permanent sealing material. The temporary sealing material was highly combustible, and caught fire. Efforts were made by the workers to extinguish the fire at its origin, but they apparently did not recognize that the fire, under the influence of the draft through the penetration, was spreading on the reactor building side of the wall. The extent of the fire in the cable spreading room was limited to a few feet from the penetration; nonetheless, the presence of the fire on the other side of the wall from the point of ignition was not recognized until significant damage to cables related to the control of Units 1 and 2 had occurred. This later resulted in the Nuclear Regulatory Commission making significant additions to the standards for fire protection through the publication of 10CFR50.48 and Appendix R. According to the Nuclear Information and Resource Service, the newly restarted Unit 1 does not comply with these standards. Unit 3 was not affected by the accident. This event was pivotal not just for firestopping in the nuclear field, but also in commercial and industrial construction. While the nuclear field went to installations of silicone foam, a wider array of firestops became prevalent in non-nuclear construction. Unit 2 Unit 2 is a 1,259 MWe net BWR/4 built by General Electric that originally came online on August 2, 1974, and is licensed to operate through June 28, 2034. Unit 2 generated 8,396 GWh of electricity in 2017, achieving a capacity factor of 86.81%. Unit 2 returned to service in 1991, after all three reactors were shut down in 1985. During a drought in August 2007, Unit 2 was shut down for one day because water temperature in the Tennessee River rose too high for the water to be used for cooling and then discharged back into the river. Beginning in 2005 Unit 2 was loaded with BLEU (Blended Low Enriched Uranium) recovered by the DOE from weapons programs. This fuel contains quantities of U-236 and other contaminants because it was made from reprocessed fuel from weapons program reactors and therefore has slightly different characteristics when used in a reactor as compared to fresh uranium fuel. By making use of this fuel, which would otherwise have been disposed of as waste, the TVA is saving millions of dollars in fuel costs and accumulating a database of recycled uranium reactions in LWR use. Unit 3 Unit 3 is