**5. Radiation resistance of commercial GFSA components**

An external γ ray source was used to test commercially available GFSA components to analyze the effect of γ radiation. The examination was carried out on the following commercial components (1) SIEMENS (type A) gas surge arresters (nominal voltage 230 V), (2) CITEL BB (type B) bipolar ceramic gas surge arresters (DC spark overvoltage 230 V). Тhе outer dimensions and shape of all components of the same type were the same. The effects of γ radiation on following GFSA characteristics were examined:


The scheme of the test cycle for investigating the radioactive resistance of GFSA by a DC voltage is depicted in **Figure 5**.

Examination of GFSA radioactive resistance was carried out in a gamma radiation field of 60Co at the Institute of Nuclear Sciences "Vinča." The average energy of the applied gamma quantum was 1.25 MeV. The dose rate in air was 87.5, 875, and 1750 cGy/h, respectively. The distance between the radioactive source and the examined overvoltage components was 272, 86, and 60 cm, respectively. All tests were performed at room temperature, 20°C.

Test specimens, consisting of 50 commercial components of a single manufacturer, having identical characteristics, have been used in the experiment. During the formation of experimental groups consisting of 50 components each, the nominal characteristics of the tested components have been measured. When the measured values for a particular component exhibited significant discrepancy with respect to the declared values, they were excluded from further testing in accordance to the Sovene's criterion [2, 8].

The GFSA prebreakdown current as a function of applied voltage without radiation and with γ radiation is shown in **Figure 6A** and **B**, respectively. The diagrams demonstrate:


Single electrons in atomic orbitals have low effective photoionization cross sections due to the small wavelength of high energy γ photons that cause ionization through the Compton effect [21].

The GFSA resistance versus applied voltage is shown in **Figure 7A** and **B**, without radiation and in Co γ field, respectively. From the volt-ampere curve, the volt-ohm characteristic can be easily determined. Formula-defining relationship between resistance and voltage is obtained by linear regression, using least-square minimal error method. The following conclusions are made:


The main conclusions of the experiment are:


**223**

**Figure 6.**

**Figure 5.**

*Influence of Gamma Radiation on Gas-Filled Surge Arresters*

decrease of the resistance was observed.

3.In the prebreakdown regime, GFSA resistance increased linearly with the applied voltage. When the voltage reached breakdown level, an abrupt

4. γ radiation shows significant influence on GFSA performance. In prebreakdown regime, the current had one order of larger magnitude values than

5.In a γ radiation field, resistance also showed a linear increase with the applied voltage, but one order of magnitude was lower than values without radiation.

6.All observed effects of γ radiation on GFSA commercial components had reversible character. Shortly after exposure (in a matter of hours), GFSA

characteristics were the same as before irradiation.

*Scheme of the test cycle for investigating the radioactive resistance of GFSA by a DC voltage.*

*GFSA prebreakdown current without radiation (A) and under γ radiation (B) [9].*

*DOI: http://dx.doi.org/10.5772/intechopen.83371*

without radiation.


#### **Figure 5.**

*Use of Gamma Radiation Techniques in Peaceful Applications*

electrodes in the observed time frame.

irradiation.

through the Compton effect [21].

reaches breakdown level.

1.Before the breakdown in the absence of radiation, the current conducted by GFSA is constant and in the order of 0.1 nA. Upon the breakdown, the current rises very sharply (breakdown voltage being 212 V for type A components and 223 V for type B components). When voltage reaches the breakdown level, an abrupt increase of the current takes place, and current values reach μA level. Radiation causes increased numbers of electron-ion pairs in the area between electrodes, leading to the increase of prebreakdown current (consisting of the free electrons and ions reaching electrodes per unit of time). In the moment of breakdown (when one of the free electrons generated in this way becomes initial), an avalanche process generates a breakdown current, the magnitude of which is independent of the prebreakdown current. Ohm's law cannot be applied in this region, given that the observed two-electrode system saturated: all electron-ion pairs generated reach the

2.The influence of γ radiation on GFSA performance is significant. The prebreakdown current is 10 times larger than the current without radiation. The increase of the radiation dose rate causes an increase in the prebreakdown current. Breakdown occurred at lower voltages (205 V) in a γ radiation field. During the transition between nonconducting and conducting regime, the current increase is not as sharp as compared to the breakdown without

Single electrons in atomic orbitals have low effective photoionization cross sections due to the small wavelength of high energy γ photons that cause ionization

The GFSA resistance versus applied voltage is shown in **Figure 7A** and **B**, without radiation and in Co γ field, respectively. From the volt-ampere curve, the volt-ohm characteristic can be easily determined. Formula-defining relationship between resistance and voltage is obtained by linear regression, using least-square

1.GFSA resistance shows linear increase with the applied voltage in the prebreakdown regime. Increase is more prominent for type A commercial components than type B. Abrupt decrease of the resistance is observed as voltage

2.Resistance also exhibits linear increase with the applied voltage in a γ radiation field but has one order of magnitude lower values than in operation without radiation. A slight decrease of the resistance is observed at voltage values near

breakdown voltage; at breakdown voltage the decrease is pronounced.

1.In a γ radiation field, breakdown occurred at lower voltages (205 V). The values of breakdown voltage for two types of commercial GFSA have been

0.1 nA. When voltage reached breakdown level, an abrupt increase of current

determined in the presence of γ radiation and without radiation.

2.Prior to breakdown, the current had constant values, of the order of

minimal error method. The following conclusions are made:

The main conclusions of the experiment are:

was observed, current values reaching μA level.

**222**

*Scheme of the test cycle for investigating the radioactive resistance of GFSA by a DC voltage.*

**Figure 6.** *GFSA prebreakdown current without radiation (A) and under γ radiation (B) [9].*

**Figure 7.** *GFSA resistance versus applied voltage without radiation (A) and under γ radiation (B) [9].*
