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Asset Retirement Obligations | 3 Months Ended
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Dec. 31, 2024
Asset Retirement Obligation Disclosure [Abstract] |
Asset Retirement Obligations | Asset Retirement Obligations During the three months ended December 31, 2024, TVA's total asset retirement obligations ("ARO") liability increased $16 million as a result of increases from periodic accretion, partially offset by revisions in estimate to non-nuclear asset AROs and settlements related to retirement projects that were conducted during the period. The nuclear and non-nuclear accretion amounts were deferred as regulatory assets. During the three months ended December 31, 2024, $55 million of the related regulatory assets were amortized into expense as these amounts were collected in rates. See Note 8 — Regulatory Assets and Liabilities. TVA maintains investment trusts to help fund its decommissioning obligations. See Note 14 — Fair Value Measurements — Investment Funds and Note 20 — Contingencies and Legal Proceedings — Contingencies — Decommissioning Costs for a discussion of the trusts' objectives and the current balances of the trusts.
Asset Retirement Obligation Activity (in millions) |
| Nuclear |  | Non-nuclear |  | Total |
Balance at September 30, 2024 | $ | 3,814 |  |  | $ | 6,992 |  |  | $ | 10,806 |  | (1)
Settlements | (7) |  |  | (61) |  |  | (68) |  |
Revisions in estimate (non-cash) | — |  |  | (24) |  |  | (24) |  |
Accretion (recorded as regulatory asset) | 43 |  |  | 65 |  |  | 108 |  |
Balance at December 31, 2024 | $ | 3,850 |  |  | $ | 6,972 |  |  | $ | 10,822 |  | (1)
Note (1) Includes $301 million and $283 million at December 31, 2024, and September 30, 2024, respectively, in Current liabilities. Revisions in non-nuclear estimates decreased the liability balance by $24 million for the three months ended December 31, 2024. The decrease was primarily attributable to a change in closure liabilities of $34 million at Paradise Fossil Plant based on scope changes, new vendor bids, and updated cost estimates for activities associated with final closure. The decrease was partially offset by increased revisions in estimates of $16 million related to the final legacy coal combustion residual rule ("Legacy CCR Rule").

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- Definition The entire disclosure for an asset retirement obligation and the associated long-lived asset. An asset retirement obligation is a legal obligation associated with the disposal or retirement from service of a tangible long-lived asset that results from the acquisition, construction or development, or the normal operations of a long-lived asset, except for certain obligations of lessees. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 410 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147481850/410-20-50-1 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 410 -SubTopic 20 -Name Accounting Standards Codification -Publisher FASB -URI https://asc.fasb.org/410-20/tableOfContent Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Name Accounting Standards Codification -Section 50 -Paragraph 2 -SubTopic 20 -Topic 410 -Publisher FASB -URI https://asc.fasb.org/1943274/2147481850/410-20-50-2 + Details
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