C.C. PONTA
IRASM Radiation Processing Center,
Horia Hulubei National Institute for Physics and Nuclear Engineering, Magurele, Romania
Email: cponta2013@gmail.com
21.1. INTRODUCTION
In Romania, radiation processing takes place at the IRASM Radiation Processing Center (Fig. 21.1), a department of the Horia Hulubei National Institute for Physics and Nuclear Engineering (IFIN-HH), the most important research and development institute in Romania. IRASM was founded in 2001 with the help of the IAEA, which partially funded the irradiator. It was designed to promote the use of radiation technology in industry and agriculture and the preservation of heritage for public benefit. To be able to fulfil its mission, the
FIG. 21.1. IRASM Radiation Processing Center.
irradiation facility is surrounded by analytical laboratories. The work of these laboratories is to measure and certify the beneficial effects of the irradiation.
IRASM’s structure is presented in Fig. 21.2. On the premises are a Dosimetry Laboratory which has a mini-irradiator and a microbiological laboratory which validates irradiation sterilization. A laboratory for physical and chemical tests is located in a nearby building. It is able to conduct tests for the identification of irradiated foods, mechanical, structural and colorimetric tests, and others. A biocompatibility laboratory works in close cooperation on some IRASM activities related to medical devices. The activities performed at IRASM are certified by DQS Germany as being compliant with ISO 9001, ISO 13485 and ISO 11137. The laboratories received proof of their competence through licensing and accreditations, both domestic and international. The dosimetry lab is traceable at the National Physical Laboratory, United Kingdom, through Risø High Dose Reference Laboratory, Denmark.
Decontamination of cultural heritage objects by irradiation has been considered an activity of national interest since the design of the IRASM facility.
The category IV irradiation facility includes a tote box conveyer and allows industrial irradiation at high doses to be delivered in a short time. In the irradiation room of the facility, there is a space next to the conveyor where oversized artefacts may be placed for irradiation. Paper and other smaller artefacts can be irradiated in containers. Since the construction of the facility (in the 1990s), IRASM staff held periodic meetings with conservators/restorers, presenting information on the irradiation method and establishing relationships of trust with museum staff.
There were also several cases in which small artefacts were decontaminated with an existing irradiator.
The activities mentioned above have brought end users from museums since 2001, the year the IRASM centre was commissioned. The first activity was furniture decontamination for the Cotroceni Museum, Bucharest (Fig. 21.3).
The purpose of the treatment was to remove fungi before restoration. The next year, in 2002, the entire wooden inventory (~10 m3) of a parish church in Izvoarele village was treated (see Chapter 15). Also in 2002, an important project for the National Film Archive took place. It included the treatment of several dozen film reels severely contaminated with fungi (see Chapter 13). The treatment was preceded by several tests.
IRASM activity related to the preservation of cultural heritage has developed continuously and now comprises undertakings ranging from research projects and doctoral theses to international cooperation.
21.2. RESEARCH PROJECTS
Radiation decontamination brings about the intended effect of destroying biodeteriogens as well as side effects consisting of modifications of the materials from which the artefacts are built. The useful biocidal effect is well known and does not require further study. Further research is still needed to learn more about the insufficiently studied area of side effects. This insufficiency is unusual for
FIG. 21.3. Wardrobe from Cotroceni Museum, Bucharest (courtesy of IRASM, IFIN-HH).
the scientific world today, when it is difficult to find an unexplored area. Certain characteristics make this an unattractive research area. These features lead to weak relevance for the tests performed and may even disqualify the research activity. Some specific drawbacks are presented below:
— To evaluate the physical and chemical properties of a material, scientists need to make repeated measurements to counteract the inaccuracy of the measuring method. The samples tested must be identical. Wood, paper, leather or textile samples cannot be identical, as their basic raw materials are not homogeneous. There are not two perfectly alike wooden pieces, sheets of paper or leather pieces. The value measured by the investigator will include variation resulting from the inaccuracy of the measuring method in addition to that resulting from the lack of homogeneity in the samples. Selecting testing samples that fall within a defined reasonable range of homogeneity is difficult and expensive even for new materials.
For aged materials, it is almost impossible. This is the reason such tests are unreliable.
— Many relevant mechanical or chemical testing methods are destructive.
Sacrificing a cultural heritage artefact for a test defies the purpose of such an action. Even when samples can be taken from the artefact for such tests (e.g. textiles), the resulting statistics are poor.
— Extrapolation of results obtained in tests performed on new materials to draw conclusions for aged materials is not relevant.
— Artificial ageing does not follow the same pattern as natural ageing. Indeed, in the United Kingdom an experiment on naturally ageing leather has been going on for several decades. After several more decades, leather samples naturally aged in different environmental conditions will become available for experiments. A similar experiment intended to last 100 years is being conducted in the United States of America on natural paper ageing.
The main consequences of these drawbacks are:
— There are very few standards applicable to the treatment of cultural heritage artefacts. For this reason, different experiments cannot easily be compared to confirm or invalidate them.
— The experiments are often presented at cultural heritage meetings and then published in conference proceedings, not in peer reviewed journals that guarantee high scientific standards. Such papers carry no recognition in the scientific area to which they belong, but sometimes are taken as references by conservators/restorers who do not have any alternative option.