ML18291A913
| ML18291A913 | |
| Person / Time | |
|---|---|
| Site: | Ohio State University |
| Issue date: | 10/16/2018 |
| From: | Kauffman A Ohio State University |
| To: | Xiaosong Yin Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| Download: ML18291A913 (6) | |
Text
16-0ctober-2018 U.S. Nuclear Regulatory Commission Document Control Desk Attn: Xiaosong Yin One White Flint North 11555 Rockville Pike Rockville MD 20852-2738
Subject:
Additional information to support a Technical Specifications amendment request for The Ohio State University Research Reactor (OSURR, License R-75, Docket 50-150)
Per a letter from the NRC dated October 3, 2018, more information was requested to support a requested change to the OSURR Technical Specifications, which was sent in a letter date August 27, 2018. (ADAMS Accession No. ML18242A075). In response to this request, we have identified the calculations in the OSURR safety analysis report (SAR) that make use of the assumed 1000 cfm volumetric flow of the exhaust fan.
There are two sections that make use of this flow rate: Section 6.3, which presents calculations to estimate Ar-41 concentrations during normal operations, and Section 8.4.4, which presents calculations to estimate releases of fission-fragment gases for a hypothetical damaged fuel plate scenario. This response describes additional information planned to.be added to those sections to show that removal of a requirement for exhaust fan volumetric flow rate will not impact safe operations.
The following changes are planned for Section 6.3 of the OSURR SAR, which analyzes the Ar-41 concentrations during normal operations:
- 1) On page 130, the first paragraph of Section 6.3.3 introduces the use of 1000 cfm as the nominal volumetric flow rate to be used for calculations. The following text will be added to this paragraph:
- a. Note that while a value of 1000 cfm is used as the nominal volumetric flow rate for calculations, calculations have also been performed for 500 cfm and 1500 cfm, and select results will be included to demonstrate that the exact flow rate does not affect safety.
- 2) On page 133, the final paragraph of Section 6.3.4.2 presents the calculated result for the building average Ar-41 concentration resulting from a puff release from the rabbit system. The following text will be added to this paragraph:
- a. Note that this result was calculated assuming a nominal volumetric flow rate of 1000 cfm. If the actual flow rate were different than this, the calculated concentration would not be different, as this methodology averages over five effective half-lives of Ar-41, in which the effective half-life takes into accbunt losses from exhaust. *
- 3) On page 133, the last paragraph of the page presents the result for the building average Ar-41 concentration resulting from a continuous release from the rabbit system. The following text will be added to this paragraph:
- a. Note that this resuit was calculated assuming a nominal volumetric flow rate of 1000 cfm. If the actual flow rate were different than this, the Ar-41 concentration would vary inversely with flow rate. For example, a volumetric flow rate of 500 cfm would yield an estimated building Ar-41 concentration of 4.62x10*6 µCi/ml, which is 54% above the DAC limit, limiting rabbit blower operation to 1298 hrs per year. This is still significantly greater than actual intended use of the rabbit. Conversely, a volumetric flow rate of 1500 cfm would yield an estimated concentration of 2.46x10*6 µCi/ml, which is below the DAC limit .
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- 4) On page 135, the final paragraph of Section 6.3.4.3 presents the calculated result for operation time of the rabbit to reach a building Ar-41 concentration equal to the DAC limit. The following text will be added to this paragraph: .
- a. Note that this result was calculated assuming a nominal volumetric flow rate of 1000 cfm. If the actual flow rate were different than this, the calculated time would vary as a function of flow rate. For example, a volumetric flow rate of 500 cfm would yield an estimated time of 1.6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> to reach the Ar-41 DAC limit, which is still much greater than the typical rabbit irradiation of 20 minutes or less. Conversely, there would be no time limit corresponding to a volumetric flow rate of 1500 cfm.
- 5) On page 135, the first two paragraphs of Section 6.3.4.5 reference and discuss the calculated results for puff releases from other experimental facilities, which are shown in Tables 6.5 and 6.6. \
The following text will be added to the second paragraph of this section:
- a. Note that these results were calculated assuming a nominal volumetric flow rate of 1000 cfm. If the actual flow rate were different than this, the calculated concentrations would not be different, as this methodology averages over five effective half-lives of Ar-41, in which the effective half-life takes into account activity losses from exhaust.
- 6) On page 135, the final paragraph of Section 6.3.4.5 presents calculated results for allowable number of puff releases from Beam Port 1 and the rabbit. The following text will be added to this paragraph:
- a. Note that these results were calculated assuming a nominal volumetric flow rate of 1000 cfm. If the actual flow rate were different than this, the calculated number of allowable puff releases would vary inversely with flow rate. For example, a volumetric flow rate of 500 cfm would yield an estimated 51 Beam Port 1 puff releases or 509 rabbit puff releases allowable, which are still unlikely to occur in a work year. Conversely, a volumetric flow rate
" of 1500 cfm would yield an estimated 95 Beam Port 1 puff releases or 956 rabbit puff releases allowable.
- 7) On page 138, Section 6.3.4.6 presents the calculated building concentration for continuous release of Ar-41 from the pool water. The following text will be added to the end of this section:
- a. Note that these results were calculated assuming a nominal volumetric flow rate of 1000 cfm. If the actual flow rate were different than this, the calculated concentration would vary inversely with flow rate. For example, a volumetric flow rate of 500 cfm would yield an estimated building concentration of 5.20x10*6 µCi/ml, which is 73% above the DAC limit and would limit operations to 1153 full-power hours per year. Conversely, a volumetric flow rate of 1500 cfm would yield an estimated building concentration of 2.77x10*6 µCi/ml, which is below the DAC limit. As will be discussed later, operational data indicates that these calculations are very conservative, likely because the calculation being performed does not account for the cooling system return sending a blanket of water above the core and reducing the amount of Ar-41 released from the pool.
- 8) On page 138, Section 6.3.4.7 presents calculated building concentration for continuous release of Ar-41 from the pool water and rabbit combined. The following text will be added to the end of this section:
- a. Note that these results were calculated assuming a nominal volumetric flow rate of 1000 cfm. If the actual flow rate were different than this, the calculated concentration would vary inversely with flow rate. For example, a volumetric flow rate of 500 cfm would yield an estimated building concentration of 9.82x10*6 µCi/ml, which is 3.27 times the DAC limit and would limit operations to 611 full-power hours per year. Conversely, a volumetric flow rate of 1500 cfm would yield an estimated building concentration of 5.23xl0*6 µCi/ml, which is 1.74 times the DAC limit and would limit operations to 1148 full-power hours per year. As 2
will be discussed later, operational data indicates that these calculations are very conservative, likely because the calculation performed for Ar-41 released from the pool water does not account for the cooling system return sending a blanket of water above the core and reducing the amount of Ar-41 released from the pool.
- 9) On page 140, Section 6.3.4.9 presents measured Ar-41 concentrations in the reactor bay for the first half of 1999. This will be updated with more recent data, with the following text being added at the end of the section:
- a. Data from the past decade (2008-2017) is consistent with these results. The average concentration for this period, assuming 2000-hr work years, is 6.0lxl0*8 µCi/ml, which is 2%
of the DAC. Note that this result is unaffected by the assumed 1000 cfm nominal volumetric flow rate of the exhaust fan, as the effluent monitor directly measures the Ar-41 concentration upstream of the exhaust fan.
This shows that the calculations for Ar-41 releases, particularly for pool water releases, are conservative. The average number of effective full-power hours during the period 2008-2017 was 72.6 hr. Given that this corresponds to 2% of the DAC, scaling to 2000 hrs results in only 55% of the DAC. Clearly, the estimate of full-power operations being limited to 1153 hours0.0133 days <br />0.32 hours <br />0.00191 weeks <br />4.387165e-4 months <br /> by Ar-41 releases from the pool in Section 6.3.4.6 is conservative, particularly given that some of the Ar-41 that contributed to the 2% of DAC average for 2008-2017 was from other releases, such as the rabbit.
- 10) On page 141, the first two paragraphs of Section 6.3.5.2 reference the results in Table 6.7 and 6.8 for Ar;41 releases from the restricted area resulting from puff releases from various facilities. In addition, the third paragraph of Section 6.3.5.2 presents the calculated result for the number of allowable releases from the most restrictive case, which is Beam Port 1. The following text will be added to the end of Section 6.3.5.2:
- a. Also note that the results of this section were calculated assuming a nominal volumetric flow rate of 1000 cfm. If the actual flow rate were different than this, the calculated concentration would vary as a function of flow rate. For example, a volumetric flow rate of 500 cfm would result in a reduction in the calculated Ar-41 concentration from a puff release for each of the experim~ntal facilities. Conversely, a volumetric flow rate of 1500 cfm would result in increased Ar-41 concentrations calculated for each facility, with a release from Beam Port 1 still being the most limiting. For this limiting case of Beam Port 1, calculations yield: for Table 6.7, 16.2 times the effluent concentration limit; for Table 6.8, 539 full-power hours of operation allowed in a year; and for number of Beam Port 1 releases allowed, 198 rather than 228. Even with this higher flow rate, these constraints would not be practically limiting.
- 11) On page 144, Section 6.3.5.3 presents the results of calculations for releases from the restricted area resulting from a continuous release from the rabbit blower. The following text will be added to the end of Section 6.3.5.3:
- a. Note that the results of this section were calculated assuming a nominal volumetric flow rate of 1000 cfm. If the actual flow rate were different than this, the calculated concentration would vary as a function of flow rate. For example, a volumetric flow rate of 500 cfm would result in a reduction in the calculated Ar-41 concentration to 1.08xlQ*8
µCi/ml. Conversely, a volumetric flow rate of 1500 cfm would result in an increased calculated Ar-41 release concentration of l.73x10*8 µCi/ml, which would limit operations to 5071 hours0.0587 days <br />1.409 hours <br />0.00838 weeks <br />0.00193 months <br /> per year.
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- 12) On page 144, Section 6.3.5.4 presents the results of calculations for releases from the restricted area resulting from a continuous release from the pool water. The following text will be added to the end of Section 6.3.5.3:
- a. Note that the results of this section were calculated assuming a nominal volumetric flow rate of 1000 cfm. If the actual flow rate were different than this, the calculated concentration would vary as a function of flow rate. For example, a volumetric flow rate of 500 cfm would result in a reduction in the calculated Ar-41 concentration to l.22x10-s
µCi/ml. Conversely, a volumetric flow rate of 1500 cfm would result in an increased calculated Ar-41 release concentration of l.94x10-s µCi/ml, which would limit operations to 4505 hours0.0521 days <br />1.251 hours <br />0.00745 weeks <br />0.00171 months <br /> per year.
- 13) On page 144, Section 6.3.5.5 presents the results of calculations for releases from the restricted area resulting from a continuous release from the rabbit blower and pool water combined. The following text will be added to the end of Section 6.3.5.5: .
- a. Note that the results of this section were calculated assuming a nominal volumetric flow rate of 1000 cfm. If the actual flow rate were different than this, the calculated concentration would vary as a function of flow rate. For example, a volumetric flow rate of 500 cfm would result in a reduction in the calculated Ar-41 concentration to 2.30x10-s
µCi/ml. Conversely, a volumetric flow rate of 1500 cfm would result in an increased calculated Ar-41 release concentration of 3.67x10-s µCi/ml, which would limit operations to 2386 hours0.0276 days <br />0.663 hours <br />0.00395 weeks <br />9.07873e-4 months <br /> per year.
- 14) On page 144, Section 6.3.5.6 presents released Ar-41 concentrations to the unrestricted area for the first half of 1999. This will be updated with an equation to show how the calculation was performed as well as with more recent data. The following text will replace Section 6.3.5.6:
- a. Using the effluent monitor data for 1/1/99 to 6/30/99 along with the calculation method shown in Section 6.3.5.1 and the data shown in Section 6.3.4.9 yields an Ar-41 outside air concentration of 8.87x10-11 µCi/ml (assuming that half of a calenda*r year is ~383 hours).
3 10-6 µCi 3 1 923 402 11 Ci/ml
- cts
- x ml *0.47195~*9.921x10- 3 ...::...=8.87x10-4383 hr* 3600 sec/hr 19.3 cts/sec sec m3 µ This is well below (0.9% of) the effluent concentration limit of lx10-s µCi/ml given for Ar-41 for unrestricted areas. Data from the past decade (2008-2017) is consistent with this result.
The average concentration for this period, assuming 8766-hr calendar years, is 6.42x10-11
µCi/ml, which is 0.6% of the effluent concentration limit. Note that a 1000 cfm nominal volumetric flow rate was assumed for the exhaust fan to yield this result (0.47195 m 3/s =
1000 ft 3/s). If the actual flow rate were different than this, the calculated concentration would vary as a function of flow rate. For example, a volumetric*flow rate of 500 cfm would result in a reduction in the Ar-41 concentration to 3.21x10- 11 µCi/ml, which is 0.3% of the limit. Conversely, a volumetric flow rate of 1500 cfm would result in an increased Ar-41 release concentration of 9.64x10-11 µCi/ml, which is still only 1% of the effluent concentration limit.
- 15) Section 6.3 ends with Subsection 6.3.7 on page 146 with a description of dose estimation from the calculated Ar-41 activities and a reference to Table 6.9, which lists calculated dose rates in the restricted and unrestricted areas from use of various reactor irradiation facilities. The following text will be added to the end of Section 6.3. 7:
- a. Note that the results of this section were calculated assuming a nominal volumetric flow rate of 1000 cfm. If the actual flow rate were different than this, the dose rates calculated for inside the restricted area will vary inversely with flow rate, and the dose rates 4
calculated for outside the restricted area will vary with flow rate. For example, a volumetric flow rate of 500 cfm would result in a calculated dose rate increase inside the restricted area for a continuous release from the rabbit and pool from 7.99 mrad/hr to 11.5 mrad/hr, and it would result in a calculated dose rate decrease outside the restricted area from 0.037 mrad/hr to 0.027 mrad/hr. Conversely, a volumetric flow rate of 1500 cfm would result in a calculated dose rate decrease inside the restricted area for a continuous release from the rabbit and pool from 7.99 mrad/hr to 6.12 mrad/hr, and it would result in a calculated dose rate increase outside the restricted area from 0.037 mrad/hr to 0.043 mrad/hr.
Also note that the calculated dose rates shown in Table 6.9 are conservative compared to hypothetical doses to the public estimated using the EPA code COMPLY each year for the annual report to the NRC. Over the past decade, the highest hypothetical doses to the*
public was estimated as 0.4 mrem, which occurred during the period July 2010 - June 2011.
It would only take about 21 hrs at the dose rate of 0.019 mrad/hr shown in Table 6.9 for the unrestricted area for continuous release from the pool water to reach 0.4 mrem. As the reactor has much higher utilization than this, it is clear that the calculated Ar-41 concentrations and resulting dose rates are conservative. Even if the exhaust fan volumetric flow rate was higher or lower than the nominal volumetric flow rate of 1000 cfm, hypothetical doses to the public will be far below the limit.
The following changes are planned for Section 8.4.4.5 of the OSURR SAR, which analyzes release of fission-fragment gases for a hypothetical damaged fuel plate scenario:
- 1) On page 203, Section 8.4.4.4 introduces the analysis for maximum hypothetical accident (MHA) doses from gaseous radionuclides. The following text will be added to the end of this section:
- a. For this analysis and the' results shown in the tables in the following section, a nominal volumetric flow rate of 1000 cfm has been assumed. However, calculations have also been performed for 500 cfm and 1500 cfm, and select re~ults will be included to demonstrate that the exact flow rate does not impact safety.
- 2) On page 204, the paragraph starting with the words "Results for the isotopes in question ... "
references calculation results in Tables 8.11 and 8.12 for doses in the building assuming an infinite cloud of gamma emitters, for the exhaust fan turned off and for the exhaust fan operating with a 1000 cfm volumetric flow rate. The following textwill be added to the end of this paragraph:
- a. The results in Table 8.12 were calculated assuming a nominal volumetric flow rate of 1000 cfm. If the flow rate were to be lower than this, the results would fall between those in Tables 8.11 and 8.12, and if the flow rate were to be higher than this, the calculated doses would be lower than those shown in Table 8.12.
- 3) On page 208, the paragraph starting with "If we take a Taylor expansion of ... " references calculation results in Tables 8.14 and 8.15 for doses in th*e building assuming a finite cloud of gamma emitters, for the exhaust fan turned off and for the exhaust fan operating with a 1000 cfm volumetric flow rate. The following text will be added to the end of this paragraph:
- a. The results in Table 8.15 were calculated assuming a nominal volumetric flow rate of 1000 cfm. If the flow rate were to be lower than this, the results would fall between those in Table 8.14 and 8.15, and if the flow rate were to be higher than this, the calculated doses would be lower than those shown in Table 8.15.
- 4) On page 212, the paragraph that starts with "Tables 8.16 and 8.17 show ... " references calculation results in those two tables for submersion doses outside of the restricted area, for the exhaust fan 5
turned off and for the exhaust fan operating with a 1000 cfm volumetric flow rate. The following text will be added to the end of this paragraph:
- a. Note that the results in Table 8.17 were calculated assuming a nominal volumetric flow rate of 1000 cfm. If the actual flow rate were different than this, the calculated doses would vary as a function of flow rate. For example, a volumetric flow rate of 500 cfm yields an estimated dose from all analyzed nuclides after 720 hours0.00833 days <br />0.2 hours <br />0.00119 weeks <br />2.7396e-4 months <br /> of 12.8 mrem, versus the estimated dose of 15.4 mrem from 1000 cfm. Conversely, a volumetric flow rate of 1500 cfm yields an estimated dose from all analyzed nuclides after 720 hours0.00833 days <br />0.2 hours <br />0.00119 weeks <br />2.7396e-4 months <br /> of 16.7 mrem.
- 5) On page 212, the paragraph that starts with "Tables 8.18 and 8.19 show ... " references calculation results in those two tables for direct doses outside of the restricted area, for the exhaust fan turned off and for the exhaust fan operating with a 1000 cfm volumetric flow rate. The following text will be added to the end of this paragraph:
- a. Note that the results in Table 8.19 were calculated assuming a nominal volumetric flow rate of 1000 cfm. If the actual flow rate were different than this, the calculated doses would vary inversely with flow rate. For example, a volumetric flow rate of 500 cfm yields an estimated cumulative dose after 720 hours0.00833 days <br />0.2 hours <br />0.00119 weeks <br />2.7396e-4 months <br /> from all analyzed nuclides of 106.0 mrem, versus the estimated dose of 63.9 mrem from 1000 cfm. Conversely, a volumetric flow rate of 1500 cfm yields an estimated cumulative dose after 720 hours0.00833 days <br />0.2 hours <br />0.00119 weeks <br />2.7396e-4 months <br /> from all analyzed nuclides of 46.0 mrem. All of these are significantly lower than the calculated dose for the fan turned off.
- 6) The last three paragraphs on page 219 reference and discuss calculation results 'tor doses at the controlled-area boundary. The following text will be added after these paragraphs:
- a. Note that the maximum dose calculated at the controlled-area boundary assumes that the exhaust fan has been shut off, so exhaust fan volumetric flow rate is irrelevant to these results. If the exhaust fan were to be running at any speed, the maximum dose at the controlled-area boundary would be lower, as the drop in direct dose from radioisotopes in the building would be reduced significantly more than the increase in submersion dose from exhausted radioisotopes.
The proposed changes above show that elimination of the phrase "a capacity of at least 1000 cubic feet per minute" regarding the exhaust fan volumetric flow rate will not affect safety of the reactor facility or the public for either normal or emergency operations. If you have any questions on this matter, please contact me at kauffman.9@osu.edu or at 614-688-8220.
I declare under penalty of perjury that the foregoing is true and correct.
Executed on 16-0ctober-2018.
Sincerely, Andrew Kauffman Sr. Assoc. Director, OSU Nuclear Reactor Laboratory 1298 Kinnear Rd Columbus, OH 43212 6