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4-1

CHAPTER 4

FUNCTIONAL DESCRIPTION

4.1 FUNCTIONAL DESCRIPTION.

The Model 3100 is intended for continuous measurement of tritium activity concentration in the ambient
atmosphere. Tritium, which is a low-energy beta emitter, must be brought inside the detector in order to be detected.
The instrument employs a pump and a flow-through pneumatic system to circulate ambient air through the otherwise
sealed ion chamber detector. The level of activity is determined by measuring the ionization occurring within the
chamber. The level of radioactivity in microcuries per cubic meter of air is shown on the digital display. Three
ranges provide full-scale levels of 10

2

, 10

3

, and 10

4

µCi/m

3

of tritium in the air. An audible alarm can be preset so

that the user is notified when the alarm level is exceeded, and must be manually reset whenever triggered.

The instrument is shown in block diagram in Figure 4-1. The unit consists of an inlet filter, tritium detector, gamma
compensation ion chamber, an electrometer amplifier, a range-dependent amplifier, display, alarm circuit, pump
drive and pump, power supply, and battery charging circuits. See overall description following the diagram.

Figure 4-1. Functional Block Diagram.

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Содержание 3100

Страница 1: ...LUDLUM MODEL 3100 TRITIUM IN AIR MONITOR July 2019 ...

Страница 2: ...LUDLUM MODEL 3100 TRITIUM IN AIR MONITOR July 2019 ...

Страница 3: ...anty of merchantability or fitness which extend beyond the description of the face there of If the product does not perform as warranted herein purchaser s sole remedy shall be repair or replacement at the option of Ludlum Measurements In no event will Ludlum Measurements be liable for damages lost revenue lost wages or any other incidental or consequential damages arising from the purchase use or...

Страница 4: ... 1 4 1 3 2 Equipment Supplied 1 6 1 4 RECYCLING 1 6 1 4 1 Recycling Materials 1 6 1 4 2 Labeling 1 6 2 OPERATION 2 1 2 1 INTRODUCTION 2 1 2 2 CONTROLS AND INDICATORS 2 1 2 2 1 Description of Controls 2 1 2 3 OPERATIONAL CHECK 2 4 2 3 1 Purpose 2 4 2 3 2 Battery Test Installation 2 4 2 3 3 Check Test 2 4 2 3 4 Instrument Test 2 5 2 4 MAINTENANCE ACTIONS 2 7 2 4 1 Scheduled Maintenance 2 7 2 4 2 Sto...

Страница 5: ...rometer 4 6 4 4 3 Main Board Radiation Signal Processing 4 6 5 INSTALLATION 5 1 5 1 MOUNTING OPTIONS 5 1 5 1 1 Case Mount 5 1 5 1 2 Rack Mount 5 2 6 SCHEDULED MAINTENANCE 6 1 6 1 CLEANING 6 1 6 1 1 Preparation 6 1 6 1 2 Clean with Care 6 1 6 2 BATTERY REPLACEMENT 6 1 6 2 1 Remove Batteries 6 1 6 2 2 Install Batteries Properly 6 2 6 3 REPLACING AIRFLOW DESICCANT 6 2 6 3 1 Inspection and Removal 6 2...

Страница 6: ...set A 4 A 1 7 Tritium Calibration A 4 A 2 USE OF THE CL 1 TRITIUM CALIBRATOR A 5 A 2 1 Equipment Required A 5 A 2 2 Unpacking A 5 A 2 3 Assemble Calibrator A 5 A 2 4 Leak Check A 6 A 2 5 Initial Procedure A 6 A 2 6 Flushing A 6 A 2 7 Closed Loop Calibration A 7 A 2 8 Calculation of Response A 7 A 3 USE OF 137 CS GAMMA CALIBRATION RANGE A 8 A 3 1 Equipment Required A 9 A 3 2 Disabling the Gamma Com...

Страница 7: ...w Latches Detail View BF 5 3 5 6 Rack Mount Safety Strap 5 3 6 1 Battery Lid Removal 6 1 6 2 Battery Compartment 6 2 6 3 Battery Selection Switch 6 2 6 4 Replacing the Airflow Desiccant 6 3 6 5 Electrometer Desiccant 6 4 6 6 Particulate Filter Replacement 6 5 7 1 Loosening Air Hose 7 2 7 2 Vacuum 7 2 A 1 Discharging Gamma Wall Voltage A 9 A 2 Calibration Setup A 10 LIST OF TABLES Number Title Page...

Страница 8: ...edicine and Surgery WARNING CAUTION AND NOTE STATEMENTS WARNING CAUTION and NOTE statements have been strategically placed throughout this text prior to operating or maintenance procedures practices or conditions considered essential to the protection of personnel WARNING or equipment and property CAUTION A WARNING or CAUTION will appear each time a related step is repeated Prior to operating or c...

Страница 9: ...ING The walls of the each ion chamber are at opposite 75 volt potentials Do not contact either wall or its mounting hardware while equipment is operating CAUTION Avoid immersing the Model 3100 in liquids or allowing spray or rainwater to collect around the instrument ...

Страница 10: ...mined that the chassis needs to be separated from the instrument case a Turn the instrument power OFF disconnect the power cord and remove the batteries b Allow the instrument to sit for one minute before accessing internal components 1 1 3 Keep Out of Water This instrument meets the standards as specified by MIL STD 810G Method 506 procedures I III for moisture exposure but it is not waterproof a...

Страница 11: ...1 2 Figure 1 2 Front View Model 3100 ...

Страница 12: ...e Open Case 1 2 1 Purpose The purpose of this manual is to provide information that will assist in the operation and user maintenance of the Model 3100 in all its modes of use Failure to follow the procedures described herein may result in unsatisfactory performance of the equipment ...

Страница 13: ...r The resulting measurement then is ideally of HT only The IN LINE airflow desiccant may also be used when purging the tritium chamber of adsorbed tritium The core of the tritium detection is the electrometer chamber using a state of the art low noise temperature compensated electrometer chip This electrometer can reliably measure the femtoamperes of current resulting from ionization caused by tri...

Страница 14: ...D Display 2 7 in 6 9 cm diagonal transflective backlit LCD housed inside the electronics enclosure Pollution Degree 3 As defined by IEC 644 Occurs when conductive pollution or dry nonconductive pollution becomes conductive due to condensation Audio 75 5 dB at 2ft at a frequency of 2500 Hz on alarm or failure conditions may be acknowledged and then reset by operator using ACK RESET button Output Se...

Страница 15: ...red but Not Supplied Category Recommended Equipment Application Calibration Tritium Gas Calibrator CL 1 or equivalent Calibration Battery No 1 Phillips Screwdriver Battery door removal Electrometer Desiccant IP10 or T10 torx drive Electrometer desiccant cover removal In line Desiccant No 6 Slotted Screwdriver Desiccant window removal 1 4 RECYCLING There are recyclable materials used in making the ...

Страница 16: ...sing the ACK RESET button once If the radiation activity decreases below the preset level a second press of the ACK RESET button will clear the Alrm text from the display The Model 3100 may be powered either by eight AA sized rechargeable nickel metal hydride NIMH batteries or eight AA sized alkaline batteries or be powered by a mains power cord connected at the back end of the instrument The Mode...

Страница 17: ...ed off Note that in this position the internal batteries are not being recharged even if the mains power cord is connected b The CHECK mode displays the results of several automatic measurement diagnostics Diagnostic results that are within tolerance are marked with a check mark while out of tolerance measurements or conditions are marked with the letter X By pressing the ACK RESET button the seco...

Страница 18: ...enever this control is adjusted the display screen temporarily switches to displaying the adjusted alarm point value The alarm point value may only be set while CHECK mode is selected As the potentiometer is rotated and the units are set to µCi m3 the amount of change varies by 5 while the value is less than 100 varies by 50 when the value is between 100 and 1000 and varies by 500 when the value i...

Страница 19: ...ation 2 3 2 Battery Test Installation The unit may be operated from the connected AC power cord or from internal batteries The batteries if used should be checked each time the instrument is turned on See Section 6 2 for the correct procedure to replace the batteries 2 3 3 Check Test When the unit is deployed the first check is to rotate the main rotary switch from OFF to CHECK The unit powers up ...

Страница 20: ...on is pressed the Fail Air audible alarm will turn on without the status message being displayed Pressing the ACK RESET button to silence the audible alarm will exit the Check Test screen Note If the Check Test value is greater than the alert or alarm values the audible alarms will be activated without the accompanying text being displayed Note At the end of the 60 seconds the instrument will disp...

Страница 21: ...ee Figure 2 8 for an example of an external test screen Figure 2 8 External Instrument Test Screen c Rotate the rotary switch to the SAMPLE position to display the following screen see Figure 2 9 as an example The following example screen shows the current tritium concentration in bold in the middle of the screen the temperature pressure and power status on the top line the current airflow in the ...

Страница 22: ...uirements as listed below 2 4 2 1 Remove Batteries The AA size batteries may be removed any time the instrument is placed into storage Battery leakage may cause corrosion on the battery contacts which must be scraped off and or washed using a solution made from lemon juice or diluted vinegar and mixed 50 with water 2 4 2 2 Fresh Desiccant The instrument should be stored with a fresh desiccant in t...

Страница 23: ...esiccant remains blue when visually checked it can then absorb moisture from the airstream If the desiccant becomes pink it should be replaced See Section 6 3 and 6 4 for the procedures to replace the desiccant The pink desiccant can be re used once it is heated to dry off the moisture See Section 6 3 2 or 6 4 2 on rejuvenation WARNING The silica used may cause irritation to the skin if handled di...

Страница 24: ...Ludlum part number for the lithium batteries is 2536 273 These batteries have been tested and passed per the UN Manual of Tests and Criteria sixth revised edition sub section 38 3 This report is available upon request from Ludlum Measurements Inc Each battery is made of 25 coin cells Panasonic CR1220 with a total of 0 25 g of lithium content in each battery The two batteries are mounted securely i...

Страница 25: ...thin the chamber The level of radioactivity in microcuries per cubic meter of air is shown on the digital display Three ranges provide full scale levels of 102 103 and 104 µCi m3 of tritium in the air An audible alarm can be preset so that the user is notified when the alarm level is exceeded and must be manually reset whenever triggered The instrument is shown in block diagram in Figure 4 1 The u...

Страница 26: ...e and tubing assembly is connected to the particulate filter Figure 4 2 Sniffer Handle 4 2 2 Filter The particulate filter s function is to filter incoming air see Figure 4 3 capturing dust or other particles that might disturb the tritium measurement The filter is normally connected to the intake nozzle on the instrument and to the incoming wand and tubing assembly The filter may become clogged o...

Страница 27: ...the level of tritium present in the air being monitored The mark on the instrument can closest to the back of the instrument identifies the center of the tritium chamber Note that ionization of the air being monitored can also be produced by either a radioactive contaminant in the air or by the action of a background gamma radiation incident to the tritium detector Since it is the purpose of this ...

Страница 28: ...stored in flash memory on the processor The processor also has variables and parameters that may be adjusted via software Inputs to the processor include analog voltages representing temperature pressure chamber bias and the amplified electrometer signal The outputs include a pulse width modulated PWM output for an electrometer offset as well as digital outputs to turn on the internal heater and t...

Страница 29: ...ll of the tritium chamber which is electrically isolated is maintained at approximately 75 VDC while the wall of the gamma chamber which is also electrically isolated is maintained at approximately 75 VDC The center electrodes of both chambers are connected electrically together at the electrometer board Since gamma background affects both chambers this parallel subtracting arrangement provides th...

Страница 30: ...el changes but internally the microprocessor controls three ranges to properly adjust the amplifier gain The microprocessor starts in the X1 range which covers from 1 to 100 µCi m3 0 037 to 3 7 MBq m3 When the chamber reaches 100 µCi m3 3 7 MBq m3 the output of the electrometer is 12 4 mV relative to guard potential and the gain on the main board is switched to the X10 range When the chamber reach...

Страница 31: ......

Страница 32: ...dheld instrument LMI offers two options for mounting it a case mount and a rack mount 5 1 1 Case Mount As shown in Figure 5 1 attach mounting plates with screws to the case These plates are supplied with the instrument Figure 5 1 Back of Case with Wall Mount Figure 5 2 Front of Case with Wall Mount ...

Страница 33: ...atch the four rotary draw latches located on the rack mount to the catches on the side of the instrument as shown in Figure 5 5 b Swing out the handles on the bottom to rotary draw latches on the instrument but do not turn them to unlatch them c Attach the safety strap on the rack mount through the opening in the latch handle as shown in Figure 5 6 ...

Страница 34: ......

Страница 35: ...5 3 Figure 5 5 Rotary Draw Latches Detail View BF Figure 5 6 Rack Mount Safety Strap ...

Страница 36: ......

Страница 37: ...wer cord if attached 6 1 2 Clean With Care CAUTION Do not immerse the instrument in any liquid Gently wipe all exposed surfaces with a damp cloth using only water as a wetting agent Allow instrument to dry thoroughly before reuse 6 2 BATTERY REPLACEMENT Turn the MODE switch to OFF and disconnect the AC power cord if attached before replacing the batteries 6 2 1 Remove Batteries Open the battery li...

Страница 38: ...batteries are placed in the battery compartment in alternating directions Ensure the battery selection switch Figure 6 3 is in the correct position for rechargeable or non rechargeable batteries Figure 6 3 Battery Selection Switch Reinstall the battery lid by tightening all the screws around the perimeter of the battery lid 6 3 REPLACING AIRFLOW DESICCANT In the event the desiccant needs to be ins...

Страница 39: ...the desiccant is replaced or rejuvenated reinstall the clear lid with the two thumbscrews See Figure 6 4 Tighten until hand tight do not use a screwdriver Figure 6 4 Replacing the Airflow Desiccant Note Overfilling the compartment with desiccant material may prevent air flow The lid should not be off for prolonged periods The instrument SHALL NOT be operated without the lid or with a damaged lid c...

Страница 40: ...e pink desiccant in an Erlenmeyer flask in a microwave oven on the high setting for a maximum of 20 seconds Then allow to cool for a minimum of 60 seconds 2 If water vapor is apparent wipe off the water and heat for 20 seconds Repeat these steps until no water vapor is seen b Once the desiccant is replaced or rejuvenated replace the electrometer lid using the four screws See Figure 6 5 Figure 6 5 ...

Страница 41: ...e input airline if used at the bottom of the particulate filter and insert the particulate filter down into its housing Reconnect the T strap to secure the particulate filter ensuring that the T strap is run between the filter nozzle and the filter bracket Reconnect the short airline previously connected to the top of the particulate filter Plastic zip ties may be used to secure the airlines See F...

Страница 42: ...xternal gamma source In either case a failure to measure the correct value within 20 may result If an external gamma source is being used ensure that it is the correct source and that the placement of the source is correct per Section 2 3 4 If this action does not result in a correct reading repair by a technician may be required 7 1 6 Problem Still Exists If after performing the operational check...

Страница 43: ...of 115 VAC power If operation is not restored by this action also ensure that the circuit breaker on the back of the instrument is not toggled to the OFF down position 7 6 LEAKS Perform the can assembly and the air circuit leak tests if a leak is suspected The leak test procedure for the Model 3100 ensures that the air circuit is functioning properly and water ingress will be limited to ensure com...

Страница 44: ...ing pressure in order to locate air bubbles 2 Spray the unit with soapy water bubbles while applying pressure to identify leaks Note The desiccant door will likely leak when applying pressure above 1 psi Continue to look for other leaks 7 6 3 Air Circuit Leak Test a Open the front panel of the Model 3100 by loosening the four latches b Ensure all air hoses are properly connected Note The desiccant...

Страница 45: ...VC clear tubing Sniffer Handle 4520 136 Ludlum 23609 Figure 4 2 Handle with grip attached to tubing AC Power Cable 8520 069 Ludlum 23609 Figure 4 2 35 ft 11 m long power cord Table 8 2 Replaceable Parts for Model 3100 Other replaceable parts referenced in this manual include Item Part Number Manufacturer CAGE Code Reference Number Description Batteries 21 8844 Duracell 90303 Figure 6 2 NIMH AA bat...

Страница 46: ...nc 501 Oak Street Sweetwater TX 39428 McMaster Car Supply Company 600 North County Line Elmhurst IL 60126 90303 Duracell Duracell Berkshire Corporate Park Bethel CT 06801 22627 Multisorb Technologies 325 Harlem Rd Buffalo NY 14224 1WRS2 IMPAK Corporation 13700 S Broadway Los Angeles CA 90061 ...

Страница 47: ... Tritium Calibration A 4 A 2 USE OF THE CL 1 TRITIUM CALIBRATOR A 5 A 2 1 Equipment Required A 5 A 2 2 Unpacking A 5 A 2 3 Assemble Calibrator A 5 A 2 4 Leak Check A 6 A 2 5 Initial Procedure A 6 A 2 6 Flushing A 6 A 2 7 Closed Loop Calibration A 7 A 2 8 Calculation of Response A 7 A 3 USE OF 137 CS GAMMA CALIBRATION RANGE A 8 A 3 1 Equipment Required A 9 A 3 2 Disabling the Gamma Compensation Cha...

Страница 48: ...ssary Use only fresh or revitalized desiccants Refer to the proper section in the manual for replacement procedures If replacements are made wait at least 24 hours before continuing calibration process b Perform mechanical checks and visual inspections to ensure that the switches buttons seals and other mechanical devices function properly and that no obvious defects are present Turn the desiccant...

Страница 49: ...A 1 4 Pressure Calibration to continue d Once the serial number is corrected tab over to the next field to get to the Update button on the lower right hand corner to turn pink Press the Update button to save the correction just made e Do a Ctrl R press the Ctrl key followed by the R key to reload all data This is to confirm that the correction just made to the serial number has been saved correctl...

Страница 50: ...ecommended for new instruments or whenever airflow miscalibration is suspected a Connect a calibrated airflow meter to the input the port labeled IN of the Model 3100 b Operate the instrument in SAMPLE mode and compare readings from the external flowmeter to the Model 3100 displayed value c If there is a significant difference between the two readings adjust the Airflow Cal Constant value on the P...

Страница 51: ...ir 137 Cs calibration range This calibration uses a manufacturer determined gamma equivalence value to determine a gamma field to establish a known reading A calibration constant is adjusted at this one concentration point to correct the displayed tritium concentration value of the Model 3100 In this mode the gamma compensation chamber is disabled by substituting the calibration kit s gamma HV rep...

Страница 52: ...st Note The calibrator is a precision instrument capable of accurate reproducible results Operation is simple but erroneous results can be obtained if an incorrect technique is used Before proceeding further note that the bellows sealed valves on either side of the metering volume have Teflon seals which close with a small amount of pressure CAUTION The valves may be damaged by the use of excess p...

Страница 53: ...ike then drop and then level off to a constant value independent of time constants or pumping speeds The indicated scale reading depends solely upon the system volume and the pressure in the aliquot as described in the next section A 2 8 Calculation of Response Using the technique described in the previous section the 11 mL metering volume is always kept filled with tritiated methane When the outl...

Страница 54: ...la Given that d decay factor HL half life 12 26 years for tritium T years elapsed since original specific activity d e 0 693 xT HL A 2 8 2 Example of Decay Calculation What is the decay factor of a tritium gas cylinder calibrated a year ago d e 0 693 x 1 12 26 d 0 945 A 2 8 3 Example of Tritium Concentration Calculation Given that a tritium gas cylinder with a concentration of 45 x 103 µCi m3 cali...

Страница 55: ...e Model 3100 instrument to OFF rotate the four quarter turn latches and open the instrument b Using a flat blade screwdriver remove the battery marked HV Gamma from its holder Be careful not to short both ends of the battery together It is good practice to put the battery into a small plastic bag c Replace the battery with the aluminum substitute slug LMI 7520 152 This action disables the gamma co...

Страница 56: ... Tritium µCi m3 Equivalence Range Test 600 56 4 9967 During effective range of measurement 450 42 3 7475 X 100 Cal 150 14 1 2492 X 100 Ref 45 4 23 748 X 10 Cal 30 2 28 498 X 10 Ref 4 5 0 42 75 X 1 Cal 1 5 0 14 25 X 1 Ref Note Be sure to account for background reading when performing calibration To calculate calibration constants Expected Reading Net Reading Existing Calibration Constant New Calibr...

Страница 57: ...en the test is performed the check should cause a reading within 20 of the target reading or else the word FAIL will be displayed See Section 2 3 4 for more detailed instructions b Print your parameters by one of two methods 1 Go to Parameters at the top of the program screen and click there to get the drop down menu to locate and select Print Parameters 2 Simply press the Ctrl and P keys to print...

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