ML17255A386

Criticality Safety Analysis for New Fuel Storage Racks.

ML17255A386
Person / Time
Site:	Ginna
Issue date:	07/31/1983
From:	Robbins T PLG, INC. (FORMERLY PICKARD, LOWE & GARRICK, INC.)
To:
Shared Package
ML17255A385	List: ML17255A384 ML17255A386
References
NUDOCS 8309160056
Download: ML17255A386 (17)

Text

for Rochester Gas and Electric Corporation

- GINNA PLANT-Criticality Safety Analysis for the New Fuel Storage Racks by Thomas R. Robbins Pickard, Lowe and Garr ick, Inc.

July 1983 8309ih0056 8309i2 PDR ADOCK 05000244 P PDR 7011R0706835

Introduction The new fuel storage racks for the Ginna Plant accommodate 44 fuel assemblies in 4 rows of 11 assemblies. Although new fuel assemblies are always stored in a dry condition in these, racks, the condition of optimum moderation is considered in this analysis even though it is inconceivable that such a condition could be achieved in these racks.'escri tion of the Anal sis A plan view of the new fuel storage racks is shown in Figure 1.

Although the center to center spacing between all fuel assembly storage locations is not uniform in the East-Nest Direction, a minimum uniform spacing was conservatively assumed in the analysis. Figure 1 also shows the conservative symmetric geometry model chosen to calculate the effects of radial neutron leakage from the racks in the North-South direction.

Symmetry boundary conditions (i.e., zero neutron current) are imposed on the North, East, and i<est boundaries of the model, and a zero neutron flux boundary condition is imposed at the outer edge of the assumed water reflector on the South boundary. The detailed dimensions and geometry of this model are shown in Figure 2.

The'uel assembly characteristics utilized for the analysis are shown in Table 1. A uniform 'axial enrichment distribution of 4.25 w/o U-235 was assumed for each fuel rod in the assembly.

The k of the fuel pin cell used to generate cross sections for the rack criticality analysis is shown as a function of water density in Figure 3. For the normal dry storage condition, the fuel assembly k will be essentially the same as or lower than the fuel pin cell Q, and therefore an upper limit for the k ff of the rack for dry conditions may be obtained by extrapolation of the fuel pin cell k: to zero water density. The resulting k is about 0.72, and the k rack will be substantially less than that value.

ff of the finite 7011R0706831

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If it is assumed the entire rack area is surrounded by a full density water reflector, then the water density in the resulting enclosed area can be varied, and the k of the rack can be determined from edits which combine the void-water and fuel assembly regions of the model shown in Figure 2. The resulting fuel rack k is also shown in Figure 3. At water densities below 0;1 gm/cc,'n optimum moderation condition is approached. The apparent, optimum moderator density is quite low because of the large volume fraction of the void-water region (0.994) as compared to that of the fuel region (;006)." However, these large k 's at low water densities are not of concern as shown by the k same calculations.

ff eff values from the The neutron multiplication factor, which includes neutron leakage effects in the North-South direction only, is shown as a function of water density in Figure 4. The maximum neutron multiplication factor is seen to be about 0.94 at an optimum water density of about :045 these calculations assumed zero neutron leakage in both the gm/cc.'owever, East-West radial direction and the axial direction.

To determine the effect of" axial neutron leakage on the multiplication factor, flux weighted cross sections representing the fuel assembly and void-water regions of the radial model were used in one-dimensional axial calculations, and the results are also shown in I

Figure 4. The maximum neutron multiplication factor is now seen to be about 0.70 at a water density of about .075 gm/cc. This low multiplication factor even at optimum moderation conditions makes it unnecessary to evaluate the neutron leakage effects in the East-West radial direction which would result in some further small but significant reduction in the neutron multiplication factor.

In addition to the other conservatisms in the calculations, no credit was taken for neutron streaming effects at low water densities.

Considering the large distances separating fuel assemblies in the rack, such effects would be expected to significantly increase neutron leakage from the racks and thereby further reduce the neutron multiplication factor.

7011R0706832

I Figure 4 also demonstrates the acceptability of the new fuel storage racks in the flooded condition which corresponds to a water density of 1.0 gm/cc. As shown, the neutron multiplication factor is somewhat less than 0;88 for the fully flooded condition and therefore clearly acceptable.

Because of the conservative techniques and assumptions used to evaluate the maximum possible neutron multiplication factor, there is more than reasonable assurance that no significant hazards based on criticality safety are involved in storing fuel assemblies of up to 4.25 w/o U-235 in the Ginna. new fuel storage racks.

7011R0706833

Table 1 FUEL ASSEMBLY CHARACTERISTICS Number of rods containing U02 179 Rod pitch (in) 0."5560 Overall envelope dimensions (in) 7.763 Weight of U (Kg U) 350;5 Active fuel length (in) 141.4 Enriched uranium region Length (in) 128.98 Enrichment (w/o) 4. 25 Natural uranium blanket region Length (in) 12. 42 Enrichment (w/o) 0. 711 Instrument tube Material Zr-4 O.D; (in) 0.4015 I.D. (in) 0.3499 Guide tubes Material Zr-4 O.D. (in), above dashpot 0.5280 O.D. (in), in dashpot 0.4825 I.D. (in), above dashpot 0.4900 I.D. (in), in dashpot 0.4425 Fuel pellet Material U02 Density (X theoretical) 95+"

-1.5 O.D. (in) 0.3444 0.0019 Cladding O.D. (in) .400 I.D. (in) .3514 Spacer Grids Number i<eights of materials*

Inconel grids (2), lbs total 3. 00 Zircaloy grids (7), lbs total 19.46

• Does not include weight of the stainless steel sleeves or inserts.

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DISTRIB UTION Docket ORB Reading GDick HSmith September 2, 1983 ELD attorney DOCKET NO(S). 50-244 Nr. John E. Mlier, Vice President Electric and Steam Production Rochester,.Gas and Electric Corporation 89 East Avenue Rochester, New York 14649 I R.E. GINNA PLANT - OPPORTUNITY FOR HEARING (APPLICATIONS 1"1,/24/81, SNUBBER REQUIREMENTS: 9/28/82, STAFF REORGANIZATION) The following documents concerning our review of the subject facility are transmitted for your information.'otice of Receipt of Application. Draft/Final Environmental Statement, dated Notice of Availability of Draft/Final Environmental Statement, dated Safety Evaluation Report, or Supplement No. , dated Notice of Hearing on Application for Construction Permit. Notice of Consideration of Issuance of Facility Operating License. Application and Safety Analysis Report, Volume Amendment No. to Application/SAR dated Construction Permit No. CPPR- , Amendment No. , dated Facility Operating License No. , Amendment No. , dated Order Extending Construction Completion Date, dated El Other(Specify) C August 23, 1983 (see 48 FR 38421); the intervention period expires Dt

                                                                      /g      Z~/8 Office, of Nuclear Reac or Regulation Division-of.'icensing

Enclosures:

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            /7 NRO FORM 318 {10/80) NRCM 0240            OFF(CIAL RECORO COPY

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    'arry  H. Voigt, Esquire              U. S. Environmental    Protection Agency LeBoeuf, Lamb, Leiby and MacRae            Region  II Office 1333 New Hampshire Avenue, N. W.           ATTN: Regional     Radiation Representative Suite 1100                                 26 Federal Plaza Washington, D. C. 20036                    New  York,  New  York  10007 Mr. Michael Slade                          Herbert Grossman, Esq., Chairman 12  Trailwood Circle                       Atomic .Safety and Licensing Board Rochester,        New Yor k   14618        U. S. Nuclear Regulatory Commission Washington, D. C. 20555 Ezra      Bialik Assistant Attorney General                 Supervisor of the    Town Environmental Protection Bureau               of Ontario New York State Department of Law           107 Ridge Road West 2 World Trade        Center                Ontario,   New  York  14519 New York, New        York    10047 Jay Dunkleberger Resident Inspector                         New York State Energy Office R. E. Ginna Plant                        .

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