ML20054L453
| ML20054L453 | |
| Person / Time | |
|---|---|
| Site: | Fort Saint Vrain  |
| Issue date: | 07/06/1982 |
| From: | PUBLIC SERVICE CO. OF COLORADO |
| To: | |
| Shared Package | |
| ML20054L444 | List: |
| References | |
| NUDOCS 8207080136 | |
| Download: ML20054L453 (14) | |
Text
ATTACHMENT C P-32229 Proposed Technical Soecifications 8207080136 820706 PDR ADOCK 05000267 p PDR
Fort St. Vralr> #1 Technical Specifications Amendment Page 2.21 Individual Refueling Region Outlet Temperature The individual refueling region outlet temperature is defined as follows:
a) For Regions 1 through 19 and 21 through 31, the measured refueling region outlet temperature.
b) For Regions 20 and 32 through 37, whichever of the following temperatures is hottest: 1) the measured refueling region outlet temperature or 2) the refueling region outlet temperature based upon the following quantities:
- 1) The ratio of the relative power in each of these regions to that in their " comparison regions" as determined from physics calculations.
! 2) The ratio of the helium flow rate through each of these l
regions to that through their " comparison regions" as I
determined based upon inlet orifice valve positions.
- 3) The measured refueling region outlet temperatures of l
their " comparison region."
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rort St. Vrain #1 Technical Specifications Amendment Page 2.22 Comparison Region A comparison region is a core refueling region whose power, flow, and coolant outlet temperature characteristics are used to determine the outlet temperature of a region for which the measured outlet temperature is unreliable. Experience has shown that Regions 20 and 32 through 37 have the potential for significant discrepancies between measured and actual region outlet temperature. These discrepancies are caused by a transverse flow of relatively cool helium from the core reflector interface along the region outlet thermocouple sleeve. This flow passes over the region outlet thermocouple assemblies of these regions and depresses the indicated outlet temperature.
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Fort st. Vrain #1 Technical Specifications Amendment Page Specification LCO 4.1.7 - Core Inlet Orifice Valves, Limiting Condition for Operation a) For a core average outlet temperature greater than or equal to 950 F, the core inlet orifice valves shall be adjusted to the following conditions: the individual region outlet temperature for the nine regions whose valves are most fully closed, and any region with control rods inserted more than two feet into the core, shall not exceed the core average outlet temperature by more than the limit (Mismatch B) shown in Figure 4.1.7-1. The individual region outlet. temperature for the remaining regions shall not exceed the core average outlet temperature by more than the limit (Mismatch A) shown in Figure 4.1.7-1.
b) For a core average outlet temperature less than 950 F, the individual region outlet temperature for all 37 regions shall not exceed the core average outlet temperature +400 F, and the conditions of LCO 4.1.9 must be met.
c) For any region being used as a comparison region, the percent
" region peaking factor (RPF) discrepancy," %ARPF, given by
%ARPF = RPF measured - RPF calculated x 100%
RPF calculated l
rort St. Vrain #1 -
Technical Specifications Amendment Page shall not be less than minus 10*; (i.e. , RPF measured less than 90's of RPFcalculated), without corrective action as specified below.
Corrective action shall be initiated at the onset of a condition exceeding the limits stated in a) and b). If these limits are exceeded by 1) 100 F or more, an immediate orderly shutriown shall be initiated: 2) 50 F or more, but less than 100 F, corrective action must be successful within two hours or an orderly shutdown shall be initiated; 3) less than 50 F, corrective action must be successful within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> or an orderly shutdown shall be initiated.
Corrective action shall be initiated upon discovery of a percent region peaking factor discrepancy exceeding the limit stated in c).
If the limit is exceeded, 1) a new comparison region which meets the limit shall be used or 2) the inferred coolant temperature rise
! (i.e., the individual refueling region outlet temperature minus the core inlet temperature) in the region (20 or 32 through 37) being controlled by the comparison region shall be increased by a percent amount equal to or greater than that by which the limit stated in c) is exceeded.
Basis for Specification LCO 4.1.7 Experience gained during rise-to power testing has shown Regions 20 and 32 through 37 have the potential for significant discrepancies
Fort St. Vrain #1 Technical Specifications Amendment Page between measured and actual region outlet temperature. These discrepancies are caused by a transverse flow of relatively cool helium from the core reflector interface along the region outlet thermocouple sleeve. This flow passes over the region outlet thermocouple assemblies of these regions and depresses the indicated region outlet temperature.
To compensate for these potential transverse flow-induced temperature measurement errors, Regions 20 and 32 through 37 shall have their region outlet temperatures determined by the power and flow characteristics of other regions in the core referred to as comparison regions. The comparison region method o' .perc. tion was first developed for use during rise-to power and fluctuation testing above 70% power in test procedure RT-5CJK. Experience obtained during that test indicates that, by use of comparison regions, Regions 20 and 32 through 37 can be operated in a manner consistent with the original reactor design intent and consistent with the criteria upon which Specification SL 3.1 is based.
If the measured region outlet temperature in Regions 20 and 32 through 37 is higher than that based upon the comparison region conditions, the measured region outlet temperature is assumed to be correct.
Fort St. Vrain #1 Technical Specifications Amendment Page Use of comparison regions requires that conditions in the comparison regions (power, flow, and outlet temperature) be well known. Region peaking factor discrepancies result from combinations of errors or uncertainties in measured region outlet temperature, region flow inferred from orifice valve position, and calculated region power.
Based upon an evaluation of data obtained during the rise-to power testing program, region peaking factor discrepancies up to 10%
(positive or negative) are not unexpected or considered to be excessive. Under the comparison region method of operation, only excessively negative region peaking factor discrepancies in a comparison region could result in prolonged, high fuel temperatures in the region being operated with the comparison region. The corrective action specified in LCO 4.1.7c will protect the fuel from such conditions.
During RT-500K testing, the difference (i.e., mismatch) between the measured region outlet temperature of any region and the core average outlet temperature at 100% power was maintained within the limits of Figure 4.1.7-1. The limits in this figure are more conservative than those used to develcp Specification SL 3.1 and those contained in Specification LCO 4.1.7 at the time RT-500K was conducted. In addition, Figure 4.1.7-1 directly limits the maximum region outlet temperature to 1,555 F, which is consistent with Table 3.6-1 of the FSAR. By requiring that the limits in Figure 4.1.7-1 be met, maximum
Fort St. Vrain #1 Technical Specifications Amendment Page fuel temperatures are kept within FSAR stated values regardless of the power level or the amount of core bypass flow which may exist.
During power operation with a core average outlet temperature less than 950 F, sufficient over-cooling of the core is provided with a
+400 F deviation between the maximum region outlet temperature and the core average outlet temperature to assure that Specification SL 3.1 remains valid and that the integrity of the fuel particles is preserved.
The times at temperature exceeding the limits given represent conditions significantly below the core safety limit.
Fort St. Vrain #1 Technical Specifications Amendment Page
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Fort St. Vrain #1 Technical Specifications Amendment Page Specification SR 5.1.7 - Region Peaking Factor Surveillance The calculated region peaking factors (RPF's) used in determining the individual region outlet temperatures for Regions 20 and 32 through 37 and the percent RPF discrepancy (see LCO 4.1.7) for Regions 1 through 19 and 21 through 31 shall be evaluated according to the following schedule for each refueling cycle:
a) Calculated RPF's: 1) Prior to initial power operation after refueling.
- 2) At the equivalent of 20 (+5) effective days at rated thermal power after refueling.
- 3) At the equivalent of 40 (+5) effective days at rated thermal power after refueling.
- 4) At monthly intervals thereafter, provided that the core has accumulated an exposure of at least the equivalent of 10 effective days at rated thermal power since the previous evaluation. If the core has accumulated an exposure of less 1
Fort St. Vrain #1 Technical Specifications Amendment Page than the equivalent of 10 effective days at rated thermal power since the previous evaluction, the evaluation may be deferred until the next applicable interval.
b) Percent RPF Discrepancy: Within a total elapsed time of 10 calendar days at reactor power levels above 40% of rated thermal power after the completion of any of the
" Calculated RPF" evaluations required above with the following qualifications:
- 1) A " Percent RPF Discrepancy" evaluation shall be performed prior to exceeding 40% of rated thermal power for the first time after refueling, but at a reactor power above 30% of rated thermal power.
- 2) If the total elapsed time at reactor power levels above 40% of rated thermal power does not exceed 10 calendar days prior to the subsequent " Calculated RPF"
Fort St. Vrain #1 Technical Specifications Amendment Page evaluation, the " Percent RPF Discrepancy" evaluation is not required, but the total elapsed time at reactor power levels above 40% of rated thermal power between
" Percent RPF Discrepancy" evaluations shall not exceed 45 calendar days.
Basis for Specification SR 5.1.7 The calculated region peaking factors for Regions 20 and 32 through 37 and their comparison regions will change during the refueling cycle as fission product inventories saturate, fissile material and burnable poison are depleted, and control rods are withdrawn from the core. Evaluations based upon operating experience gained prior to completion of rise-to power testing (i.e., Cycles 1 and 2 and part of Cycle 3) indicate that the ratio of the calculated region peaking factors in Regions 20 and 32 through 37 to the calculated region peaking factors in comparison regions as a function of control rod configuration, changes gradually in a predictable manner during a refueling cycle. A surveillance check of the calculated region peaking factors at the specified frequency will assure that the appropriate region peaking factors continue to be used in determining the region outlet temperature for Regions 20 and 32 through 37.
Fort St. Vrain #1 Technical Specifications Amendment Page The calculated and measured region peaking factors for Regions 1 through 19 and 21 through 31 (candidate comparison regions) will change during the refueling cycle as fission product inventories saturate, fissile material and burnable poison are depleted, control rods are withdrawn from the core, and region flow characteristics change. A surveillance check of the percent region peaking factor discrepancy will provide assurance that the requirements of LC0 4.1.7c are being met for comparison regions. The frequency for surveillance has been established based upon conservative evaluations of pstential fuel kernel migration, which could occur if a region with an excessively large, negative region peaking factor discrepancy were used as a comparison region.
ATTACHMENT D P-82229 ,
S.afety Evaluation Report Technical 5pecifications for Operation of Fort St. Vrain With Region Outlet Temperature Measurement Discrepancies 1