ML19339B409
| ML19339B409 | |
| Person / Time | |
|---|---|
| Site: | Yankee Rowe |
| Issue date: | 01/05/1962 |
| From: | Coe R YANKEE ATOMIC ELECTRIC CO. |
| To: | US ATOMIC ENERGY COMMISSION (AEC) |
| References | |
| NUDOCS 8011060856 | |
| Download: ML19339B409 (6) | |
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Proposed Chancs No. 13 YANKEE ATOMIC ELECTRIC COMPANY 441 STUART STREET, BOSTON 16, MASSACHUSETTS January 5,1962 8 l I I ?'y
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- 7. S. Atomic Energy Commission Washington 25, D. C.
gy E-g) h Attention: Division of Licensing and Regulation
' 7po.Let otticer License No. DPR-3 (Docket NO. 50-29) g g 0
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I D Ule Cepy rea-Sirs:
Pursuant to paragraph 3.A of License No. DPR-3, as anended, Yankee Atenic Electric Company hereby requests authorization to make the following enange:
FROPOSED CHANGE: Reference is made to Section 101 of the license application,
" Core Mechanical Design", and particularly to pages 101:7 and 101:8. At the present time, uncertainity exists as to the physical condition of the original centrol rod absorber sections and the need for their replacement during the first reactor refueling. Control rod examination at that time will dictate whether er not replacement is necessary.
The proposed change covers an alternate design of control rod absorber section, similar to the original design in all respects, except for
-he addition of longitudinal, segmented, stainless steel rubbing straps on each of the eight vane surfaces. Authorization is requested to replace the
- riginal abscrber sections with new sections of the alternate design.
Reascns for Change:
It will be remembered that the original centrol rod absorber sections are of Ag-In-Cd alloy and are provided with a diffusion bonded nickel plate for corrosion resistance. We are concerned that some wear and abrasion of the nickel plated surfaces may have taken place during operation of the reactor up to the first refueling. Any suct action would, of course, expose the base metal to undesirable cor'osion effects. The addition of rubbing straps in the alternate design, which project slightly from the blade surfaces, and which will bear against the core plate guide blocks and the fuel assembly rubbing straps will prevent any such wear or abrasion during reactor operation.'
Sa'ety Considerations:
In our opinion, the proposed c1 nge does not present significant hacards considerations not described or implicit in the license application, as amended to June 23, 1961, the date of issuance of Amendment No.' 3 to License No. DPR-3, and does not affect.,he accident analysis set forth in Section h of the license application.
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yU.S. Atomic Eriergy Cor$1ssion Propos;d Changa No.13
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Reduction of control rod worth, due to the removal of absorber material and the addition of stainless steel rubbing straps has also been considered.
Initial core startup experiments demonstrated a nominal 3.5% 6 K/K shutdown margin with the C1 core in a hot, clean, zero power condition compared to the ninimum of 3% 6 'K/K required by Paragraph D 2.a.(3) of the Technical Specifications. Analysis indicates that upon installation of a complete set of the alternate design control rods, total rod worth will be reduced by a maximum of 0 3% 6 K/K. The actual shutdown margin will be checked experimentally during startup testing.
Scheduling of Change:
This change is not subject to precise scheduling since when authorized it would nerely permit use in the reactor of the alternate design of control red absorber sect $ on at some future time. Replacement would be made only if inspection.of the original absorber section discloses objectionable. surface hear or deterioration.
The proposed change requires authorization by the Commission pursuant to jaragraph 3.A of the license, since it involves a change in the design specifications of the reactor which are set forth in the license application and incorporated by reference -in the technical specifications.
(See paragraph B.1 of Appendix A to. License NO. DPR-3).
Enclosed herewith as supporting information for the proposed chang'e, in draft form, are new or superseding pages for the license application as follows:
101:7 (to supersede page 101:7 dated 1/10/60) 101:7A 101:8A Upon authorization of this change by the Commission these new or superseding pages will be submitted in final form as an amendment to the license application.
Their, incorporation in the license application will bring the document up to date and provide for the use of the original or alternate design of control rod absorber section in the reactor as conditions may warrant.
Respectfully submitted, YANKE7 ATOMIC ELECTRIC COMPAh"I d'k
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hoger J. C^e, Vice President
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U.S. Atomic Energy Comission Proposed Change No.13 Attn. : Div. of Lic. and Reg.
January 5,1%2 Commonwealth of Massachusetts Suffolk, ss January 5, 1962 j
Then personally appeared before me Roger J. Coe, who, being duly sworn, did state that he is a Vice President of Yankee Atomic Electric Cenpany, that he is duly authorized to execute and file the foregoing request in the name and on behalf of Yankee Atomic Electric Company, and that the statements therein are true to the best of his knowledge and belief.
l (14stsb Donald G. Allen Notary Public My Comission Expires Jan. 21, 1967 1
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101:7 DRAFT Control Reds Tne reactor rods are cruciform in shape and 2h in number.
The control r:ds are fabricated from a silver-indium-cadmiun alloy (80% Ag, 15% D, 5% Cd) which has a relatively high neutron absorption cross section, is escentially " black" to thermal neutrons and has a wealth of resonance st:u::ure to enhance its worth. The Ag-In-Cd alloy has approximately the same worth as hafnium and is available at a lower cost.
Since the corrosion resistance of Ag-In-Cd is marginal even under the nornal Icw exygen conditions in the Yankee reactor, the control rods arm plated with nickel to a nominal thickness of 0.5 mils *.
Heat treatment following plating gives a diffusion bond between the Ni and Ag-In-Cd, i
anneals the Ag-In-Cd alloy and thus gives maximum creep strength, and stress relief to the naterials.
Although the initial 2h control rods are not equipped with rub-bing straps, such a feature is, however, incorporated in an alternate design which has been released for fabrication. Replacement control rods will therefore be equipped with four longitudinal (type 3h8) stainless steel straps attached to each control rod vane surface, each strap being approximately 22 inches long. Straps will be approximately 3/8 inches wide by 0.061 in:hes thick and will be. chamfered on all edges. Assembly of the four straps into a 0.05 inch recessed slot in each vane surface will create a nearly continuous rubbing surface except for approximately 1/h inch spaces between strap segments. The straps are fastened to each vane by 32 welded pins. Arrangement of the rubbing straps on the replacement control rod abscrber section may be seen on page 101:8A.
2 nne:ted to the active portien of the control rod is a Zircaloy-2 fellower Stich acts as a guide and prevents the formation of a " water-slot"
= the cere wnen the control rod is withdrawn. The follower also serves to preven; excessive by-pass coolant ficw through the control rod channel.
The joint be:veen the' absorber section and the follower has been designed
- c allow naxir.un handling flexibility in that a single hardling tool can be used to handle either the absorber or the follower.
In, addition, since the joint can be " broken", less head room is needed during handling oper-ations. The figure en page 101:8 shows the joint design. The fact that the Joint can be broken does not lead to an operational hazard because disengagement is accomplished by rotation and rotation is impossible in the assenbled vessel.
~n the reactor core, the types of fuel assemblies are limited to twc, in crder to simplify the fabrication process and the loading of the cere. This results in a core having 32 crucifo m slots of which only 2h cre occupied by movable control rods. The remaining 8 cruciform slots are filled by fixed shim rods. These fixed shim rods consist of a boron stain-less steel se:tien and a Zircaloy-2 section. Each end of the rod is i
>IAEC-lh0, J.R. Dazen, "!!ickel Plating of Ag-In-Cd Alloy and Fabrication Of A Prc:ctype Control Rod'.
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2-L 101:7A DRAFT mechanically identical with the other, so that the rod may be inverted and either secticn may be used as material in the core.
If little or no absorption effect is desired from the fixed elements, Zircaloy-2 will be placee in the core with the boron stainless steel section as the extension.
If an absorption effect is required for reactivity shim and it is desired to have a lower flux peak than would be produced by Zircaloy-2, boron l
stainless steel may be placed in the core with Zircaloy-2 as the extension.
i However, the boron stainless rods night have to be removed during core life in order to permit full core life of 10,000 full power hours.
In either case, the rod will reduce the undesirable neutron flux peaking which would occur if the water were not excluded from the slots. The decision as to which material to use will be made on the basis of the initial criticality 4
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