ML20002C983
| ML20002C983 | |
| Person / Time | |
|---|---|
| Site: | Big Rock Point File:Consumers Energy icon.png |
| Issue date: | 01/23/1970 |
| From: | Walke G CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | Morris P, Skovholt D US ATOMIC ENERGY COMMISSION (AEC) |
| References | |
| NUDOCS 8101150644 | |
| Download: ML20002C983 (5) | |
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i General Offices: 212 West Michigan Avenue. Jackson, Michigan 49201. Area Code 517 788-0550 m
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January 23, 1970 f
Re' ulatory File Cy.
g Dr. P. A. Morris, Director Re: Docket 50-155 Division of Reactor Licensing DPR-6 ZEK United States Atomic Energy Commission Washington, DC 20545
Dear Dr. Morris :
Attention:
Mr. D. J Skovholt In an informational letter to you dated January 14, 1969, we informed you of our intention to install a control rod drive support structure in the Big Rock Point Nuclear Plant. The design and procurement of materials for the structure hav'e progressed to the point that we now are planning to install it during the forth-coming Big Rock Point Plant refueling outage, scheduled for February 1970. It is the purpose of this letter to apprise you of the up-coming scheduled installation of the structure, to inform you of a design change and to discuss a few points concerning testing and surveillance raised by your staff.
First, because of a design change involving the charac-teristics of the Belleville washers, the original load-deflection calculations were redone. This necessitated a change in our original letter. On Page 4, Line 11 of the first paragraph of Stress Analysis, starting with the word "Considering," the remainder of the paragraph should read, with changes underlined:
"Considering that the control rod drive housing will travel about 0.26 inches downward before encountering the resisting support assembly, and, also considering that the support assembly will offer a resistance at each corner column of 18,100 lbs. per inch of downward travel, calculations reveal that a downward travel of 2.8h inches at the e orner column will result for the case where the failed assembly is nearest that corner column. With a corresponding dynamic load fac-tor of 2.25, this will result in a maximum dynamic load of 88.2 kips and a total downward movement of 2 37 inches for the control rod at the location of the control rod. For the case where the failed assem-bly is near the center of the support grid, the deflection will be 1 30 inches under the failed assembly and at each corner column, and a total downward movement of 1 56 inches for the control rod. With h/W b ff
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~ Dr. P. A. Morris-2 January 23,-1970 a corresponding dynamic load factor'of 2.k1, this will result in a maximum dynamic load of 9h.5 kips at the location of the control rod."
Attached is a load-deflection curve for the Belleville washer shock absorber assembly.
A question was raised by your staff concerning static load-deflection curves on the Belleville washer shock absorber assembly and the repeatability of such tests. The supplier of the Belleville washers informs us that in their experience, stacks of Belleville-washers constitute a relatively simple system, readily amenable to calculation as to their stetic load-deflection characteristics. In their judgment, such a test is generally unnecessary.
In this spe-cific case where there is a "one-time" loading design criterion, it is felt to surely be unnecessary.
Another question was raised relative to our planned sur-veillance program on the control rod drive support structure.
Bechtel Corporation is our architect-engineer-constructor on this project.
Both their Quality Control Department and Consumers Power's respon-sible project engineer closely followed the fabrication of the support assembly to provide assurance that the assembly conformed to specifi-cations. This surveillance will continue through the construction and final check-out phases.
Before the initial plant start-up with this structure installed, cold and hot clearances between the control rod housing and the supporting piece will be checked to assure proper relationships of the components. Thereafter, whenever work is per-formed on control rod drives necessitating removal of the supporting piece, cold clearances will be checked before returning to power.
At each refueling outage, a general visual inspection of the whole
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control rod support structure will be made. Special attention will be paid to the clearances.
All of these checks and inspections will be described in a written plant operating procedure. Since this structure is located in a high-radiation area, the laspections and checks will be designed to minimize personnel radiation exposure.
In conclusion, we believe that the control rod drive support structure is designed to prevent the ejection of a control rod drive in the unlikely event of a thimble failure. Consumers Power Company believes the addition of this structure will make Big Rock Point equiv-alent to BWR plants currently authorized for construction with respect to the potential excursion caused by a control rod ejection.
In our opinion, the addition of the-control rod drive support structure does not involve an unreviewed safety question or a change to the Technical
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Dr. P. A. Morris 3
January 23, 1970 Specifications of License DPR-6, Docket No 50-155, issued to Consumers P)wer Company on May 1,1964, for the Big Rock Point Nuclear Plant.
Yours very truly,
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A_h _n GJW/d=b Gerald J. Walke Nuclear Fuel Management CC: GFiorelli, Div of Administrator Compliance, USAEC EBrunner, Div of Compliance, USAEC
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DATE OF DOCUMENT DAT3 RECEIVED NOs bgg g Jackson, Michigan IN)201 I"I3-M 146-M -
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ORIG.:
CCa OTHEas Dr Peter A. Mrris 1
ACTION NECEssAJty O
CONCURRENCE O
DATE ANswEaED NO ACTION NECESSARY O COuutuT O
avi ifs POST OFFICE FtLE CODE:
I REG.No, 50-155 DESCRIPfloN: (Must Be Unclassmed)
R EFERRED TO DATE RECE1VEC BY DATE Ltr in re to their 1-1W ltr regardinig ziemann 1 26-70 installing of a control rod drive w/o era for metica support structure..... advising of pland
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to install it during refueling outrage.
DISIRIBUfIOEt ENCLOiURES:,,,,ghgggg 13 dggigg & %Yggg l Regulatory fila$
M Arc pan Compliance (2)
Ioad-deflection curve for the Belleville washer shock absorber Skovbolt astenbly.
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