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Environmental Impact Statement - radioactive monticello

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Description of Site and Environment<br />

draft SEIS, NMC issued the effluent release report for 2005 (NMC 2006) and reported no<br />

I abnormal liquid effluent releases during the calendar year.<br />

Based on the system description above, design, and previous performance, no liquid effluents,<br />

other than occasional abnormal releases, are expected from Monticello during the renewal<br />

period. If abnormal releases were to occur, they would result in doses to members of the public<br />

that are well below the dose design objectives of 10 CFR Part 50, Appendix I, as discussed in<br />

Section 2.2.7.<br />

2.1.4.2 Gaseous Waste Processing Systems and Effluent Controls<br />

The gaseous radwaste system provides for sufficient off-gas holdup time to allow decay of the<br />

short-lived radioisotopes (such as nitrogen-1 6 and oxygen-1 9) and fission product noble gases<br />

(primarily xenon and krypton). The gaseous radwaste system also removes <strong>radioactive</strong><br />

particulates and iodine from the off-gas stream, and recombines radiolytic hydrogen and<br />

oxygen to form liquid water to be treated in the liquid radwaste system. Radioactive gases are<br />

then filtered and released through the plant off-gas stack. During normal operations, the<br />

gaseous radwaste system operates on a continuous basis with effective monitoring and control<br />

provided so as not to exceed the limits of 10 CFR Part 20 or the dose objectives of Appendix I<br />

to 10 CFR Part 50 (NMC 2005b).<br />

Off gas from the main condenser air ejector effluent passes through a 42-in. diameter delay line<br />

and is stored in the compressed gas'storage system near the base of the off-gas stack. Five<br />

compressed gas storage tanks, approximately 1250 ft 3 each, provide for a minimum total<br />

holdup time of approximately 50 hours at a design off-gas release rate of 28 standard cubic feet<br />

per minute (scfm). For typical off-gas rate of 10 scfm, the holdup time could be as high as<br />

140 hours. Off gases from the steam packing exhaust system, the mechanical vacuum pump<br />

effluent, and the high-pressure coolant injection (HPCI) gland seal effluent are all collected and<br />

processed in the steam packing exhauster off-gas subsystem. These gases are discharged on<br />

a continuous basis into a 1.75-minute holdup line and mixed with the air ejector off-gases at the<br />

stack base. The off-gas stack provides for mixing, dilution with fresh makeup air, monitoring,<br />

and release of the off gas to the atmosphere at an elevation of 328 ft above ground. The stack<br />

height and plume buoyancy aids in the dispersion of the gases into the atmosphere (NMC<br />

2005b).<br />

A review of the 2004 Radioactive Effluent Release Report (NMC 2005e) provided data on<br />

<strong>radioactive</strong> effluent release rates for Monticello. For calendar year 2004, releases included<br />

1371 Ci of fission and activation gases, 1.5 x 1 0- Ci of iodine-1 31, 1.2 x 10.3 Ci of particulates,<br />

and 16.2 Ci of tritium. These activities are typical of past years, and are expected during the<br />

renewal period. See Section 2.2.7 for a discussion of the theoretical doses to the maximally<br />

exposed individual as a result of these releases. Since issuance of the draft SEIS, NMC issued<br />

the effluent release report for 2005 (NMC 2006) and gaseous releases were consistent with<br />

past years.<br />

NUREG-1 437, Supplement 26 2-10 August 2006 1

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