The nuclear industry has made a concerted effort to significantly reduce the number of unplanned rapid emergency shutdowns of a nuclear reactor— called scrams. A decade ago, the mean annual number of unplanned scrams at U.S. nuclear reactor units was four see Exercise 2.81. Assume that the annual number of unplanned scrams that occur at a nuclear reactor unit follows, approximately, a Poisson distribution.

a. If the mean has not changed, compute the probability that a nuclear reactor unit will experience 10 or more unplanned scrams this year.

b. Suppose a randomly selected nuclear reactor actually experiences 10 or more unplanned scrams this year. What can you infer about the true mean annual number of unplanned scrams? Explain.

Data from Exercise 2.81

Scram is the term used by nuclear engineers to describe a rapid emergency shutdown of a nuclear reactor. The nuclear industry has made a concerted effort to significantly reduce the number of unplanned scrams. The accompanying table gives the number of scrams at each of 56 U.S. nuclear reactor units in a recent year.

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SCRAMS 1 4 2 6 5 3 1 5 4 7 12 3. 4 7 4. 2 7 13 3 7 0 9 3 7 8 4 3 4. 1 7 3. 2. 2. す N e 00 3. 2. 3. 2. 2.