Chernobyl: reactor state and systems design

01 / Choose one

Why could the start of rod insertion increase reactivity in the lower core?

1. Graphite displaced neutron-absorbing water before sufficient absorber reached that region
2. All control rods always add reactivity when they move
3. Xenon instantly stopped absorbing neutrons

02 / Calculate · m²

One barn equals 10⁻²⁸ m². Write that area in m² using a decimal or scientific notation.

03 / Choose one

Two equal opposing neutron beams cross the same area. What happens to their scalar flux and net current?

1. Both are zero
2. The flux adds; the net current cancels
3. The current adds; the flux cancels

04 / Choose one

The chain reaction has stopped. Which heat source can still remain?

1. Only fission that continues at the previous rate
2. Radioactive decay of products already present
3. None; zero chain-reaction power means zero heat

05 / Choose one

What does an ORM value in equivalent rods describe?

1. A simple count of all rods physically touching the core
2. State-dependent reactivity worth expressed using a standard rod reference
3. A guarantee that any shutdown transition will be safe

06 / Reflection

A test begins with steady power and a trained crew. What else would you want to know before calling the test adequately controlled?