Tumours and Lifespan in Rats After Irradiation From Different Neutron Sources

Purpose: To evaluate the dose effect and dose rate relationships for irradiation with different sources of neutrons and compare different sources of neutrons, alpha particles and gamma radiation (a few experiments with a chemical co-carcinogen are also included)

Status: Part A 1977 - 1983, terminated
Part B 1982 - 1985, terminated
Part C 1990 - 1994, terminated

Data in ERAD except for those indicated in red

Treatment: Exposure at the TRITON facility (fission neutrons 0.01-0.1 Gy/h), SILÈNE reactor (flash varying from 10 to 100 msec 1.1017 fissions); (gamma/neutron ratio 1-40),
Cf-252 Source: Gy/min, fission neutrons
Orleans: 8 Gy/min 1-30 MeV Neutrons from cyclotron protons on a Be target;
Saturne: 1-5 Gy/hr, 500 MeV alpha-particles from an accelerator at Saclay
Thalie: Bremsstrahlung 2-6 MeV on a Tantal target from electron generated at 0-8 MeV;
some groups received 6 injections of 25 mg/kg BNF at an interval of 15 days

A) Triton and SILÈNE facilities
B) Orleans, Saturn and Thalie facilities and low dose rate Cf-252 neutrons
C) Low dose rate neutron exposure to a Cf-252 source

Dosimetry: Neutrons: Carbon coated ionization chamber,: double ionization chamber (Ar Te Gas) activation detectors (S, Ni, Mg, Cu, Au) passive semiconductor devices.
Saturne ionization chamber
Gamma source: ionization chamber

Endpoints: Life-span study (spontaneous death) with macroscopic/microscopic pathology

Animal: Male Sprague-Dawley SPF rats at an age of 3 months, one experiment with Wistar rats.

Results: These experiments using external whole body irradiation with neutrons yielded in our rat strain an RBE of about 45 for neutrons in relation to gamma irradiation. The experiments also revealed the different radiosensitivities of the various organs in dependence of dose.
For neutrons, the dose rate seemed to have less influence on the incidence of cancer than for gamma rays or alpha rays.

When the lung was exposed to radiation collimated at different diameters followed by the promoting agent BNF, serial sacrifices revealed that lung cancers appeared always within less than 3 months in the irradiated volume distributed over a surface corresponding to the diameter of the radiation beam.