ML19345E401
| ML19345E401 | |
| Person / Time | |
|---|---|
| Site: | Big Rock Point File:Consumers Energy icon.png |
| Issue date: | 03/12/1965 |
| From: | Boyd R US ATOMIC ENERGY COMMISSION (AEC) |
| To: | |
| Shared Package | |
| ML19345E400 | List: |
| References | |
| NUDOCS 8101160296 | |
| Download: ML19345E401 (3) | |
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HAZARDS ANALYSIS BY THE RESEARCH AND POWER REACTOR 'SATETY -BRANCH DIVISION OF PIACTOR LICENSING
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IN THE MATTER OT CONSUMERS POWER COMPANY DOCKET NO. 50-155 PROPOSED CHANGE IN TECHNICAL SPECITICATIONS
" RELOAD FUEL BUNDLES" Introduction In a letter dated February 19, 1965, Consumers Power Company requested that the Technical Specifications of License DPR-6 for the Big Rock Nuclear Plant be changed to permit:
1.
Insertion of two " reload fuel bundles," one of which contains a number of rods clad with Zr plus 1.15% Chromium (Cr) for improved cladding corrosion resistance, and 2.
Operation with a maximum of 86 fuel bundles instead of 84 Discussion The Provisional Operating License initia'.ly issued for the facility restricted reactor power to a maximum of 157 Hw(t) with a 56 fuel bundle core. On May 1, 1964, the Provisional Operating License was converted to a full Term Operating License authorizing power levels no greater than 240 Mw(t).
In June of 1964 such power was obtained using an 84 fuel bundle core configuration. High average power density tests were conducted during August and September 1964 at power levels no higher than 160 Mw(t) using only 44 fuel bundles.
(Average power density wa temporarily increased to 60 Kw/ liter in contrast to the 240 Mw(t) power level limit of 45 Kw/ liter.) The Big Rock plant has been shut down since September 18, 1964 Up to the present time, no more than 84 fuel bundles have constituted the core although there are 88 fuel bundle channels or recep-tors for fuel bundles.
Description of Reload fuel Assemblies The " reload fuel bundles" are similar to the R&D fuel bundles in that both con-tain the same total number of rods on the same pitch with reduced diameter rods at the corners to compensate for flux peaking. However, the " reload fuel bundles" use larger diameter fuel rods with free standing zirconium cladding up to 0.034 inches in thickness.
For this reason, they require only five wire spring-loaded spacers positioned axially along the bundle to hold the fuel rods in position instead of the seven required for the R&D fuel bundle rods.
Also, the inside " reload fuel bundle" rods contain fuel with 4.2% enrichment and 2.6% at the edges, whereas the R&D fuel bundles are norcally uniform in enrichment.
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One of the reload fuel bundlen may contain up to 18 rods (2 dummy and 16 fuel rods) clad with the annealed Zr-Cr alloy, up to 8 rods (2 dummy and 6 fuel rods) clad with annealed special Zr-2, and the remaining fuel rods (maximum of
- 95) shall be clad with cold worked standard Zr-2 The fuel rods of the other reload fuel bundle shall be clad with cold worked standard Zr-2. The rods clad with zirconium containing 1.15 w/o chromium will be used to evaluate the per-formance of an improved zirconium alloy against reactor grade zircaloy-2 which will be used in the remaining rods.
(Zircaloy-2 contains between 0.05-0.15 w/o chromium). The dummy rods will contain precut tensile specimens strapped to a tantalum rod inside the zirconium tube.
(Tantalum is used to prevent flux peaking at the location of the dummy ods). The bundle design allows fuel rods to be removed without destruction of the cladding.
Evaluation Consumers has proposed to substitute em fuel bundles similar to the R&D bundles designated " reload fuel bundles," with an 11 x 11 matrix of rods. Although the fuel rod diameter has been increased to 0.449 inches compared to'O.425 inches for th R&D fuel, dual enrichment used in the " reload bundles" provides a significant reduction in the core peaking factor.
Consumers has stated that when the suppressed flux at the core edge position, where the " reload fuel bundles" are to be located, is considered in conjunction with the added effect of zircaloy channels instead of stainless steel, the local peaking factor for the new fuel bundles will be 1.228, a 56% reduction from the overall peaking factor 2.83 for the original core bundles. The presence of the four dummy rods in one bundle will cause a further reduction in the local peaking factor of that bundle from 1.228 to 1.224, according to Consumers. Because of the relatively low power gener-ation, it is Consumers' intention to restrict coolant flow to these bundles by using orifices, thereby directing coolant into hotter core fuel bundles.
At some time when reactor shutdown neutron ' source strength has been restored (following the shutdown period since September) to assure a minimum of 3 cps on out-of-core detectors, two ad7!*1etal fuel bundles will be added to increase the total number from 84 to 8F
- :conding to Consumers the effect of the
" reload fuel bundles," exm W ?c 'mproved core peaking factors resulting from dual enrichment, on other r. LS) urd thermal hydraulic factors is negligible, and the special zircaloy eiaddi.4 fontaining 1.15 w/o chromium in some of the fuel rods is even more reliable than reactor grade zircaloy-2 normally used.
Increasing the number of zirconium clad fuel rods by two fuel bundles causes a relatively small change resulting from a zirconium-water reaction in the total energy releas 2 in the event of a maximum credible accident.
Conclusion Based on the above information, we agree that operation with the two " reload fuel bundles" described above, one of which contains special rods with 1.15 weight percent chromium in the zircaloy clad presents no significant hazards considerations not described'or implicit in the Hazards Summary Report and there i
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- o. is reasonable assurance that the health and safety of the public will not be
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endange re d.
Therefore, we believe that the Technical Specifications may be revised as follows to acccmmodate the proposed change:
1.
Section 5.1.5(b) General Core Data Change number of fuel bundles in core from "84" to "a maximum of 86".
2.
Add a new Section 5.2.3 Reload Fuel as follows:
"Two special fuel bundles designated ' reload fuel' may'be loaded into the core. The characteristics of the reload fuel bundles shall be essentially as follows:
Fuel UO7, ground pellets Enrichment 2.6 - 4.5 w/o U-235 UO Density 94 + 1% theoretical 2
Clad Zr-2 or Zr + 1.15 w/o Cr alloy Fuel Rod Array linx 11 Fuel Rod O. D.
0.344 - 0.449 inches Clad Thickness 0.031 - 0.034 inches One of the reload fuel bundles may' contain up to 18 rods (2 dummy and 16 fuel rods) clad with the annealed Zr-Cr alloy, up to 8 rods (2 dummy and 6 fuel rods) clad with annealed special Zr-2, and the remaining fuel rods (maximum of 95) shall be clad with cold worked standard Zr-2.
The fuel rods of the other reload fuel bundle shall be clad with cold worked standard Zr-2."
Original signed by,:
Roger S.Boyd Roger S. Boyd, Chief Research & Power Reactor Safety Branch Division of Reactor Licensing Date:
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