Fig. 7 Method Comparison
Method
RAD H
2
O 40 RAD H
2
O 250 Big Bottle System
Liquid Scintillation
Lucas Cell
Sample Size (mL)
40
250
2500
10
10
Sensitivity (cpm/pCi/
L)
0.008
0.05
0.3
0.09
0.05
Background (cpm)
0.1*
0.1*
0.1*
15
0.25
2-sigma uncertainty at 300 pCi/L (in pCi/L)
20-minute count
88
35
32
35
60-minute count
51
20
2.5
19
20
120-minute count
36
14
1.8
14
14
2-sigma uncertainty at 100 pCi/L (in pCi/L)
20-minute count
53
20
24
20
60-minute count
31
12
1.5
14
12
120-minute count
22
8.5
1.1
10
8.5
DL (C=2*(1+sqr(1+2*B)) in pCi/L) (NPDWR 40-CFR-41.25)
20-minute count
40*
6*
28
9
60-minute count
19*
3*
0.4*
16
4
300-minute count
7*
1*
0.18*
7
2
LLD (C=4*(1+sqrB)) in pCi/L (Altshuler)
20-minute count
60*
10*
41
13
60-minute count
29*
5*
0.6*
23
6
300-minute count
11*
2*
0.25*
10
3
Section 5
Accuracy and Quality Control
24
