ML19319D757
| ML19319D757 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 12/06/1974 |
| From: | Davis E, Kaplan D SACRAMENTO MUNICIPAL UTILITY DISTRICT |
| To: | |
| References | |
| NUDOCS 8003250761 | |
| Download: ML19319D757 (7) | |
Text
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1 AEC DISTRIBUTION FOR PART 50 DOCKET MATERI AL (TEf.1POR ARY FORM)
CONTROL NO: 12ho9 FILE:
FROM: SMUD DATE OF DOC DATE REC'D LTR TWX' RPT OTHER Sacramento, Calif.
95813 E K. Davis 12-6.-Th 12-10-Th X
TO:
ORIG CC OTHER SENT AEC POR XX XX Mr, A. Giambusso 1 signed 39 SENT LOCAL PDR CLASS UNCLASS PROPINFO INPUT NO CYS REC'D DOCKET NO:
XXX XXX 40 50-312 DESCRIPTION: Ltr notarized 12-6-74 requestin ;ENCLOSN:
Proposed Amdt No. 29 to oL with for Amdt to Opr. Lic. DPR-54 & trans the attached Fig. 3 5 2-1.....
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$' SACRAMENTO MUNICIPAL UTILITY SMUI]
O 6201 S Street, Box 15830. Sacramento, California 9!
December 6,1974
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Mr. Angelo Giambusso Deputy Director for Reactor Projects Directorate of Licensing U. S. Atomic Energy Commission s.
Washin9 on, D. C.
20545 t
AEC Docket No. 50-312, Proposei Amendment No. 29 Rancho Seco Nuclear Generating Station, Unit No.1
Dear Mr. Giambusso:
In accordance with 10 CFR 50.59, the Sacramento Municipal U District hereby proposes to amend its Operating License DPR-54 for Ra Seco Nuclear Generating Station, Unit No.1, by submitting forty (40) of Proposed Amendment No. 29.
This amendment follows the original correspondence with the concerning the ejected rod wor:n and contains the following changes:
1.
FSAR Page No.14.2-20 has been revised to include the conclusions of a 1.0%6 k/k rod ejection at hot zero power.
2.
FSAR Page No.14.2-21 has been revised (Table 14.2-11) to include peak neutron and thermal power values for B0L and EDL 1.0%Ak/k rod ejection at hot zero power.
The peak thermal power for a 1.0%ok/k ejected rod at hot zero power is less than a 0.65%Ak/k ejected rod at rated power and, thus, the environmental consequence are less severe.
3.
Technical Specification Page No. 33a has been revised t clarify the basis for the 1.0%Ak/k maximum rod worth a hot zero power.
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i Mr. Angelo Giambusso Decenter 6,1974 4.
Technical Specification Figure No. 3.5.2-1 has been revised to restrict group 5 to at least 49% withdrawn at zero power and to 80% withdrawn at 15% of rated power.
Respectfully submitted, SACRAMENTO MUNICIPAL UTILITY DISTRICT
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General Manager llw.
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'DfVID 5. KAP General Coun 1 of Sacramento Municipal Utility District Subscribed and sworn to before me this WE
's 6th day of December,1974
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Standby Safeguards Analysis t.) 4 - 7 'l As a check on the point kinetics calculation, the rod ejection accident was also analyzed for a limited number of cases in support of the technical speci-TWIGL digital computer program.(ll, two dimensional, space-and-time dependent fication rod worth using the exact
) The point kinetics model assumes that the flux shape remains constant during a transient.
This flux shape contains peaking factors which reflect unusual rod patterns such as the flux adjacent to a position where a high worth rod has been removed.
Therefore, these point kinetics peaking factors are much higher than any that would actually occur in the core during normal operation.
The purpose of using an exact space-time calculation is to find the flux shape during a transient.
But to have a transient where a rod is ejected from the core, one must start with a flux shape that is necessarily depressed in the region of the ejected rod.
In fact, the higher the worth of the rod, the more severe becomes the depres-sion.
This flux depression also causes a fuel temperature depression.
When the rod is ejected from this position, the flux quickly assumes a shape that shows some local peaking.
However, when this " exact" peaking is applied to a region initially at depressed fuel temperatures, as it is in the case of the regions adjacent to the ejected rod, the resultant energy deposited in these regions causes a lower peak temperature and peak thermal power than does applying an arbitrary maximum peaking factor to en undepressed peak power region.
The results from TWIGL were used to calculate the maximum total energy deposited in each region of the core following a rod ejection; the highest energy is reported in Table 14.2-10.
The result is that the hottest region simulated in the TWIGL code actually undergoes a less severe transient than the hottest fuel rod assumed in the point kinetics model.
As seen in Table 14.2-10, this result is uniformly true for all rod worths.
For certain cases where the ejected rod has a low worth, or where at least one reactivity coefficient is very negative, or the inital power level is low, there is considerable pressure buildup in the reactor coolant system because of the increased heat being added to the coolant with no increase in heat demand. Many of these transients never reach the overpower trip point.
For this class of possibility, the high pressure trip must be relied
'on, and this is incorporated in the calculation.
14.2.2.4.4 Results of Analysis A.
Zero Power Level The nominal BOL and EOL rod ejection analysis was performed at 10-3 of rated power, and the results can be seen in Table 14.2-11.
No DNB and no fuel damage would result from the transients for the 0.65% Ak/k case.
The percent of the full rods in DNB for the 29 1.0% Ak/k case would be less than the 0.65% Ak/k case at rated power.
A sensitivity analysis has been performed around these two cases in which the Doppler and moderator coefficients, trip delay time, and rod worth were varied.
Figure 14.2-2 shows the peak neutron power as a function of ejected rod worth from 0.2 to 0.7 percent Ak/k. The 14.2-20 Amendment 29
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.s Standby Safeguards Analysis TABLE 14.2-10 COMPARISON OF SPACE-DEPENDENT AND POINT KINETICS RESULTS ON FUEL ENTHALPY Ejected Peak-to-Average Values Fual Enthalpy, cal /gm Rod Worth,
%Ak/k TWIGL Point Kinetics TWIGL Point Kinetics BOL Rated Power 0.38 3.04 3.24 125 150 0.83 2.67 3.24 174 225 BOL Zero Power 0.56 4.1 3.24 38 60 0.83 4.4 3.24 48 71 TABLE 14.2-11
SUMMARY
OF CONTROL ROD EJECTION ACCIDE.'iT ANALYSIS Initia* i'over Level, Ejected Rod Worth, Peak Power, % rated power
% rated powe-
%Ak/k Neutron Thermal 0.1 (BOL) 0.65 94 70 0.1 (EOL) 0.65 1,160 32 0.1 (BOL) 1.0 8,417 132 0.1 (EOL) 1.0 16,302 102 100.0 (BOL) 0.65 700 158 100.0 (EOL) 0.65 1,600 138 curve shows two distinct parts corresponding to worths less than and values near to and greater than S.
Figure 14.2-3 shows the corres-ponding results for the peak thermal power.
It is seen that for rod worth values'near prompt critical, the period is small enough to carry the transient through the high neutron flux trip.
For lower values the pressure trip is relied on.
No DNB occurs for any'of these parameter variations.
% L h 551 omewn 9E
RANCHO SECO UNIT 1 TECHNICAL SPECIFICATIONS Limiting Conditions for Operation 3.5.2.7 The control rod drive patch panels shall be locked at all times with 29 limited access to be authorized by the superintendent or his designated
. representative.
Bases The power-imbalance envelope defined in figure 3.5.2-2 is based on LOCA analyses which have defined the maximum linear heat rate (see figure 3.5.2-3) such that the maximum clad temperature will not exceed the Interim Acceptance Criteria. Operation outside of the power imbalance envelope alone does not constitute a situation that would cause the Interim Acceptance Criteria to be exceeded should a LOCA occur. The power imbalance envelope represents the boundary of operation limited by the Interim Acceptance Criteria only if the control rods are at the position limits as defined by figure 3.5.2-1 and if a 4 percent quadrant power tilt exists. Additional conservatism is introduced by application of:
A.
Nuclear uncertainty factors.
B.
Thermal calibration uncertainty.
C.
Fuel densification effects.
D.
Hot rod manufacturing tol: 'nce factors.
The 30 percent overlap between suc sive control rod groups is allowed since the worth of a rod is lower at the upper and lower part of the stroke.
Con-trol rods are arranged in groups or banks defined as t,11ows:
Group Function 1
Safety 2
Safety 3
Safety 4
Safety 5
Regulating 6
Regulating 7
Regulating 8
APSR (axial power shaping bank)
Control rod groups are withdrawn in sequence beginning with group 1.
Group 5 is overlapped 25 percent with groups 6 and 7, which operate in parallel.
The normal position at power is for groups 6 and 7 to be partially inserted.
The minimum available rod worth provided for achieving hot shutdown by reactor trip at any time assuming the-highest worth control rod remains in the full out position.(1)
. Inserted rod groups during power operation will not contain single rod worths greater than 0.65 percentak/k. This value has been shown to be safe by the safety analysis of the hypothetical rod ejection accident.(2) A single inserted control rod worth of 1.0 percent ak/k at beginning of life, hot, zero power would result in a lower peak thermal power and therefore lese severe environmental consequences than 0.65 percent 4Lk/k ejected rod worth 29 at power.
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PERMISSIBLE OPERAT;NC REGION 20
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20 40 60 80 100 120 140 160 180 200 ROD INDEX,YWITHDRAWN O
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ROD INDEX 19 THE PERCENTAGE SUM 0F THE WITHDRAWAL OF CONTROL R0D GROUPS 5,6, & 7.
R00 POSITION LIMITS FicuRE 3.5.2-1