U-600593, Forwards Addl Info to Satisfy Requirements of TMI Action Item II.F.1 Re Accident Monitoring Instrumentation,Per Sser 5 (NUREG-0854).Correction Factor Curves for Stack Monitors & Standby Gas Treatment Sys Sample Cooler Capacity Info Encl

Forwards Addl Info to Satisfy Requirements of TMI Action Item II.F.1 Re Accident Monitoring Instrumentation,Per Sser 5 (NUREG-0854).Correction Factor Curves for Stack Monitors & Standby Gas Treatment Sys Sample Cooler Capacity Info Encl

ML20199G158
Person / Time
Site:	Clinton
Issue date:	06/23/1986
From:	Spangenberg F ILLINOIS POWER CO.
To:	Butler W Office of Nuclear Reactor Regulation
References
RTR-NUREG-0854, RTR-NUREG-854, TASK-2.F.1, TASK-TM U-600593, NUDOCS 8606250106
Download: ML20199G158 (13)

Text

.-_.

l U- 600593 L30-86 (06 -23)-L 1A.120

'lLLINDIS POWER COMPANY lIP l CLINTON PCMER STATION. P.o. BO

! June 23, 1986 Docket No. 50-461 i

Director of Nuclear Reactor Regulation Attention: Dr. W. R. Butler, Director BWR Project Directorate No. 4 Division of BWR Licensing ,

U.S. Nuclear Regulatory Commission i Washington, DC 20555

Subject:

Clinton Power Station TMI Action Plan Item II.F.1, " Additional Information on the Accident Monitoring Instrumentation"

Dear Dr. Butler:

The Clinton Power Station (CPS) Safety Evaluation Report 4 (NUREG-0854), Supplement #5, Section 11.5.1, states that CPS has met the j requirements of TMI Action Item II.F.1, Part I and Part 2 contingent '

j upon submitting additional information. The additional information l required for TMI Action Item II.F.1, Part 1, prior to exceeding 5% power

is the time-dependent correction factor curves', with basis and ,

assumptions for the noble gas effluent monitors. The additional information required for TMI Action Plan Item II.F.1, Part 2, prior to issuance of full power license is to provide the Standby Gas Treatment ,

System (SGTS) sample cooler capacity and provisions made to collect and drain the condensed water.

Attachment 1 to this letter provides the methodology, assumptions and the post accident correction factor curves for the CPS low, mid and high-range channels of the Heating Ventilation and Air Conditioning

, (HVAC) and SGTS normal and accident range stack monitors. The post accident correction factor curves for the various channels of the4 effluent monitors are provided as a function of time (10 minutes to 10 i 4

hours) for the de3ign-basis accident at CPS. These curves are used to ,

compensate the monitors' output for the decay of noble gas radionuclides  ;

during and following an accident and are incorporated into CPS plant [

procedures.  ;

. t Attachment 2 of this letter provides the SGTS sample cooler i capacity and provisions to collect and drain the condensed. water. A thermal analysis was performed on the SGTS sample line to determine the sample cooler capacity and the frequency the manual drain should be t

! opened to drain the condensed water. The frequency and method for- i removing the condensate from the drain have been incorporated into CPS plant procedures. l 8606250106 860623 d7 DR ADOCK0500g1 i

t

_ _ . , . _ , - . _ , , , , - , . 2  %

U- 600593 L30-86(06-3 )-L 1A.120 If you should have any comments on the attached information, we would be pleased to discuss them with you.

Sincerely yours, J J N'/1 A F.A.Sangeherg Manager - Licensing and Safety LRH/kaf Attachments cc: B. L. Siegel, NRC Clinton Licensing Project Manager NRC Resident Office Regional Administrator, Region III, USNRC Illinois Department of Nuclear Safety

U-600593 L30-86( 06-23) L 1A.120 Attachment 1 METHODOLOGY / ASSUMPTIONS-AND CORRECTION FACTOR CURVES FOR THE ACCIDENT-RANGE GAS EFFLUENT MONITORS Introduction In the event of an accident at Clinton Power Station (CPS), all potential release paths would be isolated with the exception of the station Heating, Ventilation and Air Conditioning (HVAC) and Standby Gas Treatment System (SGTS) effluent stacks. The HVAC and SGTS stacks are each equipped with Normal and Accident-Range Effluent Radiation Monitors (AXM-Is) which provide noble gas detection, particulate and iodine sampling capabilities. The low-range noble gas channel of the Normal Range Effluent Radiation Monitors and the mid and high-range noble gas channels of the Accident Range Effluent Radiation Monitors are considered necessary to meet NUREG-0737, Item II.F.1(1) which specifies that noble gases be gonitored from As-Low-As-Reasonably-Achievable (ALARA) levels to 10 pCi/cc. Eberline radiation detector assemblies are utilized for the low, mid and high-range channels on these monitors.

The following is a description of the methodology / assumptions and the post accident correction factor curves used for converting the low, mid and high-range channel outputs frem these monitors into terms of the noble gas mix during and following a CPS design-basis accident. The post accident correction factor curves have been incorporated into the CPS plant procedures.

Monitoring Channels The monitoring channels which will be employed in measuring the post accident noble gas effluents from each of the effluent paths are as follows:

a. The low-range channel of the Normal Range Effluent Monitoring System, which utilizes a Beta-scintillator detector (RDA-3S).

b. The mid-range channel of the Accident Range Monitoring system (AXM-1), which utilizes a G-M tube detector in the Eberline SA-14 sampler assembly.

c. The high-range channel of the Accident Range Monitoring System (AXM-1), which utilizes a G-M tube detector in the Eberline SA-15 sampler assembly.

Monitor Response Factors Monitor response factor is defined as a number that can be used to convert the monitor response in counts per minute (cpm) to the radioactivity concentration that produced the response (radioactivity concentration per cpm). The individual channel response factors are determined from the best information available either from the vendor, Eberline, or from on-site measurements. Generic response factors for each detector assembly are used; the detector specific calibration constant is determined through CPS plant procedures.

Page 1 of 9

U-600593 L30-86(06 23)-L 1A.120 A derivation of monitor response factors for each monitor channel is as follows:

Beta-Scintillator Channel The beta-scintillator channel response factors are determined on the basis of Eberline generic calibration data as follows:

• Actual measured generic responses are used for Xe-133 and Kr-85

• Responses to other nuclides are based on the following energy dependence formula, which is based on a formula developed by Eberline by fitting the measured response to beta-emitting solid sources of various energies:

6 1.37 x 10 /B r) = 4.31 x 10 _

2 _

2 .

where:

r = response to nuclide j, [(cpm at display)/

3 (pCi/cc)]

B = weighted average (based on yield per d

disintegration) of the beta end point energies greater than 35 kev and the con-version electron energies greater than 35 kev, [MeV).

SA-14 Channel The SA-14 channel response factors are determined based on Eberline's measurements using gaseous Kr-85 and Xe-133, and measurements at the plant site using several solid radioactive sources with different energy radiation. The response versus energy data measured using solid sources is normalized using the Kr-85 gas measurement. The response to gamma energies higher than the highest measured energy (1.2528 MeV) is determined by extrapolation based on the trend indicated by measurements. The response factor to various radionuclides is then determined using their decay energy spectra and interpolation / extrapolation of the measured and normalized data.

SA-15 Channel The SA-15 channel response factors are determined based on Eberline's measurements using gaseous Kr-85 and Xe-133, and Eberline's evaluation of nominal response factors in units of cpm /(Bq-MeV/cc) based on the above two measurements. With the two nominal response factors in reasonable agreement with each other, the mean of the two values is taken as the nominal response factor.

Response factors for other nuclides are then determined assuming that the channel response is proportional to the photon energy release rate (i.e., Bq-MeV/cc).

Page 2 of 9

U-600593 L30-86 (06-23)-L 1A.120 Monitor Calibration The three monitoring channels on each of the two release points will be calibrated, per CPS plant procedures, to read out in units of pCi/cc of the total normal expected noble gas effluent mix as listed in FSAR Table 11.3-9, by use of the channel response factors for this mix. The channel response factors for this mix are determined from individual nuclide response constants as discussed in the previous section.

Post Accident Noble Gas Effluent Mix The post accident noble gas effluent mix is determined based on the assumptions of NUREG-0737. Essentially, the equilibrium noble gas mix in the core is the same as the time-zero effluent mix, since no holdup in the secondary containment is assumed. Radioactive decay of nuclides I

is used to determine the composition of the mix as a function of time.

In addition, the noble gas daughters of halogens are assumed present or absent as judged appropriate for conservatism.

Correction Factors l

Correction factor is defined as the number with which the monitor j reading shnuld be multiplied to obtain the actual noble gas release rate.

The basic monitoring channel output is counts per minute (cpm). The monitor will display it in terms of the pCi/cc of the normal effluent mix because of the use of the response factor for this mix as discussed in the Monitor Calibration Section. If instead the channel response factor for the post accident mix was used, the monitor would display its response in terms of the post accident mix concentration. The ratio of the channel response factor (radioactivity concentration per cpm) for post accident mix divided by that for the normal effluent mix thus provides the needed correction factor. It is calculated as a function of time because of the change of post accident effluent mix with time due to radionuclide decay.

Two sets of correction factors are determined; one to provide the results in terms of actual pCi/cc of the post accident effluent mix and the other to provide the results in terms of the Xe-133 equivalent of the post accident effluent mix. The Xe-133 equivalency is determined based on the photon energy release rate.

Figures A-1 through A-3 and B-1 through B-3 provide the calculated correction factors for the three monitoring channels: set A for units of actual pCi/cc and set B for units of Xe-133 equivalent pCi/cc. These correction factors are applied to the channel readings in post accident conditions per CPS plant procedures.

Page 3 of 9 9

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Page 4 of 9

O FIGURE A-2 Correction Factor for Use Noble With the GasMid-Range Effluent Radiation SA-14 Channel Monitor For Post Accident 103 f

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Page 5 of 9

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Page 6 of 9

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Page 8 of 9

FIGURE B-3 Correction Factor for Noble Gas Effluent Radiation Monitor For Post Accident Use With the High-Range SA-15 Channel 30 O

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Page 9 of 9 l -- _ - _ _

- - U-600593 L30-86( 06 23)-L 1A.120 Attachment 2 STANDBY GAS TREATMENT SAMPLE COOLER CAPACITY The Standby Gas Treatment System (SGTS) High Range Radiation Monitors (Eberline AXM-l's) draw effluent samples from the SGTS vent stack. The SGTS sample flows through (1) the grab sample pallet (GSP) for particulate / iodine sampling, (2) then the bulk filter assembly (BFA) to remove particulates & iodines from the sample in preparation for noble gas measurement, (3) then through a sample cooler to reduce the sample temperature below the maximum limit of noble gas pallet (NGP) and finally (4) through the NGP for noble gas measurement prior to the exhaust line returning to the stack.

The SGTS system sample cooler is a model FNB-6133 designed and fabricated by Sentry Equipment Corporation. The cooler is a tube in shell design with sample flowing through the tube side and cooling water in the shell side. With a sample inlet temperature of 180*F (maximum expected) @ 5 to 6 liters per minute flow rate and a cooling water temperature of 105'F (maximum expected) @ 20 gallons per minute flow rate the maximum sample cooler ouclet temperature (sample side) is

120*F. Furthermore the vertical sample tubing section downstream of the sample cooler is of such a length (approximately 12 feet) that the sample will cool to approximately ambient conditions prior to reaching the NGP. Based on the above, the sample cooler and associated system design.is adequate to maintain the sample temperature at the inlet of the NGP within its maximum operating temperature limit of 120*F.

A thermal analysis (heat transfer analysis) has been performed to determine the rate of sample condensation in the sample line between the sample cooler and the NGP. The thermal analysis used a sample dewpoint temperature that represented the maximum secondary containment temperature and moisture conditions during normal operation that would~

be the initial conditions at the start of a LOCA (temperatures may increase but the moisture content of the sample would remain the same).

The thermal analysis was based on a sample cooler inlet temperature (sample side) of 180*F (maximum expected) and sample cooler outlet temperatures (sample side) of 120*F and 105'F. Condensation rates were calculated for two ambient temperatures of 65*F and 104*F (mild environment temperature range) for each condition of sample cooler outlet temperature. The thermal analysis also assumed that all sample condensation will form in the cooler or sample line immediately downstream of the sample cooler, which was subsequently proven by l thermal analysis to be a valid assumption.

s The results of the thermal analysis indicate that for the worst case ambient condition of 65'F and the maximum sample dewpoint (100.5'F) for valid accident cases, the maximum condensation rate in the sample 8

cooler and sample line downstream of the cooler is 11 cm /hr. The condensation rate is the same for sample cooler outlet temperatures of 120*F and 105"F. To collect this condensation, a manual drain with a i liquid capacity of 178 cm3 was added to the sample line immediately I

downstream of the sample cooler. The physical sample tubing arrangement is such that all condensation will collect in the manual drain.

1 Page 1 of 2 l

• • '* U-600593 L30-86 ( 06- 23)_ L Based on the drain capacity and the maximum sample condensation rate calculated, the liquid in the drain would reach its maximum fill capacity after a period of 16 hours1.851852e-4 days <br />0.00444 hours <br />2.645503e-5 weeks <br />6.088e-6 months <br />. To prevent the potential of stopping system gas sample flow, the requirement of emptying the drain after an accident has been incorpcrated in the CPS plant procedures.

Based on the. discussion above, the SGTS sample line thermal analysis, the current system design (condensate drains) and the CPS plant operating procedures, the SGTS sample cooler has an adequate cooling capacity and the system has provisions to collect and drain gas sample condensation.

Page 2 of 2

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