The accident to the NRX reactor on December 12, 1952

Technical Report · Mon Jul 13 04:00:00 EDT 1953

OSTI ID:4379334

Lewis, W. B.

Because of a complex concurrence of mechanical defects in the shut-off-rod system and operating errors which alone would not have caused serious trouble, a power surge occurred in the NRX reactor during preparations for experiments at low power. Some of the cooling arrangements at the time were adequate only for low-power operation. Consequently some of the natural-uranium metal melted and ruptured the aluminum sheathing and tubes which separated the heavy-water, air, and cooling-water systems. As a result some 20,000 curies of fission products from long-irradiated uranium were carried by a flood of 1,000,000 gal of cooling water into the basement. Fused masses of highly irradiated uranium and uranium oxide were left inside the calandria, and the core vessel of the reactor and tubes of the calandria were severely damaged. In such a high-flux reactor where the transient xenon poison may affect the reactivity by 40 milli-k (mk), the shut-off rods have to cover a reactivity range of about 70 mk. As one lesson from the accident it appears preferable to withdraw the first or safeguard bank of shut-off rods soon after shutting down, instead of making this the first step of the actual start-up.

• Research Organization: Atomic Energy of Canada Ltd. Chalk River Project, Chalk River, Ontario (Canada)
• NSA Number: NSA-10-000375
• OSTI ID: 4379334
• Report Number(s): DR--32; AECL--232
• Country of Publication: Canada
• Language: English

Related Subjects

ACCIDENTS
AIR
ALUMINUM
CANNING
CONTAMINATION
CONTROL ELEMENTS
COOLANT LOOPS
DEFECTS
EXCURSIONS
FAILURES
FISSION PRODUCTS
HEAVY WATER
IRRADIATION
MECHANICS
MELTING
METALS
NATURAL URANIUM FUEL
NRX
PHYSICS
POISONING
POWER
RADIOACTIVITY
REACTIVITY
REACTOR CORE
REACTORS
RODS
SHUTDOWN
TRANSIENTS
TUBES
URANIUM OXIDES
VESSELS
XENON