ML20094C408

Forwards Revised Pages to SAR & New Proposed TS 4.9, Surveillance of Activity in Secondary Coolant Sys, in Response to NRC 951025 RAI

ML20094C408
Person / Time
Site:	University of Virginia
Issue date:	10/26/1995
From:	Mulder R VIRGINIA, UNIV. OF, CHARLOTTESVILLE, VA
To:	Alexander Adams NRC (Affiliation Not Assigned)
Shared Package
ML20094C410	List: ML20094C408 ML20094C412
References
TAC-M938090, NUDOCS 9511020203
Download: ML20094C408 (6)

Text

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SCH00L OF ENGINEERING @

October 26,1995 & APPLIED SCIENCE i NUCLEAR REACTOR FACILITY Mr. Alexander Adams, Jr. Department of Mechanical.

Senior Project Manager Aerospace & Nuclear Engineenng i Non power Reactors and Decommissioning university of virginia l Project Directorate Charlottesville, VA 22903-2442 l U.S. Nuclear Regulatory Commission 80M82-5440 FAX: 8%982 5473 M.S.' 0-11-B-20 1 Rockville MD 20852-2738

Subject:

Second NRC Request for Additional Information (TAC No. h1938090), relative to a proposed Amendment to the Safety Analysis Report (SAR), and also a proposed Amendment to the Technical Specifications (TS), both being requested for the University of Virginia Reactor (UVAR), Docket No. 50 62, License R-66.

Dear Afr. Adams:

In response to the NRC Request for Additional Information (RAI) of October 25,1995, we agree with NRC observations in item 1 of the RAI that sewer release time averages are to be monthly,'not yearly, concentration averages. We were aware of this fact, however, I did not catch the erroneous wording when editing our response. Accordingly, we are enclosing several replacement pages to our original submittal. We have amended the table headings and discussions in the text to reflect monthly averages for sewer releases. The conclusions reached in the SAR amendment have remained unchanged.

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With regard to item 2 of the RAI, please find in attachment a new proposed UVAR Technical l Specification (TS) 4.9 Surveillance of Activity in Secondary Coolant System. This surveillance l specification has been approved by the U.Va. Reactor Safety Committee. The new TS will  !

provide additional assurance that 10CFR20 efliuents limits will not be exceeded, that credible heat exchanger leaks will be discovered within a reasonable time frame and that a change in the surveillance and analysis frequency of secondary system water will not occur without prior NRC review and approval. The proposed TS 4.9 wording is in attachment, together with a revised page 2 of the UVAR TS Table of Contents. The pages on which wording changes were made, or new pages, are listed in a " List of Enclosures," also in attachment.

We appreciate very much the expedited review NRC is giving to U.Va.'s SAR amendment request. p me know if I can provide you with additional information. j City / County of h b e ob .

Si er ly, Commonwealth cf Wrginia 1j g I hereby certify that the attached document is a t , e and Robert . hfulde , rector exact copy of a b Ho/ . presenteel before U.Va. Reactor Facility &

Assoc. Prof. of Nuclear Eng.

me this S day of 1995 by cc: hir. Craig Basset, NRC Region II, Atlanta, Ga. , l .

Document Control Desk, NRC, Washington, DC & j t$to-fat vy PubbC hVnnm J 9511020203 951026 PDR ADOCK 05000062 My commission expires 19N P PDR

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LIST OF ENCLOSURES Please find in attachment the following revised pages:

Page 9-85 Table 9.20.3 sewer-release column heading changed from " Yearly..." to

" Monthly...".

Page 9-93 Table 9.20.5 sewer-release column heading changed from " Yearly..." to

" Monthly...". Abbreviated " Regulatory" as " Reg." in table title.

Page 9-94 Paragraph 2:

Changed " calendar year" to " calendar month";

Changed " calendar-year-average" to " calendar-month-average".

Paragraph 3:

Changed " calendar-year-average" to " time-averaged".

Page 9-95 Changed " calendar-year-averaged basis" to " time-averaged bases" Page 2 UVAR Tech. Specs. TABLE OF CONTENTS; added entry for TS 4.9 Page 37a TS 4.9; newly proposed TS wording, to become amendment No. 22 1

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Revised 10/95 TABLE 9.20.3 Water Activity Cone's Compared with Regulatory Limits Yearly-Average Monthly-Average Secondary Water Release Sewer Release Water App. B Table 2 App. B Table 3 Activity Col. 2 Limits Limits Nuclide IuCi/ml. u,1 IuCl/ml.,u,1 Ratio IuC1/ml.,1,,1 Ratio H3 5 E-6 1 E-3 0.005 1 E-2 0.0005 Na-24 1.5 E-5 5 E-5 0.300 5 E-4 0.03 Mg-27 5 E-9 -- -- -- --

Cl-38 6 E-9 -- -- -- --

Mn-54 1 E-7 3 E-5 0.003 3 E-4 0.00033 Cr-51 6 E-7 5 E-4 0.001 5 E-3 0.00012 Sb-122 5 E-8 1 E-5 0.005 1 E-4 0.0005 W-187 4 E-7 3 E-5 0.013 3 E-4 0.0013 Sum of Temporary Ratios 0.327 0.033 Because sodium-24 is the dominant and most limiting radionuclide in the primary water, an additional calculation was done by assuming no loss of sodium-24 by blowdown to show that the concentration ratio (effectively infinite in this case) is not a critical parameter in these calculations. With no loss of sodium by  !

blowdown, the equilibrium sodium concentration would increase from 1.5 E-5

[ Ci/ml.,,,] to 2.6 E-5 [ Ci/ml.,,,,]. The temporary ratio for sodium effluent would increase from 0.300 to 0.530, making the corresponding sum of temporary effluent ratios increase from 0.327 to 0.557. The temporary ratio for sodium sewerage would increase from 0.03 to 0.052, making the corresponding sum of temporary sewerage ratios increase from 0.033 to 0.055. The result remains that the postulated water releases will not violate regulatory release limits.

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Revised 10/95

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however, and the resulting A," for the other listed radionuclides are presented here in TABLE 9.20.5. Results of sum-of-ratios calculations for the water- and sewer-release sub-cases are also shown in TABLE 9.20.5.

TABLE 9.20.5 Secondary Water Activity Cone's Compared with Reg. Limits Yeariv-Average Monthly-Average Secondary EITluent Release Sewer Release Water App. B Table 2 App. B Table 3 Activity Col. 2 Limits Limits Nuclide lyCi/ml.,a,1 f uCl/ml.,,,1 Ratio f uCl/ml.,u,1 Ratio H-3 2.0 E-4 1 E-3 0.20 1 E-2 0.02 Na-24 3.8 E-3 5 E-5 76 5 E-4 7.6 Mg-27 3.3 E-6 -- -- -- --

Cl-38 3.6 E-6 -- -- -- --

Mn-54 2.0 E-5 3 E-5 0.67 3 E-4 0.07 Cr-51 1.0 E-4 5 E-4 0.20 5 E-3 0.02 Sb-122 3.3 E-7 1 E-5 0.03 1 E-4 0.003 W-187 8.3 E-6 3 E-5 0.28 3 E-4 0.028 Sum of Temporary Ratios 77 7.7 i

The sum of temporary ratios, in the case of the water-only effluent release

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pathway is significantly larger than 1. However, there is no water effluent released to the environment because it is mostly retained in the secondary coolant l

[ Note: Seconday make-up shuts down automatically due to the fast leak rate l which tends to improve (lower) the conductivity of water in the cooling tower.].

At worst, some cooling tower water could overflow to the.on-site reactor pond, i also used for liquid waste dilution. The pond dilution factor is about 750,000 gallons / 2000 gallons, or 375-to-1. Only a fraction of the entire 2000 gallons of seconday water could overflow to the pond. Natural radionuclide concentration in the pond is negligible.

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Revised 10/95 With pond-water dilution, the sum of temporary ratios for water effluent is 1

reduced to 77 / 375 = 0.21, well below the allowed calendar-year-average limit of l

1. It is concluded that with a DEGTB and a water-only effluent pathway, the calendar-year-average water effluent limit would not be exceeded. Pond water is only released periodically, subsequent to radioanalysis. In the case of this event it  ;

would most likely be possible to delay a pond release long enough to achieve significant decay of the 15-hour sodium-24. l l

The sum of temporary ratios for the sanitary sewer release is marginally greater than 1 during a short period of time (about 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />). A great volume of cooling tower water with no measurable radionuclide content is released to the sewer by blowdown during any calendar month. This will ensure that the calendar-month-average sum of ratios will be less than 1. Thus, it is concluded for this case that sewer release regulations will not be exceeded.

9.20.8.8 Conclusions The primary-to-secondary heat exchanger leak scenario involving the DEGTB analyzed above is extremely conservative. The posited 600 gph leak rate and staff discovery time of 1.2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> or less represents a hypothetical situation postulated for examination of the potential maximum consequences to the public. Calculated radionuclide concentrations for limiting air-only and water-only release cases are sufficiently low and dilution sufficiently high that time-averaged release limits are not challenged. Therefore, it is concluded that even an extremely severe (hypothetical) heat exchanger tube rupture poses no significant threat to public health and safety.

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Revised 10/95 The analysis just performed reveals that the leak rate, per se, is not a critical parameter. While radionuclide concentrations in a release depend strongly upon the primary-to-secondary leak rate, this is a temporary situation. On time-l averaged-bases, it is the total activity of each isotope released, i.e., the volume of I

i primary water lost to the environment, that is significant.

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