KENO VI Volume Multiply Defined/Particle Leaking

[Nick Grenci]

Hello,

I have created a KENO VI model where I define a stack of pellets as a unit, and then define a pin as a stack of these units as holes. I am seeing volume multiply defined/neutron leaking errors with the following as an example:

***** error ***** keno message number k6-089 follows:

volume has been multiply defined.

generation = 37 neutron = 6262 unit =21

particle at position x=-1.56768E+00 y=1.34497E+00 z=1.55400E+00

is located inside the following regions in the unit:

14T

16T

Below is the definition for unit 21 from the input file:

unit 21
    com='fuel_pellet_stack'
        cylinder 249 2.4 6.156 0
        cylinder 250 2.3 0.03 0
        cylinder 251 2.4 0.03 0
        cylinder 252 2.25 0.959 0.03
        cylinder 253 2.3 0.959 0.03
        cylinder 254 2.4 0.959 0.03
        cylinder 255 2.3 0.989 0.959
        cylinder 256 2.4 0.989 0.959
        cylinder 257 2.345 1.019 0.989
        cylinder 258 2.4 1.019 0.989
        cylinder 259 2.24 1.524 1.019
        cylinder 260 2.295 1.524 1.019
        cylinder 261 2.345 1.524 1.019
        cylinder 262 2.4 1.524 1.019
        cylinder 263 2.345 1.554 1.524
        cylinder 264 2.4 1.554 1.524
        cylinder 265 2.3 1.584 1.554
        cylinder 266 2.4 1.584 1.554
        cylinder 267 2.25 2.513 1.584
        cylinder 268 2.3 2.513 1.584
        cylinder 269 2.4 2.513 1.584
        cylinder 270 2.3 2.543 2.513
        cylinder 271 2.4 2.543 2.513
        cylinder 272 2.275 2.573 2.543
        cylinder 273 2.4 2.573 2.543
        cylinder 274 2.23 3.583 2.573
        cylinder 275 2.275 3.583 2.573
        cylinder 276 2.4 3.583 2.573
        cylinder 277 2.275 3.613 3.583
        cylinder 278 2.4 3.613 3.583
        cylinder 279 2.3 3.643 3.613
        cylinder 280 2.4 3.643 3.613
        cylinder 281 2.25 4.572 3.643
        cylinder 282 2.3 4.572 3.643
        cylinder 283 2.4 4.572 3.643
        cylinder 284 2.3 4.602 4.572
        cylinder 285 2.4 4.602 4.572
        cylinder 286 2.345 4.632 4.602
        cylinder 287 2.4 4.632 4.602
        cylinder 288 2.24 5.137 4.632
        cylinder 289 2.295 5.137 4.632
        cylinder 290 2.345 5.137 4.632
        cylinder 291 2.4 5.137 4.632
        cylinder 292 2.345 5.167 5.137
        cylinder 293 2.4 5.167 5.137
        cylinder 294 2.3 5.197 5.167
        cylinder 295 2.4 5.197 5.167
        cylinder 296 2.25 6.126 5.197
        cylinder 297 2.3 6.126 5.197
        cylinder 298 2.4 6.126 5.197
        cylinder 299 2.3 6.156 6.126
        cylinder 300 2.4 6.156 6.126
        media 8 1 250
        media 4 1 251 -250
        media 9 1 252
        media 8 1 253 -252
        media 4 1 254 -253
        media 8 1 255
        media 4 1 256 -255
        media 10 1 257
        media 4 1 258 -257
        media 15 1 259
        media 12 1 260 -259
        media 10 1 261 -260
        media 4 1 262 -261
        media 10 1 263
        media 4 1 264 -263
        media 8 1 265
        media 4 1 266 -265
        media 9 1 267
        media 8 1 268 -267
        media 4 1 269 -268
        media 8 1 270
        media 4 1 271 -270
        media 13 1 272
        media 4 1 273 -272
        media 14 1 274
        media 13 1 275 -274
        media 4 1 276 -275
        media 13 1 277
        media 4 1 278 -277
        media 8 1 279
        media 4 1 280 -279
        media 9 1 281
        media 8 1 282 -281
        media 4 1 283 -282
        media 8 1 284
        media 4 1 285 -284
        media 10 1 286
        media 4 1 287 -286
        media 15 1 288
        media 12 1 289 -288
        media 10 1 290 -289
        media 4 1 291 -290
        media 10 1 292
        media 4 1 293 -292
        media 8 1 294
        media 4 1 295 -294
        media 9 1 296
        media 8 1 297 -296
        media 4 1 298 -297
        media 8 1 299
        media 4 1 300 -299
        boundary 249

I have observed a fair amount of these warnings at different locations for volumes that are multiply defined but also neutrons that have leaked but are still contained within the volume of the unit. The offending coordinate has always matched exactly the top/bottom surface of a cylinder defined in the unit (in this case z=1.554 cm). I have plotted the geometry in Fulcrum and do not see any errors. The z-dimensions where cylinders meet have the same coordinates rounded to 3 decimals and I have inspected points that have caused warnings and have not found any undefined regions due to z-dimension mismatches. Could this be a numerical precision error or is there a problem with the geometry definition or possibly something else?

Thanks for the help!

the following regions in the unit:

14 T

16 T