L. CORTELLA ARC-Nucléart, Grenoble, France
Email: laurent.cortella@cea.fr
11.1. INTRODUCTION
While it was on display at the Cairo Museum, the mummy of Ramses II began to present signs of pest infestation due to the hot and humid environment, and the unsealed glass cover used to protect it (1975). In the framework of an exhibition held in Paris (1976) on the subject of Ramses II and numerous artefacts relating to his reign, the mummy was transferred to France for examination by the French National Museum of Natural History. Having been damaged in the past by insect larvae, the mummy was also found to be infested by a dense population of various types of fungi, though without any pathogenic bacteria. In agreement with the Egyptian authorities, it was therefore decided to disinfect the mummy by gamma irradiation, a process that had been used for many years at the Nucléart laboratory (renamed ARC-Nucléart in 1987) located in the CEA’s Grenoble Research Centre.
11.2. FROM HISTORY TO PROCESS
A consortium of laboratories and museums was set-up in Paris (Anthropology Museum, Musée de l’Homme) and Grenoble, coordinated by a research laboratory in Paris, in order to manage the different steps of the project:
preliminary studies and testing, the treatment itself, and the return of the mummy to the Cairo Museum. Indeed, more than four hundred samples were taken from other mummies for testing under gamma irradiation in order to determine the irradiation dose to be applied; this had to be effective enough to eradicate all the fungi (of which there were more than sixty species) but not harm the components of the mummy such as the hair, textiles, skin and teeth. No sampling of the actual mummy of Ramses II was authorized, except for some fragments of hair and textile that were lying on the linen or on the Plexiglas plate placed under it. It was
very important to design the cover under which the mummy would be kept during irradiation, and even after, to ensure a sterile atmosphere around it and thus avoid any recontamination (Figs 11.1 and 11.2).
Due to the length (1.72 metres) and uneven shape of the mummy (especially the arrangement of the arms), as well as the presence of the sarcophagus and various other materials inside it, it was necessary to design dosimetry software based on simple geometric forms representing the whole artefact to be treated in order to determine the irradiation dose in each part of the mummy. As the density of the materials could not be estimated accurately, equivalent data were obtained from other mummies. Thanks to the calculus model, the gamma ray source was designed in a way that satisfied the irradiation parameters, which included a 18 kGy disinfection dose at an average dose rate of 1.5 kGy/h. It was possible to determine the dose rate at each point of the mummy model, depending on its position with respect to the 60Co source and the presence or absence of absorbing materials. The challenge was to apply this minimum dose of 18 kGy to all parts of the mummy. The model was validated by irradiating two mummies dedicated to the studies, one from the Museum of Fine Arts in Grenoble and the other from the Anthropology Museum in Paris. Good agreement between the calculated and measured irradiation doses was obtained [11.1].
During irradiation, it was necessary to keep the mummy, the sarcophagus and various materials in a sealed plastic envelope similar to a glove box, so
the artefact could be manipulated afterwards in a sterilized atmosphere. The irradiation phase could then be started in the facility at the CEA Research Centre at Saclay, near Paris, which at the time (May 1977) had a radiation activity of 5.92 × 1015 Bq. Irradiation lasted 12 hours and 40 minutes, with the mummy being rotated halfway through this period. The ratio between the maximum and minimum gamma ray dose was 1.33, and the measurement uncertainty was around 10%. The disinfected mummy is displayed in its sealed transparent Plexiglas cover in which the sterilized atmosphere is permanently maintained thanks to a pumping and filtering system located in the base supporting the covered sarcophagus.
Many factors contributed to the success of the operation, which preserved the mummy of Ramses II in excellent conditions that are still maintained after almost forty years. The irradiation process proved to be highly effective in handling this complex case. Last but not least, the skills of the different partners involved as well as the perfect coordination between them were key factors in meeting the challenges in applying such a unique treatment process in such a short period of time [11.2, 11.3].
REFERENCES TO CHAPTER 11
[11.1] de TASSIGNY, C., BROUQUI, M., “Adaptation à la désinfection de la momie de Ramses II du procédé de radio-stérilisation gamma”, Proc. Comité pour la conservation de l’ICOM, 5ème réunion triennale Zagreb, 1978, ICOM, Paris (1978) 1–16.
[11.2] BALOUT, L., ROUBET, C., DESROCHES-NOBLECOURT, C., La momie de Ramses II: Contribution scientifique à l’égyptologie, Editions Recherche sur les Civilisations, Paris (1985).
[11.3] RAMIERE, R., “Protection de l’environnement culturel par les techniques nucléaires”, Proc. Conf. Industrial Application of Radioisotopes and Radiation Technology Grenoble, 1981, IAEA, Vienna (1982) 255–270.
FIG. 11.2. The mummy of Ramses II.