Search results
Results from the WOW.Com Content Network
A positive void coefficient means that the reactivity increases as the void content inside the reactor increases due to increased boiling or loss of coolant; for example, if the coolant acts predominantly as neutron absorber. This positive void coefficient causes a positive feedback loop, starting with the first occurrence of steam bubbles ...
Certain aspects of the original RBMK reactor design had several shortcomings, [3] such as the large positive void coefficient, the 'positive scram effect' of the control rods [4] and instability at low power levels—which contributed to the 1986 Chernobyl disaster, in which an RBMK experienced an uncontrolled nuclear chain reaction, leading to ...
RBMK issues: 1. Using a graphite moderator in a water-cooled reactor, permitting criticality in a total loss of coolant accident. 2. A positive steam void coefficient that made the destructive power excursion possible. 3. Control rods design; taking 18–20 seconds to be fully inserted, and with graphite tips that increased reactivity initially. 4.
is the number of neutrons produced, on average, by a fission event—it is between 2 and 3 for both 235 U and 239 Pu (e.g., for thermal neutrons in 235 U, = 2.4355 ± 0.0023 [2]). If α {\displaystyle \alpha } is positive, then the core is supercritical and the rate of neutron production will grow exponentially until some other effect stops the ...
This is measured by the coolant void coefficient. Most modern nuclear power plants have a negative void coefficient, indicating that as water turns to steam, power instantly decreases. Two exceptions are the Soviet RBMK and the Canadian CANDU. Boiling water reactors, on the other hand, are designed to have steam voids inside the reactor vessel.
Lead has a positive void coefficient, or void reactivity, meaning that as voids occur in the circulating coolant an increase in fertile fission and a decrease in the capture rate of all heavy nuclides results in reactivity increases as the void content inside the reactor increases, potentially leading to a positive feedback loop unless ...
His report was noted for its great detail and relative openness in discussing the extent and consequences of the tragedy, [24] disclosed to Western media some defects in the RBMK reactor design such as the positive void coefficient, as well as problems with operator training. [25]
When the coolant is a liquid that also contributes to moderation and absorption (light water or heavy water), boiling of the coolant will reduce the moderator density, which can provide positive or negative feedback (a positive or negative void coefficient), depending on whether the reactor is under- or over-moderated.