It has been reported often that “by 2005, nuclear unit sees 50-50 chance of meltdown” according to the Nuclear Regulatory Commission (NRC) during a 1985 hearing before Congress.

Examples:

  • Example 1: NY Times, 4/17/1985:
    http://www.nytimes.com/1985/04/17/us/by-2005-nuclear-unit-sees-50-50-chance-of-meltdown.html
  • Example 2: Karl Grossman on Democracy Now, 3/17/2011:
    http://www.democracynow.org/2011/3/17/serious_danger_of_a_full_core


    From Democracy Now!

    As to the likelihood of a severe core melt accident, in 1985 the NRC acknowledged that, over a 20-year period, the likelihood of a severe core melt accident to be basically 50/50 among the 100 nuclear power plants — there’s 104 now — in the United States. They’ve known all along here in this country that disaster could come, and there’s a good likelihood of it coming, and they’ve known the consequences.

    JUAN GONZALEZ: You’re saying that the NRC itself estimated a 50/50 chance of a meltdown in our plants here within 20 years?

    KARL GROSSMAN: Over a 20-year period. That was formal testimony provided to a watchdog committee in Congress chaired by Senator Edward Markey of Massachusetts, when he asked the question, “What does the NRC and its staff believe the likelihood to be of a severe core meltdown?” So, you know, when you hear these lines about, “Oh, the chances of a severe core meltdown, infinitesimal,” and if there is, like you’re hearing these reports out of Japan, an accident, “Oh, just some minor effects among the population” — not at all.

Comments: The report is often quoted on the web without a source. It is, however, available and can be found with some searching. By posting it here I hope it will become more widely available.

The source is:

NRC authorization for fiscal years 1986-87 : hearing before the Subcommittee on Energy Conservation and Power of the Committee on Energy and Commerce, House of Representatives, Ninety-ninth Congress, first session, April 17, 1985.

The full report is available from the HathiTrust and was scanned by Google. The following links to p. 617, where the relevant part begins. I have also quoted this relevant part below.

http://hdl.handle.net/2027/pst.000013376239?urlappend=%3Bseq=623

Here is the quote. I’d encourage you to read the entire section, which consists of only a few double-spaced pages.

Under the assumption that 3 x 10^(-4) core-melt accidents per unit year remains the industry average in the future, one can calculate that the probability of one or more such accidents in 0.45 in a population of 100 plants serving for 20 years each. Another way of expressing the calculation is to say that there is 55% chance of no core-melt accidents, and 33% chance of one such accident, and a 12% chance of more that one accident over the 20-year period.

There are several reasons to believe this assessment is pessimistic. […]

One should note that although the assessment is pessimistic, meaning that the chance of a nuclear accident is likely lower than calculated, the topic concerned is nuclear power, whose dangers have been well-documented.

Also cited here:

Jeffrey A. Dubin, Safety at Nuclear Power Plants: Economic Incentives under the Price-Anderson Act and State Regulatory Commissions, Social Science Journal, vol. 26, No. 3, pp. 303-311, http://www.pacificeconomicsgroup.com/jad/2025.pdf