ML20012B425

Responds to 900202 Questions Re High/Low Enriched U Conversion at Facility.Multiplication Factor for High Enriched U Calculated to Be 0.41 & 0.46 for Low Enriched U

ML20012B425
Person / Time
Site:	University of Iowa
Issue date:	03/05/1990
From:	Hendrickson R IOWA STATE UNIV., AMES, IA
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
NUDOCS 9003140382
Download: ML20012B425 (3)

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. 1 1 Department of Nuclear Engineering 261 Sweeney llall i IOWA STATE ^"= i- 5=i :23o l

UNIVERSITY Teiceho"e5's294584o j Docket No. 50-116 .j March 5, 1990 l 1

U. S. Nuclear Regulatory Commission  !

ATTN Document Control Desk i Washington, D.C. 20555 l

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SUBJECT:

QUESTIONS REGARDING HEU/ LEU CONVERSION AT 10WA STATE UNIVERSITY i

Gentlemen:  ;

i In answer to the questions enclosed with a letter from Theodore S.  !

Michaels, NRR, dated February 2, 1990, our analysis of the ,

multiplication factor for the fuel storage pit under different loading

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configurations is conpleted.  ;

In the attached " Procedures on. Fuel Storage', Dr. Alfred F. Rohach has  !

performed an update of a report on the-same subject submitted to the US Atomic Energy Commission in 1962. He concludes that no accidental '

criticality is possible for (1) flooded, assembled HEU fuel (12 fuel plates per storage hole) in the pit, or-(2) flooded, diseassembled LEU l- fuel (48 fuel plates per storage hole).

L QUESTION #1: Vhat is the likely multiplication factor for the dry [

storage pit fully loaded with-Irradiated fuel?

l; I ANSWER TO #1:  !

-The multiplication factor was calculated to be 0.41 for the HEU  :

(irradiated) fuel stored in an infinite array with all assemblies l L flooded with water. Since dry conditions yleld a lower multiplication E factor, the answer to question #1 is 'Less than 0.41 *

. QUESTION #2 What is the likely multiplication factor for the lockable  !

storage vault containing the complete inventory of LEU fuel? l ANSWER TO #2:

l ~A calculation for the storage of two LEU assemblies (disassembled into a bundle of 48 plates) per storage pit location gave a multiplication l

factor of 0.46.. Based on this result, all of the disassembled LEU (up ,

to 336 platest can be stored in seven spaces in the 16-hole storage pit.

9003140382 900305 t

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-PDR ADOCK 05000116

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cm The. HEU fuel assemblies and'apare plate bundle (total of 14) can be l stored Iri the 12 spaces in the core tanks and in two spaces in the l storage pit. We will une oniv the reactor core tanks and the fuel i storaae olt to store HEU and f Pil fuel. .The answer to question #2 je 'We do not need to use a lockable storage vault to hold any fuel, therefore, the multiplication factor for the lockable storage vault is not needed ,

at this time.' <

Discussion of mechanisms and likellhood of .nadvertent flooding of the '

fuel pit storage f acility and potential reac'.lvity cor. sequences were not ;

considered at this time since there is no possibility for accidental .

criticality if the storage area is flooded with water.

If you have any questions, please call me at (510) 294-6422.

Slncerely,  ;

Adk&SLse -

Richard A. Hendrickson ,

Reactor Manager Attachments Procedures on Puel Storage C: G.P. Crouch, Rad. Safety Officer R.A. Danofsky, Chm., Reactor Use Comm.  :

R.A. Jacobson, Chm., Rad. Safety Comm.

B.I. Spinrad, Chm., Nuc E Dept.  ;

Regional Administrator, U.S. NRC - Region III l

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Procedures on Fuel Storage I. Calculations of Multiplication Factor for Storage Pit The analysis of accidental criticality of fuel stored in the storage pit has been updated from report, " Procedures for handling the second core for the UTR-10 reactor" which was received by the Directory of Licehing and Regulation of the U.S. Atomic Energy Commission on August 13, 1962 (Docket No.

l 50-116). In that analysis the multiplication factor for 12 fuel assemblies stored in the storage pit was calculated to be 0.55. The analysis was done with a one group model for an infinite array of stored fuel assemblies. It was reported that, "there is essentially no interaction between assemblies separated by 6" or more of water. Elements are separated a minimum of 7.5",

and separator material is steel, concrete, and water; more attenuation than water alone."

These calculations were updated with a three dimensional diffusion theory model which; included four energy groups. Again an infinite array of stored assemblies was assumed. The multiplication factor was calculated to be 0.41 for HEU stored assemblies flooded with water. A calculation for the storage of two LEU stored assemblies (disassembled) per storage location gave a multiplication factor of 0.46.

l Both studies indicate that there is no possibility of accidental criticality

.even with every fuel location (16) loaded with a HEU and/or LEU assembly.

Even if all locations contain two LEU fuel assemblies disassembled and the pit storage _ area is flooded with water there is no possibility for accidental criticality.

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