1. Tutorial 6: Case Study “Peppermint Twist” “Genie in the Bottle”
SY DE 142 – July 5, 2003
Introduction to Human Systems Engineering
Waterloo, Ontario, Canada

2. Outline Case 1: “Peppermint Twist” Question and Discussion on Case 1
Case 2: “Genie in the Bottle”
Questions and Discussion on Case 2

3. The Peppermint Twist Place: Trendy nightclub , Topeka
Time: September 1989
Results:
Dishwashing fluid, indistinguishable from watermelon-flavored mixed drink, poisoned girl and several others at the night club

4. The Peppermint Twist Question
In this case, several solutions were possible. One could have improved the situation by:
A) making the detergent less poisonous
B) locating the dishwasher farther from the bar.
Explain how these solutions would have changed system characteristics that created the accident.
Hint: Look at Lecture 2 on System Accidents

5. The Peppermint Twist Solution
Making the detergent less poisonous …
makes the system less tightly coupled
Locating the dishwasher further away …
increases the distance between dishwasher and drinks. This minimized proximity interactions.

6. Case Study #2 Genie in the Bottle
Time: January 3, 1961
Place: National Reactor Testing Station, Idaho
Synopsis: Maintenance crew removed a high-worth control rod from a nuclear reactor causing a nuclear accident.

7. Genie in the Bottle Questions
1. Explain what kind of error this was and
why.
2. What would have been the best way to prevent this error?
3. Give an example of how to do this in the Genie case.

8. Genie in the Bottle Solutions
The crew made a mistake because the actions (raising the rod higher) they took were correct given their intention.
Also they did not understand the type of control rod and the workings of the reactor, they operated with the wrong intention (to raise the rod higher) making this a mistake.
Mistake = (wrong intention right action)

9. Genie in the Bottle more Solutions
2. This error could have been prevented…
through the use of a forcing function.
A forcing function is the best way because it does not require training or manuals and physically makes it impossible for the rods to be removed.
3. An example of this …
would have been a physical barrier which would have prevented the workers from removing the rod too far.