ML19350C176

Proposed Tech Specs 2.0 Revisions Re Limiting Conditions for Operation

ML19350C176
Person / Time
Site:	Fort Calhoun
Issue date:	03/27/1981
From:	OMAHA PUBLIC POWER DISTRICT
To:
Shared Package
ML19350C174	List: ML19350C173 ML19350C175 ML19350C176
References
NUDOCS 8103310451
Download: ML19350C176 (4)

Text

. % s

.m 2.0 LIMITING CONDITIONS FOR OPERATION 2.10 Reactor Core (Continued) .

2.10.2 Reactivity Control Systems and Core Physics _ Parameters Limits Applicability Applies to operation of control element assemblies and monitor-ing of selected core parameters whenever the reactor is in cold or hot shutdown, hot standby, or power operation conditions.

Objective To ensure (1) adequate shutdown margin following a reactor trip, (2) the MTC is within the limits of the safety analysis, and (3) control element assembly operation is within the limits of the setpoint and safety analysis.

Specification (1) Shutdown Margin with Teold >2100F Whenever the reactor is in hot shutdown, hot standby or power operation conditions, the shutdown margin shall be 2,3.0% Ak/k. With the shutdown margin <3.0% ak/k, initiate and continue boration until the required shutdown margin is achieved.

(2) Shutdown Margin with T eold 12100F Whenever the reactor is in cold shutdown conditions, the shutdown margin shall be 2.3.0% Ak/k. With the shutdown margin <3.0% ak/k, initiate and continue boration until the required shutdown margin is achieved.

(3) Moderator Temperature Coefficient The moderator temperature coefficient (MTC) shall be:

a. Less positive than +0.2 x 10-4 Ao/ F including uncertaintieu for power levels at or above 80% of rated power.

b. Less positive than +0.5 x 10-b Ap/0F including uncertainties for power levels below 80% of rated power.

c. More positive than -2.3 x 10-4 Ap/0F including uncertainties at rated power.

With the moderator temperature coefficient confirmed outside any one of the above limits, change reactivity control parameters to bring the extrapolated MTC value within the above limits within 3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> or be in at least hot shutdown within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />.

Amendment No. 8, 32, h3, 47 2-50 ATTACHMENT A 810 8310 4 M

2.0 LIMITING CONDITIONS FOR OPERATION 2.10 Reactor Core (Continued) 2.10.? Reactivity Control Systems and Core Physics Parameters Limits (Continued) .

the shutdown margin requirement is based upon this limiting condition and is consistent with FSAR safety analysis assump-tions. With Teold 12100F, the reactivity transients resulting from any postulated accident are minimal and a 3.0% Ak/k shutdown margin provides adequate protection. l Control Element Assemblies The specifications of this section ensure that (1) acceptable power distribution limits are maintained, (2) the minimum shutdown margin is maintained, and (3) the potential effects of CEA misalignments are limited to acceptable levels.

The statements which permit limited variations from the basic requirements are accompanied by additional restrictions which ensure that the original design criteria are met.

The specifications applicable to one or more CEA's that are determined to be untrippable or stuck, and to one or more misaligned CEA's that cannot be restored to within 12 inches of any other CEA in their group, require a prompt shutdown of the reactor since any of these conditions may be indicative of a possible loss of mechanical functional capability of the CEA system and in the event of any untrippable CEA, the loss of shutdown margin.

For small misalignments (<18 inches absolute) of the CEA's, there is 1) a small degradation in the peaking factors relative to those assumed in generating LCO's and LSSS setpoints for DNBR and linear heat rate, 2) a small effect on the time de-pendent long term power distributions relative to those used in generating LCO's and LSSS setpoints for DNBR and linear heat rate, 3) a small effect on the available shutdown margin, and

4) a small effect on the ejected CEA vorth used in the safety analysis. Therefore, the action statement associated with the small misalignment of a CEA permits a one hour time interval during which attempts mgy be made to restore the CEA to within its alignment requirements prior to initiating a reduction in power. The one hour time is sufficient to 1) identify causes-of a misaligned CEA, 2) take appropriate corrective action to realign -the CEA's, and 3) minimize the effects of xenon re-distribution.

Overpower margin is provided to protect the core in the event of a large misalignment (>18 inches) of a CEA. However, this mis-alignment would cause distortion of _the core power distribution.

The ~ reactor protective system would not detect the degradation in radial peaking factors and since variations in other systems para-meters (e.g., pressure and coolant temperature) may not be sufficient Amendment No. 8, 20, 32, 43 2 L

DISCUSSION The previous boron dilution analysis for a cold, shutdown condition assumed that the reactor coolant system (RCS) remained full. Under certain conditions, such as reactor coolant pump seal replacement, the RCS may be drained to a level which is approximately half the normal volume.

The boron dilution incident was reanalyzed using the refueling mode volume for the cold shutdown condition, because it is the minimum volume allowed. If a 2.0% Ak/k shutdown margin is assumed for the cold shut-down mode, with a volume equal to that of the refueling condition, a dilution time to criticality of less than 15 minutes exists. To obtain a dilution time greater than 15 minutes, a shutdown margin of 3.0% Ak/k is adequate. These dilution times assume the boron concentration cor-responds to a configuration with the shutdown groups being withdrawn and all regulating rods except the most reactive being inserted. These assumptions, which are defined by the Technical Specifications, yield the highest boron concentration which gives the minimum dilution time.

Normally all rods would be inserted when in the c_old shutdown mode. An acceptable dilution time to critical has been maintained in the past (with a shutdown margin of 2.0% Ak/k) taking credit for the worth of all rods being inserted and the HZP-xenon free boron concentration.

ATTACHMENT B

O JUSTIFICATION FOR FEE CLASSIFICATION The proposed amendment is deemed to be Class III within the meaning of 10 CFR 170.22 in that it involves a single safety con-cern.

ATTAC101ENT C