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The second example of tipping point failure is Philadelphia Electric’s Limerick nuclear
power plant. Construction of the two 1065 megawatt units began in June of 1974. The
construction schedule at the issuance of the construction permit called for Unit 1 to be
competed in April of 1979 and for Unit 2 to be completed in September of 1980 (NRC, 1982).
The total estimated cost for both units in 1974 was $1.2 billion (Days & Sellers, 1985). As Figure
2 shows, both units were well behind schedule at their respective planned completion dates
(Unit 1 at 48% complete and Unit 2 at 36% complete) (NRC, 1982). Unit 1 finally came on-line in
August of 1985, five and a half years behind schedule with a final cost of $3.8 billion (Days &
Sellers, 1985). Construction of Unit 2 was halted in July 1982 by order of the Pennsylvania
Public Utility Commission due to escalating costs (NRC, 1982).
% Complete
100%
90%
80%
70%
60%
50%
40%
30%
20%
10%
0%
Original completion date: April 1979
Original completion date: September 1980
Dec-73 Apr-75 Aug-76 Jan-78 May-79 Oct-80 Feb-82 Jul-83
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Unit 1
Unit 2
9/23/80
Increase of scope due to design changes
and new regulatory requirement and design
problems associated with Mark II
containmnet.
Figure 2. Limerick Nuclear Power Plant Construction (1974-1982) (NRC, 1982)
The Philadelphia Electric company attributed at least part of the cost and schedule
problems to added new tasks and rework, two factors which Taylor and Ford (2006) showed
capable of generating tipping point dynamics. In a September 1980 report submitted to the
NRC, the estimated completion date was increased by two years for Unit 2 due to an “increase
of scope [added new tasks] due to design changes and new regulatory requirements [rework]”
(NRC, 1982). The degrading backlog behavior pattern is displayed on Unit 2 in Figure 2
between May 1979 and October 1980 as the percent complete begins to decrease. The
Limerick plant was not the only plant to experience problems. A survey of senior managers at a
firm specializing in nuclear plant construction revealed that nearly all surveys credited regulatory
changes as the major cause for delays in both design and construction of nuclear power plants
(Arditi & Kirsinikas, 1985).