ML20117M798
| ML20117M798 | |
| Person / Time | |
|---|---|
| Site: | Wolf Creek  |
| Issue date: | 09/04/1996 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML20117M788 | List: |
| References | |
| NUDOCS 9609180101 | |
| Download: ML20117M798 (5) | |
Text
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UNITED STATES 4
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,j NUCLEAR REGULATORY C,JMMISSION o
't WASHINGTON. D.C. 20565-0001 1
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION
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RELATED TO AMENDMENT NO.102 TO FACILITY OPERATING LICENSE NO. NPF-42 WOLF CREEK NUCLEAR OPERATING CORPORATION 4
WOLF CREEK GENERATING STATION i
DOCKET NO. 50-482
1.0 INTRODUCTION
By letter dated October 24, 1995, and superseded by letter dated May 16, 1996, Wolf Creek Nuclear Operating Corporation (the licensee) requested changes to the Technical Specifications (Appendix A to Facility Operating License No.
NPF-42) for the Wolf Creek Generating Station. The proposed changes would 1
i revise Technical Specification (TS) 3/4.7.6, " Control Room Emergency j
Ventilation System (CREVS);" TS 3/4.7.7, " Auxiliary Building Emergency Exhaust System;" and TS 3/4.9.13, " Fuel Building Emergency Exhaust System." The proposed TS changes pertain to the laboratory testing of the representative carbon samples taken from the charcoal adsorbers in the ventilation systems, the methyl iodide penetration limits for the test, and the output rating of the charcoal filter adsorber unit heater in the pressurization system portion of the CREVS.
2.0 EVALUATION 4
The proposed TS amendment changes the testing requirements used to determine the operability of the charcoal in the engineered safety feature (ESF) air handling units. The charcoal is provided to remove iodine from the air as it passes through the air handling units. The reduction in heater output in the pressurization system represents a change in the physical design of the plant as reflected in the Updated Final Safety Analysis Report (UFSAR). Also, Regulatory Guide (RG) 1.52, Revision 2, " Design, Testing, and Maintenance j
Criteria for Post Accident Engineered-Safety-Feature Atmosphere Cleanup System Air Filtration and Adsorption Units of Light-Water-Cooled Nuclear Power j
Plants," and military standard RDT M-16-lT are referenced in the UFSAR for the 1
testing of the charcoal filters and will require updating.
The TS Bases are j
not affected.
WCGS TS Surveillance Requirements 4.7.6.c.2, 4.7.6.d, 4.9.13.b.2, and 4.9.13.c presently specify regulatory position C.6.a of RG 1.52, Revision 2, as the requirement for the laboratory testing of the charcoal. RG 1.52 references ANSI N509-1976, " Nuclear Power Plant Air Cleaning Units and Components."
ANSI N509-1976 specifies that testing is to be performed in accordance with paragraph 4.5.3 of Military Specification RDT M 16-1T, " Gas Phase Adsorbents 9609180101 960904 PDR ADOCK 05000482 P
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l The essential elements of this test are:
70 percent relative humidity (RH) for air filtration systems designed to control the RH to 70 percent (i.e., filtration systems with heaters)
A 5 hour5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> pre-test charcoal sample equilibration at 25'C and 70 percent RH A 2 hour2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> injection of challenge gas at a test medium temperature of BO*C and 70 percent RH A 2 hour2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> post-test sweep at 25'C and 70 percent RH
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Methyl iodide penetration of les's than 1 percent The licensee proposed to change WCGS TS Surveillance Requirements 4.7.6.c.2, i
4.7.6.d, 4.9.13.b.2, and 4.9.13.c to reference ASTM D 3803-1989, " Standard Test Method for Nuclear-Grade Activated Carbon," as the requirement for the laboratory testing of the charcoal. ASTM D 3803-1989 is updated guidance based on ASTM D 3803-1979, which is updated guidance based on RDT M 16-lT.
The essential elements of the proposed TS change for testing per ASTM D 3803-1989 are:
70 percent RH A 2 hour2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> pre-test thermal stabilization at 30*C 4
A 16 hour1.851852e-4 days <br />0.00444 hours <br />2.645503e-5 weeks <br />6.088e-6 months <br /> pre-test charcoal sample equilibration at 30*C and 70 percent RH A 2 hour2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> equilibration of the sample at 30*C and 70 percent RH A 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> injection of challenge gas at a test medium temperature of 30*C and 70 percent RH A 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> post-test sweep at 30*C and 70 percent RH Methyl iodide penetration less than 2 percent The major differences between the current TS and the proposed TS change requirements for carbon testing are:
4 A test temperature of 30*C versus 25'C, 80*C, 25'C A total pre-test equilibration of 18 hours2.083333e-4 days <br />0.005 hours <br />2.97619e-5 weeks <br />6.849e-6 months <br /> versus 5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> A methyl iodide penetration of 2 percent versus 1 percent Smaller tolerances versus larger tolerances These differences will be addressed individually and will be shown to be more conservative than the present TS requirement.
As stated above, the licensee proposed to challenge the representative carbon samples at 30*C rather than 80*C.
Ir. formation Notice 86-76, " Problems Noted in Control Room Emergency Ventilation Systems," indicated that laboratory testing of charcoal at a temperature higher than that expected during the course of an accident could result in an overprediction of the capability of the charcoal to remove methyl iodine. The quantity of water retained by charcoal (carbon) is dependent on temperature.
Generally, the higher the temperature the less water retained.
The water retained by the carbon decreases the efficiency of the carbon to adsorb other contaminants. At 30*C
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1 o and 95 percent RH, carbon will retain about 40 weight percent water. At 80*C and 95 percent RH, carbon retains only about 2 to 3 weight percent water.
4 Therefore, the lower temperature test medium of the proposed TS will yield more conservative results than the present TS.
ASTM D-3803-1989 specifies a test temperature of 30'C for both the pre-and post-test sweep instead of 25'C.
There is little difference in the adsorption behavior of carbon between these two temperatures.
The 25'C parameter is more conservative.
The increase from 25'C to 30*C does not represent a significant decrease in the test results for the CREVS.
Pre-test humidity equilibration is achieved by sweeping air of the appropriate humidity through the test carbon.
The present TS reference to ANSI N509-1976 (RDT M 16-lT) requires the charcoal to be equilibrated to 25'c and 70 percent RH. The methyl iodide test medium would then be instantaneously introduced at 80*C.
Testing the charcoal with such thermal step changes is technically j
incorrect because it causes condensation on the charcoal sample.
Condensation on the charcoal sample itself (" wetting the bed") makes the test invalid.
This is supported by paragraph 12.41. of ASTM D-3803-1979, which states with respect to relative humidity of the test medium that " tests at saturation or above give very erratic results." Because of this, the ASTM D-3803-1989 standard includes a 2 hour2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> pre-test thermal-only stabilization at 30*C and specifies a temperature of 30*C for all phases of the test. Therefore, ASTM D-3803-1989 is a better test because it solves the problem of the formation of condensation on the charcoal sample.
The ASTM D-3803-1989 standard is more stringent than the RDT M 16-1T standard since it has smaller tolerances that result in mora acceptable reproducibility of the test and it requires that the carbon sample be pre-test equilibrated for a much longer duration.
The longer pre-equilibration is conservative since it will completely saturate the representative carbon sample to the condition to which the subject charcoal adtorbers are expected to be exposed during design basis conditien. During the pre-equilibration, the charcoal is exposed to a flow of air controlled at the test temperature and RH before the challenge gas is fed through the charcoal.
The purpose of the pre-equilibration phase of the test is to ensure that the charcoal has stabilized at the specified test temperature and RH for a period of time which results in the charcoal adsorbing all the available moisture before the charcoal is challenged with methyl iodide. Therefore, the measured methyl iodide removal efficiency is lower than it is if pre-equilibration is not performed. Hence, the proposed testing in accordance with ASTM D-3803-1989 standard would result in a more realistic prediction of the capability of the charcoal.
The licensee proposed a higher limit for the methyl iodide penetration through carbon samples taken from the charcoal adsorbers while still claiming an i
adsorption efficiency of 95 percent for radioiodine. Although the proposed l
2 percent penetration acceptance criterion is less conservative than the l
current 1 percent penetration, the RDT M 16-IT standard when used with a 1 l
percent penetration is less conservative than the ASTM D 3803-1989 standard when used with a 2 percent penetration because the ASTM standard is a much more stringent test. Therefore, the staff concludes that an adequate safety f
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- margin exists when the proposed ASTM D 3803-1989 standard is used to credit a charcoal filter adsorption efficiency of 95 percent for radioiodine to conform with the 10 CFR Part 100 and GDC 19 limits.
With regard to the CREVS heaters, the licensee proposed to change the output rating of the pressurization system filter adsorber unit heaters from 15 i 2 kW to 5 i 1 kW.
The heaters are designed to reduce the RH of the influent air entering the charcoal filter beds from a design ambient condition i
of 100 percent RH to s 70 percent RH.
Higher moisture content of the carbon results in lower adsorption of radiciodines. At a constant temperature the i
weight percent of water adsorbed by the carbon increases with increasing RH.
j Therefore, the heaters help ensure that the charcoal adsorbers remain j
sufficiently dry to remove radioiodine.
By letter dated May 16, 1996, the licensee submitted a revised calculation of i
the original pressurization system filter adsorber unit heater design basis j
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' calculation. This calculation documented that this system only requires i
l 3.13kW to maintain the influent air s 70 percent RH.
The calculation assumed
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a worst-case ambient condition of 97'F and 100 percent RH while taking into account the possibility of a degraded heater voltage supply. The staff j
reviewed this calculation and found it acceptable. Therefore, the staff finds that the licensee's proposed heater rating of SkW i IkW is also acceptable.
l The requested changes revise WCGS TS Surveillance Requirements 4.7.6.c.2, l
4.7.6.d, 4.9.13.b.2, and 4.9.13.c for charcoal filter laboratory testing such that existing flawed test methodology in the TS will reflect the currently utilized acceptable test methodology in accordance with industry standards.
5 The staff has evaluated this change and concludes that the testing methodology i
proposed by the licensee adequately demonstrates the operability of the air j
handling units and is therefore acceptable.
In addition, the staff has determined that the proposed heater rating of SkW i IkW is also acceptable.
3.0 CONCLUSION
The requested changes to TS 3/4.7.6, " Control Room Emergency Ventilation
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System (CREVS)," TS 3/4.7.7, " Auxiliary Building Emergency Exhaust System,"
and TS 3/4.9.13 " Fuel Building Emergency Exhaust System," revise the surveillance requirements for the charcoal filter laboratory testing. The staff has determined that using the proposed ASTM D-3803-1989 testing standard at 30*C, 70 percent RH, and a 2 percent methyl iodide penetration will result in a more realistic prediction of the capability of the charcoal.
In addition, the licensee also requested to change TS 3/4.7.6 to revise the output rating of the charcoal filter adsorber unit heater in the pressurization system portion of the CREVS. The staff has determined that the proposed heater rating of SkW i IkW will maintain the influent air s 70 percent RH even with the worst-case ambient conditions of 97'F and 100 percent RH and while taking into account a degraded heater voltage supply. Therefore, the staff concludes that the testing methodology and the heater output rating proposed by the licensee adequately demonstrate the operability of the CREVS, the auxiliary building emergency exhaust system, and the fuel building emergency exhaust system, and are acceptable.
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4.0 STATE CONSULTATION
In accordance with the Commission's regulations, the Kansas State Official was notified of the proposed issuance of the amendment.
The State official had no comments.
5.0 ENVIRONMENTAL CONSIDERATION
The amendment changes surveillance requirements.
The NRC staff has determined that the amendment involves no significant increase in the amounts, and no significant change in the types, of any effluents that may be released I
offsite, and that there is no significant increase in individual or cumulative oce.upational radiation exposure. The Commission has previously issued a proposed finding that the amendment involves no significant hazards consideration, and there has been no public comment on such finding (61 FR 28622). Accordingly, the amendment meets the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9).
Pursuant to 10 CFR 51.22(b) no environmental impact statement or environmental assessment need be prepared in connection with the issuance of the amendment.
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6.0 CONCLUSION
The Commission has concluded, based on the considerations discussed above, i
that:
(1) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, (2) such
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activities will be conducted in compliance with the Commission's regulations, and (3) the issuance of the amendment will not be inimical to the common i
defense and security or to the health and safety of the public.
Principal Contributor: John Segala l
Date:
September 4, 1996 t
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