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Asset Retirement Obligations (Tables) | 9 Months Ended
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Jun. 30, 2021
Asset Retirement Obligation Disclosure [Abstract] |
Asset Retirement Obligation Activity |
Asset Retirement Obligation Activity |
| Nuclear |  | Non-Nuclear |  | Total |
Balance at September 30, 2020 | $ | 3,278 |  |  | $ | 3,507 |  |  | $ | 6,785 |  | (1)
Settlements | (5) |  |  | (135) |  |  | (140) |  |
Revisions in estimate | 12 |  |  | 107 |  |  | 119 |  |
Additional obligation | — |  |  | 30 |  |  | 30 |  |
Accretion (recorded as regulatory asset) | 111 |  |  | 47 |  |  | 158 |  |
Balance at June 30, 2021 | $ | 3,396 |  |  | $ | 3,556 |  |  | $ | 6,952 |  | (1)
Note (1) Includes $306 million and $345 million at June 30, 2021, and September 30, 2020, respectively, in Current liabilities. The revisions in non-nuclear estimates increased the liability balance by $107 million for the nine months ended June 30, 2021. These increases were primarily driven by revisions of certain coal combustion residuals ("CCR") closure liabilities at Shawnee Fossil Plant ("Shawnee"), Paradise, and Colbert Fossil Plant ("Colbert"), resulting from revised engineering estimates for construction costs, new vendor bids, modified closure designs, and expected costs associated with post-closure care of the closed areas. In addition, TVA's use of a new CCR landfill at Shawnee resulted in a new obligation of $30 million.

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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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