ML20037B028
| ML20037B028 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 01/31/1967 |
| From: | Julie Hughes COMMONWEALTH EDISON CO. |
| To: | |
| References | |
| NUDOCS 8009030715 | |
| Download: ML20037B028 (13) | |
Text
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January 31, 1967 Dr. Peter A. Morris, Director Division of Reactor Licensing U. S. Atomic Energy Commission Washington, D.C.
20545
Subject:
Roquest for Change of Operating License DPR-2, as amended, Dresden Nuclear Power Station, including Exhibit I
Dear Dr. Morris:
Pursuant to 10 CFR 50.59 and Paragraph 3.a.(4) of License DPR-2, as amended ("DP't-2"), Commonwealth Edison Company requests that Appendix "A" of DPR-2 be changed to allow operation of fuel assembly S A-1, modified by removal of selected rods, in the Dresden linit I reactor.
Authority to operate Dresden Unit I reactor with SA-1 fuel assembly, first requested by letter dated February 26, 1964 was granted March 27, 1964 designated Change No. 5.
This request includes:
Revise item "2.
Nuclear Core" of Section "3 DESIGN FEATURES" of Appencix "A"
to JPR-2 to read in its entirety:
"2.
Nucicar Core
" Maximum core diameter (circumscribed circle) 129 in.
Maximum active fuel length - cold 112 in.
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Maximum number of fuel assemblics by types:
[
N Type I 166 Type III 192 g@CMg N,' M Type III-F (standard) 88 M
[
Type III-F (removable experimental 7_
segmented poison rod) 2
'g %,N
[
Type III-F (plutonium fuel rod) 4 As Type III-F (powder) 10 g
Type V 106 a
Type PF-10 (modified) 1 Type SA-1 (modified) 1 Maximum total number of fuel assemblies 438 "The reactor may be operated at any power up to and including rated power with any configuration of the various types of fuel assemblies installed, provided the maximum number is within the limits specified above."
ACDOWlBGE D *
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2-January 31, 1967 Dr. Peter A. Morris Revise Appendix "A" to DPR-2 by deleting TABLE II (revised 1/9/67) attached thereto and substituting Table II (revised 1/30/67) attached herewith.
Pursuant to 10 CFR 50.59 and 3.2.(4) of DPR-2, a Description and Hazards Evaluation Report in support of the proposed change to Appendix "A" is attached hereto as " EXHIBIT I".
In our opinion the proposed.~. changes shall not result in hazards which are greater than or different from, those analyzed in the Hazards Summary Report, specifically. there is (1) no increase in the probability of, or (2) no increase in the possible consequences of, or (3) the creation of a credible probability of an accident different from, those accidents previously analyzed in the llazards Summary Report as amended or in connection with amendments to License DPR-2.
Very truly yours, COMMONNEALT!! EDISON COMPANY
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John H. Hughes
- uclear Licensing Administrator N
Attachment:
Table II Exhibit I SUBSCRIBE 0 and SWORN to before me this3LWday of
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, 1967.
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TABIE II 4
(P4rised 1-31-67) pL1e Co e v
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Cladding Regultr Rods Special Corner Rods i
I W 0.D.
R ickness Rod thanter
% Fuel
%Uo2 Fuel Nianber
% Fuel
% 002 N'l Wel Tvoa f4aterini finches )
finches)
Confic1 ration Remired Crnposition Enrichment Diameter Recuired Coctposition Enrichment Diameter I
Zr-2 0.567
_ D.03o 6x6 36 loo Uo, 15 0.498 6x6 31 99.85 Uo2 99.85 III Zr-2 0.555 0.035(1) 0.055 0.15 Er201 1.83 0.h78 5
0.15 Er 1 1.83 0 k38 29 loo Uo2 2 34 c.402 III-F Zr-2 0 5625 0.035 6x6 II2) 09.3 Algo 3 o.45 6
100 002 1.77 0.h82 b.7 cd 01 2
29 4 00 %
2 3h OM2 (Spec a Poison)
Zr-2 0 5625 0.035 6x6 6
100 002 2 77 c.k82 Rods) 1 (Special test rods - see Note (b)
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III-F 9
y 2.3h O.h82 I
(flutonian Rods)
Z r.2 0.5625 0.035 6x6 6
100 00 1.77 0.h82 1
(Plutonism Fuel Rod - see Note (7) 2 i
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28 100 von 2.3h o.k925 III-F Zr-2 0.5625 0.035 6x6 1(2) 95.3 A1 023 0.45 6
loo Uo 1.77 c.t.325 2
(Powder) 4.7 od 01 2
I3) 100 Uoy 2 3k o.482 L
V Zr-2 0 5625 0.035 6x6 30
- ee note (5) 2 34 0.k82 6
loo Uop 1.77 C.k82 Y
Zr-2 0 5625 o.
6x6 30
- ee note (5) 2.34 0.k98 6
100 Uo2 1.77 6 kN R in Clad Pr-lo Zr-4 0.412 0.0e5 8x8 54 99.65 Uo2 2.0 c.358 9
99.65 U02 15 0.358 o.35 Er o3 0 35 Erpoi o
SA-1 Zr-2 o.k24 0.022 7x7 23 100 Uog 3.o-3 5 0 375 21 100 Uo, 2.76
- c. 375 (1) Five corner rods
)) Poison rod - Pelletized (3) Spacer capture rod - 1411etized (b) Six assemblies will be loaded with one of the following types of segmented burnable poison test rods: Identification DU = 97% A1 02 3 - 3 0% od o3, o.M5 inch 0.D.;
2 2 3 - 71% cd 0, o.M5 inch 0.D.; IM = 98 9% U02 - 1.1% G10,177% enriched, 0.482 inch 0.D.; Dx = 97 3% U02 - 2 7% cd 0,1.77% enriched, DV = 92 9% A10 23 23 23 o.482 inch o.D.
(5) -Selected rods contain small amounts of cd 0, remainder of rod 100% Uo2
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g (6) 1.ods containir.g Gd o use o.035 inch clad as in standard assemblies p3
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5 wk' (7) Four of the six assemblies originally shown on Table II (Revised 8/25/66) will be selected for replacement of its I '
o k{ ~~4 Special Poison Rods with Plutoniun Rods of one of the following Ptl enrichments: 1.2NTt; 1.7NTl; 1.2 and 1.4 'ftt.
L*2 O 1.2 NTl in natural uranium.
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EXilISIT I Ble CoE2'(9/
SECTION I DESCRIPTION OF PROPOSED AMENDMENT _
This amendment is proposed to obtain authority to operate a special assembly, designated SA-1, in the Dresden reactor after a modificatfen of the assembly's fuel rod configuration has been effected. This charge, in brief, consists of the formation of vacancies in the normal rod pattern resulting f rom the permanent removal of ten rods from the assembly.
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j SECTION.II' PfYSICAL CHARACTERISTICS AND MECHANICAL DESIGN OF SPECIAL ASSEMBLY SA-1 Basic Design The basic design features of SA-1 in its present form were described in detail in Table II (Revised 2/19/64) Appendix "A", of Dresden License DRP-2 and in the report, " Description and Hazards Evaluation, Special Assembly SA-1" (February 19, 1964).
Briefly, special assembly SA-1 consists of two subassemblies stacked one on top of the other in a channel of standard dimensions of the Dresden reactor. Each subassembly contains 49 nonsegmented rods in a 7 x 7 array.
The fuel rods consist of sintered UO, pellets of about 95% density clad with 1.077 cm (0.424 in.) 0.D. By 0.056 cm (0.022 in.) wall Zircaloy-2 tubing. The rods, which are about 104 cm (40.75 in.)
long, rest on a bottom grid and are held in position by 4 spring type spacers distributed axially along the length of the fuel. The spacers are supported by corner angles which are attached to the bottom grid and extend the full length of the subassembly, to form an integral basket for the fuel rods. The corner angles are fastened at the top to a band which extends about 0.6 cm above the top of the fuel rods.
The two stacked subassemblies form an active fuel length of 188 cm (74 in.).
The fission gas plenums of the rods in the bottom subassembly are pointed toward the bottom grid, and those of the rods in the top subassembly are pointed up toward the top band, so that the nonfueled gap between the subassemblies is minimized at about 3 cm.
Proposed Change in Fuel Rod Configuration At the conclusion of the current operating cycle of the Dresden reactor, special assembly SA-1 will be transferred from the reactor core to the fuel storage building. The two subassemblies will be removed from the channel and placed in a temporary storage rack. A total of ten fuel rods will be withdrawn from the subassemblies and set aside for a pro-gram of destructive examination.* The re=aining 88 rods will be arranged to form the configurations shown in Figure 1.
The subassemblies then will be re-channeled, according to the sa=e loading procedure employed for the initial operation of SA-1, and returned to the core for further eperation.
- To be performed under Contract No. AT(04-3)-189, P. A. No. 41.
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,q SECTION III OPERATI::G HISTORY A';D EXAMINATIONS _
The fuel rods contained in special assembly SA-1 initially were assembled into VBUR fy mately 3x10'gl elements and irradiated to exposures as high as approxi-fissions /cc (%10,000 NWD/STU) at peak heat flunes up to about 160 watts /cm2 (%500.000 Leu /hr-ft ).
At the end of their operation 2
l in the VBWR, all of the fuel rods subsequently incorporated into SA-1 were visually and ultrasonically inspected.
Assembly SA-l~has now operated in Dresden throughout the third and fourth reactor cycles. At the end of Cycle 3, when SA-1 had achieved an assembly-20 average burnup of 3.8x10 fissions /cc (14,000 MWD /STU), the fuel rods were determined to be in satisfactory condition by means of a " sip" test, an oper-atien in which the assembly was isolated in a can and the surrounding water sampled and analyzed for fission product iodine.
SA-1 has attained a peak heat flux of 125 watts /cm2 (%400,000 Stu/hr-f t ) during Dresden operation.
2 It is estimated that at the end of Cycle 4 SA-1 will have achieved an assembly-l of 6.8x1020 averageburnug0 fissions /cc (25,000 MWD /STU) and a peak burnup of about 11.5x10 fissions /cc (42,000 MND/STU).
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At the conclusion of Cycle 4, SA-1 will be transferred to the fuel handling pool and " sipped".
The two subassemblies then will be visually inspected by means of an underwater borescope. A selection of high power, high ex-posure rods will be removed from the subassemblies and individually inspected with the borescope. Finally, when the rod configuration changes have been accomplished and SA-1 is ready to return to the core, the assembly will be sipped again to assure its integrity. The operation of SA-1 (Modified) in Cycle 5 is contingent upon the results of this testing and examination.
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.SECTION IV NUCLEAR CHARACTERISTICS
.The nuclear characteristics of fuel assembly SA-1 and its effect en the l
reactor core were evaluated prior to the initial operation of SA-1 in Dresden. The results of these analyses were presented in " Description.
and Hazards Evaluation,.Special Assembly SA-1" (February 19, 1964), a.:d indicated that:
1.
The reactivity of SA-1 when installed in Dresden at the beginning j
of Cycle 3 would be less than the initial reactivity of a Type I or III fuel assembly.
l 2.
The corner rod peaking would not be expected to exceed 1.25.
3.
The axial power distribution within SA-1 would be that imposed by the adjacent fuel and control rod system.
l 4.
The water at the top and bottom of the fuel sections would not cause l
significant changes in the axial power' profiles of adjacent fuel assemblies.
5.
Assembly SA-1 would have a negligible effect on the power distribu-tion in the surrounding fuel and a negligible effect on other over-all core properties such as radial power distribution, temperature and void coefficients, and total core reactivity.
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No rod changes have been made in SA-1 since its initial insertion in
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the Dresden core; hence, the reactivity of the assembly has continuously l
decreased. The changes in rod configuration planned for the next cycle l
of operation call for the removal of rods from the assembly without the addition of fresh fuel rods or other replacement rods of any kind.
Subsequent power distribution considerations indicate that rods can be withdrawn from the assembly without affecting its performance limits providing that no rods in the two-by-two location at the wide-wide water gap are removed and that no two laterally or diagonally adjacent l
rods are withdrawn. Figure 1 shows that the restrictions will be accom-modated by the planned rod configurations for the two subassemblics.
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SECTION V THERMAL AND HYDRAULIC CHARACTERISTICS Thermal and hydraulic analyses of SA-1 operation, performed to decarmine the effects of the rod vacancies, are su=marized in-the following para-graphs.
As Figure 1 indicates, the locations of the rod vacancies in the two subassemblies will be vertically staggered so as to virtually eliminate any effects of flow channeling through a straight-through water hole (the entire length of the fuel assembly).
In addition, with the large number of flow disturbances in the fuel assembly,1.e., four fuel rod spacers in
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each subassembly (total of 8) and bases (or dividers) at the bottom, middle and tcp of the fuel assembly, mixing of the flow within the assembly shoulC be sufficient to eliminate any significant flow channeling through the holes left by the removed rods within individual subassemblies.
As a reference case, thermal-hydraulic data were calculated for SA-1 for its estimated conditions in the Dresden Nuclear Power Station for Cycle 5, assuming no rods removed. General conditions are:
Reactor Power, h4t
= 700 6-Total Recirculation flow, lb/hr
= 26 x,10 Number assemblies
= 464 Overpower factor
= 125%
Specific conditions for SA-1 with all rods:
Relative bundle power
= 1.0 Channel Flow, lb/hr
= 69,200 2
Peak heat flux overpower, W/cm 2
(Stu/hr-ft )
= 98 (311,000)
MCHFR* (overpower)
= 2.86 1
Next the conditions for SA-1 were calculated with the removal of the 10 fuel rods, and assuming complete mixing of the coolant in the assembly (no flow channeling). The peak-to-average rod power (local peaking) within the assembly is no greater than initially, as any increase in local power peaking due to the rod removal will occur away from and remain below the existing peak rod.
Relative bundle power
= 1.0 Channel flow, lb/hr
= 75,100 2
Rod heat flux overpower, W/cm 2
(Btu /hr-f t )
= 109 (346,000)
MCHFR (overpower)
= 2.58
- Minimum critical heat flux ratio e
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Finally, as a worst case, conditions were calculated assuming flow channeling occurs through the holes left by the re=oved rod. The calculation is conservative in that it assu=es no mixing of flow beyond mid-assembly, a single phase mixture exists with the only pressure drop due to elevation and local (spacers and dividers) losses.
It was assumed that-flow channeling through the hole was lost to the rest of the bundle for heat removal.
I Flow per hole, Ib/hr
= 5660 Total for 5 holes, lb/hr
= 28,300 Active coolant, lb/hr
= 75,100 - 28,300 = 46,800 MCHFR
= 2.40 Calculations were also performed for a case assuming flow channeling l-the entire length of the assembly. The results were similar to the channeling from mid-assembly case.
^
l The above calculations should bracket the MCHFR. Preliminary power distribution calculations for Cycle 5 indicate that the relative bundle power for SA-1 will be considerably less than the 1.0 figure l
assumed for these calculations, most probably nearer 0.75, adding further margin for the performance of SA-1 with rods removed.
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Control SUBASSEMBLY B-1 Control SUBASSE!!BLY A-1 Rod (TOP)
Rod (BOTTOM) 50 51 52 53 54 55 56 1
2 3
11 5
6 7
2.76 2.76 2.76 2.76 2.76 2.76 2.76 2.76 2.76 2.76 3.5 2.76 2.76 2.76 57 86 60 62 63 8
90 10 12 14 2.76 3.5 3.5 3.5 2.76 2.76 3.5 3.2 3.2 2.76 64 65 66 67 68 69 J3 15 17 18 19 20 21 2.76 3.2 3.5 3.5 3.5 3.2 3.5 2.76 3.5 3.5 3.5 3.2 2.76 71 72 74 75 77 22 23 24 26 27 25 2.76 3.5 3.2 3.5 2.76 2.76 3.5 3.5 3.5 3.5 3.2 78 79 80 81 82 83 84 29 31 32 33 34 35 2.76 3.2 3.5 3.5 3.2 3.2 2.76 2.76 3.5 3.2 3.5 3.2 2.76 s
85 87 59 89 58 91 36 37 38 39 40 9
42-2.76 3.2 32 3.2 3.3 2.76 2.76 3.5 3.2 3.5 3.2 3.5 2.76 92 93 94 95 96 61 98 43 44 16 30 47 48 h9 2.76 2.76 2.76 2.76 2.76 3.2 2.76 2.76 2.76 3.2
-3.2 2.76 2.76 2 76 XX
= SA-1 rod designation
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X.XX
= As-fabricated enrichment of fuel in rod
= Rod vacancy 4
Figure 1.
Planned Arrangement of Fuel Rods in Special Assembly SA-1 (Modified)for Cycle 5 Operation.
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l SECTION V1 SAFETY EVALUATION The design features of SA-1 fuel rods are similar to the fuel which is currently approved for operation in the Dresden core, and the assembly is of a conservative design that does not depend on.the fuel rods for structural support.
Removal of ten rods from special assembly SA-1 in the manner indicated l
1s expected to have a negligible effect on the assembly performance, and operation of the assembly in modified. form should have no significant ef fect on surrounding fuel and over-all core performance.
It is concluded, therefore, that SA-1 (Modified) will have a negligible effect on core L
safety.
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of selected roda......and trans:
I ENCLCSURES:
(24 cys. ree'd) i Tnes Conies tor l
Table II (revised 1-31-67) to app-*
"s" Dr. Norris i
Oxhibit. I" - which furnishes a.isseription j
and hae= 6 ovaluation report in support,of an g n---
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