ML20085F487

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Change Request 28 to License DPR-4 Re Test Fuel Subassemblies
ML20085F487
Person / Time
Site: Saxton File:GPU Nuclear icon.png
Issue date: 08/28/1967
From: Neidig R
SAXTON NUCLEAR EXPERIMENTAL CORP.
To:
Shared Package
ML20083L048 List: ... further results
References
FOIA-91-17 NUDOCS 9110220177
Download: ML20085F487 (9)
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' Ghi No. 50-146 LICi:CC D?R-4 CitAfGE Rb2U12iT NO. 28 i

' col::sta Peret:y submite Change Re.luest No. 28 in compliance wit h caragi n t iB of li cenue DPit-6 for change of the Technical Specificat tor.s tc t>e cutr.crirca by the Com:niccion as provided in 10 CFR $0.59 i

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Docket No. 50-146 DPR-4 Technical Specifications Chat.ge Request No. 28 Page 1 of 8 Pages

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1. Description of Chanff In Supplement No.1 to Technical Specifications, add the following Test Puol l Assambly to Itaa F.2.

Tent Fuel Assembly XVIII One 9 rod subassembly of standard pitch and array shall contain the followingt

a. Two burnable poison test rods containing borosilicate (Pyrex) glass tubing (0-388 nom. 0.D. x 0.251 nom. I.D.) sealed in type 304 stainless steel clad (0.4315 nom. 0.D. x 0.019 nom. wall thickness) will be suspended in a type 304 etainless steel RCC thimble guide tube (0.519 nom. 0.D. x 0.4945 nom.

I.D.). The borocilicate glass is annular in cross section (Figure 1) and is supported on the inner side by a type 304 stain 1ces steel tube (0.245 non. 0.D. x 0.007 nom. wall thickness. The composition of the borosilicate glass 12 shown in Table 1. These rods may contain a 0.02 inch dirtmeter Al-Co alloy tracer wire sealed in a 0.035 inch diameter titanium tube cuspended in the central void from an attachsent to the inner surface of the top end plug.

l l b. The four corner positions and the center position of the subassembly contain l dummy fuel rods of the same size and configuration as standard Saxton fuel rods, but contain no fuel. The five dummy rods are orificed at the top l

and bottem end plugs to pennit filling of the ?od internal volume with l primary coolant.

c. The remaining two rods will be any combination of the following:
1. Zircaloy-4 clad rode containing Zircaloy-4 c.ncapsulated stress relaxation test specimens described in Charge Request No. .*4.
2. Internally pressurized Zircaloy-4 clad rods containing 17 4% enriched UO2 fuel pellets described in Change Request No. 22,
3. Internally pressurized 304 SST clad rode containing 5 7% enriched UO2 fuel pellets described in Change Request No. 22.

The test subacsenbly may be located in one of two peripheral core positions, either the N-3 position or the N-5 position. When the subassembly contains 17.4% enriched fuel rods it may be operated at reactor power levels up to 23.5 K.it, otherwise it may be operated at power levels up to 35 MWt.

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6 Docket No. 50-146 DpE-4 Technical Specifications Change Request No. 2B Page 2 of 8 Pages

2. Purpose of Change The purpose of this change is to permit insertion of Test Fuel Assembly XVIll into the core in order toi
a. Verify mechanical performance of a burnable poison material and rod configuration in a power reactor environment. Approximately 6400 megawatt days of exposure is expected, at the end of which approximately 50% of the B

y in the pyrex glass will be consumed. Dimensional inspection of the robs will be conducted before and af ter exposure to demonstrate the ab-sence of large clad strains or diametral changes as a result of the elevated temperature and depletion of B10'

b. Continue the in-pile testing of internally pressurized rods and stress relaxat'on test specimens described in Change Requests 22 and 24 respectively.
3. Safe ty Considerations The burnable poison rods will simulate the mechanical and hydrau3tc configuration of prototype rods and will be statically positioned in RCC thimble tubes in the same manner as the test elements in the RCC test assembly (Change Request No. 10). The rods have been designed in accordance with the standard Westinghouse APD fuel rod design criteria, i.e. , the cladding is free standing at reactor operating temperature and pressures and suf ficient cold vcid volume has been provided within the rods to limit internal pressure release of all helium

-generated in the B10 n,a reaction.

The calculated stresses in the cladding for the expected beginning of life temperature and pressure condition is given in Table 3. The maximum stress is compressive and occurs at beginning of life because of the larger differ-ential pressure. The large void volume required to contain the helium generated has been obtained by using glass of an annular cross-section (tubing) to provide a central void along the length of the poison rods.

Based on available data on properties of the pyrex glass and on nuclear and thermal design calculations-for the rod, the glass is not expected to melt or undergo gross cracking or swelling during operation. However, as insurance against possible slumping of glass into the central cavity and the resulting redistribution of the poison material during operation, the glass is provided with a thin vall stainless steel tube as an inner liner.

The wall thickness of the innur liner-is sized to provide inner support for the glass in the event of possible melting or slumping due to sof tening but to

m tecket No. 50-146 DPR-4 Technical Specifications Change pequest No. 28 page 3 of 8 pages collapse locally before rupture of the exterior cladding if swelling or large volume changes due to crack.ng vi the glass should occur. The inner liner is open at the top end to receiyu the helium which will diffuse out of the glass.

Because the assembly is to be irradiated at a peripheral location in the Saxton reactor where the thernal neutron flux is lower than required for the desired buraup of the B 10 in the poison rods, a flux trap has been designed into the assembly. The increased moderator volume necessary to produce the flux peak has been obtained without an increase in bypass coolant flow by the use of the dummy fuel rods.

Although the flux peaking produced in the vicinity of the poison rods provides the desired poison depletion, the maximum heat rate in the fuel rods in the surrounding 9 x 9 f uel assembly (10.2 kw/f t 0 35 FMt)will still be well below the heat rate in the peak rods of the core. The peak heat rate in the fuel rods within the test assembly under design conditions would be as follows:

a. Zircaloy c lad 17.4 w/o enric.hed rods. . . . . . .12.4 kw/f t @ 23.5 HWt
b. Stainless clad 5. 7 w/o enriched rods. . . . . . .10.2 kw/f t 0 35 MWt To eliminate the possibility of the higher enriched zircaloy clad rods ex-ceeding the current limit on peak heat ratn, the reactor power will be limited to 23.5 MWt with these rods in the burnable poison test assembly. The heat rate in the stainless clad rods is suf ficiently below the limit to present no j problem even at 35 }Mt reactor operation. The calculated internal pressure and 4 maximum clad stresses for the interndily pressurired rods at design conditions

, are listed in Table IV.

4. Health and Safety It is our opinion that the health and safety of the publi,e is not endangered by this change.

ket No. 50-146

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Technical Specifications Change Request No. 28 Page 4 of B Pages TABLE 1 COMPOSITION OF BOR0 SILICATE CLASS 4

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Docket No. 50-146 DPR-4 e Technical Specifications 4

d Change Request No. 28 Pege 5 of 8 Pages TABLE 2 I BURNABLE POISON R0D OPERATING CHARACTERISTICS Heat Generation Rate (include 6 (n.a) and A heating) at 35 MWt 0.628 kw/ft at 23,5 MWt 0.421 kw/ft 35.0 MWt 23.5 MWt Maximum Pyrex Temperature (*F)

He Fill Air Fill He Fill Air Fill 910 690 780 640 Maximum Cap ((7 670 750 630 Nominal Cap 5.5mil) mil) 860 Pyrex Glass Annealing Temperature 1050*F ,

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Pyrex Glass Softening Temperature 1520'F

! - 870 psi Internal Pressure at end of exposure assuming total He release

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B-10 depletion after 6400 megawatt days of operation l

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  • Change Requent No. 28 Page 6 of 8 Pages TABLE 3 i

TOTAL POISON ROD CLAD STRESSES AT BEGINNING OF LIFE (OVAL CLAD)

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Component I.D. 0.D. I.D. 0.D.

Direct ~24735 -24735 -24735 -24'r35 Beriing +8461 -8461 -8461 +8461 Thermal -526 +526 -526 +526

,TAL -16800 -32670 -33720 -15750 ,

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  • Docket No. 50-146 DPR-4 l

Technical Specifications  ;

l Change Re uest No. 28 r

I Page 7 of Pages TABLE 4 t FUEL ROD CLAD STRESSES AND INTERNAL PRESSURES t Peak: Clad Stress Internal Pressure, psi psia Zircaloy Clad Rods (23.5 Mwt operation) 2'4,300 5200 Stainicas Clad Rods (35 Mwt operation) 45,200- 5450 l

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