# Help me about: problem of Thermal Hydraulic

1. Sep 17, 2010

### marlh

I'm studying about Thermal Hydraulic. When i read book :"NUCLEAR SYSTEMS I Thermal Hydraulic Fundamentals" - Neil E. Todreas and Mujid S. Kazimi.

I don't understand about : calculate "Minimum critical power ratio" & calculate "Pumping power" in problem:

a) Calculate the minimum critical power ratio for a typical 10 MWe BWR operating at 100% power using the data in Tables 1-2, 1-3, and 2-3 . Assume that:

1. The axial linear power shape can be expressed as

q'(z) = q'ref*exp (- az/L )sin (pi*z/L)
where a = 1.96. Determine q'ref such that qmax = 44 kW/m
2. The critical bundle power is 93 19kW.

b) Calculate the pumping power under steady-state operating conditions for a typical PWR reactor coolant system. Assume the following operating conditions:
Core power = 38 17 MWt
detal Tcore = 31 °C
Reactor coolant system pressure drop = 778 kPa (1 13 psi)

can anyone help me solve the problem ? or guide me solve the problem. thank!

Last edited: Sep 17, 2010
2. Sep 17, 2010

### Astronuc

Staff Emeritus
For a, that should be straightforward to calculate q'ref. Find the elevation for qmax. BWRs are not typically 10 MWe, but more like 1 GWe (1000 MWe), and actually > 1 GWe.

What is the significant of CHF?

For b, that's not really typical - 3817 MWt would be typical of the Palo Verde units. Think about Tsat as a possible constraint, and the flow rate of coolant to get a ΔT = 31°C at a power (rate of enthalpy input) of 3817 MWt. Relate flow rate to the pressure drop around the loop. Likely the plant would have 4 loops, or 2 hot legs and 4 cold legs.

3. Oct 2, 2010

### marlh

Thank for Astronuc about hint. I have solved the exercise.

4. Mar 4, 2011

### matt222

actually i have same question for these two problem, can you help me with it, i couldnt find it through the hints given

5. Mar 4, 2011

### Astronuc

Staff Emeritus
Given q'(z), at what location does one find q'max.

For pumping power, besides the pressure drop, what does one need in order to determine the power (rate of work) to pump the coolant around the loop? Relate flow rate to the pressure drop around the loop.

6. Mar 4, 2011

### matt222

we can say that, p=volumetric flow rate*pressure drop
volumetric flow rate =mass flow rate/density of water
mass flow rate=(cp*delta T)/power

is it true and what is the cp in this case?

7. Mar 4, 2011

### matt222

for first part i found the location but how about finding minimum critical power ratio MCPR

8. Mar 9, 2011

### koab1mjr

LOL!!!

You are either in my class or nuclear engineering curriculims throughout the US follows a set curriculim

for a

once you solved for qref just intergrate the function along the length of the rod so you have both numbers needed to compute the ratio.

haven't finished part b due friday got some time. I would assume the Cp of water since this is a PWR

9. Mar 10, 2011

### edgepflow

This would be the specific heat of the reactor coolant. You will need to find a suitable average value for the temperature difference or integrate if your professor requires (like mine did many years ago).

Interesting to see they are still using Todreas - used this book in graduate school in 1991.