ML21278A282

2 to Updated Final Safety Analysis Report, Chapter 14 Section 14.25, Excessive Charging Event

ML21278A282
Person / Time
Site:	Calvert Cliffs
Issue date:	09/07/2021
From:	Exelon Generation Co
To:	Office of Nuclear Reactor Regulation
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References
NEI 99-04
Download: ML21278A282 (2)

Text

14.25 EXCESSIVE CHARGING EVENT 14.25.1 IDENTIFICATION OF EVENT AND CAUSE The Excessive Charging Event initiated from maximum pressurizer level was analyzed to assure that the operator has at least 15 minutes from initiation of a high pressurizer level alarm to take corrective action and terminate the event prior to filling the pressurizer solid.

The Excessive Charging Event is assumed to occur by inadvertent initiation of charging flow.

14.25.2 CORE AND SYSTEM PERFORMANCE 14.25.2.1 Mathematical Models The time required to fill the pressurizer solid was calculated using the following equation:

=

( ) 2 1

where:

VS = steam volume in the pressurizer; VSL = equivalent saturated liquid volume pressurizer steam volume; VT = volume above the spray nozzles; FCH = charging flow rate; FLD = letdown flow rate; W1 = specific volume of liquid at charging and letdown conditions; and, W2 = specific volume of liquid at pressurizer conditions.

14.25.2.2 Input Parameters and Initial Conditions The analysis was performed for three combinations of charging and letdown flows.

Table 14.25-1 presents the initial conditions assumed in the analysis and the results of the analysis. The initial conditions assumed in the analysis are consistent with the Technical Specification limits on initial pressurizer level including appropriate instrument loop uncertainties.

14.25.2.3 Results As seen from Table 14.25-1, all three combinations of charging and letdown flow analyzed provide at least 15 minutes after initiation of high level alarm for the operator to take corrective actions and terminate the event prior to filling the pressurizer solid.

14.

25.3 CONCLUSION

S The operator has at least 15 minutes after initiation of a high level alarm to take corrective action and terminate the event prior to filling the pressurizer solid.

This event is not affected by the transition to Advanced CE-14 HTP fuel because the key parameters for this event are plant related system responses which are unchanged from, or bounded by, the current analysis.

CALVERT CLIFFS UFSAR 14.25-1 Rev. 51

TABLE 14.25-1 EXCESSIVE CHARGING EVENT - CORE AND SYSTEM PERFORMANCE FOR CHARGING FLOW AND LETDOWN FLOW TIME TO MAXIMUM INITIAL HIGH LEVEL ALARM FILL(a)

VOLUME CONTROL ASSUMPTIONS PRESSURIZER LEVEL ANALYSIS SETPOINT PRESSURIZER LETDOWN LIQUID LIQUID CHARGING FLOW FLOW VOLUME LEVEL(c) VOLUME LEVEL(c) (minutes)

(gpm) CBO (gpm) (ft )

3 (in) (ft )

3 (in)

1. 144 6 0 853 218 853 218 16(d)

2. 144 6 29(b) 952 242 1014 257 15

3. 96 6 0 952 242 1094 276 15 (a)

From time of initiation of high pressurizer level alarm.

(b)

Conservatively lower than the 30 gpm minimum letdown flow listed in Figure 4-11.

(c)

Referenced to the 1" level nozzle at the bottom of the pressurizer.

(d)

One minute to recognize computer signal leaving 15 minutes for operator response.

CALVERT CLIFFS UFSAR 14.25-2 Rev. 47