ML19345E392
| ML19345E392 | |
| Person / Time | |
|---|---|
| Site: | Big Rock Point File:Consumers Energy icon.png |
| Issue date: | 03/15/1966 |
| From: | Haueter R CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | Boyd R, Doan R US ATOMIC ENERGY COMMISSION (AEC) |
| References | |
| NUDOCS 8101160241 | |
| Download: ML19345E392 (12) | |
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- "M power Company cene,..i o..ces au west u.cn.gan Aventao. Jackson. Mich*g,in a8 9208. Area Code St 7 7HmOS'20 March 15, 1966
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Dr. R. L. Doan, Director Re: Docket 50-155 Division of Reactor Licensing
,{lleCopy, United States Atomic Energy Commission Washington, D. C.
20545 i
Dear Dr. Ioan:
Attention:
Mr. Roger S. Boyd Transmitted herewith are three (3) executed and nineteen (19) conformed copies of a request for a change to the Technical Speci-fications of License DPR-6, Docket No. 50-155, issued to Consumers Power Company on May 1, 1964, for the Big Rock Point Nuclear Plant.
This proposed change (No. 9) is based, in part, on the information submitted with Proposed Change No. 8.
It will enable Consumers Power Company to include cobalt targets in the aircaloy-clad reload fuel bundles in the next (and subsequent) refueling of the Big Rock Point reactor.
Since the next outage for refueling is scheduled for April 1966, we would appreciate your early co.. sideration of this request.
Very truly yours,
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Robert L. Haueter O
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REQUEST FOR AUTHORIZATION OF b..( [
CHANGE IN TECHNICAL SPECIFICATIONS LICENSE NO. DPR-6 9-
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t.El t Docket No. 50-155 hieCopy[
la For the reasons hereinafter set forth, it is requested that the Technical Specifications Appended to Operating License No. DPR-6, issued to Consumers Power Company on May 1, 1964, for the Big Rock Point Nuclear Plant, be changed as follows :
In Section 5 1 5, (c) Fuel Bundles (as requested in Proposed Change No. 8), replace the tabular data section describing fuel bundle principal design features with the following:
Fuel Bundles Original Reload Research & Development General Geometry, Fuel Rod Array 12 x 12 11 x 11 11 x 11 Rod Pitch, Inches 0 533 0 577 0 580 Standard Fuel Rods per Bundle 132 109 109 Special Fuel Rods per Bcndle 12*
12**
12 Spacers per Bundle 3
5 7
Fuel Rod Cladding Material 304 SS Zr-2 30h SS, Zr-2 Inconel 600 and/or Incoloy 800 Standard Rod Tube Wall, Inches 0.019 0.034 0.010 to 0.030, Inclusive Special Rod Tube Wall, Inches 0.031 0.031 0.010 to 0.030, Inclusive
- (h Special Fuel Rods at Bundle Corners Are Segmented)
Reload fuel bundles may contain (in the corner regions of the bundle) four Zircaloy-2 tubes, having encapsulated cobalt targets sealed within.
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2 Fuel Eundles Original Heload Berearch & Development Fuel Rods Standard Rod Diameter, Inches 0 388 0.4h9 0.425 Special Rod Diameter, Inches 0 350 0 344 v.320 UO Density, Percent Theoretical 9h
- 1 94
- 1 90 to 95, Inclusive 2
Active Fuel Length, Inches Standard 70 70 68 to 70, Inclusive Corner 59 Fill Gas Helium Helium Helium" GENERAL DISCUSSION It is an often-stated position of the United States Atomic Energy Commission that the investor-owned segment of the atomic energy industry should develop its own sources of supply of radioisotopes and not rely wholly on various agencies of the Federal Government. Consumers Power Company, after carefully examining the experience gained in the complex research and development program conducted at its Big Rock Point Nuclear Plant, has developed plans for a program of radioactive cobalt production.
It is proposed that cobalt targets be inser ted into the Big Rock Point nuclear reactor and irradiated to the extent necessary to produce use-ful radioactive sources.
The cobalt irradiation program would consist of placing doubly encapsulated cobalt target assemblies in the corner regions of the reload fuel bundles. As currently ticualized, four cobalt assemblies would be substituted for corner fuel rods in selected reload fuel bundles.
Initially, during the April 1966 refueling shutdown,14 fuel bundles containing a total of 56 cobalt assemblies would be inserted into the Big Rock Point nuclear reactor.
At subsequent refuelings, additional reload fuel bundles containing cobalt assemblies will be added so that of the full core loading of 84 fuel bundles, about 60 fuel bundles will ultimately contain cobalt assemblies. These cobalt assemblies would remcin in the reactor core for a period of from 2 to 3 years, after which it is expected that they will have attained an average specific activity of about 20 curies per gram. The equilibrium cobalt-60 production cycle will consist of removal and replacement of from one fourth to one third j
of the fuel bundles containing cobalt assemblies at much normal refueling.
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- CCHANICAL CONSIDERATIONS The cobalt targets will be fabricated from 0.Oh6-inch or 0.060-inch diameter, nickel-plated cobalt metal wire arranged as a helical coil within a 304L stainless steel capsule having an 0.Oll-inch thick wall. Targets will be f abricated in two lengths : The 0.060-inch diameter cobalt wire will be used for targets to be inserted into a 12-inch long capsule. The 0.0L6-inch diameter cobalt wir( vill be used for targets to La inserted into a 10-inch long capsule.
Details of the cobalt target and target capsule design are shown on an attached manufacturing drawing.
Before assembling the cobalt helical coil into the capsules, the targets and capsules will be quality-control tested for dimensional accuracy, cleanliness, weight uniformity and uniformity of the nickel plat-ing on the targets. Fabrication of a target capsule will consist of in-serting cobalt coils into a stainless steel capsule and welding the end plug. Welding will be done in a helium atmosphere. The end dimensions of the capsule will be certified by mounting each capsule (after velding) in a lathe chuck and machining if necessary.
After welding and dimensional checking, the capsules will be 100-percent helium leak tested.
Leaking capsules will either te repaired or discarded.
Each cobalt assembly will consist of five 10-inch long cap-sules and one 12-inch long capsule in a standard Zircaloy-2 corner fuel tube. Details of the cobalt assembly are shown on an attached manufactur-ing drawing. Tolerances of the capsules will be at least as stringent as the tolerances of the UO fuel pellet which would normally be used in the 2
fuel tube. In certain instances, tolerances may be more stringent in order to guarantee proper fit in the Zircaloy-2 tube. The normal fuel spacers and springs will be used to position the capsules within the Zirca]oy-2 tube. To distinguish the corner cobalt-bearing Zirealoy-2 tubes from the corner fuel-bearing tubes, the top end plug of each cobalt assemoly will be made about one-quarter of an inch longer. However, even in the dimen-4 siona11y worst hot operating case, there will still be at least 1/8-inch clearance between the top end plug on the cobalt assembly and the top hold down bar on the fuel bundle.
The 1/4-inch additional length of the cobalt assemblies also will serve as an aid in locating cobalt assemblies in a fuel bundle.
k MECHANICAL CONSIDERATIONS (Contd)
ThecapsuleswillbefabricatedbyNeutronPhoductsIn-corporated (Washington, D. C. ).
The capsales vill be loaded into the zircaloy tubes to produce the final cobalt assembly by General Electric Company. General Electric will continue tc produce the final cobalt assemblies for the next several years. General Electric will, of course, employ the same stringent manufacturing standards, quality control and procedures as they use in their normal nuclear fuel fabrication operations.
PLANED OPEhATIONS The cobalt assemblies will be removed frcm the fuel bundles at the end of an irradiation period. Remcynl of the cobalt assemblies can be readily achieved because the reload fuel utilizes the same fuel bundle hardware as the Big Rock Point R&D fuel which was specifically designed to permit removal of any or all fuel rods.
In addition, since the cobalt sesemblies extend above the fuel rods, they are even more readily acces-sible for removal. After a delay time to permit the short-lived radio-activity to decay, the cobalt assemblies will be shipped off-site for processing in a manner conforming with all applicable State and Federal regulations.
It is planned that cobalt assemblies will be inserted into reload fuel bundles by General Electric Company during fabrication of the reload fuel. However, this will not be possible for the initial 3 4 fuel bundles which will contain cobalt assemblies as the first batch of reload fuel bundles is already on-site. These fuel bundles already hLve fuel rods in the corners where the cobalt assemblies are to be inserted.
Re-moval of these corner fuel rods and insertion of the cobelt assemblies will be done on-site. The techniques for removal and insertion of both unirradiated and irradiated fuel rods have been well established through experience gained from the R&D program activities.
Both unirradiated and irradiated fuel rods are stored in special cans with rod spacings such that reactivity of a fully loaded can is less than that of a fuel bundle. Un-irradiated and irradiated fuels are stored in the new fuel storage area and the spent fuel pool, respectively.
The cobalt assemblies will be removed from a fuel bundle after that fuel bundle has been irradiated for about two-thirds of its expected life time burnup. Fuel rods with selected reactivities will I
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1 PLANNED OPERATIONS (Contd) thenbeinsertedinthefuelbundJaswherevercobaltassembkieshave i
been removed. The reinsertion of fuel rods will help in recovering part of the reactivity lost when the fuel rods were removed originally.
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Physics calculations show no flux peaking problems even when the orie,inal i
fresh' fuel rods are reinserted in the corner locations.
PHYSICS CONSIDERATIONS
.All present p ys cs limits vill be observed and all re-h i 4
actor operations will be within those limits whether or not cobalt is present in a fuel bundle. It is apparent from the physics calculations that the addition of cobalt to a reload fuel bundle does not signifi-cantly change the nuclear characteristics of that fuel bundle. The perturbations are small and analogous to the changes in fuel bundle I-nuclear characteristics vrought by the addition of boron carbide or gadolinium poison rods, or even the substitution of stainless steel channels for Zirceley-2 channels. These three methods of auxiliary re-1 1
activity control have been used successfully at Big Rock Point.
The principal calculated nuclear characteristics of the first 14 fuel bundles containing cobalt are:
(a) Reactivity (km) 4 b
i Temperature No Cobalt 4 Cubalt Assemblies 68 F, Zr Channel 1.275 1.215 572 F, Zr Channel 1 303 1.241 5TP F, Zr Channel 20% Steam Void 1.296 1.231 (b) ModeratorTemperatureCoefficient(bkgp/k per F in Zr Channels'kt77 F) g 4
-6
-6 Start of. Cycle
+3 2 x 10
+8 3 x 10
-5
-5 End of Cycle
+5 5 x 10
+5 1 x 10 i
l (c) VoidCoefficient(dk,ff/k,ff per Unit Void Within the Channel)
No Cobalt h Cobalt Assemblies l
Cold
-0.04
-0.06
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Hot
-0.09
-0.09
V FHYSICSCONSIDERATIONS(Contd) q I'
(d) Doppler Coefficient (bkg/k per F) g The Doppler Coefficient 1. dependent on moderator-to-fuel volume ratio.
Since the reload fuel with and without echalt assemblies and the original fuel have essentially the same moderator-to-fuel volume ratio, their Doppler Coefficients e
are the same. The Doppler Coefficients are tabulated talow for reference purposes:
Fuel Temperature Moderator bk/kper F
-5 68 F 68 F,
O Voids
-1.4 x 10
-5 1323 F 550 F,
O Voids
-1.1 x 10
-5
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1323 F 550 F,20% Voids
-1.h x 10 x
All subsequent batches of fuel containing cobalt assemblies (after the first ih-fuel bundle loading with cobalt assemblies in April j
1966) will be designed expressly to compensate for the reactivity loss re-
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sulting from the addition of cobalt assemblies. Since each batch of re-i load fuel is also designed expressly for expected conditions existing in the reactor at the time the fuel is to be inserted, it is not reasonable to calculate nuclear characteristics for future core loadings at this time.
l The requirements for each reload batch depend in a complex manner on, among other things, the failure rates of the original fuel and the various types of R&D fuel in the reactor.
The maximum control rod worth for the initial loading of lh fuel bundles with cobalt assemblies will be less than would be experi-f enced if the cobalt assemblies were not being inserted. In a later core loading containing only fuel bundles designed to compensate for the cobalt i-assemblies, control rod worths will not be significantly different than rod worths presently being experienced.
THERMAL-HYDRAULIC CONSIDERATIONS All present limits on heat flux, center melting, fuel tem-perature,and critical heat flux ratio will be observed, and operation of the reactor will be within those limits with or without cobalt present in the fuel bundle. The effects of cobalt have been shown to be minor with respect to thermal-hydraulic considerations.
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7 THER4AL-HYDRAULIC CONSIDERATIONS (Contd)
With the expected ultimate loading of about 60 bundles containing cobalt assemblies (about 2h0 corner rods), the average core heat flux will increase by about 2 percent in order to generate the same power in the absence of the 2h0 fuel rods. This is compensated for by the fact that the presence of cobalt assemblies in the corner locations depresses the local peaking factor thus making the maximum heat flux in a fuel bundle containing cobalt assemblies approximately equivalent to the maximum heat flux in a normal reload fuel bundle.
Dependins on fuel bundle placement, however, the few fuel bundles without cobalt assemblies may encounter peak heat fluxes some 2 percent greater than otherw'se.
2 Since the normal overpower heat flux is approximately 400,000 Btu /hr-ft for the 8h-fuel bundle core, neither the license heat flux of 530,000 Btu /hr-f t.
nor the center melting limits are approached with this small potential increase.
The critical heat flux ratio will also be affected sote-what. Since power, flow and consequently the quality will be essentially unaffected, the critical heat flux will be unchanged from the no-cobalt situation. The critical hest flux ratio, therefore, will be decreased proportionate to the indicatcd maximum heat flux increase.
The above applies specifically to the ultimate loading of 60 fuel bundles containing cobalt assemblies. The-thermal-hydraulics effects of any loading less than that (the ultimate 60 fuel bundles) are smaller than those indicated in the foregoing.
HAZARDS CONSIDERATIONS Various modes of accidentally changing the configuration or location of the cobalt assemblies have been inv stigated and analyzed.
From these analyses, it is apparent that the close clearances between turns of the cobalt coil, coupled with the spring action of the coil, will hold the target in position within the capsule.
Since the cobalt coils are fully annealed, it is unlikely that the coils would lose their spring action under reactor operating conditions. In addition, since each cobalt assembly contains six independert cobalt capsules, it is ex-tremely unlikely that the capsules could appreciably change their eixial l
position in the core. The capsules have been autoclaved at 1500 psi and 1
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HAZARDS CONSIDERATIONS (Contd) l
'have demonstrated they can maf ntain their integrity outside}of the Zircal y-2 I'
outer rod in a simulated react,or environment.
In general, all tolerances on the cobalt capsules are within the tolerances of the UO pellets used in normal fuel rods. Calculations 2
show that under reactor operating conditions of temperature, pressure and radiation flux, no problems are expected to exist from stress levels caused.
i by the interaction of the stainless steel target capsule and the Zircaloy-2 outer tube. Under these conditions, the performance of the cobalt bearing tubes should be'as good, if not better, than the fuel bearing tubes.
1 Incorporation of cobalt assemblies into as many as 250-fuel bundle corner. locations has been evaluated in connection with consequences of the maximum credible accident. The prese1ce of cobalt contributes negli-d
.gibly to the total activity release. The chemical energy derived from a postulated cobalt-water reaction is also a minor perturbation. Hydrogen derived from such a reaction is negligible in ita contribution to contain-l ment pressure and to the flammability level.
Each cobalt assembly contains approximately 200 grams of cobalt. Assumirs a gradual buildup to an equilibrium core content of I
about 250 such rods (first loading will be approximately 56 cobalt assem-blies), the expected activity. level will average 20 curies per gren.
Discharge: levels for the cobalt assembly will be up to 40 curies per gram 4
of cobalt. Power output for the reactor with cobalt present will be un-changed and, hence, the fission product generstion will be unchanged following table presents the total inventory and that which is releat,a... a containment as a result of the maximum credible accident. It is assumed, as with nonvolatile solids in the fuel rods, that only one percent of such products are released from the encapsulation. In view of the 30hL stainlesc steel cladding on the cobalt, which in turn is housed in the normal helium-filled zirealoy cladding, this release is considered conservative. Release of 30 percent of this amount from the containment, therefore, is compatible l
with previous accident analyses for nonvolatile solids.
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' HAZARDSCONSIDERATIONS(Contd)
Curies in UO2 Curies in Cobalt Inventory Release Inventory Release 0
Noble Gases 118.5 x 1C 118 5 x 10 Halogens 102 x 10 25 5 x 10 hl.h x 10' Volatile Solids 276 x 10 6
6 3
L Nonvolatile Solids 838 x lo 2 5 x 10 1 x 1g 3 x 10 The contribution of cobalt to the total' curie inventory of fission products is less than 0.1 percent and the total release from contain-
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ment is less than 0.002 percent.- In the category of only the nonvolatile solids, the cobalt contribution is again insignificant, contributing leen than a 0.2 percent increase to either the fission product inventory or the fission product release from the containment.
'A further comparison shows 4
that the fission products released from just one rod and correspondingly from the containment for the postulated accident would be 10,000 curies for an -
average corner fuel rod and 12 curies for an average corner cobalt assembly.
The fuel fission product activity is based on an exposure of 10,000 Mvd/T.
In view of the consideration given to the metal-water re-action, the contribution of the cobalt-water reaction has been determined and again gives a completely insignificant effect. Using 110 lb of cobalt, I'
corresponding to 250 cobalt bearing rods, a very conservative assumption of a 100 percent reaction yields 192,000 Btu of chemical energy.
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The original submittcl on Change No. 8 indicates in Appendix j
I that the Zr-H O reaction yields chemical energy of 9 23 x 10 Btu with'a 2
26.8 percent reaction. This postulated total reaction of cobalt with water, very unlikely because of the physical properties of cobalt and its double 1
encapsulation, is still only 2 percent of that already considered in. con-l nection with operation of an all Zr core (Change No. 8). It is also negli-gible in its calculated effect on containment temperature and-pressure.
I Similarly, the mole fraction of hydrogen only increases 0.08 percent to 3 35 percent due to the added 3 7 lb of hydrogen generated in the cobalt reaction l
end the flammability mole fraction of approximately 5 percent is not reached.
Based upon the calculations and considerations discussed I
above, we have concluded that the addition of cobalt to the Big Rock Point L
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10 HAZARDS CONSIDERATIONS (Contd) nuclear reactor does not present a significant change in th,e hazards conciderations described or implicit in the Final Hazards Summary Report.
CONSUMERS POWER COMPANY By Vice President Date: )fC,t +c d /Y /Id[
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Sworn and subscribed to before me this /Y day of March 1966.
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Notary Public, Jackson County, Michigan My commission expires February 24, 1969
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