ML20002E032
| ML20002E032 | |
| Person / Time | |
|---|---|
| Site: | Big Rock Point File:Consumers Energy icon.png |
| Issue date: | 02/25/1971 |
| From: | Morris P US ATOMIC ENERGY COMMISSION (AEC) |
| To: | Walke G CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| Shared Package | |
| ML20002E033 | List: |
| References | |
| NUDOCS 8101260155 | |
| Download: ML20002E032 (3) | |
Text
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UNITED STATES
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WASHINGTON, D.C. 20545 T'~
February 25, 1971 e
Docket No. 50-155 Consumers Power Company ATTN:
Mr. Gerald J. Walke-
' Nuclear Fuel Management Administrator 212 West Michigan Avenue Jackson, Michigan 49201 Change No. 25-License No. DPR-6 Centlemen:
Your letter dated January 28, 1971, requested approval of Proposed Change No. 26 to the Technical Specifications of Facility License No. DPR-6 for insertion of " Type 2A" control rods into the Big Rock Point reactor during the next refueling outage. The proposal, redesignated Proposed Change 25, involves the substitution of control rod blades with stainless No.
steel boron absorber tubes of slightly larger diameter and thickness than the swaged absorber tubes in the " Type 2" control rods that are to be replaced. As a result of the increased tube diameter, it has been necessary to decrease the number of poison tubes from 17 to 16, to decrease the number of empty tubes from 12 to 10 and to decrease the sheath thickness.
Based on our evaluation of the proposed change, we have concluded that substitution of the Type 2A control rods for the Type 2 control rods does not present significant hazards considerations not described or implicit in the Big Rock Point Nuclear Reactor Saf ety Analysis Report.
There is reasonable assurance that the health and safety of the public will not be endangered by operation of the Big-Rock Point Nuclear Reactor using Type 2A control rods 'as replacements for control rods that are j
to be permanently removed.
l to Section 50.59 of 10 CFR Part 50, Section 5.1.2 Accordingly, pursuant of the Technical Specifications of Facility License No. DPR-6 is hereby changed in its entirety to read as follows:
" 5.1. 2 Control Rods _
t I f Number of Control Rods:
16 Type 1 16 Type 2A 7/Ol M o a f D =Hi&&
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-j Consumers Power Company February 25, 1971.
Poison Material'- B C Powder 'in 304 SS 4
Tubes and ' solid 304 SS rods' or B C Powder in 4
304 SS Tubes"and empty.304 SS Tubes:
Pitch (Square Array), Inches 10.466 Active Length, Inches 68 Cruciform Shape-Width, Inches 11-1/2
- Blade Thickness, Inches 5/16
' Sheath Thickness, Inches:
Type 1
.062 Type 2A
.056 Number of B C Filled, 304 SS Tubes 4
per Control Rod:
.r Type 1 116 Type 2A 64 Number of Empty 304 SS Tubes per Control Rod:
9 0
Type 1 Type 2A 40 304 SS Tube, B C' Filled, Outer 4
Diameter, Inches:
Type 1 0.175 Type 2A 0.188 304 SS Tube, B C Filled, Wall 4
Thickness,. Inches:
Type 1 0.020 0.025 Type 2A l
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' 304:SS Tube', Empty, Outer Diameter, Inches:
-Type 1 None
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. Type'2A 0.188 304 SS Tube.. Empty, Wall Thickness,.
Inches:
. Type 1 None Type 2A 0.025" Sincerely,'
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Peter A. Morris, Director
- Division of Reactor Licensing
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. Washington, D.
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FEB 2 51971 Docket No. 50-155 Consumers Power Company ATTN.
Mr. Gerald J. Walke Nuclear Fuel Management Administrator 212 West Michigan Avenue Jackson, Micnigan 49201 Change No. 25 Gentlemen License No. DPR-6 Your letter dated January 28, 1971, requested approval of Proposed Change No. 26 to the Technical Specifications of Facility License No. DPR-6 for insertion of " Type 2A" control rods into the Big Rock Point reactor during tue next refueling outage. The proposal, redesignated Proposed Change No. 25, involves the substitution of control rod blades with stainless steel boron absorber tubes of slightly larger diameter and thickness than the swaged absorber tubes in the " Type 2" control rods that are to be replaced. As a result of the increased tube diameter, it has been necessary to decrease the number of poison tubes from 17 to 16, to decrease the number of empty tubes from 12 to 30 and to decrease the sheath thickness.
Based on our evaluation cf the proposed change, we have concluded that substitution of the Type 2A control rods for the Type 2 control rods does not present significant hazards considerations not described or implicit in the Big Rock Point Nuclear Reactor Safety Analysis Report.
There is reasonable assurance that the health and safety of the public will not be endangered by operation of the Rig Rock Point Nuclear Reactor using " Type 2A control rods as replacements for control rods that are to be permanently removed.
Accordingly, pursuant to Section 50.59 of 10 CFR Part 50, section 5.1.2 of the Technical Specifications of Facility License No. DFR-6 is hereby changed in its entirety to read as follows:
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"5.1.2 Control Rods N
Number of Control Rods:
8M 8/T Type 1 16
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FEB 2 51971 Conctmers Power Company Poison Material - B C Pow er in 304 SS 4
d Tuues and solid 304 SS rods or B C Powder in 4
304 SS Tubes; and empty 304 SS Tubes:
10.46C Pitch (Square Array), Inches 68 Active Lengtn, Inches Cruciform Saape 11-1/2 Width, Inches Blade Thickness, Inchca 5/16 Sheath Tnickness, Inches:
.062 Type 1
.056 Type 2A Nuraber of B C Filled, 304 SS Tubes 4
per Control Rod:
11L-Type 1 64 Type 2A Number of Ec:pty 304 SS Tubes per Control Rod:
0 Type 1 40 Type 2A 304 SS Tube, B C Filled, Outer 4
Diameter, Inches:
0.175 Type 1 0.188 Type 2A 304 SS Tube, 5 C Filled, Wall 4
Thickness, Inches c
0.020 Type 1 0.025 Type 2A
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Consumers Power Company ' FEB 2 5 1971 304 SS Tube, Empty, Outer Diameter, Inches Type 1 None Type 2A 0.188 304 SS Tube. Empty, Wall Thickness, Inches Type 1 None Type ?A 0.025" Sincerely, Peter A. Morris, Director Division of Reactor Licensing cc: George T. Trowbridge, Esquire Shaw, Pittman, Potto, Trowbridge & Madden 910 - 17th Street, N. W.
Washington, D. C.
20006 Distribution W. Dooly, DR R. H. Vollmer, DRL R. Engelken, CO (2)
D. L. Ziemann, DRL H. Shapar, OGC J. J. Shea, DRL N. Dube, DRL (5)
R. M. Diggs, DRL J. R. Buchanan, ORNL R. DeYo$ng, DRL T. W. Laughlin, DTIE
.R.
S. Boyd, DRL Document Room
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- 4. ' The sheath thickness.of the " Type 2A" control rod blades is
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0.006_ inch less than the_0.062 inch thickness of the " Type 2" sheathing,-and f5. The number of empty tubes in each wing is 10 compared with 12 in the " Type: 2" control rods and the number of poison tubes is 16 compared with 17.
The change eliminates the large amount of cold working during the swaging operation -to the advantage of the f abricator (General Electric Company).
The same nonswaged design has been adopted by GE'for the new product-line control rods.
We concur that the 25% increase in tube wall thickness is ' sufficient to maintain wall strength becarse 'the yield strength is not reduced a corresponding amount by omission of cold working, but note that the
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increase in diameter does not completely explain the reduction in the number of tubes per blade.
Consumers rechecked the fabrication drawings and by telecon on 2/19/71 reported that the metal stack at the center of -the blade-had been increased from 0.571 inch to 0.758 inch.
This increase accounts for one less tube in each wing and the increased
" Type 2A" tube diameter, we agree, then accounts for the remaining reduction of'two tubes per wing.
The proposed change reduces the B C content by about 2% and_ increases 4
the surface by about 1%.
The neutron absorbing characteristics of these changes are opposite and small; therefore, we ha7 2 concluded that the nuclear characteristics are not' changed significantly in-relation to normal reactor operation or accident considerations.
The 10% reduction in the thickness of the sheath provided to maintain the tubes in the cruciform configuration and preserve alignment will result in less resistance to distortion stresses; however, in the absence of such symptoms in " Type 2" control rods and considering the 30% increase in center metal resulting in less longitudinal flexibility (increased axial stiffness), we have concluded that the thinner sheathing for the control rod tubes necessitated by the increased diameter.of the tubes'is acceptable.
In addition to the applicant's statement that his Quality Assurance Program meets the criteria of 10 CFR 50, Appendix B, a measure of the effectiveness of his program was demonstrated by the fact that these
' design changes'were initially detected by Consumers Power Company during routine radiographing examination of the control rods after receipt from GE before the < changes were identified by GE.
l 9
File.IEC 2 5 1971 On the basis of the above, we have concluded that the mechanical and nucicar differences between " Type 2" control rods,- which have been used successfully for control of the Big Rock Point reactor for the past six years, and the " Type 2A" control rods to be substituted are r.inor and reactor operation with the " Type 2A" control' rods installed in the Big hock Point reactor will not increase the probability of an.
accident, impair the effectiveness of the installed engineered safety features, or change the consequences of the design basis accident.
The.
proposed change does not present significant hazards considerations not '
described or implicit in the Safety Analysis Report and there is reason-able assurance that operation of the Big Rock Point reactor in the i
manner. proposed will not endanger the health and safety of the public.
Therefore, the Technical Specifications should be revised as proposed.
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'geratingReactorsBranch#2 Division of Reactor Licensing cc:
D. J. Skovholt, DRL R.11. Vollmer, DRL D. L. Ziemann, DRL J. J. Shea, DRL
.R. M. Diggs, DRL Mary Jinks (2) i i
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