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Callaway Energy Center | 12 Months Ended
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Dec. 31, 2025
Nuclear Waste Matters [Abstract] |
CALLAWAY ENERGY CENTER | CALLAWAY ENERGY CENTER Spent Nuclear Fuel Under the Nuclear Waste Policy Act of 1982, as amended, the DOE is responsible for disposing of spent nuclear fuel from the Callaway Energy Center and other commercial nuclear energy centers. As required by the act, Ameren Missouri and other utilities have entered into standard contracts with the DOE, which stated that the DOE would begin to dispose of spent nuclear fuel by 1998. However, the DOE failed to fulfill its disposal obligations, and Ameren Missouri and other nuclear energy center owners sued the DOE to recover costs incurred for ongoing storage of their spent fuel. Ameren Missouri’s lawsuit against the DOE resulted in a settlement agreement that provides for annual reimbursement of additional spent fuel storage and related costs. Ameren Missouri received immaterial reimbursements from the DOE in the years ended December 31, 2025, 2024, and 2023. Ameren Missouri will continue to apply for reimbursement from the DOE for allowable costs associated with the ongoing storage of spent fuel. The DOE’s delay in carrying out its obligation to dispose of spent nuclear fuel from the Callaway Energy Center is not expected to adversely affect the continued operations of the energy center. Decommissioning Electric rates charged to customers provide for the recovery of the Callaway Energy Center’s decommissioning costs, which include decontamination, dismantling, and site restoration costs, over the expected life of the nuclear energy center. Amounts collected from customers are deposited into the external nuclear decommissioning trust fund to provide for the Callaway Energy Center’s decommissioning. It is assumed that the Callaway Energy Center site will be decommissioned after its retirement through the immediate dismantlement method and removed from service. The Callaway Energy Center’s operating license currently expires in 2044. Ameren and Ameren Missouri have recorded an ARO for the Callaway Energy Center decommissioning costs at fair value. Annual decommissioning costs of $7 million have historically been included in the costs used to establish electric rates for Ameren Missouri’s customers. Every three years, the MoPSC requires Ameren Missouri to file an updated cost study and funding analysis for decommissioning its Callaway Energy Center. An updated cost study and funding analysis was filed with the MoPSC in December 2023 and reflected within the ARO. In May 2025, the MoPSC issued an order that approved a non-unanimous stipulation and agreement between Ameren Missouri and the MoPSC staff that reduced annual customer contributions for funding the Callaway Energy Center decommissioning costs from $7 million to zero, as the trust fund level exceeded the estimated present value of future decommissioning costs at the time of the agreement. This MoPSC order removed Ameren Missouri’s funding obligation effective in June 2025. Ameren and Ameren Missouri have classified the investments in debt and equity securities that are held in the nuclear decommissioning trust fund as available for sale, and have recorded all such investments at their fair market value at December 31, 2025 and 2024. Investments in the nuclear decommissioning trust fund have a target allocation of 60% to 70% in equity securities, with the balance invested in debt securities. The fair value of the trust fund for Ameren Missouri’s Callaway Energy Center is reported as “Nuclear decommissioning trust fund” in Ameren’s and Ameren Missouri’s balance sheets. This amount is legally restricted and may be used only to fund the costs of nuclear decommissioning. Changes in the fair value of the trust fund are recorded as an increase or decrease to the nuclear decommissioning trust fund, with an offsetting adjustment to the regulatory liability related to AROs. This reporting is consistent with the method used to account for the decommissioning costs recovered in rates. See Note 2 – Rate and Regulatory Matters for the regulatory liability recorded at December 31, 2025. If the assumed return on trust assets is not earned, Ameren Missouri believes that it is probable that any additional funding requirements resulting from such earnings deficiency will be recovered in customer rates. The following table presents proceeds from the sales and maturities of investments in Ameren Missouri’s nuclear decommissioning trust fund and the gross realized gains and losses resulting from those sales for the years ended December 31, 2025, 2024, and 2023:
| 2025 |  | 2024 |  | 2023
Proceeds from sales and maturities | $ | 416 |  |  | $ | 564 |  |  | $ | 240 |
Gross realized gains | 37 |  |  | 44 |  |  | 6 |
Gross realized losses | 7 |  |  | 28 |  |  | 11 |
The following table presents the cost and fair value of investments in debt and equity securities in Ameren’s and Ameren Missouri’s nuclear decommissioning trust fund at December 31, 2025 and 2024:
Security Type | Cost |  | Gross Unrealized Gain |  | Gross Unrealized Loss |  | Fair Value
2025 |  |  |  |  |  |  |
Debt securities | $ | 488 |  |  | $ | 7 |  |  | $ | 9 |  |  | $ | 486 |
Equity securities | 179 |  |  | 858 |  |  | 9 |  |  | 1,028 |
Cash and cash equivalents | 8 |  |  | — |  |  | — |  |  | 8 |
Other(a) | 4 |  |  | — |  |  | — |  |  | 4 |
Total | $ | 679 |  |  | $ | 865 |  |  | $ | 18 |  |  | $ | 1,526 |
2024 |  |  |  |  |  |  |
Debt securities | $ | 437 |  |  | $ | 2 |  |  | $ | 17 |  |  | $ | 422 |
Equity securities | 179 |  |  | 740 |  |  | 8 |  |  | 911 |
Cash and cash equivalents | 10 |  |  | — |  |  | — |  |  | 10 |
Other(a) | (1) |  |  | — |  |  | — |  |  | (1) |
Total | $ | 625 |  |  | $ | 742 |  |  | $ | 25 |  |  | $ | 1,342 |
(a)Represents net receivables and payables relating to pending securities sales, interest, and securities purchases. The following table presents the costs and fair values of investments in debt securities in Ameren’s and Ameren Missouri’s nuclear decommissioning trust fund according to their contractual maturities at December 31, 2025:
| Cost |  | Fair Value
Less than 5 years | $ | 207 |  |  | $ | 208 |
5 years to 10 years | 139 |  |  | 141 |
Due after 10 years | 142 |  |  | 137 |
Total | $ | 488 |  |  | $ | 486 |
Insurance The following table presents insurance coverage at Ameren Missouri’s Callaway Energy Center at January 1, 2026:
Type and Source of Coverage | Most Recent Renewal Date | Maximum Coverages |  | Maximum Assessments for Single Incidents |
Public liability and nuclear worker liability: |  |  |  |  |
American Nuclear Insurers | January 1, 2026 | $ | 500 |  |  | $ | — |  |
Pool participation | (a) | 15,763 |  | (a) | 166 |  | (b)
|  | $ | 16,263 |  | (c) | $ | 166 |  |
Property damage: |  |  |  |  |
NEIL and EMANI | April 1, 2025 | $ | 3,200 |  | (d) | $ | 22 |  | (e)
Accidental outage: |  |  |  |  |
NEIL | April 1, 2025 | $ | 490 |  | (f) | $ | 9 |  | (e)
(a)Provided through mandatory participation in an industrywide retrospective premium assessment program. The maximum coverage available is dependent on the number of United States commercial reactors participating in the program. (b)Retrospective premium under the Price-Anderson Act. This is subject to retrospective assessment with respect to a covered loss in excess of $500 million in the event of an incident at any licensed United States commercial reactor, payable at $25 million per year. (c)Limit of liability for each incident under the Price-Anderson liability provisions of the Atomic Energy Act of 1954, as amended. This limit is subject to change to account for the effects of inflation and changes in the number of licensed power reactors. (d)NEIL provides $2.7 billion in property damage, stabilization, decontamination, and premature decommissioning insurance for radiation events and $0.7 billion in property damage insurance for nonradiation events. EMANI provides $490 million in property damage insurance for both radiation and nonradiation events. (e)All NEIL-insured plants could be subject to assessments should losses exceed the accumulated funds from NEIL. (f)Accidental outage insurance provides for lost sales in the event of a prolonged accidental outage. Weekly indemnity up to $4.5 million for 52 weeks, which commences after the first 12 weeks of an outage, plus up to $3.6 million per week for a minimum of 71 weeks thereafter for a total not exceeding the policy limit of $490 million. Nonradiation events are limited to $291 million. The Price-Anderson Act is a federal law that limits the liability for claims from an incident involving any licensed United States commercial nuclear energy center. The limit is based on the number of licensed reactors. The limit of liability and the maximum potential annual payments are adjusted at least every five years for inflation to reflect changes in the Consumer Price Index. The most recent five-year inflationary adjustment became effective in October 2023. Owners of a nuclear reactor cover this exposure through a combination of private insurance and mandatory participation in a financial protection pool, as established by the Price-Anderson Act. Losses resulting from terrorist attacks on nuclear facilities insured by NEIL are subject to industrywide aggregates, such that terrorist acts against one or more commercial nuclear power plants within a stated time period would be treated as a single event, and the owners of the nuclear power plants would share the limit of liability. NEIL policies have an aggregate limit of $3.2 billion within a 12-month period for radiation events, or $1.8 billion for events not involving radiation contamination, resulting from terrorist attacks. The EMANI policies are not subject to industrywide aggregates in the event of terrorist attacks on nuclear facilities. If losses from a nuclear incident at the Callaway Energy Center exceed the limits of, or are not covered by insurance, or if coverage is unavailable, Ameren Missouri is at risk for any uninsured losses. If a serious nuclear incident were to occur, it could have a material adverse effect on Ameren’s and Ameren Missouri’s results of operations, financial position, or liquidity.

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- Definition This disclosure describes the utility's legal obligations to perform retirement activities for long-lived nuclear assets and spent nuclear fuel. The disclosure includes the retirement obligation, regulatory authorities, recent activities, cost recoveries expected, trust funding and assets, and the regulatory assets and liabilities associated with decommissioning. + References No definition available. + Details
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- Definition Nuclear Waste Matters [Abstract] + References No definition available. + Details
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