EXPERIMENTAL RESULTS

The experimental results of system linearity for an in-core and out-of-core fission chamber are shown in Figures 7-1 and 7-2, respectively. In both cases, the system exhibits ±5 percent linearity over about 5. 5 decades. For the in-core detector, there is no noticeable roll-off at the maximum flux tested so it is very possible that its range can be extended. The range of the out-of-core detector can possibly be extended a little by operation at a higher voltage.

TABLE 7-1

VALUES OF SYSTEM PARAMETERS AND
RESULTING SYSTEM PROPERTIES

Flux, ф(nv)

108

109

1010

1011

1077

1012

1013

1014

Count Rate, ,,, , -1. 41 kij>(sec )

1.6 x 104

1.6 x 105

1. 6 x 106

1.6 x 107

1.6’x 107

1.6 X 10°

1.6 x 109

1.6 x 1010

Input Imped­ance, Z(ohms)

5000

5000

5000

5000

185

185

185

185

(rad sec, )

Л

0

Л

О

10®

10®

3.8 x 10e

3.8 x 10®

3.8 x 10®

3.8 x 10®

4 і

cvL(rad sec )

0. 5 x 10b

0. 5 x 10®

0. 5 x 10s

0. 5 x 105

1.9 x 106

1.9 x 10®

1.9 x 10®

1.9 x 10®

t(sec)

10”1

10”1

10”1

10”1

10”2

10”2

10”2

10"2

PUe-up (2) . Factor

0.2

2

20

2 x 102

6

0.6 x 102

0. 6 x 103

0. 6 x 104

Fractional ^ Std. Dev.

1.9 x 10”2

1 x 10”2

0. 8 x 10”2

0.8 x 10”2

0.4 x 10”2

0.4 x 10”2

0.4 x 10”2

0. 4 x 10”2

False Trip ^ Rate(sec”7)

Reactor Noise ^ Contribution ‘

1 x 10’13

1 x 10”13

X

t—»

О

1

CO

1 x 10”13

.0.8 x 10”16

0.8 x 10’16

0.8 x 10”1®

0.8 x 10”1®

Flux Transient Error

1.6 x 10’5

1.6 x 10”4

1.6 x 10”3

1.6 x 10”2

1.1 x 10”4

1.1 x 10”3

1.1 x 10"2

0.11

NOTES:

(1) Count rate is based on a calculated counting sensitivity of 1. 6 x 10”4 sec”7 nv”7.

(2) The pile-up factor is given by 2 k ф/ (u>H + u>L) and is a measure of the ratio of pulse width

to average interval between pulses. "

(3) The fractional standard deviation is given by Equation (3-55). .

(4) The false trip rate is given by Equation (3-110). Tabulations of values of this property for various operating conditions are shown in subsection 3.4.

(5) The fraction of the signal contributed to by reactor noise is given by Equation (3-100) or (3-108). These values are based on the following assumptions:

(a) Mass of U23® in detector is 0. 6 x 10”® g,

(b) Mass of U235 in reactor is 2 x 10® g,

(c) So e. is 3 x Ю’10,

(d) v(v-)/v’1 is 0. 795, .

(e) Kp is unity,

(f) v is 0. C5 x 10”3 sec, and

(g) /3 is 0. 65 x Ю”2.

(6) The flux transient error tabulated is the value of the second term in Equation (3-66) for

a +100 percent step in flux. . . ■

PERCENT OF MAXIMUM MMSVM READING

104 106 108 1010 1012 1014

NEUTRON FLUX LEVEL IN nv

Figure 7-1. In-Core Fission Chamber Response

PERCENT OF MAXIMUM MMSVM READING

Figure 7-2. Out-Of-Core Fission Chamber Response.

SECTION VIII

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