Enriched Uranyl Nitrate Tanks in Annular Tank Array

1. Analysis of Enriched Uranyl
Nitrate in Nested Annular
Tank Array
John Bess
James Cleaver
Idaho National Laboratory
ANS Annual Meeting, Atlanta, GA
June 14-19, 2009

2. Objective
Benchmark analysis of an array of
nested annular tanks containing
highly enriched uranyl nitrate
solution
Follow guidelines for inclusion in
the International Handbook of
Evaluated Criticality Safety
Benchmark Experiments
2

3. Background
Rocky Flats Critical Mass Laboratory
during the 1980s
Tanks of typical sizes found in nuclear
production plants
Series of experiments:
¤ 1) Co-located set of tanks (Benchmarked)
¤ 2) 1x2 array of nested tanks
¤ 3) 1x3 array of nested tanks
3

4. Basic Experimental Configuration
Six stainless steel tanks
Surrounded by concrete slabs,
walls, and floor
357.4 g/L uranium in dilute nitric
acid
Two to six tanks filled until
criticality achieved

5. Annular Tank Experimental Setup

6. Variations of the Experimental Design
Addition of neutron absorbers
¤ Borated concrete plugs
One with cadmium lining
Placed in center of a pair of annular
tanks
¤ Borated plaster plugs
¤ Borated plaster slabs
Placed between pairs of tanks

7. Plugs and Slabs

8. Critical Solution
Case No. Absorbers/Moderators Tanks with Solution
Level (cm)
1 None 1-2-2*-3*-3-4 103.24
2 None 1-2-2*-3* 116.08
3 None 2*-3* 174.48
4 None 1-2*-3* 150.04
5 3 Concrete Plugs 1-2-2*-3*-3-4 166.54
6 3 Concrete Plugs 1-2-2*-3* 194.58
7 Large Concrete Plug + 2 Plaster Plugs 1-2-2*-3*-3-4 164.575
8 Large Concrete Plug + 2 Plaster Plugs 1-2-2*-3* 196.46
2 Concrete Plugs + Small Cd-Lined
9 1-2-2*-3*-3-4 158.89
Concrete Plug
Large Concrete Plug + 2 Plaster Plugs
10 1-2-2*-3*-3-4 207.9
and 2 Plaster Slabs
Large Concrete Plug + Small Plaster
11 1-2-2*-3*-3-4 121.41
Plug and 2 Plaster Slabs
Large Concrete Plug + Small Plaster
12 Plug and 2 Plaster Slabs 2*-3*-3-4 135.12

9. Additional Non-Benchmark Experiments
Placement of nested hemispheres
of highly enriched uranium
between the tank pairs
Placement of bottled highly
enriched uranyl nitrate between
the tank pairs
Subcritical configuration

10. Benchmark Model Development
Both detailed and simple models were
developed
Simplification include the following:
¤ Omission of rebar and steel reinforcements in
concrete
¤ Omission of wood
¤ Leveling the bottom of the tanks
¤ Simplification of room layout
¤ Correction of solution temperature for difference
between experimental conditions (25ºC) and
measurement of solution density (20ºC)
Removal of impurities is essentially negligible

11. Side

12. Cases 1-4

13. Cases 5-6

14. Cases 7-8

15. Case 9

16. Case 10

17. Cases 11-12

18. Uncertainties Analysis
Perturbation analysis of
parameters compared to the
detailed benchmark model
Monte Carlo N-Particle (MCNP)
version 1.5.1.4
ENDF/B-VI.8 cross-section library
for evaluation of uncertainties

19. Uncertainties Analysis
Experimental Tanks
measurements ¤ Steel properties
¤ Temperature ¤ Thickness
¤ Solution critical ¤ Diameter
height
¤ Annular thickness
Solution
Composition ¤ Eccentricity
¤ Density ¤ Placement
¤ Acid concentration Wood
¤ Uranium ¤ Physical properties
¤ Solution impurities ¤ Thickness
and chemistry

20. Uncertainties Analysis
Concrete and Largest
plaster contributors to the
¤ Water content total uncertainty
¤ Boron content ¤ Boron-free concrete
density
¤ Density ¤ Solution annular
¤ Isotopic abundance region thickness
of boron and lithium
¤ Thickness

21. Results
Uncertainties determined to be
between 0.79 and 0.90 %∆k/k
Expected benchmark eigenvalues
approximately 1.0000
Calculated results within ~1σ-2σ of
benchmark values
¤ Unique experiments because they use
Gerstley borate in concrete and plaster

22. MCNP5
Case No. Absorbers/Moderators Tanks with Solution ENDF/B-VII.0
keff
1 None 1-2-2*-3*-3-4 0.9984
2 None 1-2-2*-3* 0.9999
3 None 2*-3* 0.9871
4 None 1-2*-3* 0.9907
5 3 Concrete Plugs 1-2-2*-3*-3-4 1.0047
6 3 Concrete Plugs 1-2-2*-3* 1.0089
7 Large Concrete Plug + 2 Plaster Plugs 1-2-2*-3*-3-4 0.9933
8 Large Concrete Plug + 2 Plaster Plugs 1-2-2*-3* 1.0011
2 Concrete Plugs + Small Cd-Lined
9 1-2-2*-3*-3-4 1.0000
Concrete Plug
Large Concrete Plug + 2 Plaster Plugs
10 1-2-2*-3*-3-4 0.9855
and 2 Plaster Slabs
Large Concrete Plug + Small Plaster
11 1-2-2*-3*-3-4 0.9810
Plug and 2 Plaster Slabs
Large Concrete Plug + Small Plaster
12 Plug and 2 Plaster Slabs 2*-3*-3-4 0.9747

23. Conclusions
Benchmark analysis of an array of
nested annular tanks containing highly
enriched uranyl nitrate solution was
performed
Report to be published in the
International Handbook of Evaluated
Criticality Safety Benchmark
Experiments
¤ HEU-SOL-THERM-026, September 2009
23

24. Questions?
Rocky Flats
This work was done by Battelle Energy Alliance, LLC under Contract
No. DE-AC07-05ID14517 with the U.S. Department of Energy