ML110900059

Washington State University, Response to Request for Additional Information Regarding Triga Reactor License Renewal

ML110900059
Person / Time
Site:	Washington State University
Issue date:	03/23/2011
From:	Wall D Washington State Univ
To:	Office of Nuclear Reactor Regulation, Document Control Desk
References
TAC ME1589
Download: ML110900059 (14)

Text

WASHINGTON STATE

%pUNIVERSITY Nuclear Radiation Center March 23, 2011 Document Control Desk U.S. Nuclear Regulatory Commission Washington, DC 20555-0001

Reference:

Washington State University Docket No. 50-27, License No. R-76

Subject:

Response to: WASHINGTON STATE UNIVERSITY - REQUEST FOR ADDITIONAL INFORMATION REGARDING THE WASHINGTON STATE UNIVERSITY TRIGA REACTOR LICENSE RENEWAL (TAC NO. ME1589)

Washington State University (WSU) has applied to renew operating License Number R-76 (Docket number 50-27). As part of the license renewal process, the U.S. Nuclear Regulatory Commission has submitted a Request for Additional Information (RAI) to Washington State University in a letter dated February 23, 2011. This letter provides a response to the Request for Additional Information.

I declare under penalty of perjury that to the best of my knowledge the foregoing is true and correct.

Date Executed 3

232201 Respectfully Submitted Donald Wall, Ph.D.

Director Attachments cc:

Frank DiMeglio Linh Tran kAo'Qo P.O. Box641300, Pullman, WA 99164-1 300 509-335-8641 - Fax: 509-335-4433

• www.wsu.edu/nrc

Response to Request for Additional Information dated February 23, 2011 This response provides a dose assessment for the maximally exposed individual member of the public in the unrestricted area of the Dodgen Research Facility for the Maximum Hypothetical Accident-the loss of cladding integrity of a single TRIGA fuel element in air.

In order to calculate the dose rate for an individual member of the public in an unrestricted area within the Dodgen Research Facility, the following conservative assumptions were made:

1. The barometric air pressure in Room 201 is lower than the surrounding area.

2. A five minute time period is allowed for evacuation of the Dodgen Research Facility.

3. No credit is taken for attenuation due to gamma-ray absorption by air or the door to Room 201.

4. The maximally exposed person remains stationary for five minutes immediately outside the door leading into Room 201.

5. All airborne radioactive material is approximated as a point source in the geometric center of Room 201.

6. An instantaneous loss of pool water is accompanied by the immediate failure the cladding of a single fuel rod in air.

7. A power density of 30 kW is assumed for the defective fuel rod.

8. Volatile fission product inventory was calculated for an infinite irradiation time for the defective fuel rod prior to shutdown.

Assumption Justification Assumption 1.

It is assumed that the barometric air pressure within the reactor pool room (Room 201) is lower than the air pressure in surrounding areas, thus restricting movement of airborne radioactive materials such that there is no leakage of radioactive materials from the pool room into public areas. As a result, there is no inhalation hazard in public areas or exposure due to immersion in radioactive gaseous or airborne particulate material. Maintenance of barometric pressure within Room 201 assures that, in the event of release of airborne fission products, there would be no leakage of airborne particles or gaseous effluent into the unrestricted area of the Dodgen Research Facility. As a result, radiation exposure due to beta particles in the unrestricted area is ruled out because beta particles are unable to penetrate through the concrete walls or doors leading from Room 201 into unrestricted areas. The radiation exposure rate, and concomitant dose rate is due only to penetration of gamma rays through the door and concrete wall.

Bremmstrahlung radiation is not considered in the present analysis due to the limited range of beta-particles in air and the concomitant low bremmstrahlung intensity, as well as the existence of a relatively high linear attenuation coefficient for absorption of low-energy bremmstrahlung radiation.

Assumption 2.

Building evacuation drills are conducted on a regular basis. A five minute evacuation time is conservative because building evacuations have been observed to be executed more rapidly than five minutes.

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Assumption 3 Beta particles emitted by airborne radionuclides cannot pass through the walls or door leading to Room 201.

The concrete wall separating Room 201 from the public areas of the Dodgen Research Facility provides considerable shielding due to its thickness, therefore, it was decided to calculate the radiation exposure rate in the area outside the double doors leading into Room 201, assuming no attenuation of gamma rays due to shielding by the doors. Furthermore, the attenuation by air is sufficiently small that it can be reasonably neglected-a conservative assumption.

Assumption 4 It was assumed that a member of the public (the maximally exposed individual) remains outside the door leading into Room 201 for the five minute period of evacuation. The exposure rate was calculated for a person standing at the double doors for the entire five minutes.

Assumption 5 It was assumed that all of the airborne radioactive release forms a point source in the geometric center of Room 201.

A point source in the geometric center of Room 201 was chosen as a reasonable approximation, rather than using a uniform distribution of airborne radioactive materials throughout Room 201. A point source in the geometric center of Room 201 provides greater exposure to the door under consideration than would be the case if a uniform distribution was used as the basis for the calculation.

Assumption 6 The MHA for the WSU reactor is the failure of the cladding of a single fuel rod in air. In order to be exposed to air there must be a loss of pool water based upon a hypothetical catastrophic failure of a beam port. There is no credit taken for pool drain time with regard to radioactive decay, i.e. pool drain time is assumed to be instantaneous upon shut down of the reactor. As a result, no decay corrections are used in the calculations.

Assumption 7 The power density in Core 35A (the core analyzed for the HEU to LEU conversion and in current operation) is such that the hot rod position (D4NE) produces approximately 22.5 kW of power.

Thus, assuming 30 kW for the sake of the present calculation is considerably conservative, and will encompass power densities that may accompany future core changes. A power density of 30 kW was used in the present calculations because the volatile radioactive material inventory, as presented in the WSU Safety Analysis Report of 2002, was used as a baseline.

Assumption 8 An infinite irradiation time was assumed in order to assure that radioactive isotopes of the volatile fission products, Br, Kr, I, and Xe have reached steady-state concentrations.

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Calculation of Dose Rate The dose rate was calculated using the following volatile fission products: Br-82, 83, 84, 85, 87; Kr-83m, 85m, 87, 88, 89; 1-131, 132, 133, 134, 135, 136; Xe-131m, 133m, 133, 135m, 135, 137, 138. The quantity of fission products released from the hypothetical failed fuel rod is described in Table 13.2 in the WSU Safety Analysis Report of 2002. The amount of activity released for each isotope is reproduced in the following table.

Volatile Fission Products and Quantities Isotope Activity Isotope Activity released (mCi) released (mCi)

Br-82 4.8 Kr-83m 15.7 Br-83 15.8 Kr-85m 39.6 Br-84 25.8 Kr-85 8.0 Br-85 7.0 Kr-87 71.2 Br-87 0.1 Kr-88 106 1-131 88.1 Kr-89 26 1-132 129 Xe-131m 0.8 1-133 201 Xe-133m 4.8 1-134 221 Xe133 201 1-135 186 Xe-135m 28 1-136 2.5 Xe-135 195 Xe-137 49 Xe-138 103 The gamma-rays due to the decay of each radionuclide were compiled to determine the exposure rate due to each gamma-ray.

All of the radionuclides under consideration are beta-particle emitters accompanied by a suite of gamma-rays of varying intensities (i.e. yields) and energies.

The gamma-ray energies which were chosen for the compilation all have yields greater than 1%,

relative to each beta-particle emission, i.e. no gamma-rays with yields less than 1% were used in the calculations. The 1% cutoff was chosen to assure that the highest intensity gamma-rays would be properly accounted for, while those with yields less than 1% make negligible contributions to the exposure rates.

The exposure rate was calculated with the following equation (1):

mR/hr = 6AEn 1000d 2 (1)

Where exposure is given in millir6ntgens per hour, A is the activity in millicuries, E is the energy of the gamma ray in keV, n is the number of gamma-rays emitted per decay event, and d is the distance from the source in feet. The distance from the geometric center of the room to the geometric center of the door under consideration is 20.04 feet. For gamma-rays in the present case, the exposure in millir6ntgens is approximately equal to the dose in millirads, and using a 3 of 13

relative biological effectiveness factor of 1 for conversion of millirads to millirem one obtains the dose rate in millirem per hour. The dose rate due to each gamma-ray of greater than 1%

yield for each radionuclide was calculated, and then the dose rates of all the gamma-rays were summed to determine a total dose rate. The gamma-ray energies, percent yields, and dose rates due to each gamma-ray are compiled in tables in Appendix A. The total dose rate due to the sum of all the gamma rays listed is 26 mrem/hr. Therefore, given a five minute exposure time, the dose to a person standing outside the door leading into Room 201 would be 2 mrem.

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Appendix A Gamma-ray energies, percent abundances and dose rates in millirem per hour are compiled for each gamma-ray with greater than 1% abundance. Dose rates were calculated using equation (1).

Br-82 Energy (keV) 221 554 619 698 776 828 1044 1317 1475

% abundance dose rate (mrem/hr) 2.3 3.66E-04 70.6 2.82E-02 43 1.92E-02 28 1.41E-02 83 4.64E-02 24 1.43E-02 28 2.1OE-02 27 2.56E-02 16.6 1.76E-02 total 1.87E-01 Br-83 Energy (keV) 0.009 530

% abundance 5

1.3 total dose rate (mrem/hr) 1.07E-07 1.63E-03 1.63E-03 Br-84 Energy (keV) 605 736 802 882 1877 1898 2824 3045 3235 3366 3928

% abundance 1.75 1.3 6

41.6 1.1 14.7 1.1 2.5 2

2.9 6.8 total dose rate (mrem/hr) 4.1OE-03 3.70E-03 1.86E-02 1.42E-0 1 7.99E-03 1.08E-01 1.20E-02 2.95E-02 2.50E-02 3.78E-02 1.03E-01 4.92E-01 5 of 13

Br-85 Energy (keV) % abundance 802 1.3 832 5.3 925 1.1 total dose rate (mrem/hr) 1.09E-03 4.63E-03 1.07E-03 6.79E-03 Br-87 Energy (keV) 327 345 424 434 465 604 908 947 1032 1062 1374 1419 1465 1476 1578 2005 2073 2561 3021 3941 4136 4367 4777 4956

% abundance 1.8 2.6 7.7 5.5 1

50 2.9 4.1 2.5 5.6 2.4 100 37.2 32.8 7.4 9.1 4.2 10.6 4.3 3.7 18.6 4.7 2.2 2.3 total dose rate (mrem/hr) 8.83E-06 1.35E-05 4.90E-05 3.58E-05 6.98E-06 4.53E-04 3.95E-05 5.82E-05 3.87E-05 8.92E-05 4.95E-05 2.13E-03 8.17E-04 7.26E-04 1.75E-04 2.74E-04 1.3 1E-04 4.07E-04 1.95E-04 2.19E-04 1.15E-03 3.08E-04 1.58E-04 1.71E-04 7.70E-03 Kr-83m Energy (keV) 9 13 14

% abundance 5.4 13.5 2.3 total dose rate (mremihr) 1.14E-04 4.13E-04 7.58E-05 6.04E-04 6 of 13

Kr-85m Energy (keV) % abundance dose rate (mrem/hr) 13 1.1 8.49E-05 13 2.2 1.70E-04 151 75.5 6.77E-02 304 14 2.53E-02 total 9.33E-02 Kr-87 Energy (keV) 403 674 846 1176 1740 2012 2554 2558

% abundance 48 1.8 7.25 1.1 2

2.9 8.6 4.3 total dose rate (mrem/hr) 2.32E-02 1.46E-03 7.36E-03 1.55E-03 4.18E-03 7.OOE-03 2.64E-02 1.32E-02 8.43E-02 Kr-88 Energy (keV) 28 166 196 362 835 986 1141 1179 1251 1370 1518 1530 2030 2035 2196 2232 2392

% abundance dose rate (mrem/hr) 2 8.90E-04 3.1 8.18E-03 26 8.1OE-02 2.3 1.32E-02 13 1.73E-01 1.3 2.04E-02 1.3 2.36E-02 1

1.87E-02 1.1 2.19E-02 1.5 3.27E-02 2.2 5.31E-02 11 2.68E-01 4.6 1.48E-01 3.8 1.23E-01 13 4.54E-01 3.4 1.21E-01 35 1.33E+00 total 2.89E+00 7 of 13

Kr-89 Energy (keV) 198 221 345 356 369 411 498 499 577 586 738 777 836 867 904 1108 1117 1274 1324 1473 1500 1530 1533 1694 1903 2012 2866 3140 3362 3533

% abundance 1.86 20.4 1.2 4.2 1.4 2.61 6.8 1.16 5.75 16.9 4.3 1.14 1.1 6

7.32 2.98 1.69 1.4 3.1 7

1.3 3.4 5.2 4.5 1.1 1.6 1.8 1.1 1.1 1.4 total dose rate (mrem/hr) 1.44E-03 1.76E-02 1.61E-03 5.83E-03 2.01E-03 4.18E-03 1.32E-02 2.26E-03 1.29E-02 3.86E-02 1.24E-02 3.45E-03 3.59E-03 2.03E-02 2.58E-02 1.29E-02 7.36E-03 6.96E-03 1.60E-02 4.02E-02 7.61E-03 2.03E-02 3.11E-02 2.97E-02 8.16E-03 1.26E-02 2.01E-02 1.35E-02 1.44E-02 1.93E-02 4.25E-01 8 of 13

1-131 Energy (keV) % abundance 29 1.4 30 2.6 80 284 364 637 723 2.6 6

81 7.3 1.8 total 1-132 dose rate (mrem/hr) 5.37E-04 1.03E-03 2.75E-03 2.25E-02 3.90E-01 6.15E-02 1.72E-02 4.95E-01 Energy (keV) %

262 506 523 547 621 630 651 668 670 672 727 727 728 773 780 810 812 877 955 1136 1143 1173 1291 1295 1372 1399 1443 1921 2002 abundance dose rate (mreni/hr) 1.4 7.1OE-03 5

4.90E-02 16 1.62E-01 1.3 1.38E-02 1.6 1.92E-02 13.7 1.67E-01 2.7 3.40E-02 98.7 1.28E+00 5

6.48E-02 5

6.50E-02 2.2 3.09E-02 3.2 4.50E-02 2.2 3.1OE-02 76 1.14E+00 1.2 1.81E-02 2.9 4.55E-02 5.6 8.80E-02 1.1 1.87E-02 18.1 3.34E-01 3

6.59E-02 1.4 3.1OE-02 1.1 2.50E-02 1.1 2.75E-02 2

5.01E-02 2.5 6.64E-02 7.1 1.92E-01 1.4 3.91E-02 1.2 4.46E-02 1.1 4.26E-02 total 4.19E+00 9 of 13

1-133 Energy (keV) 510 529 707 856 875 1237 1299

% abundance dose rate (mremlhr) 1.5 2.31E-02 88 1.40E+00 1.6 3.41E-02 1.2 3.1OE-02 4.6 1.21E-01 1.6 5.97E-02 2.2 8.62E-02 total 1.76E+00 1-134 Energy (keV) 30 135 235 405 433 459 489 514 541 566 595 613 628 677 731 767 847 857 884 948 975 1040 1072 1136 1456 1614 1741 1807

% abundance dose rate (mrem/hr) 1.2 1.19E-03 3.3 1.48E-02 1.7 1.32E-02 7.4 9.94E-02 4.4 6.32E-02 1.4 2.13E-02 1.6 2.59E-02 2.4 4.09E-02 8.6 1.54E-01 1.2 2.25E-02 11 2.17E-01 10.9 2.21E-01 2.3 4.79E-02 8.2 1.84E-01 2.2 5.33E-02 3.8 9.66E-02 96 2.70E+00 6.6 1.88E-01 66 1.93E+00 4

1.26E-01 4.9 1.58E-01 2

6.90E-02 14 4.98E-01 9.2 3.46E-01 3

1.45E-01 4

2.14E-01 3

1.73E-01 5.6 3.35E-01 total 8.16E+00 10 of 13

1-135 Energy (keV) 221 288 418 527 546 837 973 1039 1101 1124 1132 1260 1457 1503 1566 1678 1706 1791

% abundance dose rate (mrem/hr) 1.7 1.05E-02 3.1 2.49E-02 3.5 4.08E-02 13 1.91E-01 7.1 1.08E-01 6.7 1.56E-01 1.2 3.26E-02 7.9 2.29E-01 1.6 4.91E-02 3.6 1.13E-01 22 6.95E-01 28.6 1.01E+00 8.6 3.50E-01 1

4.19E-02 1.3 5.68E-02 9.5 4.45E-01 4.1 1.95E-01 7.7 3.85E-01 total 4.13E+00 Xe-131m Energy (keV) 29 30 34 34 164

% abundance dose rate (mrem/hr) 16 5.57E-05 29 1.04E-04 8.5 3.47E-05 1.7 6.94E-06 2

3.94E-05 total 2.41E-04 Xe-133 Energy (keV) 31 31 35 36 81

% abundance dose rate (mrem/hr) 13 1.22E-02 25 2.34E-02 7.2 7.60E-03 1.6 1.74E-03 37 9.04E-02 total 1.35E-01 11 of 13

Xe-133m Energy (keV) % abundance 29 15.9 30 30.6 34 8.6 dose rate (mrem/hr) 3.32E-04 6.61E-04 2.1 1E-04 3.67E-05 1.68E-03 2.92E-03 34 233 1.5 10 total Xe-135 Energy (keV) % abundance 31 1.3 31 2.4 250 90 608 2.9 total dose rate (mrem/hr) 1.18E-03 2.18E-03 6.58E-01 5.16E-02 7.13E-01 Xe-135m Energy (keV) 29 30 34 527

% abundance dose rate (mrem/hr) 4 4.87E-04 8

1.01E-03 2

2.86E-04 80 1.77E-01 total 1.79E-01 Xe-137 Energy (keV) 456

% abundance 30 total dose rate (mrem/hr) 1.01E-01 1.01E-01 12 of 13

Xe-138 Energy (keV) 31 31 154 242 258 396 401 434 1114 1768 1851 2005 2016 2252

% abundance dose rate (mrem/hr) 1 4.79E-04 2

9.58E-04 5.9 1.40E-02 3.5 1.31E-02 81 3.23E-01 6.3 3.85E-02 2

1.24E-02 20 1.34E-01 1.5 2.58E-02 16.7 4.56E-01 1.4 4.OOE-02 5.4 1.67E-01 12 3.74E-01 2.3 8.OOE-02 total 1.68E+00 13 of 13