LB 124 Scint User and Service Manual ver 3.26 Rev 10 Jan 2012

LB 124 Scint

Contents

Contents HOW TO WORK WITH THIS MANUAL ... III SAFETY INSTRUCTIONS ... IV 1. 1.1 1.2 1.3 1.4

THE PRINCIPLE OF OPERATION OF THE LB 124 SCINT... 1 Overview ... 1 The Principle of Operation of Scintillation Counters ... 2 What’s Being Measured? ... 3 Measurement Modes ... 5

2. 2.1 2.2 2.2.1 2.2.2 2.2.3 2.3 2.4 2.4.1 2.4.2 2.4.3 2.4.4 2.5 2.6 2.7

SYSTEM DESCRIPTION ... 7 Housing with Electronic System ... 7 Operating and Display Elements ... 9 Design of the Display ... 9 Function Keys ... 10 Alerts ... 10 Scintillation Counter ... 11 Power Supply ... 12 Batteries ... 12 Rechargeable Batteries and Power Supply Unit ... 13 Power Supply of the Photomultiplier (PM) ... 13 Power Supply and Program Memory ... 13 Data Interface ... 14 Equipment Delivered ... 14 Wall Bracket (Optional Accessory)... 15

3. 3.1 3.2 3.3 3.4 3.5

GETTING STARTED ... 16 Connecting the Device ... 16 The First Control Measurement ... 17 Setting Basic Parameters ... 17 Installation of the Wall Bracket ... 18 Possible Errors During Start-Up ... 19

4. 4.1 4.2 4.3 4.3.1 4.3.2 4.4 4.4.1 4.4.2 4.4.3 4.4.4 4.4.5

SOFTWARE DESIGN AND OPERATION ... 20 Software Structure... 20 Measurement Menu Display... 21 Key Functions ... 23 Push Buttons ... 23 Softkeys ... 24 Operation... 25 Selecting Menus and Options ... 25 Editing: Entering Numbers and Letters ... 25 Selecting Items from a List ... 26 How to Switch to the System Menu? ... 27 LED Indicators ... 27

5. 5.1 5.1.1 5.1.2 5.1.3 5.2

CONTAMINATION MEASUREMENTS ... 28 Contamination Measurement Requirements... 29 Performance Check ... 29 Measuring and Storing the Background ... 30 Creating the Small Nuclide Table ... 33 Explanations of the Different Measurement Modes ... 37 I

Contents

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LB 124 Scint

5.3 5.4

Accuracy of the Display in Bq/cm² ... 38 Exceeding of Threshold Values ... 39

6. 6.1 6.2 6.3 6.4 6.4.1 6.4.2 6.4.3 6.4.4 6.4.5 6.5 6.6 6.7 6.8 6.8.1 6.8.2 6.8.3 6.8.4 6.8.5 6.8.6 6.8.7 6.8.8 6.8.9 6.8.10 6.8.11 6.9 6.9.1 6.9.2 6.9.3 6.9.4 6.9.5

SOFTWARE FUNCTIONS ... 40 Measurement ... 42 Background ... 44 Measurement Mode ... 48 Measurement Parameters... 49 Ratemeter... 49 Scaler-Timer ... 50 Survey ... 52 Clearance ... 53 Half-life ... 54 Cycles ... 56 Nuclides ... 58 Memory ... 62 Parameters ... 64 Language ... 64 Date/Time ... 64 Radiationmode ... 65 Calibration ... 65 Grid Transmission ... 65 Alarm ... 65 Ticks ... 66 Light ... 66 RS232 ... 67 Power Supply ... 67 Hardware ... 68 Profile ... 69 Overview ... 69 Editing Profiles ... 70 Preset Profiles ... 72 Factory Settings ... 72 Transmit/Receive Setup ... 73

7. 7.1 7.2 7.3 7.4

MAINTENANCE ... 74 Cleaning the Detector Window ... 74 Changing the Window Foil with Scintillator ... 75 Exchanging the Battery ... 76 Charging the Rechargeable Batteries ... 77

8. 8.1 8.2 8.3 8.4 8.5 8.6

BASIS OF CALCULATION ... 78 Count Rate Calculation ... 78 Ratemeter Function ... 79 Survey Mode ... 81 Scaler-Timer Function ... 81 Half-life Measurement ... 82 Bq-Calculation and Determination of the Calibration Factors ... 82

9.

TECHNICAL DATA ... 88

10.

INDEX ... 90

LB 124 Scint

How to Work with this Manual

How to Work with this Manual A brief overview of the structure of the present operating manual will help you to find the pertinent information quickly and easily: Chapter 1

provides basic information on the principle of operation of the digital contamination monitor: How does a scintillation counter work? What is the significance of the units cps and Bq/cm²?

Chapter 2

contains the description of the monitor: The construction of the device, including operating and display elements, the functions of the keys, as well as the assembling and handling of the detector.

Chapter 3

describes how to take the LB 124 Scint into operation.

Chapter 4

describes the software structure and operation.

Chapter 5

provides information on the contamination measurement: measurement conditions, measuring process and explanations of the individual measuring methods.

Chapter 6

documents all software functions of the LB 124 Scint on the System Menu. This is the reference part of the operating manual.

Chapter 7

contains the description of the maintenance work required.

Chapter 8

deals with the calculation methods used by the LB 124 Scint, and the statistical measuring accuracy. Moreover, the chapter describes how to convert the unit of measurement from counts per second into surface activities, so that you are able to determine your own calibration factors with the help of the given formula and by means of a calibrating source, and to enter this data in the LB 124 Scint.

Chapter 9

contains the technical specifications.

III

Safety Instructions

LB 124 Scint

Safety instructions Use and function

The digital contamination monitor LB 124 Scint can be widely and flexibly used for contamination measurements in radiation protection. It is used wherever contamination caused by radioactive substances is encountered and has to be monitored: in medical nuclide laboratories, in nuclear research, in nuclear power plants, as well as the environment in general.

Safety instructions

If official regulations exist concerning the installation and/or operation of radiation measurement devices, the operator must ensure that these regulations are complied with. The manufacturer has undertaken everything to ensure the safe operation of the instrument. The user has to make sure to use and handle the LB 124 Scint in such a manner that the safe operation is not endangered. In particular, this applies to: The sensitive window foil of the counter tubes:  Whenever you are measuring uneven or pointed objects, be careful not to damage the foil. To be able to handle the monitor LB 124 Scint properly and according to its intended use, one has to have a thorough knowledge of the operating manual. Although the handling is very easy, you should nevertheless read the manual. In order to make sure that the device works properly, please follow the manufacturer’s instructions concerning the functional checks and maintenance work. All maintenance and repair work exceeding the steps described in the operating manual must only be carried out by BERTHOLD TECHNOLOGIES or else by technicians authorized by BERTHOLD TECHNOLOGIES.

IV

LB 124 Scint

1.

1. The Principle of Operation of the LB 124 Scint

The Principle of Operation of the LB 124 Scint

1.1 Overview The portable contamination monitor LB 124 Scint is used for detecting and measuring radioactive alpha, beta and gamma contamination on various surfaces such as floors, walls, desks, objects, clothes or the skin. It consists of a display unit with microprocessor electronics, the photomultiplier, and a ZnS scintillation counter with an effective window size of 118 mm x 145 mm, which can easily be replaced, and which is inserted in the bottom of the instrument. The LB 124 Scint is able to distinguish alpha nuclides from beta/gamma nuclides and measure them simultaneously. The data can alternatively be displayed as count rate (cps = counts per second) or as area activity (Bq/cm²). The device is protected as much as possible against environmental conditions such as humidity, dust or extreme temperatures, and is therefore also suited for outdoor use and rough operating conditions. The entrance window of the detector is protected against damage by a metal grid. Since not only professionals will work with the Contamination Monitor, we would like to give you some quick information on the working method of scintillators and on how to perform radioactivity measurements.

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1. The Principle of Operation of the LB 124 Scint

1.2 The Principle of Operation of Scintillation Counters With conventional scintillation counters the radiation to be measured hits one or several scintillator layers. The flashes of light which are created in this process are propagated – either directly, or bundled by a suitable reflector – to a photomultiplier and measured. Former state of the art To be able to measure alpha as well as beta and gamma radiation, so-called sandwich detectors have been used which comprise two layers: ZnS for the alpha radiation and plastic scintillators for the beta and gamma radiation, with the ZnS layer facing the sample. The drawbacks of this method are the low sensitivity to the lowenergetic beta radiation, which has to pass through the ZnS layer, and inadequate discrimination of the radiation types (strong spillover effects in the beta channel) as well high production costs. New measuring method by BERTHOLD TECHNOLOGIES The Contamination Monitor LB 124 Scint is using a single scintillator made of zinc sulphide (ZnS) to measure radioactivity. The radiation to be measured hits the scintillator. The flashes of light created in this process are passed to a photomultiplier via a suitable reflector with suitable preamplifier and discriminator stage and measured. The individual types of radiation, i.e. alpha and beta, gamma, X-ray radiation, can be distinguished by means of special evaluation and correlation circuits, and thus separated and measured at the same time. The spillover of alpha particles into the beta channel is corrected by the software, so that only the beta-gamma parts of the alpha sources, i.e. Am-241, will be indicated in the beta channel. The benefits of this method are:  high measurement accuracy  exact distinction of the types of radiation and the individual nuclides (very low spillover)  high sensitivity even at low energies  the negligible spillover of Alphas into the Beta channel  low costs for the scintillator and  ease of maintenance.

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LB 124 Scint

LB 124 Scint

1. The Principle of Operation of the LB 124 Scint

1.3 What’s Being Measured? a) Counts per second (cps) The Contamination Monitor is used to measure the radiation activity on the surface of persons or objects in counts per second. With this measuring method, all alpha, beta and gamma counts are then counted and displayed every second (cps). Since the count rate registered each second is subject to statistical variations, the average is calculated on a continuous basis, so that the displayed result is adapted to the count rate and the displayed results is less and less subject to statistical variations after a very short measuring time.

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b) Area activity (Bq/cm ) 2 When you choose to measure the contamination in Bq/cm (i.e. the radiation area activity), the count rate has to be converted into surface activity. There is a different conversion factor for each nuclide. The individual factors are stored in the LB 124 Scint. It is therefore necessary to select the nuclide or nuclide compound to be measured at the device before each measurement. An alpha nuclide can be set for the alpha channel and a nuclide with beta or gamma radiation can be set for the betagamma channel. The types of radiation are distinguished during measurement. The measurement takes place simultaneously. This does not mean, however, that the contamination monitor is able to measure this particular nuclide selectively; but the monitor just values the contamination (i.e. the count rate measured) as if it was caused by the respective radio nuclide. The conversion is based upon calibration factors determined for each nuclide and for your monitor. They do not only depend on the - radiation type, - radiation energy and - decay scheme of the respective nuclide; but other factors are of importance as well, such as the: - detector sensitivity, - measuring geometry, - self-absorption in the calibrating source. The calibration factor thus indicates the value with which the counts per seconds have to be multiplied to obtain a result dis2 play in Bq/cm . 2

Accordingly, a measurement in Bq/cm is only correct if the selected nuclide and the measured nuclide are one and the same.

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1. The Principle of Operation of the LB 124 Scint

LB 124 Scint

2

When you select the unit Bq/cm and the respective nuclide, the LB 124 Scint automatically converts the cps measured into 2 Bq/cm . To measure the area activity, the software comprises an (editable) nuclide library containing at present approx. 60 different nuclides and the respective calibration factors. Moreover, two free entry positions are available, where you can enter e.g. calibration factors for other nuclides.

What can you do if you don‘t know the nuclide? As things are not always that clear in practical operation, but you are often dealing with nuclide compounds, unknown or only partly known nuclides, the following solutions are at your disposal: Determine an unknown nuclide

Nuclide compound of unknown composition

Nuclide compound of known composition

An unknown nuclide can be determined by means of a half-life measurement. Proceed as follows: On the Measurement menu, select the item Half-life Value (see chapter 6.4.5).

When you are dealing with unknown compositions, you can select a calibration factor representing an average value of the most frequently occurring beta radiation sources after nuclear power station accidents. When the nuclides are not known, please select the option Tot (Beta total).

If you wish to measure the activities of several nuclides that are known to you at the same time, you can do the averaging yourself (and also the weighting, if required), and then enter the calibration factor. The free entry positions that are at your disposal for this purpose are dealt with in chapter 6.6. Another possibility is to preset a so-called radioactive tracer. This means that you select one of the isotopes stored in the nuclide library of your device; this isotope should be one of average energy and should correspond with the nuclide compound to be measured.

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LB 124 Scint

1. The Principle of Operation of the LB 124 Scint

1.4 Measurement Modes The LB 124 Scint offers the following measurement modes: a) Survey mode for fast detection of contaminations. In this mode the instrument reacts very sensitive to different types of radiation activities and shows changes very quickly. b) The Ratemeter mode does not react quite as quickly to activity differences, but a higher accuracy can be achieved. c) The Scaler-Timer mode is designed for high measuring accuracy. Here you can choose between two standards for the length of a measurement: the measuring interval and the statistical accuracy d) For a clearance measurement, a limit value is defined and if this value is exceeded, a signal will be triggered. e) The half-life measurement is used to determine the nuclide.

Alarm thresholds

One alarm threshold can be defined for each nuclide; if this threshold is exceeded, an optical and acoustic signal will be actuated.

Storing measured values

Up to 1000 individual measured values on average can be stored and transferred to a PC or printer. The respective relevant parameters are stored together with the measured values. These parameters depend on the measurement mode.

Measuring accuracy

With both measuring methods (count rate and decay rate), you can use either the survey or ratemeter function (quick measurement function), or the scaler-timer function. In the ratemeter mode the measuring accuracy can be estimated based on the display accuracy (few or no decimals). Up to 3 decimals are displayed.

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1. The Principle of Operation of the LB 124 Scint

Range of application of the ratemeter, scaler-timer and survey modes Measurements in the operating modes "Survey" and "Ratemeter" are used to detect contaminations. In this mode, every change in the radiation field is quickly indicated. In the Survey mode a lower measurement accuracy is accepted in order to detect changes even more quickly. An accurate measurement requires - in contrast to the Survey mode - averaging of the count rates over a longer period of time. The LB 124 Scint does this automatically in the Ratemeter mode, provided that the mean count rate remains constant within the statistical significance range during this period. This can for example be assumed for a contamination measurement, if the device is not moved during measurement. To carry out stationary measurements with a given accuracy for the average value, however, it is advisable to select the operating mode Scaler-Timer. In this measurement mode, you can preset either the averaging interval or – by selecting the number of pulses per unit time – the statistical accuracy of the measured value. For great demands concerning the accuracy, you are also able to determine the background (immediately before the actual measurement) in the CPS (raw data) mode by means of the scaler-timer, and to enter this background value immediately.

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LB 124 Scint

LB 124 Scint

2.

2. System Description

System Description

2.1 Housing with Electronic System The splash-proof housing accommodates the measuring and control electronics, the software and the operating elements of the monitor (see Figure 1).

RS232 Interface

Connection for power supply unit

Figure 1: LB 124 Scint

Electronics

The complete electronic system with photomultiplier (incl. the software and the high voltage generator) is located inside the housing.

Scintillator

The scintillator is deposited on a transparent carrier. The foil is stretched over a frame and protected by a metal grid. The detector is fixed to the bottom side of the device with two fixing screws that it can easily be unscrewed with the help of a coin. The frame with foil and scintillator can easily be exchanged. Make sure to change the frame in semi-darkness, as the photomultiplier and scintillator are sensitive to light. Then do not work with the device for 12 hours to allow the phosphorescence radiation to subside.

Protection plate

The radiation entrance window can be protected by a metal protection plate. 7

2. System Description

LB 124 Scint

Connections

The connections for the power supply unit and the PC/printer (RS232 interface) are located on the right side of the device.

Operating voltage

The device can be operated either with the help of a power supply unit, with rechargeable batteries (baby 1.2 V), or with batteries (baby 1.5V) located on the bottom side of the device (see ). When the power supply unit is connected, the operating voltage is supplied via mains and the rechargeable batteries can be charged. The charging process is started via the menu Power Supply/Charge Mode. During the charging process, the device works with mains voltage. If the LB 124 Scint is connected to power or placed into the charging station, the device is turned on automatically.

Fixing screws for counter tube

Fixing screw for battery case

Figure 2: Contamination Monitor (view from below)

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LB 124 Scint

2. System Description

2.2 Operating and Display Elements Measurement, operation and display are controlled by the software integrated in the LB 124 Scint. Measured values, menus and user information are displayed on a monochrome LCD graphics module (192 x 64 pixel) with LED backlighting and a scratch resistant Plexiglas screen. The operation takes place with the help of the six function keys below the screen. Alerts and status signals are output via 2 LED’s and a buzzer.

2.2.1 Design of the Display Measurement menu

For more detailed information, please refer to chapter 4.2 Top line (black shading): Shows status information and the profile name (user). Center field: Net measured value(s) with unit of measurement and measured nuclide(s) or the net value (= cps measurement). In case of simultaneous -/-measurement, both measurement values will be displayed. Below these values, you find information on the measurement which can be selected via the softkey function Info/Mod: e.g. the gross values or the representation in the form of a scale from 0-100% in proportion to the alarm threshold of the selected nuclide.

Measuring mode Measuring value (-ch.) 100% scale or Alpha display Softkeys (menus) Function keys

Figure 3: Display and function keys

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2. System Description

LB 124 Scint

Bottom line (black shading): Here the menus or functions are displayed that can be selected via the keys under the display (so-called softkey functions. Softkey functions). On the Measurement Menu, the four function keys in the center have the significance that is assigned to them via the softkeys above.

System menu

On the System Menu, the menus and functions that can be selected are displayed, and parameters can be edited. The selection and the parameter input takes place via the push keys. The functions of the individual push keys can be seen from their respective labels. See chapter 4.1.

Softkey buttons

2.2.2 Function Keys The operation of the device and the software takes place via six push keys with the respective function names. The 4 keys in the middle have additional functions on the Measurement Menu; these functions are assigned to them via the softkeys above them (this is made clear by means of the vertical lines). The softkeys are indicated in the bottom line of the display (black shading). See chapter 4.2.

2.2.3 Alerts LED displays Left LED Right LED

The LED’s on the foil keyboard indicate the following states: Alert: the threshold has been exceeded When a button has been pressed, this LED is lit as long as the processor is busy with the actuated function.

Acoustic signal

When the threshold is exceeded, an alarm signal sounds (if set on the Parameter menu). The red LED (on the left) is flashing. On the Parameter menu you can choose visual, acoustic or vibration as signal type.

Battery exchange

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When the battery/rechargeable battery voltage indicated after power on of the device is below 3V for batteries and below 3.5V

LB 124 Scint

2. System Description

for rechargeable batteries, the running time left is max. 2-4 hours! In this case, the batteries have to be replaced.

2.3 Scintillation Counter The scintillator is deposited on a transparent carrier. The foil is stretched over a frame and protected by a metal grid. The detector is fixed to the bottom side of the device with two fixing screws that can easily be unscrewed with the help of a coin. The frame with foil and scintillator can easily be exchanged. The reflector and the photomultiplier are located inside the housing, directly behind the scintillator. Also inside the housing there is the power supply, the electronics with evaluation and correlation circuits as well as the evaluation electronics with the software. The high voltage is factory-set. The high voltage can only be checked or modified with the help of a service adapter and by experienced maintenance personnel. The scintillator which has been deposited on the foil, can easily be exchanged without having to use any special tool, e.g. if the foil is damaged (see chapter 7.2). When you replace the foil, please make sure that  the replacement takes place in a dry and dust free place  no humidity or dirt whatsoever can get into the gap!  you change the frame in semi-darkness, as the photomultiplier and scintillator are sensitive to light. Then do not work with the device for 12 hours to allow the phosphorescence radiation to subside.

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2. System Description

LB 124 Scint

2.4 Power Supply 2.4.1 Batteries The fixing screw of the battery case cover can be unscrewed using a coin, so that the cover can be taken off.

Figure 4: Open battery case

Using batteries

The device can be run with 3 batteries (baby 1.5V). To ensure the correct arrangement of the batteries, their respective polarities are indicated at the bottom of the battery compartment (see Figure 4). Any time the device is started up, the user is informed about the state of the batteries: The voltage can be queried on the menu Parameter/Power Supply/Voltage Battery. For this purpose, Battery has to be selected as software setting on the Hardware menu. Please note: The RAM memory storing the measured data, the settings and the date is permanently supplied with power via a lithium battery when the device is not being run with supply voltage or with batteries/rechargeable batteries. In order to avoid a data loss, the lithium battery should therefore be replaced while the device is being supplied with power with supply voltage or via batteries/rechargeable batteries. The lithium battery is located on the motherboard and should therefore only be replaced by trained staff.

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LB 124 Scint

2. System Description

2.4.2 Rechargeable Batteries and Power Supply Unit When an accumulator is used for the power supply, the option Accu on the menu Parameter/Power Supply has to be selected. With this option, the Charge Function is activated when the charging mode is set to ON. Do not enable the charging function if batteries are in the device. If the LB 124 Scint is connected to power or placed into the charging station, the device is turned on automatically. The charging process is started new depending on the settings for cell type, charge mode and charge time. The charging process takes place only when the device is turned on. An activated System Timeout is not taken into account while the charging function is active.

2.4.3 Power Supply of the Photomultiplier (PM) Batteries and rechargeable batteries do not only supply the basic device with power. Using a fixed control voltage between 0.5 and 1.3 Volt, the high voltage of the photomultiplier is controlled.

2.4.4 Power Supply and Program Memory 1. The software program, the calibration factors as well as all fixed settings are stored in the FLASH and are independent of the power supply. 2. The calibration factors, threshold settings, dates, measured values, etc. defined by the user are stored in the RAM (lithium battery-buffered). By means of the reset function (the factory settings can be found under parameters/factory settings), these values can be deleted; in this case, the factoryset default values will be loaded. This function is only accessible if the respective authorization to access has been assigned.

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2. System Description

LB 124 Scint

2.5 Data Interface Data is output to a PC or printer via the RS 232 data interface (see Figure 1).

Software for data transfer to PC

Data transfer between the LB 124 Scint and a PC is at present only possible in one direction, i.e. when the respective output function is activated (e.g. output of stored measured values or through cyclical printout), the data is output via the interface. In order to receive the data, a standard terminal program has to be installed on the PC. The terminal program integrated in Windows has been tested by the manufacturer. For correct data transfer, it is necessary to adapt the transmission parameters in the terminal program to the parameters of the output device. The LB 124 Scint issues 8 data bits, no parity and one stop bit. The transfer rate (baud rate) can be modified on the menu Parameter / RS232. The default setting of the device delivered is 19200 baud. When you start a printout of the measured values, these have to be readable in plain text on the screen. The file generated during this procedure can be further processed with any standard ASCII editor, or else transferred to a printer. The data (separated by Tab and CR/LF) can be processed further using a spreadsheet program such as EXCEL.

2.6 Equipment Delivered Standard equipment

The measuring and display unit LB 124 Scint with ZnS scintillation counter.

Standard accessories

1 set of spare batteries Operating manual

Optional accessories

1 plate with a test source with Sr 1 aluminum transport box, 40 cm x 26 cm x 25 cm. 1 power supply unit 1 wall bracket

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90

LB 124 Scint

2. System Description

2.7 Wall Bracket (Optional Accessory) The optionally available wall bracket (ID No. 38789) is used as  Charging station (only if you are working with rechargeable batteries). If the power supply unit is connected to the wall bracket and to mains supply, the LB 124 is turned on automatically (with some older devices, the LB 124 has to be turned on manually). The charging process takes place only when the device is (still) turned on and Battery Type / Accu is set on the Power Supply menu! See also chapter 6.8.10.  Stationary contamination control. The wall bracket is designed such that the Monitor stands out from the wall at an angle of 17.5°, so that one can hold one's hand below the detector for contamination measurement. Insert the hand from the side to make sure the complete hand can be measured by the detector (see Figure 2, which shows the measurement area of the LB 124). The measurement can be carried out in the battery or rechargeable battery mode. Ideally, the device is employed with connected power supply unit (see Charging station). Scope of delivery

The delivery includes the wall bracket and one set of dowels (ID No. 12117, type S 6) and screws (ID No. 39335, head of rivet 4, 5 x 30). These dowels and screws should be adequate for most walls. Depending on the property of the wall, you may have to use other dowels/screws. Wall bracket (with mounting plate)

Set of screws and dowels

Stationary measurement

Connection for power supply unit

Figure 1: Wall bracket Installation of the wall bracket see chapter 3.4

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