase is estimated to be 21% of the annual water demand during the operations phase, or a total of 1,330 acre-feet of water per year, which is equivalent to continuous diversion at 3.64 cfs. During the decommissioning phase, the main water demand will be for spent fuel cooling. This demand will decrease as the fuel ages. The decommissioning phase is assumed to occur over a 10-year period.

WATER SUPPLY The following supplies of water are available to the project:

The primary water supply for the Project will be from VNR, under Permit Nos. 6418R and 7476R, through agreement with PacifiCorp. These two permits combined allow for storage of up

4 Natrium Demonstration Reactor Water Supply and Yield Analysis - SEO Final Opinion, 01/08/2025 to 45,465 acre-feet of water in the Reservoir for Industrial - steam power plant purposes. Water from VNR will be released into the Hams Fork River and then pumped from the river and delivered through an existing, 7-mile pipeline system known as the Cooling Water Intake System, which currently has a 20 cfs design capacity.

During the construction phase, dewatering activities will displace up to 120 acre-feet of groundwater. Some of this water will be used onsite for uses such as, but not limited to, dust suppression and compaction. Any of this water not needed for construction purposes will be discharged to North Fork Little Muddy Creek. Any use of this water will be permitted through the SEO and any discharge of water from the Project will be permitted, as required, under the WYPDES Program.

The remainder of the water needed during the construction phase, approximately 25.3 million gallons, will be supplied from the Hams Fork River under existing municipal water rights.

This water will be diverted through the Kemmerer-Diamondville Water Treatment Plant and will be trucked to the site.

USO is also in the process of contracting for 6,323 acre-feet of water per year stored in Fontenelle Reservoir. If the contract is approved, it is anticipated that water from Fontenelle Reservoir will be pumped from the Green River through an intake structure located below the Reservoir and conveyed through a 34-mile pipeline to the Project.

The Project will not use groundwater as a source of cooling or potable water, or for other plant needs during the operations or decommissioning phases. The primary water supply for all phases of the Project is surface water.

AVAILABILITY OF WATER IN PROPOSED SOURCE The primary source of water supply for the Project is proposed to be from VNR. To demonstrate the ability of VNR to supply water for the Project, the Naughton Power Plant, and the Kemmerer Mine (collectively termed NatNaughtKem), while meeting all other legally obligated water right demands, WWE used simulation models under three scenarios:

• Scenario 1: Water right demands as guided by the Hams Fork Water Users Association (HFWUA) Agreement1

• Scenario 2: Water right demands per water rights absent the HFWUA Agreement

• Scenario 3: Curtailment2 Models utilized in the Report included:

1 The HFWUA members are irrigators on the Hams Fork River, both above and below VNR. HFWUA members hold senior water rights capable of calling out VNR and Naughton Power Plant water rights. Under the HFWUA Agreement, HFWUA members agree not to place a call for priority regulation, which could prevent VNR from filling, in exchange for use of water released from VNR for irrigation purposes. This agreement was renewed in April 2023 and may continue up to 10 years from the effective date.

2 WWE defined curtailment as a State of Wyoming mandate to cease storing water in VNR with all direct runoff from Hams Fork River passing through VNR dam without storage in VNR or being withdrawn for use by NatNaughtKem and the only water available to NatNaughtKem would be that which was in VNR storage at the commencement of curtailment.

5 Natrium Demonstration Reactor Water Supply and Yield Analysis - SEO Final Opinion, 01/08/2025

• The Sequent Peak Method Model (SPMM), an Excel spreadsheet model that is independent of reservoir characteristics. The SPMM does a simple daily accounting of the inflow supply and demands of a system, computing a daily net inflow and a daily deficit (shortage) of water.

• The HEC-ResSim Model, a computer model developed by the U.S. Army Corps of Engineers that simulates the performance of a system based on the inflows, demands, evaporation from the reservoir surface, leakage from the reservoir, and the reservoirs physical and operation characteristics.

• The Time-to-Empty Model, an Excel spreadsheet model that computes the days until a full VNR is empty based on daily demand from NatNaughtKem, average daily evaporation, and average daily seepage from the dam and reservoir.

Results of this modeling demonstrated the following:

• Under the current operation of VNR and with the HFWUA Agreement in place (Scenario 1), there is adequate supply of water available to VNR to supply NatNaughtKem.

• Without the HFWUA Agreement in place (Scenario 2), the Hams Fork River and VNR do not meet the demands of NatNaughtKem 12% of the time.

• Under curtailment (Scenario 3), if VNR is at full capacity going into the curtailment, the demands of NatNaughtKem could be met for approximately 870 days. If VNR is at half-capacity going into the curtailment, the demands could be met for approximately 435 days.3 USO is in the process of contracting for 6,323 acre-feet of water per year stored in Fontenelle Reservoir to offset possible shortages in water supply, as evidenced by the letter from Jason Mead, P.E., director of the Wyoming Water Development Office, to Brandon Gebhart, P.E., Wyoming State Engineer, dated September 16, 2024, which is available as Appendix G of the Report. If approved, it is anticipated that water under this contract will be pumped from the Green River through an intake structure located below Fontenelle Reservoir and conveyed through a pipeline to the Project. The pipeline will begin near Fontenelle Reservoir and head southwest approximately 34 miles to the Project site. It is anticipated that construction of the pipeline could take approximately 5 years to complete, not including time needed for design or permitting.

Conveyance losses related to transporting Fontenelle Reservoir water to the Project site were not calculated as part of the Report. However, the 6,323 acre-feet of annual proposed Fontenelle Reservoir water could provide the full amount of the Projects currently estimated annual demand (5,950 acre-feet), assuming 6% of conveyance losses.

The Report states that USO is able and willing to accommodate shortages in water supply and adjust operations, as needed. In addition to the possible use of water from Fontenelle Reservoir, USO could make use of a water rights exchange or implement adjustments in operations to reduce water consumption, including increased cycles of concentration for cooling tower makeup or use of dry cooling methods. According to the Report, TerraPower and USO have indicated that the Project remains viable with possible water shortages under the alternatives provided.

3 It is unclear based on the Report whether or not the Project will be allowed to continue to use water from VNR to meet the Projects full demand during a curtailment under the terms of the agreement between PacifiCorp and TerraPower (on behalf of USO).

6 Natrium Demonstration Reactor Water Supply and Yield Analysis - SEO Final Opinion, 01/08/2025 FINAL OPINION The State Engineers Office/Surface Water Division completed a comprehensive review of the Water Supply and Yield Analysis Report submitted by Wright Water Engineers, Inc. on behalf of US SFR Owner, LLC for the proposed Natrium Demonstration Reactor Project in Lincoln County, Wyoming.

Wright Water Engineers, Inc. conservatively based the Water Supply and Yield Analysis Report on an annual water demand of 6,323 acre-feet of water per year, which is equivalent to continuous diversion of 8.73 cfs. 6,323 acre-feet of water per year is the maximum amount allowed under the agreement between TerraPower, LLC (on behalf of US SFR Owner, LLC) and PacifiCorp, Inc. for use of water from Lake Viva Naughton Reservoir. The projected life of the Project is 60 years including construction, operations, and decommissioning. US SFR Owner, LLC proposes providing the water supply for the Project through the following mechanisms:

The primary water supply for the Project is proposed to be from Lake Viva Naughton Reservoir, under Permit Nos. 6418R and 7476R, through agreement with PacifiCorp, Inc., the owner of the Reservoir. These two permits combined allow for storage of up to 45,465 acre-feet of water in the Reservoir for Industrial - steam power plant purposes. Water from Lake Viva Naughton Reservoir will be released into the Hams Fork River and then pumped from the river and delivered through an existing, 7-mile pipeline system with a 20 cfs capacity, known as the Cooling Water Intake System.

During the construction phase, dewatering activities will displace up to 120 acre-feet of groundwater. Some of this water will be used onsite for uses such as, but not limited to, dust suppression and compaction. Any of this water not needed for construction purposes will be discharged to North Fork Little Muddy Creek. Any use of this water will be permitted through the State Engineers Office and any discharge of water from the Project will be permitted, as required, under the WYPDES Program.

The remainder of the water needed during the construction phase, approximately 25.3 million gallons, will be supplied from the Hams Fork River under existing municipal water rights.

This water will be diverted through the Kemmerer-Diamondville Water Treatment Plant and will be trucked to the site.

US SFR Owner, LLC is also in the process of contracting for 6,323 acre-feet of water per year stored in Fontenelle Reservoir. If the contract is approved, it is anticipated that water from Fontenelle Reservoir will be pumped from the Green River through an intake structure that would be located below the Reservoir and conveyed through a 34-mile pipeline to the Project.

The Project will not use groundwater as a source of cooling or potable water, or for other plant needs during the operations or decommissioning phases. The primary water supply for all phases of the Project is surface water.

The Report states that US SFR Owner, LLC is able and willing to accommodate shortages in water supply and adjust operations, as needed.

The final opinion is unchanged from the preliminary opinion. Based upon the submitted Water Supply and Water Yield Analysis Report, it is the opinion of the State Engineers Office that a sufficient quantity of water for the Project has been adequately demonstrated.

7 Natrium Demonstration Reactor Water Supply and Yield Analysis - SEO Final Opinion, 01/08/2025 REFERENCES Wright Water Engineers Inc. 2024. Natrium Demonstration Reactor Water Supply and Yield Analysis Report. Submitted to the Wyoming State Engineers Office. November 2024.