ML20064N521

Forwards Criticality Analysis of Seabrook Spent Fuel, in Response to Auxiliary Branch Request for Addl Info.Rept to Be Incorporated in OL Application Amend 49

ML20064N521
Person / Time
Site:	Seabrook
Issue date:	02/10/1983
From:	Devincentis J PUBLIC SERVICE CO. OF NEW HAMPSHIRE, YANKEE ATOMIC ELECTRIC CO.
To:	Knighton G Office of Nuclear Reactor Regulation
References
SBN-462, NUDOCS 8302160263
Download: ML20064N521 (17)

Text

{{#Wiki_filter:. 1671 WorceWer Road Pub 5c Service of New Hampshire 00 February 10, 1983 SBN-462 T.F. B7.1.2 United States Nuclear Regulatory Commission Washington, D. C. 20555 Attention: Mr. George W. Knighton, Chief Licensing Branch No. 3 Division of Licensing

References:

(a) Construction Permits CPPR-135 and CPPR-136, Docket Nos. 50-443 and 50-444

Subject:

Open Item Response: (SRP 9.1.2; Auxiliary Systems Branch)

Dear Sir:

In response to the open item and Request for additional Information (410.18) regarding the criticality analysis for the Spent Fuel Pool, we have enclosed a repcrt entitled " Criticality Analysis of Seabrook Spent Fuel." The enclosed report will be incorporated in OL Application Amendment 49. Very truly yours, YANKEE ATOMIC ELECTRIC COMPANY O' Qu J. DeVincen is rof; Project Manager ALL/fsf cc: Atomic Safety and Licensing Board Service List ( l I B302160263 830210 l PDR ADOCK 05000443 A PDR 1000 Elm St.. P.O. Box 330. Manchester, NH 03105 Telephone (603) 669-4000. TWX 7102207595

ASLB SERVICE-LIST Philip Ahrens, Esquire Assistant > Attorney Cecrf 1-Department of the Attorncy General Augusta, ME 04333 Representative Beverly Hollingworth Coastal Chamber of Commerce 209 Winnacunnet Road Hampton, NH 03842 William S. Jordan, III, Esquire Harmon & Weiss 1725 I Strect, N.W. l Suite 506 Washington, DC 20006 E. Tupper Kinder, Esquire Assistant Attorney General Office of the Attorney General 208 State House Annex Concord, NH 03301 Robert A. Backus, Esquire 116 Lowell Street P.O. Box 516 Manchester, NH 03105 Edward J. McDermott, Esquire Sanders and McDermott Professional Association 408 Lafayette Road Hamp ton, NH 03842 Jo Ann Shotwell, Esquire Assistant Attorney General Environmental Protection dureau Department of the Attorney General One Ashburton Place, 19th Floor Boston, MA 02108 i

}D n2/ SIS Ob f/E l 3 1 Seabrook Sped Fue/ The criticality of Seabrook's spent fuel storage racks has been studied as a function of fresh fuel enrichment, canister center-to-center spacing, and Boraficx B10 loading and abnormal configurations. Analysis indicates that 235 the racks can accommodate f resh fuel with an enrichment up to 3.5 w/o U and still maintain a K gg below 0.95, the NRC limit. Analysis of abnormal e configurations indicates that the refueling concentrations of soluble boron, 2000 ppm, will suppress the reactivity insertion of a fresh unpoisoned assembly on top or near the sides of the racks and maintain a K gg well e below 0.95. Re Seabrook Spent Fuel Rack Geometry The Seabrook spent fuel pool will eventually contain 12 free standing and self supporting modules allowing spacing for a total of 1236 fuel assemblies, Figure 1. Each rack module consists of an array of Boraflex poisoned storage cells with a center-to-center spacing 10.35 inches, Figure 2. Each storage cell is welded to a grid base and welded together at the top through an upper grid to form an integral structure 173.75 inches in height, Figure 3. Criticality control in the rack is by a flux trap principle; f ast neutrons leading f rom stored assemblies are thermalized in the 1.086 inch water gap between cells and are then absorbed in the Boraflex sheets. The KENO Model and Analysis Assumptions Criticality analysis for the Se.Nrook spent fuel racks was dose with the NITAWL-KENO methodology and the 123 neutron energy group XSDRN library. %c analysis was done with Seabrook standard fuel with no shims or control inserted into the assembly. Assembly grid structure was not included in the analysis since the lack of structure yields a wetter, more reactive lattice. A 2-0 KENO model was developed to do the criticality analysis. This included a single standard fuel assembly and storage cell with associated flux trap water gap, Figure 4 R is model includes conservative neutronic and mechanical assumptions. Bey are: i) Fresh fuel at 3.0, 3.5, and 4.0 w/o U2M, ii) A system temperature of 680F, iii) No soluble boron in the pool water, 2-D infinite array), iv) No radial of axial leakage (i.e., a vi

10. D-inch ~ cani ster center-to-center spac ing,

i / iL

p g3 ~ vi) 0.061-inch Boraflex thickness, and vii) 7.385-inch Boraflex width. Items i through iv are conservative neutronic assumptions. The use of fresh fuel with no burnable poison shims insures that fuel of the highest reactivity is placed in the racks. A system temperature of 680F insures that the fuel and water, especially, are at the most res.ctive censities. A refueling concentration of 2,000 ppm soluble boron under refueling conditions will be in f the pool vater, but credit for this neutron absorber is taken only for l abnormal situations. The " worst case" mechanical assumptions given by Items vi, and vii are generated by subtracting one tolerance from the nominal v,dimensions. The shorter canister center-to-center spacing reduces the ef fectiveness of the flux trap by reducing flux trap water gap thickness. The shorter Boraflex dimensions insures minimum poison control. Abnormal Configurations The criticality of Seabrook's Spent Fuel Storage Rack was studied for abnormal configurations. Three basic configurations were studied: 1. A fresh unpoisoned assembly near the unpoisoned side of racks (Figure 5), 2. A fresh unpoisoned assembly near a concave corner of racks (Figure 6), and 3. A fresh unpoisoned assembly or. top of the racks (Figure 7). Each one of these models was done with 3.5 w/o fuel, a system temperature of 680F and the " worst case" mechanical dimensions given for the KENO model. The LEOPARD-RODWORTH-PDQ methodology was used in this analysis, and each one of the configurations was modeled by a la rg e, 2-D, PDQ array with a water reflector region. Configurations 1 and 2 were modeled with all the heterogeneities that are present in the racks, i.e., flux trap water gap, boraflex sheets, canister wall, inner water gap and fuel assembly. Configuration (3) was modeled by homogenizing the racks axially. In the study of abnormal configurations, credit can be taken for refueling soluble boron, which in Seabrook's case is 2,000 ppm. In this analysis, the configurations are studied with soluble boron in the pool water. RESULTS The effective multiplication factor. K gt, is shown as a function of fuel e 10 loading in enrichment, canister center-to-center spacing, and Boraflex B Figures 8 9, and 10, respectively. From Figure 8, it can be seen that 3.5 235,ill be the highest fuel enrichment allowable and still maintain a w/o U w

K,gg below 0.95 when uncertainties are added to the 0.9331 KENO result. 10 herefore, the canister center-to-center soacing and Bot aflex B 235 fuel. It should be noted that-sensitivity studies were done at 3. 5 w /o U the highest fuel enrichment in Seabrook's first cycle will be 3.1 w/o U235, and subsequent reloads are at 3.18 w/o U235 %erefore, the presenc 235 or about 0.02AK (from Figure 8) calculation is conservative by 0.32 w/o U higher in K,gg than one would expect for fresh reload fuel. Also note that f rom Figure 9, it can be concluded that the decrease in center-to-center, pacing to the 10.29 inches " worst case" from 10.35 inches [ causes ~ 0.011K penalty. From Figure 10, it can be seen that the racks are 10 insensitive to large changes Q 25%) in Boraflex B loading, and therefore, r minor variations in Boraflex quality do not pose a concern. of this analysis was redone on the single assembly model with l-Re first part the LEOPARD-RODWORTH-PDQ methodology in order to establish the sensitivities This and basis of this method against NITAWL-KENO, the " truth" calculations. is shown in Figures 8, 9, and 10. In general, it can be seen that LEOPARD-RODWORTH-PDQ consistently under predict a NITAWL-KENO by 1 to 2% d K. 2% AK should be added to the results of PDQ in order to give a

Thus, conservative answer. Also, both KENO and PDQ show that 2,000 ppm of soluble boron in the pool water produce a 32% reduction in reactivity over the 0.93 to unborated situation, Table 1, and Kegg is thus reduced from about about 0.72.

I Re study of abnormal configurations was then done with the large array PDQ model. Fresh unpoisoned assemblies were placed at the rack-reflector interface; results are shown in Table 2. In general, it can be seen that this analysis meets the requirements of NUREG 0800, Section 9.1.2, on Spent Fuel Storage, and clearly demonstrates that the K gg of the racks is below 0.95 under normal and abnormal situations with fuel of up to 3.5 w/o U235, e i i l l

i hb ) 1 i TABLE 1 THE CHANGE IN REACTIVITY DUE TO THE REFUELING BORON CONCENTRATION OF 2000 PPM i KENO IV PDQ-7 0.9331+.0063 0.9189 K,gg (0 ppm) 0.7192+.0043 0.7080 K,gg (2000 ppm) -31.9 -32.4 1Af' i i l l l l 4 l

p I TABLE 2 THE CHANGE IN REACTIVITY DUE TO A FRESH UNPOISONED ASSEMBLY NEAR THE RACK-REFLECTOR INTERTACE K gg* K,gg* e (w/o Assembly) (with Assembly) % s98 HODEL 1 0.7393 0.7532 2.50 MODEL 2 0.7394 0.7911 8.84 MODEL 3 0.7260 0.7263 0.06 .02 AK edded to PDQ results

yb i FIGURE 1. THE'SEABROOK STATION SPENT l 7 FUEL POOL es.coacr.q j l c------------{;///////////;.//////]. n.oo ner. 3 ....o a c r. l I i j I l rEr"uTc ru ru'o ac ru v u'o S= s= ac m.so acr. 'pt _ _ ___ __ _ _ _ __ _ _ +y'_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ *y+_ _ _ _ _ _ _ _. _ _ _ _ _ +j ....a .or o .or.o woo FUfunc 8 FUTURc ruTUnc 8 3-zt.w acr. l j. I is.so acr. 1s.or ner.I + + + + + +- a.oo ner. I t O l S t.e 5 .TYP. h h 8o3.55 acr. TTra ~ i l-t- + + +- g, f 14.8 5 . T YP. " 00*42 .TYP. - S3.85 R c r. T YP.= - 32 4.co a c r. l l l d

83 s FIGURE 2. STORAGE RACK MODM.E TOP VIEW 10.35" BORAFIIJ. FLUI TRAP SHEETS WATER CAP / [ \\ [ I o i l _ a -yj e t 1 i 'l 1 J !,l 1 ,1-f,I-l h i i r I .I (I -:l 1: l I. I 8 i 1 l l ll i ltl l y[__ l =- i l t l l 7

TIGURE 3. STORAGE RACK MODULE, SIDE VIEW UPPEitGRID~ k h / ~ I T m FLUX TRAP WATER CAP / / v / - BORAFLEX SHEET ? l / 173.75" 141.25 i ^ s )# e + qs - s j I I s I. I I l I _LowEn on:o L,, Q LJ Lf' -LEVELING PA7, em e-i n. s ELEVATION or FOOL FLCOR 8 i

M FIGURE 4. 2D KENO MODEL " WORST CASE" DIMENSIONS GUIDE TUBE CELL 1 r--RTEL PIN CEf?- [ [ - INNER WATER CAP RACK WALL (0.09") O @O @O O6@C[O OO h9 O @O ") ' f .BORAFLEX (0.061 0 0 0 0 0 00 0 @ O 0 0 6 0 9 O O A OUTER WRAPPER O s e 0 00@ 0 0 0 0 0 e @ e 0 0 i - n.ux mr WATER car / l O o e Os e e c e s e e od e e o ' 0 0 G O 0 0 0 0 0 @ O @ @ G O 0 0 0 0 0 0 0 0 0 0 0: 0 0 00 0 0 0 0 I O G@ O O O O O @ C'O @ O.@_O O O @ G O O O O @ @ @ @. O O O O @- G O 0 0 0 0 0 D0 0 0 00 0 0 0 0 @ O G o O O O @ @ O G G O @ o O O O O O O G O G O O O @ O @ @ G O @ O O @ O OD e.G e o Q o c O O C D 0 0 l O 0 0 0 0 @ @ @ @ O @ O 0 0 @ O 0

O O O Q e e e e s o s e oO @ o o 0 0 0 0 0 00 0 0 e e O 0 0 0 0 0 o e o o s e e e e e e G o o o o e

e o e e s eo c e e e e s o e s e

• 0.496" 7.385" 8.432"

~ 8.900" a 10.29" a 6 9

') j Figure 5. A LARGE ARRAY PDQ MODEL OF AN ASSEMBLY NEAR THE SIDE OF THE RACKS i ',,n n n Io~nnn WAR R REGION ooc OOD nnn o a o o n o OOOOO OOOOO unnno unnon unnOO o o OOOOO OOOOO netnnO n si n n n n el n n O OOO O O OOOGO u ti se o O n to si u n u ti t e u O 8 000 0, o oO u O o "O u 0" "O u 0" i nnn o o oO O 0, nnn OOO COO o o o o o o unOOO OOOOO uOnOO OOOOO OOOOO ^ "i O O OOOOO nnnc0 00000 00000 oonuO OO OO O unnuO OOOc0 00000 A FRESH O OO 8 D 0OO "o u O OOO O O 0" ASSEMBLY 10.29" r oOo aon OO0 nnn 0 O0 0O0 r g g g o o 0 n o 0 0 0 0 0 0000 00000 000 00 0 0000 00000 00000 ~. aOO ntiono CD00O n el t' n O OOOOO OOOOO u n (1 O O O n in u n OOOOO u n ti ut OOOO O OOOO O 0 0 0 0 0 0 0 0 0 0 0 0 00 0 00 000 0 00 000 000 0 o (1 O 000 0 nn 0O0 0nn g n 0 0 0 o 0 0 0 g Oa Oun OOOOO Onuuo OOOOO O n as u n O O O n to OOOOO OO O es u OOOOO Ououo OOOOn OOOOO O O O O (1 OOOO O OOuOn 0 0 0 0O0 0 O' 00 n O 0 0 nts O U" OoU 000 0On nnn 0O0 UU U nan 0 o O o 0 0 n D O n OOuon uOnOO O OeOO uoOOO Onnun OOOOu n 11 ti nO OOOOO n t1 onD 0 0 u it O NONPOISONED EDGE 0000n O onuO OO12 OO u tt 4 oO 0000n 4 0 0 O 0 0 0 0 0 0 0 0O0 gg9 0ll 0 0 si0 0u0 I ~ 10.29"-W o W w M

j Figure 6. A LARGE ARRAY PDQ MODEL OF AN ASSEMBLY ON TOP OF THE RACKS WATER A FRESH REGION ASSEMBLY l ooa o o OOOOO OOOOO OOOOO O GDD A i i f-HOMOGENIZED RACK 71.85" l I o ~ 10.29" \\ FUEL MIDPLANE //

'O% Figure 7. A LARCE ARRAY PDQ MODEL OF AN ASSEMBLY IN THE CONVEX CORNER OF TIIE RACKS OOD ~ o o oO O 0, uuD nun o o o o ,,n u n O OOOO OOO OO OnnnO O onUo onnOo o OOOOO OOOOO n as u O O n et OnO O en (1 O O WATER REGION OO OOO OOOOO u et uOO o to n u n o ti u o n C U 0 0 O U D0O 0O0 .I ~ t 9 nOU "O u n" U UO* U -*~) U 000 nnn 000 000 D O 0 0 r o 0 0 0 uDD0O OOOOO UOnOO OOOOO OOt OO 0 m OO OOOOO n es D n O OOOOO O O tJ O O O OOOO OOOOO U (1 Il u O f3 O O O O OOOOO 0 0 0 0 0 0 0 0 0 0O 0O0 s 0 u0 0O0 0O0 0 10.29" 000 I 0 0 O O 0 0 n"""O 0 0 0O0 0O0 O OOOO unoOO OOOOO uoOoo OOOOO NONPOISONED EDGE u is o n D DDpnO OOOOO Ot1ooO OOOOO uonO O O ti et nU OOOOO uouOO POOOC 0 0 O 0 0 0 0 0 0 0 00 n30 000 000 000 0 m oO o 0, o o o n oO O 0, OOC nOn DD0 nnn C 0 FRESil ASSEMBLY o o 0n000 00000 Unuun 00000 OOnnn 00000 OOOOO OOOOO O O O 19 O OOOOO O n et u u OOOOO 00 00n 000 00 OOOun 00000 00000 00000 0 0 0 8 0 O0 0O0 "O o n" 0 0 n 0 0O0 0 0O0 uOu ~ NONPOISONED EDGE _f 0OO OOU DDG nnn COC 0 D O O O a o o o o D O DnUU n OOOOO O OOOO unOOO O n 41 u n OQC0D / OOOOu nuDnO O O fl O O nOOnD 0nonO O O 3,0 0 OOOOn O n E1 0 0 00ti GO u to rp On nOOOn OOOOO D D G D 0 D G 0 0 0 D 0 O OO uuO 0n O utl 0 0u0 ooa _n

• - 10.29" +

N \\ M

hb FIGURE 8 RACK K VS. FUEL ENRICHMENT ff n 1.00 - NITA!il-KENO I LEOPARD-RODWORTH-PDQ 0.95 - _ f' / e Rack ,/ / / (0.95 NR9 LIMIT) K,gg / l / / / W / 0.90 r. / / O.85-3.0 3.5 4,0 FUEL ENRICHMENT (w/o U ) i /3

~.. gg F FIGURE 9 RACK K VS. CANISTER CENTER-TO-CENTER SPACING

• df n

1.00- ' NITAWL-KENO 2 __ LEOPARD-RODWORTH PDQ v _A N, N 0.95 (0.95 NRC LIMIT) w w R:ck 's 'I ' N \\ Koff N N s N' i 0.90 's f 0.8% 10.00 10.25 10.50 CANISTER CENTER-TO-CENTER SPACING (INCHES) i l

• 3.5 w/o FUEL i

?,

y 88 i ~ FIGURE 10. RACK K,gg VS. BORAFLEX B LOADING

• d 1.00 l

,,NITA L KENO LEOPARD-RODWORTH-PDQ 0.95 (0.95 NRC LIMIT) Rtck ' I' T +- A K,fg 3_ i O.90 0.85 x 0.6 0.8 1.0 BORAFLEX B LOADING (ata/b-cm

• 10~ )

8

• 3.5 w/o Fuel, 10.29" center-to-center spacing l

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