Three Mile Island — How Bad UX Almost Destroyed a State | by Jamieson Silver | Mar, 2023

Image by Midjourney

There have been many UX design failures in history.

Most are funny and pretty harmless, but there’s one UX failure that was very close to becoming an outright national tragedy.

This UX failure was so major that it caused billions of dollars in damage, and permanently changed the energy landscape of America. Today we are going to delve deep into the dark side of UX.

That’s right we are talking about how bad UX almost turned America’s east coast into a nuclear wasteland.

Let’s talk about Three Mile Island.

Not going to go into every little detail about the actual facility itself, but I want to give some context to the narrative.

Three Mile Island, which I will call TMI from here on, was a nuclear power plant located on a small island in Pennsylvania (bonus points if you can tell me how big the island is). It was your typical power plant, until March 28, 1979.

Early that morning TMI suffered a partial meltdown leading to the radioactive material being released into the environment.

To this day it is still considered the most significant nuclear accident in U.S history. All of this could have been prevented.

This is where UX comes into play.

Quick question when you think of a nuclear control room, what do you picture…….if you said a sterile looking room with a lot of screen and buttons then you would not be far off.

The exact number I could not find but it was believed to be over 2000 switches and buttons in the one control room. Yes you read that right over 2000 I can’t even count that high let alone sit in a room with that many buttons.

Entering the control room at Three Mile Island Unit 1 is like stepping back in time. Except for a few digital screens and new counters, much of the equipment is original to 1974, when the plant began generating electricity. Jeff Brady/NPR

The reason the control room was like this can best be described by UX godfather Don Norman

“They spent so much time designing the technical parts, and none on understanding what it was like to work there”

This is the exact opposite of what a lot of us UX designers learn, which is to focus on the user in the design. When doing that you have to view things through the user’s eyes and take into account human foibles and limitations.

Humans are not machines we make mistakes.

The amount of buttons and switches made things extremely complex. It essentially took Hick’s Law which states that the greater the number and complexity of a choice the longer it takes to make a decision, and through it out the door.

But there is more to this than just a lot of buttons.

Since we spoke briefly about Hicks Law, let’s talk about another UX law in relation to TMI. That being the Law of Proximity which states that:

Objects in close proximity to each tend to be grouped together

Easy enough but not for whoever designed TMI. The layout of buttons in the control room was all over the place with no logical grouping.

They had the light to indicate reactor leakage beside the elevator button. Some buttons had lights on top while some had lights on the bottom you can imagine the confusion that would in sue on a normal day.

Which light goes with which button? Guess you should probably read the manual and read it quickly because this place is about to explode.

But the tom foolery continues

In society there are some designs that are standard. So standard that they become part of our unconscious lexicon. Good example would be that beep sound when there is an emergency broadcast.

That sound is so unique to its situation in America that we instantly know something is wrong.

These design standards are based on the society they are in, but should never be ignored or altered when used in a design. I don’t care how clever you think you are.

Well going back to TMI no one got this memo or they thought they were reinventing the wheel.

When you see a green light you usually think good or go, vice versa for red. A green light at TMI had 11 different meanings while red had 14 different meanings.

I’m just going to let you think about that for a sec………also some buttons are active when the light is off, not on. That last statement is what caused all this mess but we will come back to that in just a moment.

I want to speak about one more failure of TMI

Feedback in a major element of UX design, it is a must that we design feedback into our designs. Without it users are left mindlessly wondering what is going on.

Part of this feedback loop is accurate information. If a user pushes a button you want to give them some type of feedback to confirm to them they pushed that button.

Now I’m not going to talk about those damn buttons anymore but the instruments themselves.

The technicians that day had to rely on their instruments to tell them what was going on in the reactor.

This information would allow them to determine the issue and react accordingly. During the early moments of the incident the feedback loop was working properly.

The technicians would do a procedure and the machine would tell them what change happened in the reactor most of this was focused around the temperature.

The machine continued to give accurate info showing the temperature of the core rising. Then suddenly it stopped, instead of numbers question marks were being printed.

The feedback loop was only designed to read up to a temperature of around 600 degrees Fahrenheit (about 316 degrees Celsius). Any higher and it would just fall apart.

This was not a technological limitation. The designers just never thought the temperature would ever get that high.

The temperature of the reactor got all the way up to 4,300 degrees Fahrenheit ( about 2,371 degrees Celsius). All while the crew was stuck with a machine that could not count past 600 degrees.

With the collapse of their feedback loop the technicians were left completely in the dark. They did not know if what they were doing was making the situation better or worse.

Luckily, the technicians were able to get the reactor under control and avoided a complete meltdown.

When an investigation was conducted the company came to the conclusion that the technicians essentially did not know what they were doing.

The cause of the incident was a pressure valve that was open that needed to be closed.

The system told the technicians this all they had to do was look at the pressure valve button to see that it was on.

Everyone knows that when the green light is off that means it’s on. They should have paid attention in training.

What do you think?

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