ML19224B483

Section II Operation

ML19224B483
Person / Time
Site:	Crane
Issue date:	11/01/1976
From:	Metropolitan Edison Co
To:
References
PROC-761101, TM-0623, TM-623, NUDOCS 7906150158
Download: ML19224B483 (18)

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TMI DOCLHE'iTS T M - 4_4 M DOCUME!E NO:

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OF DOCUME 2 PROVIDED BY

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METROPOLITAN EDISON COMPANY.

41c Supervisor, Document Control, NRC l

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OPERATION

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2.1 AREA MONITORS.

2.1.1 855 Series Area Monitors.

2.1.1.1 General Description.

See Table R-1.

An 855 Series G-M Area Monitoring System includes a number of channels, each of

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which detects, indicates and initiates alarms in response to radiation.

The readout module / detector combination may be designed for HI, MED or L0 ranges of activity The HI range covers 1 mR/hr to 105 mR; the MED range 0.1 mR/hr to 104 niR/hr; the LO range 0.01 mR/hr to 103 mR/hr.

In each range the radiation indication is presented on a 5-decade log meter on the readout module front panei.

Simultaneous meter readouts may be presented at one or more field units and computer outputs. The recorder autouts are 0 to 10 mV and the computer outputs may be connected for 0-50 mV, 0-1V or 0-5V.

The computer outputs have been furnished connected for 0-50 mV output.

Each readout module incorporates two independently adjustable electronic comparator type radiati.n alarm trips.

The alarm trips operate an audible annunciator system and a light on the readout module front panel.

Each alarm may be connected to cne or more remote field alarm boxes.

Each radiation alarm trip causes a 4 PDT relay to energize, which, in addition to controlling the alarm annunciation system, has

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contacts available for customer use.

k The readout module front panel controls and indicators consist of the follcwing:

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A.

The Panel Meter.

B.

Function Switch - This is the only rotary switch on the front panel.

It turns the module on and off, selects the operating conditions and allows alarm set points to be indicated by the front panel meter.

C.

Green Button / Indicator - Green (Fail) light off indicates pcwer is not available to the module, the module is in the off state or a module or detector failure. Green light on indicates normal module / detector functioning.

Pressing the green button aci-Stes the check source.

D.

Amber Button / Indicator - Amber indicator on indicates alert radiation alarm trip.

Amber indicator off indicates alert radiation alarm is de-energized.

Amber buttor. c.sse<* while function switch,is et ALARM, displays alert alarm set point on meter.

Butson pressed with function switch at OPER. resets the alert radiation alarm if the displayed radiatica level on the meter is less than the alert alarm set point.

The alarm reset function is not applicable if the alarm is being operated on the automatic reset mode.

E.

Red Button / Indicator - Red indicator on indicates high radiation alarm trip.

Red indicator off indicates high radiation alarm is de-energized.

Red button pressed while function switch is at ALARM, displays high alarm set point on meter.

Button

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1 pressed with function switch at CPER. resets the high radiation alarm if the dis-l i

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played radiation level on the meter is less than the high alarm set' point.

The

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alarm reset function is not applicable if the alarm is being operated in the auto-matic reset mode.

2.1.1.2 Performance Specifications.

2.1.1.2.1 Detector / Readout Module.

Ranges:

5-decade; 10-2mR/hr to 103mR/hr; 10-I 4

mR/hr to 10 mR/hr; ImR/hr to 105mR/hr Accuracy:

Each decade - within 120% of reading Circuitry:

Solid state except G-M and HV regulator tubes

Response

Gamma radiation Er argy Dependence:

+15% from 100 kev to 2.5 MeV Direction Dependence? Less than 30% from any direction Detector Type:

Geiger-Mueller (G-M) tube 0

Temperature Limits:

Readout Module; 320F (00C) to 120 F (490C).

Detector;

-200F (-200C) to 1400F (600C)

Humidity:

Readout Module; 0 to 95%.

Detector; C to 1005 Radiation Alarms:

Two (2) alarms, ALERT and HIGH, independently adjustable across the range of the readout rodule; reset is manual or automatic - jumper selected Fail Alarm:

Non-adjustable; autcmatic reset only Internal Alarm Relay Contacts:

DPDT, 5 ampere resistive at 120V ac External Alarm Relay Contacts:

4 PDT, 10 amperes inductive at 120V ac, 1 ampere inductive at 125V de Recorder Output: 0 to 10mV, 13%

Computer Output:

0 to 50mV, O to IV, 0 to SV, 13%

Input Power:

120V, 1 phase, 60 Hz; 115%

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Internal Power Supplies:

+600V dc regulated, 1167; +22V dc unregulated, 13V; x

+10V dc regulated,10.5V; -6.8V dc regulated,10.5V Readout Module Terminations:

Rear panel terminal strips Detector Terminations: AN3102-18-1P connector or equiv:tlent Detector Dimensions:

3 in. (7.63cm) diameter; 6-1/2 ir. (16.Scm) high Detector Weight:

1 pound (0.45 kg)

Detector Mounting: Wall bracket Readout Module Dimensions:

5-5/8 in. (14.4cm wide, 3-1/2 in. (8.90cm) high, 11-1/8 in. (28.3cm) deep Readout Module Weight: Approximately 3 pounds (1. 3 kg)

Readout Module Mounting: 848-3 single channel enct ;sure or 848-1 rack chassis 2.1.1.2.2 Local Alarm, 858-1.

Visual Alarms: ALERT (amber light); HIGH (red light).

Both lights are 1 inch (2.54cm) square and mimic readout module alarm lights Audible Alarm: Horn which activates with either alarm light Temperature Limits:

-200F (-29cC) to 1400F (60 T)

Humidity Limits: 0 to 95%

Enclosure:

Heavy duty industrial junction box with wall mounting flange Dimensions (not including horn):

7 in. (17.8cm) square; 4 in. (10.2cm) deep Weight (not including horn): 4-3/4 pounds (2.15 kg)

Alarm Horn Dimensions:

4-1/2 in. (11.4cm) square; 3 in. (7.6cm) deep Alarm Horn Weight:

1-1/2 pounds (0.68 kg) r2Ok 207 @M 2-2

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i 2.1.1. 2. 3 Local Alarm / Indicator; 858-2 (L0 Range), 858-3.{MED Range).

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Visual Alarms: ALERT (amber light); HIGH (red light).

Both lights are 1 in.

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(2.54cm) square and mimic readout module alarm lights Audible Alarm: Horn which activates with either alarm light Temperature Limits:

-200F (-290C) to 1400F (600C)

Humidity Limits: 0-95%

Enclosure:

Heavy duty industrial jur.ction box with wall mounting flange Dimensions (not including horn):

7 in. (17.8cm) square; 4 in. (10.2cm) deep Weight (not including horn): 5 pounds (2.27 kg)

Panel Meter:

3-1/2 in. (8.89cm) wide with 5-decade display Alarm Horn Dimensions:

4-1/2 in. (11.4cm) square; 3 in. (7.6cm) deep Alarm Horn Weight:

1-1/2 pounds-(0.68 P.9) 2.1.1.2.4 Single Channel Readout Enclosure, 848-3.

Application: Houses one area monitor readout module Mounting: Rubber pads for sitting on bench or shelf Dimensions:

4-1/2 in. (11.4cm) high, 6-1/2 in. (16.5cm) wide, 12-1/2 in. (31.6cm) deep Weight (less readout module):

5-3/4 pounds (2.6 kg) 2.1.1.2.5 Rack Chassis, 848-1.

Application: Mounts in standard 19-inch relay rack and accepts up to three area monitor readout modules Dimensions:

3-1/2 in. (8.4cm) high, 19 in. (48.3cm) wide, 12-1/2 in. (31.6cm) f deep I

Weight (empty):

7-3/4 pounds (3.5 kg) 2.1.1.2.6 Blank Readout Module Panel, 858-4.

Application:

Cover blank rack chassis spaces Dimensions:

3-1/2 in. (8.9cm) high, 5-5/8 in. (14.4cm) wide Weight:

1/2 pound (0.23 kg) 2.1.1.2.7 Detector Cable, 848-6-5.

Type: Multiconductor, waterproof outer insulation Conductors:

Refer to engineering drawing 848-6-3 Outer Diameter:

1/2 in. (1.27cm) 0 Temperature Limits:

-400F (-400C) to 153 F (70c )

C 2.1.1.3 Start-Up Procedure.

The start-up procedure assumes; ths unit has been correctly installed including the detector and any field alarm boxes, cabling has been correctly termir.ated, correct power is available to the readout module.

A.

Rotate the function switch to OPER.

The green light should ccme on _ad the meter should begin giving upscale readings.

It may be necessary to activate the check source nonentarily by pressing the green button for the meter to begin indicating.

B.

Allow the unit to operate for a few minutes and actuate the check source.

See k

paragraph 2.1.1.5.

After the check source eading has stabilized compare it with 207 <W6 2-3 203 i

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.7 that noted in most recent calibration data sheet.

It is normal for radiation indi-cations on the module front panel meter including those from the check source to vary slightly around trw =ctual reading.

The meter variations should be averaged to approximate the correct reas ng.

i C.

The radiation alarm set points may be adjusted by the procedure in Section III.

See Section III if set point changes are required.

2.1.1.4 Shutdown Procedure.

e Rotate the function switch to off.

2.1.1.5 Design Data and Description.

2.1.1.5.1 Detector.

The 855 Series Area Monitors use Geiger-Mueller (G-M) tubes as radiation detectors. A G-M tube basically consists of a positive electrode (anode) surrounded by a negative electrode (cathode).

The anode is usually a metal wire or rod running down tha center of the tube.

The cathode is usually a metal cylinder which actually forms the body of the tube.

Within the tube is a mixture of rare gases and a quenching agent.

For use with the 855, a potential of 600 volts dc is applied between the tube electrodes.

Beta radiation striking the tube will interact with the tube wall liberating ions, or will liberate ions from (ionize) the internal gas directly.

Eitner interaction is called a primary event.

The potential (600V dc) difference between the electrodes will cause the freed electrons (negative ions) produced by the primary event to be

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accelerated through the gas mixture toward the anode.

Some of the accelerating electrons will strike gas molecules causing additional ionization called secondary s

ionization.

The secondary ionization process continues greating more and more free electrons (gas amplification) which also accelerate toward the anode.

The large number of electrons arriving at the anode is sometimes called an avalanch.

The avalanch is a result of the tube gas amplification of the primary event electrons accelerating throuch the gas mixture.

The avalanch of electrons arriving at the anode produce a c; rent pulse at the tube electrodes.

The number of current pulses produced per unit time is proportional to the radiation intensity (number of primary events per unit time) at the G-M tube.

To accept additional prim _cy events, the ionization within the tube must cease follcwing each current pulse.

This action called quenching is assisted by a gas mixture containing a quenching agent which serves to reform or heal the ionization paths of the accelerating electrons follow-ing passage through the gas mixture.

The time required for a G-M tube to respond to a primary event and quench is called dead time.

Additional primary events cannot be resolved since they will be masked by the a'ctivities already taking place within the tube.

It is possible for a G-M tube to be exposed to a number of primary ever.cs so great that the tube dead times overlap and the tube cannot recover from one evcnt before another occurs.

This results in continuous conduction of the tube called saturation (or jaaning) and unless special anti-jam circuitry is employed, could cause a radi-ation reading of zero at the readout module while very high radiation levels existed at the detector.

A zero reading would result because the indicator circuitry counts pulses and a G-M tube in continuous conduction producJs a steady current rather than a series of pulses.

The 855 series area monitor readout modules do incorporate anti jam circuitry described in paragraph 2.1.1.5.2.

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Gamma radiation acts on the G-M tube through Compton ScattUring, Pair Production of Photoelectric Effect.

Any of the preceding processes will cause affected atoms C

or molecules to give up one or more electrons. Since elt.ctrons are, by definition, beta particles, the tube reacts ac described in the preceding paragraph.

The detector assembly includes a radiu.n check source which may be actuated from the readout module to verify i.he ability of a channel to :espond to radiation.

Under normal conditions it is unreasonable to expect to see an increase in the read-out module meter reading due to check source actuation if the meter reading prior to check source actuation is equal to or greater than 2 times the expected check source reading.

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Detector-Pulse Schematic and Anti-Jan Circuitry 2.1.1.5.2 Detector Circuitry.

See Figures 2-2, 2-3, 2-4, 2-5 and 2-6.

Puises from the G-M tube are fed to the pulse amplifier and anti-jam circuit.

The pulse amplifier Q1 is a transistor switch triggered from G-M tube V1.

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s 2.1.2 845 Series Area Monitor.

2.1.2.1 General Description.

See Table 1-1.

The 845 Series Area Monitor is used to monitor gama radiation levels in the reactor building dome. The 847-1 detector is installed in a special 904120 housing with stainless steel walls and a 2-inch lead shield for extended radiation level response.

The 846-1 readout module is located in panel 12. The radiation alarm system cf the readout module is connected into the evacuation alarm system.

See drawing 905474.

The radiation level is presented on the readout module panel meter and also as recorder and computer outputs from the unit.

The recorder output is 0 - 10mV and the computer output is 0 - 50mV.

The readout incorporates two independently adjustable electronic comparator type raciation alarm trips.

The alarm trips actuate the audible annunciator system and a light on the readout module front panel.

The readout module front panel controls and indicators consist of the following:

A.

The Panel Meter; B.

Function Switch - This is the only rotary switch on the front panel.

It turns the unit on and aff, selects the ranges to be displayed and activates the check source.

C.

Amber Button / Indicator - Light on indicates alert radiation alarm trip.

Button pressed causes meter to indicate alert alarm trip set point.

D.

Red Button / Indicator - Light on indicates high radiation alarm trip.

Button

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pressed causes meter to indicate high alarm trip set point.

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E.

Green Button / Indicator - Green light off indicates' a power supply or collector supply voltage failure.

Green light on indicates normal unit functioning.

Green button pressed resets either or both radiation alarms.

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8.45 Series - Model 846-1 Readout Module 207 G@

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u 2.1.2.2 Performance Specifications.

2.1.2.2.1 Detector /Deadout Module.

7 2

3 Ranges:

8-decade:

0.1mR/hr to 10 mR/hr;7mR/hr 3-decade:

0.1 to 10, I to 10,

10 to 10, 102 to 10, 10 4

5 3 to 10, 104 to 10 6

Accuracy:

Decade accuracy will be within 110%

Circuitry: All solid state Type of Radiation: Gamma or X-ray Energy Dependence: +10% from 80 kev to 3 MeV t

Directional Dependence:

Less than 10% from any direction with 60 o C

Type of Detector:

Dual coadal ionization chamber filled at atmospheric pressure Pressure Limits:

15 psig, for both detector and readout module Temperature Limits: Detector:

-200C to 600C (-40F to 1400F', Readout Module:

0 0

0 0

0 C to 60 C (32 F to 140 F)

Humidity: 0 to 95% for both readout module and detector Alert Alarm: Adjustable trip level, indicated by meter deflection when alert light is pressed High Alarm: Adjustable trip level, indicated by meter deflection when high light is pressed Internal Alarm Contacts:

One (1) set of Form C (SPDT) contacts rated at 115V de, 5 amperes for each alann: fail, alert, and high Alarm Level Adjustment:

Both the high and low level trip points are adjusted by means of a 15-turn potentiometer, located on the printed circuit board.

High and Alert Alarm Reset: There are two modes of reset available.

The standard made is a latching type alarm action with manual reset, reset for either alarm is by pressing the green (fail) light.

The system can be converted to automatic reset by removing a jumper on the readout module printed circuit board.

In this mode the alarms will automatically reset when the radiation levels drop below the trip level set points

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Fail Indicator:

Indicates a failure in the system power supply, the bias supply, the collector power supply, or loss of power.

The indication is by means of the green light turning off Recorder Output: 0 to 10mV,10.14mV (Qlways indicating the full 8 decades)

Computer Output: 0 to 50mV, 10.68mV (Always indicating :he full 8 decades)

Power Supply:

14.0V, 110mV Input Power:

120/240V, +15%, 47 to 65 Hr Detector Connector: AN 3102-16-1P

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Readout Module Connectnr:

Rear terminal strip Detector Dimensions:

7-3/4 in. (19.7cm) diameter,11-3/4 in. (29.9cm) high Detector Housing Dimensions:

14-3/8 in (36.43cm) high, 21.95 in. (55.73cm) high Readout Module Dimensions:

3-1/2 in. (8.9cm) high, 5-5/8 in. (14.3cm) deep allowing 1 inch cable radius Detector Weight:

5 pounds (2.27 kg)

Detector Housing Weight:

550 pounds (250.25 kg)

Detector Housing (904120) Mounting:

By customer Readout Module Weight:

3 pounds (1.36 kg) 2.1.2.2.2 Detector Cable 848-7.

Type: 6 conductor, shielded; cuter insulation waterproof,' Alpha 1254 Outside Diameter: 0.35 in. (0.9cm) s' Temperature Limits:

-400C to 70cC ( a00F to 158cF) k 2 07 207 60 2-19 i

A 2.1.2.3 Start-Up Procedure.

The start-up procedure assuming the unit has been correctly installed including the detector, cabling has been correctly terminated, correct power is available to the readout module.

A.

Rotate the function switch to ALL.

A nearly fullscale meter deflection will result which will require several minutes to fully decay.

The initial deflection may cause the radiation alarms to trip.

The alarms should be reset following meter decay.

See paragraph 2.1.2.3.F.

B.

The range is selected with the function switch.

The ALL position selects the full 8-decade rance which is displayed on the upper (red) arc of the meter.

Positions 102 thru 107 select any one of six 3-decade expanded ranges.

The 3-decade ranges are read on the lower (black) scale of the panel meter.

The number opposite the function switch pointer indicates the fuliscale value of the 3-decade range selected.

Figure 2-17 shows the meter scale.

If a function switch pointer indi-cation of 105 is assumed the meter indication must be read on the lcwer black meter scale arc shown in Figure 2-17. } b pg v a ven t a n e e s..=e v av e = e p.v. s.o= iOLACK Figure 2-17. Meter Scale C. The ch ck source may be activated by rotating the function suitch to the pc.; tion labeled C.S. The meter deflection indicates the actual radiation intensity of the t t ek source. Upon de-energizin,g the check source, the green pushbutton lignt should be depressed to avoid activating the alarm (if it is set below the reading of the check source). Since the check source is an actual response to external radiation, the recorder outputs will indicate the check source readings. D. The amber alert alarm light till turn on when the radiation intensity ' exceeds the preset level. When the amber 1,ght is depressed, the meter pointer deflection will indicate the value of the prese' level. This meter deflection can be read on any range and will not be indicated a? the recorder output:. E. The red alarm light will turn on when the radiation intensity exceeds the preset level. The preset level will be indicated by the meter deflection when the red pushbutton light is depressed. This value can be read on any range and will nut be indicated on the recorder output. F. The manual alarm reset mode is the made in which the alarms will lcck after they exceed their preset levels. Cepressing the green (fail light) pushbutten light will reset both alarns. G. To switch either or both alarms to the autcoatic reset mode of operation, a jumper (s) located on the printed circuit board of the readout mcdule must be removed. In this mode of operation the alarm (s) will trigger when the radiation exceed:. the h preset levels, and automatically reset when the radiation intensity falls belcw the \\ preset level. 207 GTS 2-20 2O3 7

k 2.1.2.4 Shut-Down Procedure Rotate the function switch to DTF. 2.1.2.5 Design Data and Descriptions. 2.1.2.5.1 Detector. An ion chamber detector was chosen because; 1) it has the ability to produce flat l Roentgen response; 2) it has an excellent dynamic range and; 3) there is an absence of jamming at high radiation intensity levels. Next, a brief explanation will be given of how currents are forced within the chamber. These currents (by definition) reveal the radiation intensity in Roentgens per hour. Figure 2-18 is a basic ion chamber circuit. The outer walls are connected to a high voltage source which is called the collecting voltage. The center electrode is referred to as the collecting electrode, and is supported from the walls by guarded insulators. The guarding serves to prevent any leakage currents (from the high voltage through the the insulators) from being read at the collecting electrode. These currents are inter-cepted by the guard ring which by-passes them to ground. Another function of the guard ring is to shape the electric field in the region around the collecting electrode. I O i CUARPED IN SUL AT OR i INSUL A TO R CUARD l ( L A i i T CCLLECTION v0LTAGE SUPPLY '+ - + .CCLt.f CT1N C ELECTRODE = i I l I m l CU ARDED IN SULA TCR T INSUL ATO R CUARD l ' Figure 2-18. 847-1 Detector Ion Chamber Schematic J20'l m 2-21 207 i

When the chamber is ev. posed to radiation, one or more electrons are. removed from a number of the gas molecules within the chamber. The result is the formation of free electrons I and positive charged io'ns. The behavior of these charged particles depends on the chamber, the electric field and type of gas within the chamber. The free electrons drift toward the positive electrode making many collisions with the gas molecules, the drift being in a direction away from the chamber wall. The positive ions drift in the opposite direction. The net result of these drif ting charged particles is a current flow which can be measured between the collecting electrode and ground. The amount of current depends on the amount of charge collected per second, which in turn, depends on the radiation intensity. - COLL ECTICH VOL TAGE R b } I/ f I\\C > AMPLtFIERS SCAOE -A I \\ j ELECTRCOE e e 0 IMPECANCE g l SWITCH CHAuBER C i CAPACITANCE P R E AM PLIFI E R } l o j l D V = Figure 2-19. 847-1 Detector Schematic s( / The 845 system detector is a dual coaxial ion chambt. with a'high and icw range ion current output. The high range covers the highest four decades while the low range covers the lowest fcur decades. The chambers operate synchrcacusly, each output is measured in a like manner. The output ionization currents are measured by averaging or integrating themm over a constant recycling time interval. Therefore, the magnitude of constant repetition rate pulses are measured. The mechanism chosen to produce these pulses is described in next paragraph. A high impedance switch is placed between the collecting electrode and a charge sensitive preamplifier. This switch is normally open, it closes for a duration of 4 milliseconds at a rate of 3 times per second, see Figure 2-19. During the :/3 of a second time interval, in which the switch is open, the ionization current l charges the chamber capacitance to,a value proportional to the radiation o intensity. Unen the switch closes the charge is transferred to the charge sensitive amolifier, resulting in a positive pulse at its output, with a decay determined by the time constant of R and C. The peak magnitude of that pulse is dependent on the collected charge and the value of feedback capacitor (C) in the charge sensitive amplifier. Figure 2-20 shows all wave forms and illustrates hcw the output is derived. If C and T are held constant, then the output pulse is directly proportional to the ionization current. Thus, by definition, a measurement of the pulse magnitude is u measurement of the radiation intensity. Figure 2-21 shows the block diagram of the ccmplete system. Remember that the two chambers cperate synchronously, each with the L' same type of electronic measuring system. Only one chamber system will be discussed. 207EGA 2-22 alD i

E 's (,9 AT I A OPfN SulT CH PC5 t TION i CLOSE CL CS E g l I I I I l l i 3 r a t ?,"!. I + C AP ACIT AN C E I l ~ 0, = 1, O T = Q, h v =..OT N IN >Y, l PRfAMP 3 l 7 RC

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I i i + 4 u$ + 4 WS 0 AMS 3 33 Mi 337WS / Figure 2-20. 847-1 Detector Waveforms The two guarded cylindrical chambers are arranged with chamber 2 in the center of chamber 1, the collecting electrode of chamber 1, being a cylinder surrounding the tube which holds the smaller chamber 2 in place. The theory of how the pulses are formed by the high impedance switch, the ion chamber charged output capacity and the preamplifier has already been presented. The magnetic coupling and switch drive block will be described in paragraph 2.1.2.5.2. The amplifier subsystem function can be detailed in another b~ ;ck diagram as shown in Figure 2-22. Pulres from the charge sensitive amplifier of the chamber are amplified by three cascaded pulse amplifiers having gains of nine, ten and ten respectively. Each of the cascade amplifiers has its output voltage limited or clipped by the diode CR, the clip voltage level being set at 9.0 volts. The output voltage pulses from each cascade - amplifier are converted to current pulses by virtue of the series resistor R, the o resulting current pulses are summed at the summing amplifier. It can be shown* that the output of the summing amplifier of this type of system is a composite pulse, whose peak value is related to the radiation intensity in a discontinuous-linear manner. The gain of the suming amplifier is adjusted to result in an output pulse magnitude of 1 volt per decade of radiation intensity.

Reference:

1. Chapman, R.; Recbrder Preamplifier for Displaying Three Decades On One Linear Scale. RSI 37: 12, 1966. 207 R$ 2-22 Mll 7

Fail indicator drive Q9 is just a switch which turns the indicMor on when an input signal is 9 resent. Regulated 14V supply consists of a series regulating element, Q11 with driver Q10, ( the driver is feo from the differential amplifier Q12 and Q13. Q14 provides a constant current for Q13. The reference CR14 is temperature compensated by CR12 and CR13. 2.1.3 Evacuation Alarm System. See Drawing 9C4550, Sheet 11. l The evacuation alarm system consists of three Klaxton type alam horns plus the actuating circuitry. The horns may be energized from a pushbutton in the control room or high radiation alarms from area monitor channels HP-R-209, HP-R-210, HP-R-211, HP-R-212, HP-R-213, and HP-R-214. The alam, once actuated by any of the above means, can be silenced only from a pushbutton in the control room. Victoreen has only supplied the alam horns, pushbutton and drawing 905474 showing the suggested hook-up of the alam components and therefore, cannot guarantee the proper installation or wiring of the evacuation alarm system. [ l o:a ...x- ~.. ., m m z.. m m.=m2nmer m.mm i I c a l.

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i 5 f g. 10 109 ./ i } jh aQ Y{*l E I 0 C p rT) 9%. y f 4 0 4 sq i i alert high a.-g n.wx.=.-$ [. x K m 1 .=. l __..u. m L - Ci;J!i _ M -e-Tc1 I j r -. -,.. q'.m.; ma a c s _:~ x 9 nar$" cran _ l VICTO AEEN power on 1 .g m-m r.... Figure 2-31. 842 Series Log Ratemeter \\ 7n1(BM = 2 36 c) l i

s 2.2 PROCESS MONITORS. ( 2.2.1 842 Series Ratemeter. See Figure 2-31. 2.2.1.1 General Description. See Table 1-2. The 842 Series Ratemeters comprise a portion of the process monitoring system./ The ratemeter is in most cases installed in panel 12 although a number of the ratemeters are field mounted in their respective sampler enclosures as noted in Table 1-2. ~ 6 The ratemeters are available with either 5-decade (10 cpm to 10 cpm) log or linear readouts with or without single channel analyzer optional circuit boards J installed. Simultaneous meter readouts may be presentea at one or more tield indication / alarm units. The ratemeters will accept and process input signals f .n any of the 843 Series Radiation Detectors; alpha, beta or gamma scintillators; end-window or thin wall G-M tubes. Signals from the 843 series detectors are processed by the ratemeters to provide a front panel meter indication, a 0 to 10mV recorder output, a 0 - 50mV computer output which may be altered for either a 0 to IV or 0 to 5V output, two independently adjustable electronic ccmparator type radiation alarm trip circuits, and a fail alarm circuit which indicates channel malfunction. The radiation alarm trips provide outputs to 4PDT relays which, in addition to controlling the alarm annunciation system including field alarms, have contacts available for customer use. b The fail alarm ccntinuously monitors the performance of the channel (ratemeter/ detector combination) and trips if any portion of the detector, pulse processing, power supply or analog output circuitry should malfunction. The fail alarm output is similar to that described above for the radiation al5rms. Note that the fail alarm trip point is not user adjustable. Each channel operates from its own integral high i.nd low voltage power supplies. All controls which may adversely affect the ratemete: operation are located internal-ly making access more difficult. Two operational tests have been designed into the ratemeter. A calibration (CAL) oscillator provides pulses for an electronic calibration of the signal pro-4 cessing circuitry. The CAL frequency of approximately 6 x 10 cpm when routed to 4 the ratemeter input, cause a 6 x 10 cpm meter indication from a co rectly function-ing ur.i t. A radioactive check source near the detect.r is actuated from the ratemeter front panel causing an upscale response from a correctly functioning channel. The 500 to 2500V adjustable high voltage (HV) power suppiv provides the required voltage for operation of the 843 series radiation detectors. The actual HV setting is determined during factory calioration of each channel. The recorder and computer output circuitry includes protective devices to preserve the integrity of the module alarm and indicator functions in the event of up to 120V ac or dc faults occuring on either or both the recorder and ccmputer (L output. 207@B g 2-37 i

s Plug-in circuit boards have been provided for easy maintenancc-of the ratemeter. There are three plug-in boards; ratemeter circuit board, alam circuit board and the optional analyzer circuit board in addition to the mother board which contains the I power supply and signal routing components plus connectors for the three plug-in ( boards. The mechanical configuration of the ratemeter allows side by side mounting of two ratemeters in a standard 19-inch relay rack with a rack chassis adapter. A single ratemeter enclosure is also available. The ratemeter front panel controls and indicators consist of the following: A. The Panel Meter - A 4-1/7 inch, 5-decade meter providing either a linear or logarithmic count rate (counts pe minute) scale plus a 0 to 2500V HV scale. The 4 count rate output scale also pro ides a CAL indication mark at 6 x 10 cpm. B. Function Switch - This is the only rotary switch on the front panel. It turns the ratemeter on and off, allows the high voltage reading to be displayed on the meter, allows the CAL signal frequency to be displayed on the meter and allows the radiation alarm set points to be displayed on the meter. C. Check Source Button - Pressing will cause the channel detector to be exposed to the check source and an upscale meter reading will result from a properly function-ing channel. Care should be taken that enough time is allowed with the button pressed for the channel tu respond to the check source. A sharp upscale meter indication is not unusual when the button is pressed or released and is caused by inductive ringing in the check source circuitry. available to the ratemeter, the fuaction switch is off, a ratemeter or detector failur(e D. Green Button / Indicator - Green (fail) light off indicates power is not has occurred, or the green indicator lamp has failed. Green light on indicates normal ratemeter/ detector functioning. Pressing the green button will res tr. radiation alanns if the displayed radiation level is below the alam set points,nd it manual alarm reset mode has been jumper selected on the alarm circui'. soard. Iha alarm reset function is not applicable if the alanns are being operated in the automatic reset mode. E. Amber Button / Indicator - Amber indicator on indicates alert radiation alarm trip. Amber indicator off indicates alert radiation alarm is de-energized. Amber indicator off but alarm relay tripped indicates a failed amber indicator lamp. Amber button pressed while function switch is at CAL causes the alert alarm set point to be displayed on the module front panel meter. Note that the alarm set point is displayed only with the button pressed - CAL is indicated with thej button released. F. Red 3utton/ Indicator - Red indicator on indicates high radiation alarm tiip. Red indicator off indicates high radiation alarm is de-energized. Red indicator off but alarm relay tripped indicates a fail red indicator lamp. Red button pressd while function switch is at the CAL causes the high alarm set point to be displayed on the module front panel meter. Note that the alarm set point is displayed only with the button pressed - CAL is ind_icated_with the; button released. 2.2.1.2 Performance Specifications. 2.2.1.2.1 Ratemeter. ( Voltage Requirements: 100-130/200-230V ac, 50 - 60 Hz ?h7 @o 2-38 N/Y i

e Power Consumption: 10 watts ~ Operating Terrperature: 320F (00C) to 1300C (550C) ([ Dimensions: 5-1/4 in. (13.3cm) high, 8-1/2 in. (21.6cm) wide,13 in. (33.0cm) deep Two units can be mounted side by side in a Model 844-7 rack chassis, which in turn, mounts in a standard 19-in. (48.3cm) relay rack Meter: 6 Black 10 - 10 cpm, log or linear Scales: Red 0 - 2500V dc Accuracy: +2% of full scale + Size: 4-1/7 in. (11.4cm) Front Panel Controls: e Function Switch: 0FF, CAL, HV, OPER. positions Check Source Button ALERT Alarm Button / Indicator: amber lens HIGH Alarm Button / Indicator: red lens FAIL Alarm RESET Button / Indicator: green lens Outputs: Fail, Alert and High alarm trips,1PDT relay contacts actuating 4PDT alarm transfer relays Computer: 0 - 50mV, 0 - IV, 0 - SV Recorder: 0 - 10mV Power Supplies: High Voltage: regulated, adjustable 500 to 2500V ac at 100uA Low Voltage: -6.2V dc regulated, +16V dc regulated, +25V dc unregulated 2.2.1.2.1.1 Ratemeter Circuit Board, 6 ( Range: 10 - 10 cpm Sensitivity: 200mV 1N Input Pulse Polarity: flegative (-) Input Impedance: 120 ohms at SIG. terminals f Discriminator Level: 0.2 - 5.5V adjustable Calibration Oscillator: Repetition Rate: 60,000c Amplitude: negative (-)pm, nominal 6V 2.2.1.2.1.2 Analyzer Circuit Board. Sensi tivi ty: 100mV Input Pulse Polarity: Negati/e (-) Resolution: 10usec Gain: 1 to 6, adjustable Window Width: 50 mV to integral Base Line Range: 0 - 5.5V 2.2.1.2.1.3 Alarm Circuit Board. Accuracy: +5% Contacts: { Pilot duty to activate alarm transfer relays. See paragraph 2.2.1.5.4.1. 5 amperes at 120V ac resistive 2.2.1.3 Start-Up Procedure. / The start-up procedure assumes; the channel has been properly installed including ( detectors, but with the detector high voltage lead properly disconnected, see 3.2.3, 207 @@ l2-39 t 2{ 1

? 2.2.2.1 General Description. The 843-30 Gamma Scintillation Detector consists primarily of a sodium crystal (NaI) scintillation crystal optically coupled to a photomultiplier tube, a preampli-fier and a metal housing. This detector is operated as part of a channel which also includes a companion 842 Series Ratemeter and a sampler which provides shielding and mounting for the detector. 2.2.2.2 843-20 and 843-20A Beta Scintillation Detectors. See Figure 2-52. l The 843-20 and 843-20A Beta Scintillation Detectors consist primarily of a beta e sensitive plastic crystal optically coupled to a photomultiplier tube, a preamplifier and a metal housing. These detectors operate as d part of channels which also include a companion 842 Series Ratemeter and a sampler which provides shielding and counting for the detector. 2.2.2.2.1 Performance Specifications. The beta and gamma detector performance specifications are the same except for the scintillation crystal. Housing: Weatherproof Dimensions: 12 in. (30.5cm) long; 2.5 in. (6.35cm) outer diameter Weight: 3 pounds (1.36 kg) Photcmultiplier Operating Voltage: 500 to 14007 (maximum) Photomultiplier Operating Current: 100 microam: -es (maximum) Photomultiplier Resolving Time: 3 microseconds { Pgotomultiplier Output Pulse Polarity: Negative (-) s HV Connector: MHV Series UG 931/U Signal Connector: AN3102E-165-1P Preampli fier: Operating Vcitage: +15V dc Operating Current: 33 ma dc Input Impedance: 56 kohms Output Impedance: 9.3 chms Input Pulse Polarity: Negative (-) Output Pulse Polarity: Negative (-) Signal Level: 0 - 5.5V-peak Gain: Approximately 25 Beta Detector Scintillation Crystal: NE 102; 2 in. (5.0Scm) diameter by 0.1 in. (0.25cm) thick Temperature Limits: 320F (00C) to 1200F (500C) Gamma Detector Scintillation Crystal. Nal; 1.5 in. (3.81cm) diameter by 1 in. (2.54cm) thick Temperature Limit s: 320F (00C) to 1200F (500C) gradier.t musi. be less than 40cF (100C) per hour 2.2.2.3 Start-Up Procedure. There are no special procedures for the 843-30 gamma or 843-20, 843-20A beta detectors as they will be used as part of a channel with the companion 842 Series Ratemeters. Refer to paragraph 2.2.1.3 for start-up of the ratemeter. N 207 $9 2-s3 21h i

e 2.2.2.4 Shut-Down Procedure. Same as noted above in paragraph 2.2.2.3 except refer to paragraph 2.2.1.4 for ratemeter shut-down procedure. 2.2.2.5 Design Data and Description. The primary differences between gamma and beta scintillation detectors are in the crystal structure and the mechanism by which-the crystal interacts with various types of radiation to give off pulses of light. 2.2.2.5.1 Gar =a Scintillator. See Figure 2-53. Sodium iodide (flaI) crystals as used in the 843-30 gamma scintillation detector emit pulses (photons) of light when photons frcm radioisotopes. entering the crystal interact with atoms of the crystal. The magnitude of the light pulse emitted by the crystal for a single radiation input event is dependent upon the characteristic gamma energy of the photon entering the crystal and which of the following conversion proce ces occurs.

1) Pair Production - an absorption process for X and gamma rad'ation in which 'the incident photon is annihilated in the vicinity of the nucleus of the absorbing atom, with subsequent production of an electron and positron pair. This reaction will only occur for incident photon energies exceeding 1.02 MeV.

Energy greater than the 1.02 MeV required is imparted to the pair as kinetic energy which is presented to the crystal via ionization causing light to be emitted. The position will eventually combine with free electron (annihilation) and the enercy of the two particles, in-cluding rest energy, is converted into electromagnetic radiation called annihilation radia ti on. This process is not very prevalent with photon energies less than 2 MeV. (

2) Compton Scattering - an attenuation process observed for X and gamma radiation in wtich an incident photon interacts with an orbital electron of a crystal atom to prodi ce a recoil electron and a scattered photon of energy less then the incident photin.

The recoil electron causes low energy secondary ionization of the crystal atomt resulting in Compton Smear. 3) Photoelectric Process - a process by which an incident photon ejects an electron from an atom. All of the energy of the photnn is absorbed and imparts kinetic energy to the electron. The ejected electron travels an ionization path within the crystal resulting in a light output proportional to the incident photon energy. The photoelectric process is important because the proportional crystal light output for a given incident photon energy input allcws qualitative determinations to be made of the isotope or isotopes near the sensitive portion of the detector. Since each radionuclide emits photons of characteristic energies, a device sensitive to the characteristics of those photon energies may form the basis of either a quantitative (gress or al' energies) indicating sys m or a qualitative (analyzer or differential) indicning system. See also the rate: 1r section of this manual, paragraph 2.2.1. The scintillation crystal is coupled to the sensitive portion of the photomulti-plier (PM) tube via a lucite light pipe and optical coupling grease. Photons of light from the crystal travel through the light pipe and impinge upon the photo-cathode of the PM tube where one or more electrons are ejected. W @7 2( 2-64

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