AN ANALYSIS OF A REACTIVITY TRANSIENT IN IRRADIATED THORIUM
Technical Report
·
OSTI ID:4251961
The irradiation of thorium in the MTR is being carnied out primarily for the purpose of producing a quantity of slugs containing U/sup 233/ for use in an exponential assembly. From time to time some of these slugs are removed in order to make reactivity measurements from which the U/sup 233/ content may be estimated. Immediately following removal from the MTR the measured reactivity will vary with time due to the presence of U/sup 233/ fission products, Ii/sup 35/ and Xe/sup 135/, and due to the decay of Pa/sup 233/ to U/sup 233/. The first effect is of negligible importance at the flux levels to which it is feasible to subject slugs of this size. The decay of Pa/sup 233/ however produces a long- term reactivity transient of easily observable magnitude. Measurements of reactivity were made on a Savannah River type slug after irradiation for three MTR cycles at a flux level of about 2.5 x 10/sup 13/ nv. Such measurements continued at intervals for a period of about 161 days. From the results it is estimnted that the net production of U/sup 233/ and Pa/sup 233/ during the irradiation was 0.15 and 0.33 grams. The irradiation flux based on these production figures is estimated to be 1.4x 10/sup 13/ nvt. Conclusions drawn from the results are summarized as follows: (1) The change in reactivity in the slugs is due, within the accuracy of measurements, to the change in U/sup 233/ content. Hence the U/sup 233/ content can be determined at any time, after proper correlation with standards, by a simple reactivity measurement. (2) Because of this, thorium is suitable as a high nvt monitor when used in conjunction with RMF measurements. (auth)
- Research Organization:
- phillips petroleum co. Atomic Energy Div., Idaho Falls, Idaho
- NSA Number:
- NSA-13-019435
- OSTI ID:
- 4251961
- Report Number(s):
- IDO-16513; AT(10-1)-205
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
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