Veritasium
May 15, 2026
Alpha Particles and Single Event Upsets: How Radioactive Contamination Causes Computer Chip Errors
Key Takeaways
- 1In 1978, Intel discovered that radioactive uranium and thorium in ceramic chip packaging were causing spontaneous bit flips in DRAM memory
- 2Alpha particles emitted by radioactive materials ionize silicon, creating electron-hole pairs that flip stored bits from 1 to 0
- 3Single event upsets are 'soft errors'—the chip is not permanently damaged and bits can be rewritten
- 4The problem became critical only after miniaturization made chips sensitive enough for individual alpha particles to cause bit flips
- 5Intel's ceramic packaging was contaminated because the manufacturing plant was located downstream from a uranium mill in Colorado
- 6The industry immediately adopted stricter controls on radioactive materials in chip manufacturing after findings were widely circulated
Chapters
1. Discovery of the Problem
Intel discovered unexplained bit errors in 16 kilobit DRAM chips in 1978, with ones spontaneously flipping to zeros
2. Source of Contamination
A new semiconductor packaging plant in Colorado was built downstream of an old uranium mill, allowing radioactive atoms to contaminate ceramic chip packaging
3. How Alpha Particles Cause Bit Flips
Alpha particles from uranium and thorium emit enough energy to ionize silicon, creating charge carriers that accumulate in memory wells and flip bit values
4. Single Event Upsets
Bit flips caused by alpha particles are soft errors—the chip is not damaged and bits can be rewritten, unlike hard errors
5. Why It Happened in the 1970s
Miniaturization of chip components had reduced dimensions enough that a single alpha particle could produce sufficient charge to flip a bit
6. Verification and Industry Response
Controlled exposure tests confirmed the correlation between alpha particle exposure and bit flips, leading industry-wide adoption of stricter radioactive material controls
Glossary
- DRAM
- Dynamic Random Access Memory; volatile computer memory that stores data as the presence or absence of electrical charge in semiconductor wells
- Alpha Particle
- A highly energetic form of radiation emitted by radioactive materials; consists of two protons and two neutrons
- Single Event Upset (SEU)
- A type of soft error where a single ionizing particle flips a bit in memory without permanently damaging the device
- Soft Error
- A temporary data corruption that does not physically damage the chip; can be corrected by rewriting the affected memory
- Ionizing Radiation
- Radiation with enough energy to remove electrons from atoms, creating charged particles and free charge carriers
- Electron-Hole Pair
- A free electron and the absence it leaves behind (hole) in a semiconductor material, created by ionizing radiation