| Abstrakt: | CONCLUSION. A high dose rate such as 3 Mrad/h is not suitable for use as a source of radicals and reactive species in a suspension of pulp. At this dose rate, a small increase in the ISO brightness is observed, while at the same time a large loss of paper physical properties is seen. With the dose rate around 300 krad/h one can increase the ISO brightness, and not adversely affect the physical properties of the pulp. Some of the reactive species formed during the y rays irradiation are relatively non selective in their attack of the surrounding pulp suspension: they attack both cellulose (in the micro fibrils) and lignin. However, when OH are generated, they attack the same chromophores as H2O2 during alkaline bleaching (phenolic hydroxyl groups, coniferaldehydes, quinones) and H2O2 and OH radicals are thus in direct competition with one another. |
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