# Presentation: 522959

## Robotics in Extreme Radiation Environments

## Outline

- Context: the environment of Chernobyl
- Pioneer as an example of a rad-hard robot
- Lessons learned

## Chernobyl

- reactor

**Notes:**
Brief summary of the accident
April 26, 1986, right before Mayday.
Nuclear power plants are consumers of energy as well as producers.
Engineers wanted to test whether, in case the reactor had to be quickly shut down, and it was off the grid,
there was enough momentum in the turbines to continue generating electricity for 90 secs until the diesel emergency generators kicked in.
They dropped the power down from the normal 3.2 GW to 1 GW, but the power level kept dropping until it hit 30MW.
(One of the problems with this reactor design was it’s ‘twitchiness’. It was unstable and needed continuous, active control.
This allowed the buildup of Xenon-135, which is normally consumed under higher power conditions. 
The Xe-135, however, absorbed neutrons and when the operators tried to raise the power back up to 1 GW it wouldn’t go above 200 MW
In an effort to increase the power, the control rods were pulled out farther than would normally be allowed, and the emergency safety controls were shut down.
This caused the power to quickly spike to 30 GW, causing the coolant, liquid water, to boil into steam.
The RBMK reactors had a positive void coefficient, which means that the reaction would increase if the coolant was replaced with a void, or steam.
This made the reactor inherently unstable: hotspots could cause coolant to flash into steam, resulting in increased local reaction and more heat. 

## After

**Notes:**
The steam exploded and blew the concrete upper biological shield off the top of the reactor. Core material may have also been blow out.
The intense heat caused the graphite blocks to burn; the core, along with all the pipes and rods and other stuff, melted into a liquid and flowed out the bottom.

## Upper Bio Shield

**Notes:**
Here’s a more intimate picture of the upper bio shield today. 
I think the lampshade-things are gamma ray detectors

## UBS 

- UBS

## Aerial view of UBS

## Aerial view after explosion

## Scale of radiation dispersal

## Aerial view of construction

## South end of roofMammoth Beam

- South end of roofMammoth Beam

## Final stages of shelter construction

## The Finished Shelter

## View from inside

## Mammoth beam

## NG

- UBS

- corium

**Notes:**
This is an illustration from National Geographic. Here you can see the upper biological shield and the corium beneath.

## Steam distribution headers

## Corium in Steam Distribution Header

## Close-up of corium in steam header

## LLFCM distribution

## Level 9

## Lava-like Fuel Containing Mass

## LLFCM

## Corium stalactite

## The Elephant’s Foot

## Korneev at the Elephants Foot

## Robot track

## Robot track Room 308

## Level 9

## 304 from 301

## Robotic design constraints for high radiation environments

- Minimal onboard electronics
- Heavy shielding for any onboard electronics
- No RC
- Heavy tether
- No internal combustion
- Filters become nuclear waste
- Heavy tether

## Houdini

## Early concept

## Pioneer CAD

## Pioneer

## Pioneer control system

## Mass-compounding problem

- Component (e.g. stereo camera) requires heavy shielding, mechanical systems
- Shielded camera requires massive pan-tilt motor to move it
- Motor requires lots of current, heavier cable
- Heavier load requires heavier frame, wheel motors, etc.

## Instability problem

- Increasing mass moves center of gravity up
- Minimizing motor weight risks under-powering unstable vehicle

## Pioneer at Chernobyl

## Room 305

## MarsMap

## CMap

## Cmap Acquisition UI

## Problems with Cmap

- Built on Silicon Graphics machines
- Unfamiliar to operators
- Little likelihood of repair
- No migration path
- Awkward user interface

## Lessons learned

- Beware mass-creep
- Simulation would have been useful
- Keep it simple

## The end