CR-39 acceptance test and optimisation for fast neutron dosimetry applications

Area of Science:

• Nuclear Science and Engineering
• Radiation Detection and Measurement
• Materials Science

Background:

• The ENEA fast neutron dosemeter utilizes planar poly allyl diglycol carbonate (PADC) in a polyethylene holder.
• CR-39 plastic has been integral to the ENEA Individual Monitoring Service (IMS) for neutron dosimetry since 1998.
• Routine quality control involves acceptance tests for background track density and neutron sensitivity of new CR-39 batches.

Purpose of the Study:

• To analyze acceptance testing data for CR-39 plastic sheets used in ENEA's neutron dosemeters.
• To compare the dosimetric performance of standard CR-39 with CR-39 modified with dioctylphthalate (DOP).
• To evaluate the impact of CR-39 quality on dosemeter performance and lower detectable dose limits.

Main Methods:

• Analysis of acceptance testing data from over 30 CR-39 sheets produced between 1998 and 2000.
• Irradiation of dosemeters with a 241Am-Be neutron source at ENEA-IRP.
• Chemical etching procedure involving pre-etching and extended etching in KOH solutions.

Main Results:

• Demonstrated significant variability in background track density and neutron sensitivity among CR-39 batches.
• Identified that CR-39 composition, including the addition of DOP, affects background fluctuations and neutron sensitivity.
• Established a correlation between CR-39 plastic quality and the overall dosimetric performance of the fast neutron dosemeter.

Conclusions:

• Rigorous acceptance testing of CR-39 plastic is essential for ensuring the quality and reliability of fast neutron dosemeters.
• The intrinsic properties of CR-39, such as background track density and neutron sensitivity, directly impact dosimetry accuracy.
• Material quality control is paramount for maintaining the effectiveness of individual monitoring services.