PWR heat, materials, and feedback

01 / Choose one

Why is the primary water in a PWR kept at high pressure?

1. To make all primary water turn into steam
2. To keep the bulk coolant liquid at a higher temperature
3. To keep the primary and secondary water at the same pressure

02 / Choose one

Which statement correctly separates nucleate boiling from departure from nucleate boiling?

1. Every bubble means cooling has already failed
2. Steam conductivity alone determines all boiling heat transfer
3. Nucleate boiling can improve heat transfer; departure from it can sharply degrade surface cooling

03 / Calculate · kW

An ideal solid path has k = 400 W/(m·K), A = 1 m², L = 1 m, and ΔT = 100 K. What heat rate does Q̇ = kAΔT/L predict, in kW?

04 / Calculate · m²

Keep k = 400 W/(m·K), L = 1 m, and ΔT = 100 K. What cross-section would the ideal conduction model require to carry 100 MW?

05 / Choose one

The pellet model runs cooler when conductivity increases. What does that establish about the Doppler coefficient of a different fuel?

1. Nothing by itself: the model has no neutronics calculation
2. It proves that all negative feedback disappears
3. It proves that conductivity alone determines the coefficient

06 / Choose one

Two generated power fields have the same whole-volume mean. What can still differ?

1. Nothing; equal averages require identical local values
2. Their local peaks and where those peaks occur
3. Their total power must differ if either has a peak

07 / Choose one

A component operates at nearly steady temperature. Which conclusion follows?

1. Irradiation embrittlement cannot accumulate
2. Every component has the same lifetime limit
3. Some thermal cycling is reduced, but irradiation damage and other stresses can still matter

08 / Reflection

Someone proposes replacing water with a more conductive coolant. What would you ask before calling it an improvement?