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Asset Retirement Obligations Asset Retirement Obligations (Tables) | 12 Months Ended
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Sep. 30, 2021
Asset Retirement Obligation Disclosure [Abstract] |
Asset Retirement Obligation Activity |
Asset Retirement Obligation Activity
| Nuclear |  | Non-Nuclear |  | Total |
Balance at September 30, 2019 | $ | 3,136 |  |  | $ | 2,480 |  |  | $ | 5,616 |  |
Settlements | (1) |  |  | (113) |  |  | (114) |  |
Revisions in estimate | — |  |  | 1,077 |  |  | 1,077 |  |
Accretion (recorded as regulatory asset) | 143 |  |  | 63 |  |  | 206 |  |
Balance at September 30, 2020 | 3,278 |  |  | 3,507 |  |  | 6,785 |  | (1)
Settlements | (11) |  |  | (231) |  |  | (242) |  |
Revisions in estimate | 12 |  |  | 191 |  |  | 203 |  |
Additional obligations | — |  |  | 43 |  |  | 43 |  |
Accretion (recorded as regulatory asset) | 149 |  |  | 64 |  |  | 213 |  |
Balance at September 30, 2021 | $ | 3,428 |  |  | $ | 3,574 |  |  | $ | 7,002 |  | (1)
Note (1) Includes $266 million a nd $345 million at September 30, 2021 and 2020, respectively, in Current liabilities. TVA implemented revised depreciation rates during the first quarter of 2022 applicable to its completed plant as a result of the completion of a new depreciation study. The study includes a decline in the service life estimates of TVA’s coal-fired plants based on current planning assumptions to potentially retire the remainder of the coal-fired fleet by 2035. As a result of the accelerated retirements reflected in the depreciation study, TVA performed an assessment of the assumptions used in the timing of cash flows related to its non-nuclear AROs. Based on the assessment, TVA identified changes to its projections of timing of certain asset retirement processes, that will be recorded in 2022.

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- Definition Tabular disclosure of the carrying amount of a liability for asset retirement obligations. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 20 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6392692&loc=d3e7535-110849 + Details
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