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244Cm contributions to the alpha source term of CANDU reactors

244Cm-Beiträge zum Alpha-Quellterm von CANDU-Reaktoren
F. R. Greening
From the journal Kerntechnik

Abstract

In this report the expected rate of buildup of 244Cm in a CANDU neutron flux is evaluated and used to explain cases of high 244Cm in alpha-active samples from Bruce and Pickering Units. It is demonstrated that 244Cm is enriched on the surface of irradiated pressure tubes where it is associated with Zr/Nb activation products. It is further shown, using 94Nb as a fluence monitor, that the 244Cm/(239Pu + 240Pu) ratio for Bruce and Pickering irradiated pressure tube deposits exhibits a power law = 0.0042 (Fluence)3.1982. For non-pressure tube samples, such as feeder pipes, steam generator deposits and PHTS cruds, it is observed that Zr/Nb activation products are also associated with elevated 244Cm activities. Thus, based on the data presented in this report, the inference is that all CANDU Units may be expected to exhibit significant levels of 244Cm activity on PHTS surfaces, both in and out-of-core, with 244Cm/(239Pu + 240Pu) ratios significantly greater than one.

Abstract

In diesem Bericht wird die erwartete Rate der Anreicherung von 244Cm in einem CANDU-Neutronenfluss ausgewertet und verwendet, um Fälle von hohem 244Cm in alpha-aktiven Proben aus den Blöcken Bruce und Pickering zu erklären. Es wird gezeigt, dass 244Cm auf der Oberfläche der bestrahlten unter Druck stehenden Rohre angereichert wird, wo es mit Zr/ Nb-Aktivierungsprodukten assoziiert ist. Es wird weiter gezeigt, unter Verwendung von 94Nb als Fluenzmonitor, dass das 244Cm/(239Pu + 240Pu) -Verhältnis für bestrahlte Druckrohrablagerungen aus Bruce und Pickering ein Potenzgesetz = 0,0042 (Fluenz)3,1982 aufweist. Für drucklos durchströmte Rohrsegmente wie Einspeiserohre, Dampferzeugerablagerungen und PHTS-Rohre, wird beobachtet, dass Zr/Nb-Aktivierungsprodukte ebenfalls mit erhöhten 244Cm-Aktivitäten verbunden sind. Auf der Grundlage der in diesem Beitrag präsentierten Daten kann daher gefolgert werden, dass bei allen CANDU-Blöcken erhebliche Mengen an 244Cm-Aktivität auf PHTS-Oberflächen sowohl innerhalb als auch außerhalb des Kerns zu erwarten sind, wobei das Verhältnis von 244Cm/(239Pu + 240Pu) deutlich größer als 1 ist.

References

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Received: 2019-06-03
Published Online: 2021-03-30
Published in Print: 2021-04-30

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