ML19343A513
| ML19343A513 | |
| Person / Time | |
|---|---|
| Site: | Yankee Rowe |
| Issue date: | 10/22/1970 |
| From: | Burger A US ATOMIC ENERGY COMMISSION (AEC) |
| To: | Schemel R US ATOMIC ENERGY COMMISSION (AEC) |
| Shared Package | |
| ML19343A512 | List: |
| References | |
| NUDOCS 8011140430 | |
| Download: ML19343A513 (3) | |
Text
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UNITED STATE 3
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WASHINGTON D.C.
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001 2 2 blu File (Docket No. 50-29)
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R. J. S Q, ORB-1,DRL SAFETY REVIEW 0F PROPOSED CHANGE No. 94 W R YANKEE ATOMIC ELECTRIC COMPANY'S YANKEE R0WE REACTOR By letter dated July 15, 1970, Yankee Atomic Electric Company requested authorization of Proposed Change No. 94 to the Technical Specifications of License No. DPR-3, to allow operation of the Yankee reactor with the fuel loading ccnfiguration of Core IX.
Loading of Core IX during the next scheduled refueling outage will involve replacement of some, and rearrangement of other fuel assemblies in the existing 76-assembly array of Core VIII. Thirty-six new fuel assemblies, 4.94% enriched uranium, will be placed in the outermost region of the core; thirty-six fuel assemblies which have been irradiated in Core VIII to an average burnup of 8,300 MWD /MTU will be placed in the intermediate region of the core; and four fuel assemblies which have been irradiated in Cores VII and VIII to an average burnup of 18,300 MUD /MIU will be placed in the central cota region. All of these assemblies are stainless steel clad and are of established Yankee design. Their original enrichment, viz 4.94% uranium, is the same as that of the fuel assemblies loaded in previous cores.
The licensee has evaluated the thermal capabilities of Core IX based on calculated values of DNB ratios, heat fluxes, hot channel outlet tempera-tures and maximum UO2 temperatures.
These values have been determined as a function of rod position and power level up to and including the licensed 600 MWt power level. The heat flux and enthalpy rise factors (Fq and F ) were also calculated as a function of rod position and power H
level. The calculational techniques used, including the use of the W-2 and W-3 correlations for determining DNB ratios, the engineering factors included in the calculated values of Fq and Ih, are the same as those used in the analysis of previous cores which have been evaluated and found to be acceptable. Based on our examination of the calculated values of the Core IX thermal conditions, we have concluded that these are less severe than the thermal conditions calculated previously for the present Core VIII, as authorized in Change No. 89.
A comparison of the more important thermal parameters for steady-state operating conditions arc given below:
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rile OCT 2 2 B70 Core VIII Core IX Power Level, MWt 600 600 Heat Flux Hot Channel Factor, F 2.51 2.49 q
Enthalpy Rise, Hot Channel 2.26 2.23 Factor, FAH Coolant Temperature at Outlet of Hot Channel, 'F 605 603 Maximum UO Temperature, *F 3,160 3,109 2
Maximum Linear Heat Rate, kW/f t 8.41 8.34 Minimum DNB Ratio, W-3 Correlation 5.52 5.77 As predicted by analyses of previous core loadings and subsequently verified by measurements, the hot channel factors calculated for Core IX will also' improve as burnup of fuel progresses, as xenon builds up in the core and control rods are withdrawn. To keep Core IX thermal conditions equal to or less severe than the values of previous cores for which acci-dent analyses have been evaluated to be acceptable, Yankee will use a control rod program similar to that used in preceding cores. Power will be limited to 485 MWt until control rod groups 3, 4 and 5 are fully with-drawn from the core and xenon approaches equilibrium.
Thus, operation at the licensed 600 MWt power will be allowed with control rod groups 1 and 2 only in the core.
Core IX will be operated with borated coolant as was Core VIII. The excess reactivity of Core IX will not significantly differ from that of preceding cores; therefore, no increase in the current authorized limit of 1700 ppm boron concentration (above 15 MWe) is required. Reactivity coefficients applicable to Core IX are the same as those used in the analyses of pre-ceding cores and verified by measurements. Hot shutdown margins in Core IX were calculated to be 4.3% delta k/k with all rods in and 2%
delta k/k with the highest worth rod fully withdrawn (with the boron in the coolant maintained at a level to prevent criticality when rod group 6 7
is at its withdrawal limit). Boron would be added to maintain the reactor at least 5% subcritical during any cold shutdown, and 7% suberitical during refueling.
These shutdown margins are essentially the same as those calculated for preceding cores and they meet the requirements of the Technical Specifications.
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3-OCT 2 2 B70 File i
Based on our review of the power distribution, the thermal conditions, and the shutdown margins calculated for Core *IX, and based on our review of Yankee's past and present experience with similar core loadings, we have concluded that acceptable margins are available and that the Yankee i
reactor can be safely operated with the proposed Core IX fuel loading.
In view of the foregoing, we have concluded that the Proposed Change No. 94 does not involve significant hazards considerations not described or implicit in the safety analysis report and there is reasonable 3
assurance that the health and safety of the public will not be endangered by operation of the Yankee reactor with the Core IX loading.
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Alfr Burger Operating Reactor Branch #1 Division of Reactor Licensing cc:
D. J. Skovholt R. H. Vollmer R. J. Schemel A. Burger S. A. Teets Mary Jinks (2) i e
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