ML21278A293

2 to Updated Final Safety Analysis Report, Chapter 14, Section 14.22, Waste Gas Incident

ML21278A293
Person / Time
Site:	Calvert Cliffs
Issue date:	09/07/2021
From:	Exelon Generation Co
To:	Office of Nuclear Reactor Regulation
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NEI 99-04
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Text

14.22 WASTE GAS INCIDENT 14.22.1 GENERAL The most limiting waste gas incident is defined as an unexpected and uncontrolled release to the atmosphere of the radioactive xenon and krypton fission gases that are stored in one waste gas decay tank.

As the components of the waste gas system are subjected to pressures no greater than 150 psig, a failure is certainly not likely. However, a rupture of a waste gas decay tank is analyzed to define the limit of the hazard that could result from any malfunction in the radioactive waste gas system.

14.22.2 METHOD OF ANALYSIS It is assumed that the maximum activity in any one waste gas decay tank would occur shortly after a heatup and subsequent reactor startup from a cold shutdown condition of one unit near the end of a 24-month operating cycle. It is further assumed that this unit has been operating for an extended period with 1% defective VAP fuel and that all of the coolant is let down and the noble gases from one RCS volume are stored in one tank. On this basis the noble gas activity in the tank, neglecting decay after letdown, is as follows:

Isotope Activity, curies (Reference 1)

Kr 85m 672 Kr 85 7,637 Kr 87 393 Kr 88 1,242 Xe 131m 1,749 Xe 133 106,943 Xe 135 4,325 Xe 138 188 The activity is assumed to be released into the Auxiliary Building with the ventilation system discharging into the turbulent wake of the plant buildings. Therefore, the 0-2 hour meteorological model described in Chapter 2 is applicable. Doses were computed using the dose conversion factors and methodology described in ICRP-30.

14.22.3 RESULTS For this incident the whole body immersion dose at the nearest exclusion zone boundary is 0.182 REM, using Chi/Q = 1.3x10-4 sec/m3.

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22.4 CONCLUSION

S In the unlikely event of rupture of a gas decay tank resulting in a release of the maximum stored gaseous activity from one RCS volume, the dose at the nearest exclusion zone boundary is a factor of approximately 100 less than the 10 CFR Part 100 dose guideline value. Therefore, a waste gas incident does not represent undue hazard to the public health and safety.

This event is not affected by the transition to Advanced CE-14 HTP fuel.

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22.5 REFERENCES

1. J.R. Massari, RC Waste Processing System Incident and Waste Gas Incident Dose Analysis, CA05994, October 18, 2002 CALVERT CLIFFS UFSAR 14.22-1 Rev. 51