TEST METHOD
WA 135.2
CHECK OF THE CONSISTENCY OF MEASUREMENTS
BY NUCLEAR MOISTURE/DENSITY METERS:
SECONDARY STANDARD BLOCKS
SCOPE
This method describes the procedure for checking the consistency of measurements by a
nuclear moisture/density meter. The measurements of density and moisture content are
carried out on one or two secondary standard blocks, at two selected direct transmission
depths. The consistency of the density and moisture measurements, at each selected depth,
are assessed by comparison with initial datum values of density and moisture established in
accordance with Test Method WA 2040.2 prior to operational use of the nuclear
moisture/density meter. Allowable deviations of consistency measurements, from the initial
datum values, are also detailed in Test Method WA 2040.2.
Note: It is recommended that the measurements of density and moisture content be carried out in a single
operation. However if the nuclear moisture/density meter has valid calibration equations for the density system
only or moisture system only the check of the consistency may be carried out for that system only. If during the
test valid standard counts can be obtained only for the density or moisture system the procedure should be
continued only for the system with the valid standard counts.
REFERENCED DOCUMENTS
The following documents are referenced in this Test Method:
MRWA Test Methods
Test Method WA 135.1
Test Method WA 2040.2
Calibration of nuclear moisture/density meters: standard blocks.
Operational checks for nuclear moisture/density meters.
APPARATUS
1.
Nuclear moisture/density meter with appropriate valid calibration equations.
Nuclear moisture/density meter manufacturers reference block. A manufacturer's
instruction manual should be available.
Note: Two appropriate valid calibration equations, for the density system, are the low density series,
100 mm and 150 mm direct transmission equations. However other depths may be used for
consistency checks. If a spacer block is being used, then the depth at which the spacer block has
been calibrated should be used as one of the consistency check depths.
For the moisture system the valid calibration equation is that obtained by calibration on the standard
moisture blocks. The intercept of this calibration equation is to be used in the subsequent checks of
consistency.
MAIN ROADS Western Australia
T:WA135_2.doc
Check of the Consistency of Measurements
by Nuclear Meters: Secondary Standard Blocks
Test Method 67/04/135.2
Issue January 2001
Page 1 of 10
TEST METHOD
2.
WA 135.2
Secondary standard blocks. Each block shall be a rectangular prism of natural
stone, concrete or stabilised material. Each block shall have minimum dimensions
of length - 500 mm, width - 500 mm and depth - 250 mm. Each block shall be dried
to a stable moisture content prior being used for checks of consistency of nuclear
moisture/density meters. During storage and transportation, the block(s) shall be
protected from ingress of water. Each block shall be provided with two, source rod
access holes for checks of consistency in the direct transmission mode for density
and moisture determination. These access holes shall be designated and marked as
holes A and B.
Note: A consistency check may be performed on a single block, however the use of two blocks, of
different density, will produce a better check on the consistency of performance of the nuclear
moisture/density meter.
Note: Source access holes may pass through the entire depth of the block. The diameter of a source
access hole shall be sufficient to accommodate the source probe. A 19 mm diameter hole has been
found to be suitable.
3.
Worksheet to record and store the data obtained during the calibration (optional).
Data also may be recorded and stored electronically.
4.
Suitable storage facilities for the block(s) and the nuclear moisture/density meter.
PROCEDURE
Statutory regulations cover the use and transport of radioactive substances. Users shall
ensure that these are complied with for the State or Territory in which the nuclear
moisture/density meter is to be used.
1.
Moisture and Density Consistency Check
1.1
Switch on the nuclear moisture/density meter not less than thirty minutes prior to
initiating the first standard count.
1.2
Ensure that the results of checks specified by the manufacturer are within
specification. Ensure that the results of the stability test, and of the drift test if
required, are within the manufacturer's specification.
Note: It is necessary that these tests be performed not more than one day prior to the check of
consistency. If the manufacturer’s function test includes a drift test this may be carried out during or
following the check of consistency, after the appropriate time lapse.
1.3
Ensure that the secondary standard blocks are at least 600 mm from any vertical
projection with a height more than 50 mm above the surface of the blocks. Ensure
that the surfaces of the secondary standard blocks are free of contamination and the
source rod access holes are clear of obstruction to a depth 25 mm greater than the
depth at which the consistency check(s) are to be conducted.
1.4
Ensure that the base of the nuclear moisture/density meter and the surfaces of the
reference block are free of contamination.
MAIN ROADS Western Australia
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Check of the Consistency of Measurements
by Nuclear Meters: Secondary Standard Blocks
Test Method 67/04/135.2
Issue January 2001
Page 2 of 10
TEST METHOD
1.5
WA 135.2
Locate the reference block at least 2m from any vertical projection more than
50mm above the base of the reference block and at least 5m from any surface
water, or material having a hydrogen content similar to water, and at least 0.5m
above the ground water level. The reference block must be supported in
accordance with the manufacturer's requirements.
Note: Ensure that during the subsequent checks of consistency the location of the reference block
remains the same for all four-minute standard counts.
1.6
Place the nuclear moisture/density meter on the reference block in the position
specified by the manufacturer.
Note: Unless adequately shielded ensure that any gamma radiation source not exceeding 370 MBq
(10 mCi) or neutron emitting source not exceeding 1.85 GBq (50 mCi) is at a distance of not less
than 16 m from the nuclear moisture/density meter. For the definition of adequate shielding and/or
for appropriate clearance distances for sources of greater activity, singly or combined, advice should
be obtained from the Radiation Safety Officer.
1.7
With the source in the shielded position apply downward force to the handle of the
source rod to ensure that the latch is firmly against the location stop.
1.8
Initiate and record two four-minute density and moisture counts. Designate the two
pairs of four-minute counts as d1.1 and d1.2 and the two four-minute moisture counts as
m1.1 and m1.2.
1.9
Calculate
d +d 
C1.1 = d1.1 - d1.2 , E1.1 =  1.1 1.2 
2


and
 m + m1.2 
H 1.1 = m1.1 − m1.2 , I1.1 =  1.1

2


If C1.1 is less than 0.008 (E1.1 ) then d1.1 and d1.2 can be accepted as the first pair
of valid density standard counts.
If H1.1 is less than 0.016(I1.1) then m1.1 and m1.2 can be accepted as the first pair of
valid moisture standard counts.
1.10
If either C1.1 or H1.1 exceeds the stated limits a third four-minute density and
moisture count shall be taken.
Designate these counts as d1.3 and m1.3.
MAIN ROADS Western Australia
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Check of the Consistency of Measurements
by Nuclear Meters: Secondary Standard Blocks
Test Method 67/04/135.2
Issue January 2001
Page 3 of 10
TEST METHOD
1.11
WA 135.2
Calculate
d +d 
C1.2 = d1.1 - d1.3 , E1.2 =  1.1 1.3 
2


and
d +d 
C1.3 = d1.2 - d1.3 , E1.3 =  1.2 1.3 
2


and
H1.2 = m
1.1
-m
,I
 m + m1.3
=  1.1

2





-m
,I
 m + m1.3
=  1.2

2





1.3
1.2
and
H1.3 = m
1.2
1.3
1.3
If C1.2 is less than 0.008 ( E1.2 ) and C1.3 is less than 0.008 ( E1.3 ) then select the
pair d1.1 / d1.3 or d1.2 / d1.3 with the smallest difference as the first pair of valid
density standard counts. If only one pair satisfies the stated limit accept this pair.
If neither of the two pairs satisfies the stated limit, the check of consistency of the
density system should be abandoned and the nuclear moisture/density meter
checked for defects.
If H1.2 is less than 0.016 (I1.2) and H1.3 is less than 0.016 (I1.3) then select the pair
m1.1/m1.3 or m1.2/m1.3 with the smallest difference as the first pair of valid moisture
standard counts. If only one pair satisfies the stated limit accept this pair. If neither
of the two pairs satisfies the stated limit, the check of consistency of the moisture
system should be abandoned and the nuclear moisture/density meter checked for
defects.
1.12
Designate
d +d 
d +d 
 d + d1.3 

E1.0 =  1.1 1.2  or  1.1 1.3  or  1.2






2
2
2






and
 m + m1.2 
 m + m1.3 
 m + m1.3 
 or  1.1
 or  1.2

I1.0 =  1.1






2
2
2






MAIN ROADS Western Australia
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Check of the Consistency of Measurements
by Nuclear Meters: Secondary Standard Blocks
Test Method 67/04/135.2
Issue January 2001
Page 4 of 10
TEST METHOD
1.13
WA 135.2
Place the nuclear moisture/density meter on the secondary standard block. The
source rod should be located over the source access hole marked A and the long
axis of the nuclear moisture/density meter should be parallel to the line connecting
the two access holes.
Note: The correct location of the nuclear moisture/density meter will be facilitated if the outline of
its base at this location is marked on the upper surface of the block. Alternately, a template used in
conjunction with the site preparation plate and drill rod used to prepare the test sites in the field, may
be utilised.
1.14
Depress the source rod handle to the first selected direct transmission depth. If any
resistance to penetration is felt before achieving this depth, the source should be
returned to its shielded position, and the source access hole should be checked for
obstruction. Attention must be given to the correct location of the source rod
handle. Apply downward force to the handle to ensure that the latch is firmly
against the location stop.
1.15
Move the nuclear moisture/density meter carefully until the source rod is felt to touch
the side of the source access hole closest to the detector(s) of gamma radiation.
Remove the template if used.
1.16
Initiate one four-minute density and moisture count. Record the counts with the
identification of the secondary standard block.
1.17
Move the nuclear moisture/density meter carefully to locate the source rod centrally
in the source access hole.
1.18
Depress the source rod handle to the second selected direct transmission depth. If
any resistance to penetration is felt before achieving this depth, the source should
be returned to its shielded position, and the source access hole should be checked
for obstruction. Attention must be given to the correct location of the source rod
handle. Apply downward force to the handle to ensure that the latch is firmly
against the location stop.
1.19
Initiate one four-minute density and moisture count. Record the counts with the
identification of the secondary standard block.
1.20
Move the nuclear moisture/density meter carefully to locate the source rod centrally
in the source access hole and return the source to its shielded position.
1.21
If using one secondary standard block go to Procedure 1.22. If using two secondary
standard blocks repeat Procedures 1.13 to 1.20 with the nuclear moisture/density
meter positioned over the source access hole marked B of the first block used.
1.22
Place the nuclear moisture/density meter on the reference block in the position
specified by the manufacturer.
Note: Unless adequately shielded ensure that any gamma radiation source not exceeding 370 MBq
(10 mCi) or neutron emitting source not exceeding 1.85 GBq (50 mCi) is at a distance of not less
than 16 m from the nuclear moisture/density meter. For the definition of adequate shielding and/or
for appropriate clearance distances for sources of greater activity, singly or combined, advice should
be obtained from the Radiation Safety Officer.
MAIN ROADS Western Australia
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Check of the Consistency of Measurements
by Nuclear Meters: Secondary Standard Blocks
Test Method 67/04/135.2
Issue January 2001
Page 5 of 10
TEST METHOD
WA 135.2
1.23
With the source in the shielded position apply downward force to the handle of the
source rod to ensure that the latch is firmly against the location stop.
1.24
Initiate and record two four-minute density and moisture counts. Designate the pair
of four-minute density counts as d2.1 and d2.2 and the pair of four-minute moisture
counts as m2.1 and m2.2.
1.25
Calculate
C 2.1 = d 2.1 - d
2.2
,E
 d + d 2.2 
, F = E - E
=  2.1
1.0
2.1 
2.1
 2.1
2


and
H
2.1
= m 2.1 - m
2.2
,
I
2.1
+m
m
2.2
=  2.1

2


, L
= I
 2.1

1.0 -
I
2.1
If C2.1 is less than 0.008 (E1.0) and F2.1 is less than 0.013 (E1.0) then d2.1 and d2.2
can be accepted as the second pair of valid density standard counts.
If H2.1 is less than 0.016 (I1.0) and L2.1 is less than 0.011 (I1.0) then m2.1 and m2.2
can be accepted as the second pair of valid moisture standard counts.
1.26
If either C2.1 /H2.1 and/or F2.1 /L2.1 exceed the stated limits a third four-minute
density and moisture count shall be taken. Designate these counts as d2.3 and m2.3.
1.27
Calculate
C
2.2
=d
2.1
-d
2.3
,E
 d + d 2.3
=  2.1
2.2 
2


, F = E - E
1.0
2.2
 2.2

,E
 d + d 2.3
=  2.2
2.3 
2


, F = E - E
1.0
2.3
 2.3

and
C
2.3
=d
2.2
-d
2.3
and
H
2.2
= m 2.1 - m
2.3
,I
 m + m 2.3
=  2.1
2.2 
2


, L = I - I
1.0 2.2
 2.2

,I
 m + m 2.3
=  2.2
2.3 
2


, L = I - I
1.0 2.3
 2.3

and
H
2.3
= m 2.2 - m
MAIN ROADS Western Australia
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2.3
Check of the Consistency of Measurements
by Nuclear Meters: Secondary Standard Blocks
Test Method 67/04/135.2
Issue January 2001
Page 6 of 10
TEST METHOD
WA 135.2
If C2.2 and C2.3 are less than 0.008 (E1.0) and F2.2 and F2.3 are less than 0.013 (E1.0)
then select the pair d2.1/d2.3 or d2.2/d2.3 with the smallest difference as the second
pair of valid standard counts. If only one pair satisfies the stated limits accept this
pair. If neither of the two pairs satisfies the stated limits the consistency check of
the density system should be abandoned and the nuclear moisture/density meter
checked for defects.
If H2.2 and H2.3 are less than 0.016 (I1.0) and L2.2 and L2.3 are less than 0.011 (I1.0)
then select the pair m2.1/m2.3 or m2.2/m2.3 with the smallest difference as the second
pair of valid standard counts. If only one pair satisfies the stated limits accept this
pair. If neither of the two pairs satisfies the stated limits the check of consistency
of the moisture system should be abandoned and the nuclear moisture/density meter
checked for defects.
1.28
If only one secondary block is used repeat Procedures 1.13 to 1.20 with the nuclear
moisture/density meter located over the source access hole marked B of that block.
If two secondary standard blocks are used repeat Procedures 1.13 to 1.20 with the
nuclear moisture/density meter on the second block, over the source access hole A,
then repeat Procedures 1.13 to 1.20 with the nuclear moisture/density meter located
over the source access hole B of that block.
1.29
Place the nuclear moisture/density meter on the reference block in the position
specified by the manufacturer.
Note: Unless adequately shielded ensure that any gamma radiation source not exceeding 370 MBq
(10 mCi) or neutron emitting source not exceeding 1.85 GBq (50 mCi) is at a distance of not less
than 16 m from the nuclear moisture/density meter. For the definition of adequate shielding and/or
for appropriate clearance distances for sources of greater activity, singly or combined, advice should
be obtained from the Radiation Safety Officer.
1.30
With the source in the shielded position apply downward force to the handle of the
source rod to ensure that the latch is firmly against the location stop.
1.31
Initiate and record two four-minute density and moisture counts. Designate the pair
of four-minute density counts as d3.1 and d3.2 and the pair of four-minute moisture
counts as m3.1 and m3.2.
1.32
Calculate
C
3.1
=d
3.1
-d
3.2
,E
 d + d 3.2
=  3.1
3.1 
2


, F = E - E
1.0
3.1
 3.1

and
H
3.1
= m 3.1 - m
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T:WA135_2.doc
3.2
,I
 m + m 3.2
=  3.1
3.1 
2


, L = I - I
1.0 3.1
 3.1

Check of the Consistency of Measurements
by Nuclear Meters: Secondary Standard Blocks
Test Method 67/04/135.2
Issue January 2001
Page 7 of 10
TEST METHOD
WA 135.2
If C3.1 is less than 0.008 (E1.0) and F3.1 is less than 0.013 (E1.0) then d3.1 and d3.2
can be accepted as the third pair of valid density standard counts.
If H3.1 is less than 0.016 (I1.0) and L3.1 is less than 0.011 (I1.0) then m3.1 and m3.2
can be accepted as the third pair of valid moisture standard counts.
1.33
If C3.1/H3.1 and/or F3.1/L3.1 exceed the stated limits and the second pair of valid
standard counts was accepted only after carrying out Procedure 1.26 and 1.27, the
check of consistency should be abandoned.
1.34
If C3.1/H3.1 and/or F3.1/L3.1 exceed the stated limits and the second pair of valid
standard counts was accepted without carrying out Procedure 1.26 and 1.27, a third
four-minute density and moisture count shall be taken. Designate these counts as
d3.3 and m3.3.
1.35
Calculate
C
3.2
=d
3.1
-d
3.3
,E
 d + d 3.3
=  3.1
3.2 
2


, F = E - E
1.0
3.2
 3.2

,E
 d + d 3.3
=  3.2
3.3 
2


, F = E - E
1.0
3.3
 3.3

and
C
3.3
=d
3.2
-d
3.3
and
H
3.2
= m 3.1 - m
3.3
,I
 m + m 3.3
=  3.1
3.2 
2


, L = I - I
1.0 3.2
 3.2

,I
 m + m 3.3
=  3.2
3.3 
2


, L = I - I
1.0 3.3
 3.3

and
H
3.3
= m 3.2 - m
3.3
If C3.2 and C3.3 are less than 0.008 (E1.0) and F3.2 and F3.3 are less then 0.013 (E1.0)
then select the pair d3.1/d3.2 or d3.2/d3.3 with the smallest difference and satisfying
the stated limits as the third pair of valid standard counts. If only one pair satisfies
the stated limits accept this pair. If neither of the two pairs satisfies the stated limits
the check of consistency of the density system should be abandoned and the nuclear
moisture/density meter checked for defects.
If H3.2 and H3.3 are less than 0.016 (I1.0) and L3.2 and L3.3 are less than 0.011 (I1.0)
then select the pair m3.1/m3.3 or m3.2/m3.3 with the smallest difference as the third
pair of valid standard counts. If only one pair satisfies the stated limits accept this
pair. If neither of the two pairs satisfies the stated limits the check of consistency
of the moisture system should be abandoned and the nuclear moisture/density meter
checked for defects.
MAIN ROADS Western Australia
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Check of the Consistency of Measurements
by Nuclear Meters: Secondary Standard Blocks
Test Method 67/04/135.2
Issue January 2001
Page 8 of 10
TEST METHOD
WA 135.2
CALCULATIONS
1.
Density consistency check
1.1
Calculate the mean density standard count using the formula:
E=
E1.0 + [E 2.1 + (E 3.1 or E 3.2 or E 3.3 )] or [(E 2.2 or E 2.3 ) + E 3.1 ]
3
Where E is the mean density standard count and E1.0 and E2.1, E2.2, E2.3 and E3.1,
E3.2, E3.3 were found by selecting pairs of valid standard counts in accordance with
Procedures 1.8 to 1.12 and 1.22 to 1.26 and 1.29 to 1.33.
1.2
Calculate mean of the two four minute density counts, for each transmission depth
on each secondary standard block, to the nearest 0.5. Calculate the count ratios to
the nearest 0.0001 by dividing the mean density counts by E .
1.3
Calculate the density in t/m3, for each transmission depth on each secondary standard
block by substituting of the mean density count ratios in the appropriate low-density
calibration equations. Record densities to the nearest 0.001 t/m3.
1.4
Calculate the absolute difference between the density values calculated in Calculations
1.3 and the datum density value established in accordance with Test Method WA
2040.2, for each relevant secondary standard block and transmission depth.
2.
Moisture Consistency Check
2.1
Calculate
I1.0 + [I 2.1 + (I 3.1 or I 3.2 or I 3.3 )] or [(I 2.2 or I 2.3 ) + I 3.1 ]
3
Where I is the mean moisture standard count and I1.0 and I2.1, I2.2, I2.3 and I3.1, I3.2, I3.3
will be found by the selection of pairs of valid standard counts in accordance with
Procedures 1.8 to 1.12 and 1.22 to 1.26 and 1.29 to 1.33.
I=
2.2
Calculate the mean of the two four minute moisture counts, for each transmission
depth on each secondary standard block, to the nearest 0.5. Calculate the count ratios
to the nearest 0.0001 by dividing the mean moisture counts by I .
2.3
Calculate the moisture contents in t/m3, for each secondary standard block by
substitution of the moisture count ratio in the calibration equation established on the
standard moisture blocks. Record the moisture content to the nearest 0.001 t/m3.
2.4
Calculate the absolute difference between the moisture values calculated in
Calculations 2.3 and the datum moisture value established in accordance with Test
Method WA 2040.2, for each relevant secondary standard block and transmission
depth.
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Check of the Consistency of Measurements
by Nuclear Meters: Secondary Standard Blocks
Test Method 67/04/135.2
Issue January 2001
Page 9 of 10
TEST METHOD
WA 135.2
REPORTING
Report the following:
1.
The Test Method used for the check of consistency, i.e. WA 135.2.
2.
Identification of the nuclear moisture/density meter
3.
Identification of the reference block.
4.
Date of the check of consistency.
5.
Location of the check of consistency.
6.
Density consistency check:
6.1
The identification of the secondary standard blocks used for check of consistency.
6.2
The mean standard density count as calculated in Calculations 1.1
6.3
For each transmission depth, the identification of the calibration equation used.
6.4
For each secondary standard block and transmission depth the density, calculated in
Calculations 1.3, to the nearest 0.001 t/m3.
6.5
The value(s) of the datum density, established in accordance with Test Method WA
2040.2, to the nearest 0.001 t/m3.
6.6
The absolute difference between the datum density value and the secondary
standard block density, calculated in Calculations 1.3 to the nearest 0.001 t/m3.
7.
Moisture consistency check
7.1
The identification of the secondary standard blocks used for the consistency check
7.2
The mean standard moisture count calculated in Calculations 2.1.
7.3
The identification of the calibration equation used.
7.4
For each secondary standard block and transmission depth the moisture content,
calculated in Calculations 2.3, to the nearest 0.001 t/m3.
7.5
The value of the datum moisture value, established in accordance with Test Method
WA 2040.2, to the nearest 0.001 t/m3.
7.6
The absolute difference between the datum moisture value and the secondary
standard block density, calculated in Calculations 1.3, to the nearest 0.001 t/m3.
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Check of the Consistency of Measurements
by Nuclear Meters: Secondary Standard Blocks
Test Method 67/04/135.2
Issue January 2001
Page 10 of 10