ML20245L529

Summarizes NRR Insp of Noble Gas Monitors at Plant on 890412,to Obtain Understanding of Monitor Sys Improvement

ML20245L529
Person / Time
Site:	Callaway
Issue date:	05/03/1989
From:	Alexion T Office of Nuclear Reactor Regulation
To:	Hannon J Office of Nuclear Reactor Regulation
References
NUDOCS 8905080066
Download: ML20245L529 (4)

Text

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May 3, 1989 s

rtEMORANDUM FOR: John N. Hannon, Director DISTRIBUTION:

Project Directorate III-3 ["pocketfiles NRC & Local PDRs Division of Reactor Projects - III, JSniezek" ' PDIII-3 r/f IV, V and Special Projects JHannon TAlexion 0GC EJordan FROM: Thomas W. Alexion, Project Manager Bhimes ACRS(10)

Project Directorate III-3 JClifford LCunningham Division of Reactor Projects - III, WSnell, RIII CGill, RIII IV, V and Special Projects

SUBJECT:

SUMMAP.Y OF NRR INSPECTION OF NOBLE GAS MONITORING AT CALLAWAY On April 12, 1989, JohnMinns(PRPB)andIconductedanNRRinspectionofthe noble gas effluent monitors at Callaway. The purpose of the inspection was for NRR.to obtain a better understanding of the monitors in order to respond to Region III concerns regarding their location and the lack of technical specifications (TS). Representatives from Union Electric Company (UE), the licensee, included Dave Shafer (Supervising Engineer Licensing), Neal Slaten (Supervising Engineer) and Brian Holderness (Health Physicist).

We. Observed the location of the 4 stationary secondary noble gas monitors.

They are Geiger-Mueller tube detector assemblies (General Atomics Model Number RD-12).. They are on the auxiliary building roof and they sit between the i

safety valve exhaust stacks at the base of those stacks. However, the licensee indicated that they are shielded and collimated to detect the plume from the secondary power operated relief valve (PORV) stacks, which are about 10 to 15 '

feet from the 4 monitors. There are 4 secondary PORV stacks (with silencers) and 40 safety valve exhaust stacks.

i We also obcerved the portable monitor and identified the type (ionization chamber), manufacturer (EberlineModelNumbersR0-2andR0-2A),andcapabilities (0 to 5 R/hr and 0 to 50 R/hr). We also observed the location where the l t portable monitor reading would be taken (in the event the secondary PORV i<

blocked). The location:is l' foot from the containment building on the main steam line. The E0RV tee-offs are downstream from the portable monitor locations, the safety valve tee-off_s tre downstream from the PORV's, and th'e MSIV's are downstream from the safety valves. The steam tunnel appears adequate for taking readings with the portable monitor with regard to lighting and room

. configuration. The licensee stated that physical environment of the room (temperature, radiation) would be evaluated by the appropriate emergency personnel for the specific accident irvolved and by the portable monitor l operator as the steam tunnel is approached. The portable monitor has no hook j, up capability for a recorder.

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John N. Hannon -2 The licensee stated that in the event a reading with the portable monitor is needed, the TSC would call the OSC. The OSC would identify the monitor to be used and dispatch two HP technicians to the steam tunnel to take a reading (during backshift there are at least one HP foreman, two HP technicians, and two radiation technicians available). The HP technicians would then take the reading and relay the information back via portable radio or the nearest gaitronics device (about 50-100 feet away). The licensee estimated that the worst case time between a request for a reading and an actual reading being taken and communicated would be about 5 minutes.

The licensee provided us with sample calculations from a hypothetical portable monitor reading. A reading of 500 mrem / hour with one safety valve open (4,816 cfm) on the main steam line (with a conversion factor of 18.0 which also corrects for low energy gamma attenuation) results in a release rate of 4.34 E7 microcuries/second. This release rate is converted into a whole-body dose of 0.14 rem and 'a thyroid dose of 0.87 rem at the exclusion area boundary when consideration for stability class C meteorological conditions (factor of 3.2),

wind speed (2.5 meters /second), and a steam-generator-tube-rupture. accident conversion factor of 1.3E-9 are factored in. By a similar process, the licensee back-calculated that a whole-body dose of I rem (over 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />) at the exclusion area bounoary would result in a portable monitor reading of 1,600 mrem / hour (assuming stability class D meteorological conditions).

We also observed the lab where the portable monitors are calibrated. They are calibrated every 6 months in a calibration chamber with a known radioactive source. The licensee also stated that the portable monitors are a very common and widely used monitor at the plant.

Additionally, the following questions were answered during the course of the inspection and during discussions with the licensee:

Q1 - Under what conditions would a portable monitor be used?

Al If there was a SGTR event and the secondary PORV in the affected icop was blocked, then the portable monitor would be used, l Also, the T5 will limit the amount t,f time a secondary PORV can be blocked, threby minimizing the likelihood of portable monitoruse(applicationunderreview). ,

Q2 - Should the portable monitor be placed in a collimated, shielded assembly?

A2 -

No. The reading is taken right on the main steam line at point-blank range. Any background or other radiation will only make the monitor reading more conservative.

Q3 - Does the portable monitor require a special calibration program?

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John N. Hannon 1 A3 -

No. The current calibration program calibrates up to the upper j range of the monitor, and it is therefore acceptable. l J

Q4 -

Can the portable instrument and its operator survive the environment? l

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A4 -

The technician will monitor the radiation levels and observe J other factors (heat, humidity) as the steam tunnel is approached. Also, the R0-2A monitor can read (and therefore ~

operate) in a 50 rem / hour radiation field.

QS -

If a PORV is blocked and the steam tunnel environment is unacceptable, what will be done?

A5 - A steam enclosure space contact reading can be taken (on the outside wall) and this contingency is provided for in the calculation worksheet. Also, field data will be available

• to support the necessary dose calculations.

Q6 -

What correction factors are provided for the portable monitor as a function of time after shutdown?

A6 -

None. The detector response is not energy dependent and the radionuclidespectrumdoesnotchangeduringtheshort(2 hour2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />) accident duration assumed in the FSAR.

Q7 - Is adequate training provided for the portable monitor use?

A7 - Yes, this is included in emergency training. Also, this is a very common instrument.

Q8 - Why is the primary monitoring not done on the steam line?

A8 - The current arrangement more directly detects what is arteally

released to the environment and it does not have to account j for low energy gamma attenuation.

QS - Are these monitors being propoly controlled by plant addnistrative '

l procedures?

A9 - Yes. The primary monitor is calibrated every 18 months and if it fails there is a loss-of-count alarm. Thebackup(portable) monitor is calibrated every 6 months and has a functional tett at each use.

Q10 - What is the primary monitor calibration technique?

l A10 - A calibrated source is taken up to the monitor.

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John N. Hannon J Are representative measurements assured with the primary

- l Q11 monitor?

!- All - Yes. At most there is a 1% attenuation by air and negligible attenuation by steam. l l

Q12 - Does the primary monitor have the capability to obtain readings ,

during and following an accident? j A12 - Yes. Also, the RM-11 and RM-23 display monitors display the  !

I data in the control room.

! Q13 - Do release rates for the primary monitor consider radionuclides 1 l spectrum distribution as a function of time after shutdown?  ;

l i A13 - No. The primary monitor (Geiger-Mueller tube) response is )

not energy dependent and the licensee does not assume that the l spectrum changes in 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> ( in accordance with FSAR Chapter 15 i analyses). If the accident progressed beyond 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />, the {

i licensee indicated they would consider spectrum changes if  :

l necessary.

At the end of the inspection, we thanked the licensee for their time and effort 3 l provided on our behalf, and told them that all of our questions (at this time) {

l have been answered and that our understanding of their monitoring system was i significantly improved. We also informed them that the NRC will be evaluating j their noble gas monitoring system for adequacy. l

/s/

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Thomas W. Alexion, Project Manager I

Project Directorate III-3 l Division of Reactor Projects - III, j IV, V and Special Projects j l

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• SEE PREVIOUS CONCURRENCE Office: LA/PDIII-3 PM/fDi PRPB PRPB PD/P III-3 Surname: PKr utzer T lex!o- t *JMinns *TEssig J nnon Date: r; s /89 / 2 /89 04/24/89 04/25/89 /)/89

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