TSA PRM-470B Service manual

PORTAL RADIATION MONITOR
MODEL PRM-470B
OPERATING AND SERVICE MANUAL
Version 1.01z
December 20, 2004

PRM-470B
TABLE OF CONTENTS
1. INTRODUCTION.....................................................................................................................1
1.1. SCOPE AND PURPOSE OF MANUAL....................................................................1
1.2. GENERAL DESCRIPTION.......................................................................................1
1.3. SAFETY PRECAUTIONS.........................................................................................3
1.4. SPECIFICATIONS.....................................................................................................4
2. INSPECTION AND SETUP ....................................................................................................6
2.1. INSPECTION..............................................................................................................6
2.2. SET-UP PROCEDURES ............................................................................................7
2.3. INITIAL SETUP CHECKLIST..................................................................................9
3. OPERATING INSTRUCTIONS...........................................................................................10
3.1. POWER-UP AND SELF TEST................................................................................10
3.2. SEARCH MODE ......................................................................................................11
3.3. BACKGROUND MODE..........................................................................................11
3.4. MODE CHANGE AND RESET...............................................................................12
3.5. DISPLAY BACKLIGHT..........................................................................................12
3.6. LOW BATTERY DETECT......................................................................................12
3.7. RECOMMENDED SETTINGS................................................................................13
3.8. TYPICAL SEARCH PROCEDURES......................................................................13
4. THEORY OF OPERATION..................................................................................................15
4.1. COMPONENTS AND SUBASSEMBLIES.............................................................15
4.2. SELF TEST (SYSTEM RAM) .................................................................................16
4.3. BACKGROUND MODE..........................................................................................17
4.4. SEARCH MODE ......................................................................................................17
4.5. AUDIO ALARM.......................................................................................................18
5. MAINTENANCE....................................................................................................................19

5.1. MAINTENANCE PROCEDURES ..........................................................................19
5.2. ELECTRONIC CALIBRATION PROCEDURE.....................................................19
5.3. TUNE-UP AND CALIBRATION CHECKLIST.....................................................21
6. TROUBLESHOOTING .........................................................................................................22
6.1. COMPONENT ACCESS..........................................................................................22
6.2. TROUBLESHOOTING GUIDE ..............................................................................25
6.3. PRCB-001 BOARD ..................................................................................................28
APPENDIX..................................................................................................................................29
A. WARRANTY..........................................................................................................................29
B. GLOSSARY............................................................................................................................30
C. FORMULAS...........................................................................................................................32
C.1. ACTIVITY FROM COUNTS..................................................................................32
C.2. EFFICIENCY...........................................................................................................32
C.3. N*SIGMA ALARM LEVEL ...................................................................................32
C.4. RELIABLE DETECTABLE ACTIVITY (RDA) FORMULA................................33
C.5. SIGNAL TO BACKGROUND RATIO...................................................................33
C.6. VARIANCE..............................................................................................................34
D. CONFIGURATION TRACKING SHEET..........................................................................35
E. PARTS.....................................................................................................................................36
E.1. RECOMMENDED SPARE PARTS.........................................................................36
E.2. SPARE PARTS ORDERING INFORMATION......................................................37
F. DRAWINGS............................................................................................................................38

1. INTRODUCTION page 1
Model PRM-470B
1. INTRODUCTION
1.1. SCOPE AND PURPOSE OF MANUAL
This manual is designed to enable operating and service personnel to properly operate and care
for the PRM 470B. Since applications are necessarily site-specific, operation procedures are
given in general terms. Service and repair are covered to the board or assembly level. Anything
more complex than this requires that the instrument or assembly be returned to TSA.
1.2. GENERAL DESCRIPTION
The TSA Model PRM-470B Portable Radiation Monitor is a light-weight, portable, hand- held
instrument designed to detect radioactive materials. The standard detector is a large plastic
scintillator that is both gamma and neutron sensitive. A display backlight is supplied to permit
use in low light conditions.
Uses for the PRM include Special Nuclear Material (SNM) searches at plant exits and material
access areas, as well as contamination and background monitoring. The small size and light
weight make it ideal for extended search time applications.
Upon power-up, the instrument goes through a self-test and warm-up period followed by an
initial ten second background count. In background mode it continues to update background
counts at ten second intervals; the display flashes the current background. In search mode, the
current background is stored and the instrument makes alarm comparisons every 50
milliseconds. The display will show counts per second, divided by 1000, updated every second.
If the detected radiation level exceeds the pre-programmed alarm level, an audio alarm is
sounded.

1. INTRODUCTION page 2
Model PRM-470B
The instruments covered by this manual have been modified to operate on a set of four AA size,
alkaline batteries. The instrument will operate for approximately 24 hours on a fresh set of
batteries.
The PRM-470B operates in two modes:
• Search mode - to locate radioactive material
• Background mode – to measure radiation intensity
Two rotary switches control sensitivity while in the search mode. The switches are located on
the PRCB-474 PC board inside the instrument. The range of the sensitivity adjustment is 0.1 to
10.0 sigma.
There are two options for displaying the data:
• cps
• µsieverts
There are two rotary dip-switches located on the PRCB-001 board that control the display mode.
If both switches are set to "0", the display is in cps.
NOTE:
The µsievert conversion is not compensated for energy. It is strictly a linear conversion of
counts per µsievert.

1. INTRODUCTION page 3
Model PRM-470B
1.3. SAFETY PRECAUTIONS
Cautions and warnings related to specific procedures are cited at appropriate places in this
manual. A summary is given here.
WARNINGS:
Since the PRM-470B uses high voltage during operation, care must be taken during service
procedures. Service should be done only by qualified personnel.
The electroluminescent backlight utilizes 400 volts ac for operation, and care must be taken to
avoid accidental contact while servicing the instrument.
CAUTIONS:
The PRM-470B is water resistant, but will not withstand immersion in water.
The instrument should not be overcharged, as this will shorten the battery life. The instrument
should not be constantly shallow charged refer to Maintenance Procedures (section 5.1.).
As with any sensitive electronic instrument, the PRM-470B should not be dropped or subjected
to severe mechanical shock.
Damage to the copper coating inside the instrument can result in unacceptable RFI levels.

1. INTRODUCTION page 4
Model PRM-470B
1.4. SPECIFICATIONS
Sensitivity: Will detect 10g HEU or 1g 239Pu
when tested in accordance with ASTM Standard C 1237-93
Detector: One, 3.5"h x 2.88"w x 1.25"d (8.8 x 7.2 x 3.1cm)
plastic scintillator detector; provides 12.6 in3(206 cc) of detector volume
Alarm Levels: Set by two internal rotary switches from 0.1 to 9.9 sigma
Alarm Indication: Audible tone and LED
Count Time: Search mode: 0.05 sec. count with .4 sec. moving average.
Background time: 10 sec.
Display: LCD, one line x 4 characters, with backlight
Power: The internal NiCad battery pack provides more than 60 hours of
continuous operation on a full charge.
Battery Charger: The instrument is shipped with a universal input battery charger which
operates on 90 – 250 Vac, 47 – 63 Hz.
Recharge time is less than 16 hours.
Optional 4 "AA" alkaline batteries will provide more than 24 hours
of operation.
Conversion: µsievert conversion: set by two internal rotary dip-switches;
Range: 100 to 9900 cps/µsievert

1. INTRODUCTION page 5
Model PRM-470B
Dimensions: 8"h x 5"w x 3"d (20 x 12.5 x 7.5cm)
Weight: 2.4 lb (1.1kg) with batteries
Environmental:
Temperature: 32˚ to 100˚F (0˚ to 38˚C)
Humidity: Up to 95% non-condensing

2. INSPECTION AND SET-UP page 6
Model PRM-470B
2. INSPECTION AND SETUP
The following procedures should allow on-site personnel to correctly inspect and set up the
PRM-470B for normal operation. Follow the procedures in the order given. It is recommended
that a copy of the Initial Set-Up Checklist (section 2.3.) be filled out after initial installation and
whenever the PRM-470B is put into service after prolonged storage.
If necessary, consult TSA Systems for assistance in case of unusual site conditions or special
requirements.
2.1. INSPECTION
2.1.1. Incoming Inspection:
Immediately inspect the instrument for mechanical damage, scratches, dents or other defects. It
should be examined for evidence of concealed, as well as external damage.
2.1.2. Damage Claims:
If the instrument is damaged in transit or fails to meet specifications upon receipt, notify the
carrier and TSA Systems immediately. Shipping cartons, packing materials, waybills and other
such documentation should be preserved for the carrier’s inspection. TSA will assist in
providing replacement or repair of the instrument if necessary.
2.1.3. Storage:
If the instrument is to be stored for any length of time, first disconnect power to the instrument
and remove and store any batteries separately in a cool place. If batteries are to be stored for
any length of time, they should be inspected and charged if necessary at least once a month.
Care should always be taken to avoid subjecting the instrument to severe mechanical or
environmental shock. The instrument should be stored in a dry, temperature constant location.

2. INSPECTION AND SET-UP page 7
Model PRM-470B
2.1.4. Shipping:
Before returning the instrument for any reason, notify TSA Systems of the difficulty
encountered, giving the model and serial numbers of the equipment. TSA will furnish specific
shipping instructions.
2.2. SET-UP PROCEDURES
An Initial Setup Checklist is included at the end of this section (section 2.3.). It is recommended
that a copy of this be filled out when the PRM-470B is first set-up, and whenever it is put into
service after prolonged storage.
After initial inspection, charge the battery for several hours. Although the battery is fully
charged before the instrument leaves the factory, some discharge is possible if the instrument has
been in storage for any length of time.
After charging, turn the instrument on and test the controls, display and alarm According to the
steps outlined in Power-Up and Self-Test (section 3.1.) in this manual. While the instrument
comes from the factory tuned and calibrated, the calibration should be verified before putting the
instrument into service.
2.2.1. Alarm Level:
To set the sigma level, open the instrument. Refer to Component Access (section 6.1.) and use a
small slotted screwdriver to turn the two rotary switches marked "sigma" to the desired setting.

2. INSPECTION AND SET-UP page 8
Model PRM-470B
2.2.2. µsievert Conversion:
The cps/µsievert conversion is set in the same manner as the alarm level. Turn the two rotary
dip-switches marked "k-factor" to the desired setting. This setting is multiplied by 100, so a
setting of 19 would result in 1900 cps per µsievert.
NOTE:
Setting both k-factor switches to "0" will display cps.
The settings will appear on the display for approximately 3 seconds each during the warm-up
period. They will be displayed in the following order:
• sigma
• cps/µsievert
After the settings are displayed, the instrument will initiate a 10 second countdown for the initial
background.

2. INSPECTION AND SET-UP page 9
Model PRM-470B
2.3. INITIAL SETUP CHECKLIST
____ Initial inspection done
____ Battery charged
____ Initial self-tests show no error codes
____ Power switch operates correctly
____ Background in operating area = _____________________________
____ Mode change operates correctly
____ Sonalert works properly
____ Alarm test - source used: __________________________________
____ Sensitivity (Sigma switch setting): __________________________
____ µsievert conversion switch setting: __________________________
Performed by: ________________________________________________Date: _____________

3. OPERATING INSTRUCTIONS page 10
Model PRM-470B
3. OPERATING INSTRUCTIONS
3.1. POWER-UP AND SELF TEST
3.1.1. Power On:
For power-up, press and hold the power switch for 2 seconds. It is the dark blue area on the front
panel marked "POWER". The instrument will sound a series of beeps to indicate that the power
on signal has been latched.
3.1.2. Self Test:
The instrument will perform a display test, with all segments and decimal points "ON" for 2
seconds, accompanied by the audible alarm.
The instrument will then display the current settings for 3 seconds each.
If any of the power-up tests fails, an error code will be displayed. If no errors are present, the
background countdown will be displayed.
3.1.3. Power Off:
Press and hold the power switch for 2 seconds to turn the instrument off. Power off will be
acknowledged by displaying "----".
NOTE:
The instrument will not turn off until it has completed its power-up tests and displayed either an
error code or the background countdown.

3. OPERATING INSTRUCTIONS page 11
Model PRM-470B
3.2. SEARCH MODE
After the initial 10 second background countdown, the instrument will automatically go into
search mode. In this mode the display will be steady (not flashing) and will update the display
every second.
There is an internal motion switch in the instrument that will automatically enable the search
mode when the instrument is moved.
This feature can be enabled or disabled with jumper X1 on the PRCB-001 board.
To enable the motion switch, place the jumper between X1-1 and X1-2.
To disable the motion switch, place the jumper between X1-2 and X1-3.
When the motion switch is enabled, each time the instrument is moved, a 15 second timer is
activated. The instrument will stay in search mode until the 15 second timer expires.
The instrument will produce an audio alarm from time to time in a search mode. When
radioactive materials are present, it will alarm more rapidly. This is dependent on the intensity
of the radiation and the sigma switch settings.
3.3. BACKGROUND MODE
The background mode is characterized by the display flashing once per second, and will update
with a new background every 10 seconds. Pressing the mode switch and holding it until it is
acknowledged with a "beep" toggles between search and background modes.
While in background mode the audio alarm is disabled and the display will continue to flash.

3. OPERATING INSTRUCTIONS page 12
Model PRM-470B
3.4. MODE CHANGE AND RESET
The instrument may be switched between search and background modes at any time by pressing
and releasing the mode switch.
If the internal motion switch is enabled, the modes may be switched by setting the instrument on
a stable platform like a table and waiting for the 15 second timer to expire.
To reset, the instrument must be power cycled. The instrument will go through another self-test
and wait period. It will then display a new background count.
3.5. DISPLAY BACKLIGHT
The display backlight is turned on automatically at power-up. The display backlight will turn off
again when the instrument enters the initial background countdown.
After the countdown starts, and at any other time while the instrument is operating, pressing the
light switch will turn on the backlight for 30 seconds. Excessive use of the light will shorten the
useful life of the battery by up to 50%.
3.6. LOW BATTERY DETECT
The PRM-470B is equipped with an automatic low battery detect circuit.
When the battery voltage drops to 5.2Vdc, all signal processing will stop, the display will show
"LO", and the beeper will sound for five seconds.
The instrument will automatically power down at the end of the five seconds to avoid damage to
the batteries. The PRM-470B will resume normal operation after replacing the batteries.

3. OPERATING INSTRUCTIONS page 13
Model PRM-470B
3.7. RECOMMENDED SETTINGS
There are two user adjustable parameters.
• n*sigma
• counts/µsieverts.
Both of these parameters are set using rotary dip-switches mounted on the main circuit board.
When the instrument is shipped from the factory the switches are normally set for n*sigma = 3.0,
and counts/µsieverts = 00.
The switches are read on power-up, so changing the switches while the instrument is operating
will have no effect.
3.8. TYPICAL SEARCH PROCEDURES
The following search techniques are drawn from examples given in the Los Alamos National
Laboratories User’s Manual, "Hand-Held Search Monitor for Special Nuclear Materials", by
Paul E. Fehlau (1984).
These techniques may serve as a general guide for search procedures. It is recommended to refer
to your specific site regulations and Operating Procedures prior to search operation.
The efficiency of the search improves with close proximity to the article or person being
searched, a thorough scan of all surfaces, and adequate time to allow the instrument to respond.

3. OPERATING INSTRUCTIONS page 14
Model PRM-470B
Personnel:
All articles in hand should be searched separately. The PRM should be held
within 3 inches (7.5cm) of the person and moved slowly, from head to foot
anteriorly and posteriorly.
Vehicles:
The engine should be off. All personnel are requested to leave the vehicle for an
individual scan. All compartments (hood, trunk and glove box) should be opened
and scanned with particular attention paid to possible areas of concealment, such
as wheel wells, hub caps and relatively inaccessible areas.
If contamination or suspect material is located, follow site regulations.
As stated above, these search techniques are drawn from examples given in the Los Alamos
National Laboratories User’s Manual, "Hand-Held Search Monitor for Special Nuclear
Materials", by Paul E. Fehlau (1984). For more information, contact the Los Alamos National
Laboratories staff directly.

4. THEORY OF OPERATION page 15
Model PRM-470B
4. THEORY OF OPERATION
The PRM-470B is designed to locate radioactive sources and measure intensity in the field. It
uses low power CMOS electronics to provide over 60 hours of operation from the NiCad
batteries. For emergency response or other applications where rechargeable batteries are not
suitable, the PRM-470B features a self test during power-up, automatic background count and
user determined alarm settings.
For wiring, and signal flow information, refer to "PRM-470B Internal, 3D View" Drawing 2 and
"PRM-470B Wiring Diagram" Drawing 3 (Appendix F).
4.1. COMPONENTS AND SUBASSEMBLIES
4.1.1. Main Circuit Board, PRCB-001:
Refer to "PCRB-001 Control Board Schematic Diagram" Drawing 4 and "PCRB-001 Control
Board Component Designator" Drawing 5 (Appendix F.).
The PRCB-001 microprocessor control board is the computer board for the system. Its program
runs the PRM and processes the incoming signal from the detector assembly. The signal is
analyzed with the resultant count rate output to the display. The board also accepts input from
the various switches and outputs to the display and beeper.
4.1.2. High Voltage Power Supply, HHV-454:
Refer to "HHV-454 High Voltage Power Supply Schematic Diagram" Drawing 6 and "HHV-454
High Voltage Power Supply Component Designator" Drawing 7 (Appendix F.).
The HHV-454 high voltage power supply supplies regulated high voltage to the voltage divider
assembly to power the PMT (photo-multiplier tube). This assembly is shielded to reduce RFI.

4. THEORY OF OPERATION page 16
Model PRM-470B
4.1.3. Detector Assembly:
The detector assembly converts gamma radiation into a voltage pulse. The voltage pulse is
amplified on the PRCB-001 board so it can be counted and analyzed. The detector consists of
organic plastic scintillation material, with a PMT coupled to it using optical adhesive. The
whole assembly is wrapped in light tight materials.
4.1.4. Voltage Divider Assembly:
Refer to "PB-10M Voltage Divider Schematic Diagram" Drawing 8 and "PB-10M Voltage
Divider Component Designator" Drawing 9 (Appendix F.).
The Voltage Divider Assembly is made up of the tube socket and voltage divider (resistors and
capacitors). It divides the incoming high voltage for the dynodes in the PMT, and decouples the
signal from the high voltage.
4.1.5. Batteries and Battery Charger:
The instrument operates on four, AA size, alkaline batteries. When the batteries have discharged
to the point that they will no longer reliably operate the instrument, it will display "LO" and stop
operating. Replace the batteries with a fresh set.
NOTE:
The alkaline batteries are not rechargeable. The charger jack has been disabled.
4.2. SELF TEST (SYSTEM RAM)
When the PRM is turned on it will automatically test the system RAM. Immediately after
turning the instrument on, the display will show "8.8.8.8" and the beeper will sound. The beeper
continues to sound for approximately two seconds while the instrument goes through the RAM
test.

4. THEORY OF OPERATION page 17
Model PRM-470B
If the RAM test passes, the PRM-470B will display the current settings. If the RAM test fails, it
will display "---1".
After the instrument has completed the RAM test it will display the current settings for
approximately 3 seconds each. This delay also gives the high voltage time to stabilize.
The instrument will then count down from 10 seconds and will display a flashing background
count followed by an automatic switch to "SEARCH" mode.
4.3. BACKGROUND MODE
The PRM may be returned to background mode by pressing and holding the mode switch until it
is acknowledged with a beep. The display will flash in background mode, while the instrument
constantly updates the background count to reflect changes in the environment. The background
is accumulated in 10 second increments, with the current background displayed as the one
second average.
4.4. SEARCH MODE
In search mode, the alarm threshold is determined by the Sigma switch setting. The instrument
updates the display each second.
The instrument counts incoming pulses in 50 millisecond periods, and sums eight of these
periods into a 400 millisecond moving average.
That is, the most recent 50 millisecond count is added to the moving sum and the oldest count
discarded. This moving average sum is then compared to the alarm threshold.