Asset Retirement Obligations (Tables)

6 Months Ended

Mar. 31, 2024

Asset Retirement Obligation Disclosure [Abstract]


Asset Retirement Obligation Activity (in millions)
	Nuclear		Non-Nuclear		Total
Balance at September 30, 2023	$	3,808	$	3,681	$	7,489	(1)
Settlements	(3)		(119)		(122)
Revisions in estimate	(161)		253		92


Accretion (recorded as regulatory asset)	86		47		133

Balance at March 31, 2024	$	3,730	$	3,862	$	7,592	(1)

Note

(1) Includes $311 million and $272 million at March 31, 2024, and September 30, 2023, respectively, in Current liabilities.

Revisions in non-nuclear estimates increased the liability balance by $253 million for the six months ended March 31, 2024. The increase was primarily attributable to a change in closure liabilities of $184 million at Gallatin Fossil Plant based on new vendor bids associated with final closure and $76 million at Cumberland based on scope changes to the interim closure plan and updated cost estimates for activities associated with final closure.

Revisions in nuclear estimates decreased the liability balance by $161 million for the six months ended March 31, 2024. The decrease was primarily attributable to an estimate revision of $164 million following the filing of a subsequent license renewal ("SLR") application with the Nuclear Regulatory Commission for Browns Ferry Nuclear Plant ("Browns Ferry"). If approved, the SLR will allow for an additional 20 years of operations for each of Browns Ferry's three units, resulting in a total operating life of 80 years.