DURRIDGE RAD7 User manual
!
OPERATIONAL CHECK
Operational Check Accessory for the RAD7
User Manual
TABLE OF CONTENTS
TABLE OF CONTENTS 2
1 INTRODUCTION 3
Figure 1 Operational Check Components 3
2 OPERATIONAL CHECK 4
Figure 2 Operational Check Setup 4
2.1 Purge the RAD7 5
2.2 Hook up to the Operational Check 5
2.3 3-Hour Test 5
2.4 Cumulative Spectrum 5
2.5 Leak Check 5
2.6 Multiple RAD7s 6
Figure 3 Multiple RAD7 Sensitivity Check Con!guration 6
Table of Contents 2
1 INTRODUCTION
e Operational Check is essentially an uncalibrated sister product to the Natural Rock Sample. Whilst
the Natural Rock Sample provides reproducible, ‘rock steady’ radon and thoron activity concentrations
under conditions of secular equilibrium, the Operational Check is instead intended to be used to make
a quick check that your RAD7 is seeing and correctly identifying counts from radon and thoron. With
careful record-keeping, it can also be used to check for leaks in the RAD7’s internal sample path.
e Operational Check is a 21oz (600g) sample of granite gravel, enclosed in a container that may be
sealed using a pair of ball valves and end caps. Granite generally contains trace amounts of both
uranium and thorium that has been in the rock since it was formed, millions if not billions of years ago.
erefore all the progeny of both the uranium and thorium decay chains are fully supported and in full
equilibrium down to 226-Ra and 224-Ra.
Figure 1 Operational Check Components
Sec$on 1 Introduction 3
2 OPERATIONAL CHECK
Aer sitting sealed on a shelf for one month, the radon in the Operational Check container will have
reached within 1% of a steady value, in which the rate of emission of radon into the container is equal
to the rate of loss by decay and leakage.
Figure 2 Operational Check Setup
Sec$on 2 Operational Check 4
2.1 Purge the RAD7
First, purge the RAD7 with dry air in an open loop for at least 5 minutes, then switch to 1-day protocol:
select Setup, Protocol, 1-day, and push [ENTER]. Start a reading, still sampling fresh air through a
drying unit. Go to the third status window (push the [Menu] key, then push [ENTER], [ENTER], Rt
Arrow, Rt Arrow, and observe the relative humidity in the top right corner. Keep the reading going
until the RH is below 9%, then switch offthe RAD7.
2.2 Hook up to the Operational Check
Hook the RAD7 up to the Operational Check in a closed loop, using the tubing and Small Drying Tube
provided with the device. Use the configuration shown in Figure 2, with the Small Drying Tube
upstream of the RAD7, and the Operational Check connection upstream of the Small Drying Tube. If
one end of the Small Drying Tube has started to turn pink, indicating that it is wet, that end should be
positioned closest to the RAD7 outlet.
2.3 3-Hour Test
Switch on the RAD7 and press the menu key. Select 1-day protocol (Setup, Protocol, 1-day,
[ENTER]). Change the Recycle number to 6 (Setup, Protocol, Recycle, 06, [ENTER]), and the
Format to Long (Setup, Format, Long, [ENTER]). Put the RAD7’s infrared printer in place and
switch offthe RAD7.
Switch on the RAD7 printer. Switch on the RAD7 and let it print out the header, including a review of
the settings. Check the printed review to make sure the Cycle time is 00:30 (30 minutes), the Recycle
number is 06, and Format is set to Long (which ensures that a spectrum is printed at the end of each
Cycle). Open the ball valves on the Operational Check container and start a test (Test, Start,
[ENTER]).
Keep the measurement going until all six cycles are complete and the summary, including the
cumulative spectrum, is printed out (3 hours). When the test is complete, ensure that the RAD7’s pump
is idle, then close the inlet and outlet valves on the Operational Check before disconnecting the tubing.
Once sealed, the Operational Check will begin to build up radon again, and will be ready for another
check in a few weeks’ time.
2.4 Cumulative Spectrum
e cumulative spectrum (based on counts from multiple cycles) gives excellent diagnostic information
on the health of the instrument. With the Recycle set to 6 cycles, as indicated above, at the end of the
sixth cycle the RAD7 will automatically finish the run and print out a run summary. is consists of
some data, a bar chart of the six readings and then the cumulative spectrum. at spectrum should
show a sharp peak in the A window, about midway between the boundaries. ere may also be peaks in
the other three (B, C, D) windows and at 5.3 MeV (210-Po) just to the leof the A window. Please see
the RAD7 manual for a description and image of some possible pathological spectra to watch out for.
2.5 Leak Check
If the RAD7 had developed a leak, the radon concentration in the loop would fall rapidly. us for each
month, a record of the slope should also be maintained, as the radon concentration falls offover time
from decay and any leakage. If during one month the slope is steeper than usual, that would be an
indication of a leak in the loop somewhere.
Sec$on 2 Operational Check 5
2.6 Multiple RAD7s
Before using the Operational Check to check a RAD7, the Operational Check must be lesealed for a
month, in order for the radon inside the container to reach equilibrium. at means a RAD7 can have
its operation checked each month on a regular basis. However, there is nothing to stop us hooking up
multiple RAD7s in series in the loop connected to the Operational Check. is increases the volume of
the loop and hence decreases the radon concentration in the loop. is method is recommended for
checking up to six RAD7s on a monthly basis.
Figure 3 Multiple RAD7 Sensitivity Check Configuration
Each month, all four RAD7s can be connected in series with one another and thoroughly purged and
dried out, before being connected to the Operational Check to check that the instruments are counting
and obtain spectra. During the measurement all the RAD7 pumps, except one, should be set to OFF
(Setup, Pump, Off, [ENTER].)
Sec$on 2 Operational Check 6
Sec$on 2 Operational Check 7
DURRIDGE Company Inc.
900 Technology Park Drive
Billerica, MA 01821
Telephone:!(+1) 978-667-9556
Fax:! ! (+1) 978-667-9557
Web:! ! www.durridge.com
Email:! ! [email protected]
© Copyright 2021 DURRIDGE Company Inc. All rights reserved.
DURRIDGE, the DURRIDGE logo, and the Works with the DURRIDGE logo are trademarks of DURRIDGE
Company Inc., registered in the U.S.
Revision 2021-12-16
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