ML073240523
| ML073240523 | |
| Person / Time | |
|---|---|
| Site: | University of Missouri-Rolla |
| Issue date: | 11/16/2007 |
| From: | Bonzer W Univ of Missouri - Rolla |
| To: | Janice Nguyen NRC/NRR/ADRO/DPR |
| References | |
| Download: ML073240523 (8) | |
Text
>.Lar R -a~ctr- Fz i Pho 5c .3;~4-1-23 Fr" 1J7 4, 7j UNIVERSITY OF MISSOURI-ROLLA November 16, 2007
'US Nuclear Regulatory Commission Mr. John T,. Nguyen Mail Stop: 012-G15 Washington; D.C. 20555-000,1
Subject:
Response, to request for additional information regarding the University of Missouri-Rolla Reactor Facility, Novemberl 6, 2007. License R-79; Docket no.
50-123.
Mr. John Hguyen:.
The attachment with this letter addresses the enivironmental information you requested to, be submitted to the Nuclear Regulatory Commission by November 16, 2007.
I declare under*enalty of perjury that the foregoing isltrue and correct.
Executed on Sincerely, V
William Bonzer UMRR Manager Cc: Peter Kohut
Enclosure:
Response to RequestTor Additional Information University of Missouri-Rolla Reactor Facility License R-79, Docket No. 50-123) November 16; 2007
Response to Request for Additional Information University of Missouri-Rolla Reactor Facility License R-79, Docket No. 50-123 November 16, 2007 The following addresses radioactive airborne effluent releases at the University of Missouri-Rolla Reactor (UMRR) Facility for restricted and unrestricted areas.
Occupational Derived Air Concentration (DAC) Compliance:
10CFR20 Appendix B, Table 1, Column 3 establishes the Occupational Values for Ar-41 Derived Air Concentration (DAC) quantities at 3.00E-06 gCi/mL. This DAC assumes the reactor is operating at full power 40 hours4.62963e-4 days <br />0.0111 hours <br />6.613757e-5 weeks <br />1.522e-5 months <br /> a week, 52 weeks a year.
The highest sample concentration value was calculated to be 4.OOE-06 jiCi/ml. This value was found by taking a total of six air grab samples 6 inches above the reactor pool near the bridge.
The first 3 grab samples were taken at 180 kW, without HVAC operation, and the second 3 were taken at 100 kW also without HVAC operation. These samples were graphed and a linear trend line was found. From this trend line the value of the Ar-41 concentration at 200 kW without HVAC operation was found. It is important to note, however, that this figure is assuming the reactor operates at full power (200 kW), 40 hours4.62963e-4 days <br />0.0111 hours <br />6.613757e-5 weeks <br />1.522e-5 months <br /> a week, 52 weeks a year, when in fact the reactor is in operation for only a very small fraction of this time. Therefore, the actual DAC for the UMR Reactor would be much less than the occupational limit.
Table 1: Occupation Derived Air Concentration (DAC) Compliance Data Ar-41 Analysis without HVAC operation Reactor Power @100 kW: Reactor Power @180 kW:
Ar-41 Cone. ([tCi/mL) Ar-41 Conc. (gCi/mL) 1.24E-06 3.52E-06 1.73E-06 3.91E-06 2.54E-06 4.22E-06 Avg. Ar-41 Conc. (J.tCi/mL) Avg. Ar-41 Conc. (pgCi/mL) 1.84E-06 3.88E-06
_________ I__ I _________
From Figure 1 the approximate Ar-41 concentration found at 200 kW without HVAC operation is 4.OOE-06 gCi/mL.
Response to Request for Additional Information University of Missouri-Rolla Reactor Facility License R-79, Docket No. 50-123 November 16, 2007 Ar-41 Concentration 7.OOE-06 6.OOE-06 5.00E-06 E y = 2E-08x r* 4.00E-06 R2= 0.9623 4 Ar-41 Conc.
3.OOE-06 0
Cu
- Linear (Ar-41 Conc.)
O O 2.OOE-06 1.OOE-06 0.OOE+00 0 50 100 150 200 250 Reactor Power (kW)
Figure 1: Ar-41 concentration found at 100 kW and 180 kW without HVAC operation From April 2006 to March 2007 the reactor was operated for a total of 18.7 MW-hours for the year (number taken from 2006-2007 UMRR progress report). If the reactor operates at full power, forty. hours per week, then the reactor operates for 416 MW-hours. By dividing the number of MW-hours actually operated by the number of MW-hrs if the :reactor were at 200 kW for 2080 hours0.0241 days <br />0.578 hours <br />0.00344 weeks <br />7.9144e-4 months <br /> per year, would decrease the concentration by a factor of 0.04495, thus decreasing the Ar-41 concentration to well below the 10CFR20 Appendix B limit as shown below.
4.OOE-06
- 0.04495 = 1.80E-07 gCi/mI The Occupational Derived Air Concentration (DAC) Compliance statement demonstrates the Ar-41 concentration in the reactor bay, a restricted area, without HVAC operation is 1.80E-07 pCi/ml, which is well below the 10CFR20 Appendix B, Table 1, Column 3 Occupational Values for Ar-41 Derived Air Concentration (DAC) quantities of 3.OOE-06 PCi/mI.
Table 2 shows historical data of Ar-41 concentration in the reactor bay with HVAC operation.
Response to Request for Additional Information University of Missouri-Rolla Reactor Facility License R-79, Docket No. 50-123 November 16, 2007 Table 2: Ar-41 Concentration in reactor over the past 10 years Ar-41 Conc. *Dilution Actual Conc.
Year (uCVmL) Factor (uCVmL) 1997 1.14E-06 0.0163 1.86E-08 1998 1.50E-06 0.0244 3.66E-08 1999 6.29E-06 0.0176 1.11E-07 2000 2.78E-06 0.0147 4.09E-08 2001 2.41 E-06 0.0092 2.22E-08 2002 3.94E-06 0.0309 1.22E-07 2003 3.13E-06 0.0809 2.53E-07 2004 7.63E-06 0.0730 5.57E-07 2005 1.09E-06 0.0981 1.07E-07 2006 1..85E-06 0.0448 8.29E-08 2007 4.11 E-06
- Thedilution factor is found by dividing the actual MW-hrs the reactor operated by the total MW-hrs the reactor would operate if it operated 40 hours4.62963e-4 days <br />0.0111 hours <br />6.613757e-5 weeks <br />1.522e-5 months <br /> per Week, 52 weeks per year UMRR requests Section 14.3.5 Ventilation System be removed from the Technical Specifications. HVAC operation at full power is not needed to maintain radioactive airborne material concentrations of Ar-41 below 10CFR20 Appendix B, Table 1, Column 3 Occupational Values.
Reactor Fan Release Compliance:
10CFR20.1302b(21) states the annual average concentrations of gaseous radioactive material shall not exceed the vales in Appendix B, Table 2 of 10CFR20. For an unrestricted. area, Appendix B, Table 2, Column 1 of 10CFR20 states a constraint for Ar-41 airborne releases of 1.OOE-08 jtCi/ml which corresponds to an annual dose limit of 50 mrem to a member of the general public, if the constraint concentration is released for the entire year.
The average Ar-41 concentration in unrestricted areas will be verified to be below the constraints. To verify this, the method used will use the highest concentration measured over the past 10 years from the reactor roof fan exhaust (Table 3) since the fan exhaust is released to the general public. 2002 had the highest concentration at 1.24E-06 gCi/ml. The method will calculate the worst case. concentration based on a 40 hour/week reactor operations, and then calculate the concentration due to the actual operating history.
The following assumptions were made to calculate the average Ar-41 ground level concentration:
" reactor operates 40 hours4.62963e-4 days <br />0.0111 hours <br />6.613757e-5 weeks <br />1.522e-5 months <br /> per week 52 weeks per' year (2080 operating hours/year = Top)
- all reactor operations are at full power
" Ar-41 is always at a maximum of 1.24E-06 gLCi/ml (CAr-41)
Response to Request for Additional Information University of Missouri-Rolla Reactor Facility License R-79, Docket No. 50-123 November 16, 2007
" the unit-less correctionfactor (Cf) 4.66E-02 which is based on the dilution factor (D.), taken from SAR Section 11.2.3.1 and the volumetric flow rate of fan #2
- 1.24E-06 gCi/ml is discharged from the fans Ar-41(gCi/ml) = Cf_ Csr-41_L 8760hrs/yi Ar-41(gCi/ml) = (1.24E-06 KCi/ml) x (4.66E-02) x (2080 operating hours/yr) = 1.37E-08 RCi/ml (8760 hr/yr)
The data from the 2002-2003 UMRR progress report states the reactor operated for only 12.86 MW-hrs during the time between April 2002 - March 2003. This figure will be used for future calculations. The concentration can be shown to be below the NRC constraints by adjusting for the-actual operating time.
(1.37E-08 LCi/ml) x (12.86 MW-hrs) =4.24E-10 gCi/ml (0.2 MW) x (2080 hrs)
Average Annual Ground Level Concentration: 4.24E-10pgCi/ml NRC Constraint for Ar-41 (10CFR20 Appendix B, Table 2, Column 1): 1.00E-08 gCi/ml NRC Regulatory Guide 4.20 Limit (20% of 1.0 x 10-8 gCi/ml): 2.OOE-09 gCi/ml.
The NRC limit for Ar-41 (10CFR20 Appendix B, Table 2, Column 1) is 1.OOE-08 gCi/ml, which is equivalent to 50 mrem per year. This is stated in 10CFR20 under Appendix B part
- 20. The dose corresponding to this concentration is:
4.24E-10 gCi/ml
- 50 mrem = 2.12 mrem 1.OOE-08 ptCi/ml In 10CFR20 under 20.1101(d) it states that "an individual member of the public likely to receive the highest dose will not be expected to receive a total effective dose equivalent in excess of 10 mrem per year from these emissions."
Therefore, the Ar-41 concentration is in compliance with NRC Regulations.
Response to Request for Additional Information University of Missouri-Rolla Reactor Facility License R-79, Docket No. 50-123 November 16, 2007 Table 3: Reactor Fan Release Compliance Data:
Year Ar-41 Concentration (uCi/mL) 1997 9.45E-07 1998 8.05E-07 1999 1.27E-07 2000 3.32E-07 2001 O.OOE+00 2002 1.24E-06 2003 4.76E-07 2004 4.25E-07 2005 6.83E-07 2006 3.10E-07 2007 6.80E-07 Note: This data was collected from air grab samples at the fan exhaust Ar-41 Concentration Data (over 10 year period) 1.40E-06 1.20E-06 E 1.OOE-06 y = -9E-09x + 2E-05 0 R2 = 0.0065 C .08.OOE-07 Ar-41 Release Data O~O7- Linear (Ar-41 Release Data) 2 6.00E-07 o
S4.OOE 2.OOE-07 O.OOE+00 1995 2000 2005 2010 Year Figure 2: Ar-41 concentrations found by grab air samples at the fan exhaust over the past 10 years Response to Request for Additional Information University of Missouri-Rolla Reactor Facility License R-79, Docket No. 50-123 November 16, 2007 Ar-41 Releases:
Table 4 below shows the Ar-41 release over the past 10 years. These values were calculated at full power (200 kW) and based off the concentration found from an air grab sample taken at the fan exhaust on July 11, 1984 (4.57E-07 gCi/mL). The Ar-41 concentration is calculated each year by an air grab sample to verify that the concentration is similar to that found in 1984 and therefore it is still acceptable to calculate the air releases based off this concentration.
Table 4: Ar-41 release amounts in microcuries over the past 10 years, Year Ar-41 Release Amount (uCi) 1997 1.01 E+05 1998 9.16E+04 1999 6.08E+04 2000 4.52E+04 2001 4.36E+04 2002 4.87E+04 2003 7.44E+04 2004 4.66E+04 2005 1.13E+05 2006 6.18E+04 2007 9.09E+04 Note: 2007 is only through Oct.
Response to Request for Additional Information University of Missouri-Rolla Reactor Facility License R-79, Docket No. 50-123 November 16, 2007 Ar-41 Release (10 Years) 1.20E+05 1.OOE+05 y = 183.96x -297644 Z8.OOE+04 R2 = 0.0006 0
- Senesl 6.OOE+04
-Linear (Sedesl) 4.OOE+04 2.OOE+04 O.OOE+00 1995 1997 1999 2001 2003 2005 2007 2009 Year Figure 3: Graphical representation of data from Table 4 UMRR proposes to cease reactor operations requiring HVAC usage for the remainder of the calendar year when release of concentrations of gaseous radioactive material exceeds values in Appendix B, Table 2, Column 1 of 10CFR20.