ne.gif (2791 bytes)     NE571 Reactor Theory and Design
Fall semester 1998

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Material Input Processor (MIP) reading assignment

In the Material Information Processor manual (SCALE section M7), read sections M7.1 and M7.2.  Also take a look at the input section M7.4 and the notes in section M7.5.  We will use it in the exercie below (and in the take-home Final). 
 

Performing Pin-cell Calculations with the MIP

Computational environment setup

First of all, we need to establish the computational environment.  I will assume that you will be working in the 3rd floor computer room.  If you are somewhere else, setup of the environment will be different (and left up to you to figure out.) 

Throughout the rest of the course, we will be using the Sequoyah PWR reactor as an example.  I chose this because the SAR for this plant is readily available in the graduate student office bookcase.  The reactor characteristics of interest to us are in Chapter 4 of the SAR (which is Vol. 5 in the set).  Later, I will be sending you to the SAR for information that you will need, but for this assignment I did the legwork for you.  (You WILL, however, have to translate the SAR information into the form that CSASIN needs.) 

The reactor contains 193 assemblies, each of which contains a 17x17 square array of pin positions.  Of these 289 pins, 264 are fuel pins, 1 (in the middle) is an instrument tube, and the other 24 are control positions (usually filled with moderator).  Reactivity control is maintained (as far as we are concerned) by borating the coolant water.  There are three cycles.  In the first cycle, some of the assemblies have poison (boron) pins in place of some of the fuel pins.  In any individual assembly, all of the fuel pins are initially identical, but there are three different assembly pin enrichments:  2.1%, 2.6%, and 3.1 %. 

In this exercise, we will be calculating some of the physics parameters associated with the 2.6% enriched pins.  The pins consist of a fuel pellet of 0.3225 inches OD, surrounded by a diameter gap of 0.0065 inches, surrounded by a Zircalloy cladding of 0.0225 inch thickness.  The resulting pin OD is 0.374 inches.  (I know. That's not what I got the first time either, but it IS consistent.) 

The pin pitch (i.e., center-to-center distance between adjacent pins) is 0.496 inches.  The UO2 density is 0.364 lb/ft. (I am not trying to be difficult -- this is the way the data are presented in the SAR.) 

As best I can deduce, the nominal coolant temperature is 582 degrees F., the nominal clad temperature is about 700 degrees F., and the average fuel temperature is about 1050 degrees F.  (SCALE requires temperature in Kelvin.)  The pressure is 2205 psia. 

Okay.  Let's set up a problem. 

1. Get an MS-DOS prompt.

This is done in the WindowsNT system by clicking on the "Start" button, then "scale4.4a", then "DOS prompt for SCALE4.4A".

2. Enter “cd yourdirectory”.

"yourdirectory" is any alphanumeric that you want to use for your private subdirectory (with all the necessary prefixes, e.g., “\pevey\ne571\outputfile”). 
 

3. Use your work processor of choice to make an input deck named "edit reg2.in". 

Enter the following input deck.  Some of my numbers have been x'd out.  ;) 

=csas1x    parm=size=400000
SEQUOYAH 2.6% FUEL PINS 
44groupndf5                 latticecell 
uo2            1  den=10.xx 1.0 8xx 92234  0.0005 92235 2.6 92238 97.4 end 
zirconium      2  1.0 6xx end 
h2o            3  den=.7xxx 1.0 5xx end 
B              4  den=.7xxx 1.0 5xx end 
       end comp 
squarepitch 1.xx .8xxxx 1  3  .9x 2  .8xxxx 0  end 
end

The input consists of only 10 lines.  You should be able to refer to the SAS2H manual (from SCALEMAN subdirectory of the SCALE directory) and figure out what each line means. 

Complete the assignment:

Modify the basic deck that we have created above to check the following values from the SAR: 
  • The Doppler coefficient, which is the sensitivity of k-effective to the fuel temperature, is supposed to be low but negative: -1 to -2 pcm/deg F.  (A "pcm" is "per cent milli-k".  1 pcm is a k-effective of 0.00001)  Try cooling the fuel off by 100 degrees, rerunning the case and see what you get for this value (in comparison to the "hot,clean" case we ran in the tutorial). 
  • The Moderator temperature coefficient, which is the sensitivity of k-effective to changes in moderator temperature is expressed as 0 to -40 pcm/deg F.  Try cooling the moderator by 100 degrees or so (and changing the water density appropriately) to find this value. 
  • The sensitivity of k-effective to the moderator boron concentrations is supposed to be -8 to -16 pcm/ppm.  Check this by adding 100 ppm of B to the moderator by changing the boron line to: 
B              3  DEN=.7xxx 0.000100 5xx END 
  • Finally, the maximum assembly k-effective is supposed to be 1.39.  This will undoubtedly be for the "cold, clean" case for fuel loadings of 3.1% enrichment.  Check this by modifying the UO2 isotopics and setting the temperatures to room temperature (293 K).  (Don't forget to change the water density back to 0.9982.) 
E-mail me your results: 
 

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