---
category: Nuclear Concept
location: Weizmann Institute of Science, Rehovot, Israel
summary: Heavy water (deuterium oxide, D2O) is a form of water that contains a higher
  than normal concentration of the isotope deuterium, rather than the common hydrogen-1
  isotope.
tags:
- Concept
- Nuclear
- Technology
---

Heavy water (deuterium oxide, D2O) is a form of water that contains a higher than normal concentration of the isotope deuterium, rather than the common hydrogen-1 isotope. It is used in certain types of nuclear reactors, known as heavy-water reactors, as a neutron moderator to slow down neutrons and increase the probability of nuclear fission.[^1]

By 1953, Israeli researchers at the [Weizmann Institute of Science](/organizations/weizmann-institute-of-science/) had pioneered a new process for creating heavy water. This development was crucial for [Israel](/places/israel/)'s nuclear ambitions, as [David Ben-Gurion](/people/david-ben-gurion/) had repeatedly stated that [Israel](/places/israel/) would build its own atomic reactor utilizing locally manufactured heavy water.[^1]

[^1]: Hersh, Seymour M. *The Samson Option: Israel's Nuclear Arsenal and American Foreign Policy*. Random House, 1991. Chapter 2.