Fuel debris assessment for Three Mile Island Unit 2 (TMI-2) reactor recovery by gamma-ray and neutron dosimetry
As a result of the accident on March 28, 1979, fuel debris was dispersed into the primary coolant system of the Three Mile Island Unit 2 (TMI-2) reactor. Location and quantification of fuel debris is essential for TMI-2 recovery. TMI-2 fuel debris assessments can be carried out nondestructively by neutron and gamma-ray dosimetry. Efforts to date have been directed toward fuel debris characterization of the makeup and purification demineralizers, will maintain reactor coolant water purity. Two highly specialized dosimetry methods were applied: solid state track recorder (SSTR) neutron dosimetry and continuous gamma-ray spectrometry. The most recent dosimetry results are reviewed and compared. To reduce the intense background radiation from /sup 137/Cs, the Si(Li) detector was surrounded by a 5.5 diameter lead shield 8'' shield in length. The spectral data were used to determine the intensity of the 2.18 MeV gamma ray from the fission product /sup 144/Ce. Assuming this fission product does not migrate out of the fuel, the quantity of /sup 144/Ce is directly related to the quantity of fuel present. Based on the observed source geometry and the measured flux of the /sup 144/Ce 2.18 MeV gamma rays, the fuel content of the A demineralizer was calculated to be 1.3 +- 0.6 Kg. The /sup 137/Cs content was calculated to be 3400 +- 2500 Curies. Both estimates are as of mid-October, 1982. Due to the intense gamma ray fields present near the demineralizers, SSTR neutron dosimeters had to be placed remotely on stringers from outside the cubicle. Background measurements gave a track density of about 5 tracks/cm/sup 2/, whereas baseline measurements in the demineralizer A cubicle was about 10 tracks/cm/sup 2/. This difference is due to room return neutrons. Based on this room return response, the SSTR neutron dosimetry result was 1.7 +- 0.6 kg of fuel in demineralizer A. Consequently the results of SSTR neutron dosimetry and continuous gamma-ray spectrometry are in excellent agreement.
- Research Organization:
- Hanford Engineering Development Lab., Richland, WA (USA)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC06-76FF02170
- OSTI ID:
- 5376146
- Report Number(s):
- HEDL-SA-2867-FP; CONF-831175-1; ON: DE84003950
- Country of Publication:
- United States
- Language:
- English
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Applications of solid state track recorder neutron dosimetry for fuel debris location in the Three Mile Island Unit 2 reactor coolant system
Calibration of SSTR neutron dosimetry for TMI-2 applications
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