The offsite power looks like it won’t be repaired soon and the station has about 2-3 days of diesel fuel available to run critical equipment. They might be able to stretch it further if they can access on-site equipment to minimize generator hours or share a generator among the most critical needs at the plant site.
The 2011 stress tests for Chernobyl provide some insight into the capability at the site.
“there are 75.6 tons of diesel fuel ensuring autonomous operation of two DGs at full load during 3.5 days, or operation of one DG during 7 days ensuring power
supply to makeup systems of SFA storage locations.”
Under more normal conditions diesel fuel could be replenished in a week. Now, it is anyone’s guess.
“5.1.3 Ch Loss of Off-site Power and Loss of the Ordinary Backup AC Power Sources, and Loss of Permanently Installed Diverse Backup AC Power Sources
Power loss scenarios, including loss of off-site power, were considered in the stress tests. Loss of pool water cooling and hydrogen removal functions are the most critical scenarios under loss of power. The following has been defined based on ChNPP stress tests results:
− in case of loss of pool water cooling function, SFA temperature will increase but
will not exceed 70°С (under water presence in the cooling pool), and thus it will
not cause an accident,
− if hydrogen removal function is lost, hydrogen concentration in the cooling pool
will increase and achieve the lower explosive limit (4%) during 10 days according
to the conservative calculations. Experimental studies at ISF-1 demonstrated that
hydrogen concentration stabilizes at 0.2%”
These are the estimates on spent fuel pool heat up if there is a total loss of power and cooling:
The typical time values to achieve the following parameters were obtained in the result of calculations performed:
− fuel cladding temperature will reach 48°С during 2 months in case of pump
failure, and it will be limiting value (stationary state at cooling pool walls and
environment temperature of 20°С),
− fuel cladding temperature can reach maximum 64°С in the cooling pool central
part under the worst environmental conditions when cooling pool walls heat up to
45°С, and environmental temperature is equal to 45°С,
− conditions of fuel cladding heating to higher temperatures during pump failure
and water presence in the cooling pool were not identified (100°С is not
− if there is no water in the cooling pool, fuel cladding temperature (natural air
cooling) will exceed 300°С in 57 days in the cooling pool central part;
The stress test data is somewhat good news but the circumstances of the occupation of the site throws all normal expectations out the window.
Some new photos of the Russian occupation of the Zaporizhzhia nuclear plant were posted on Twitter. The unit occupying the plant has newer well maintained equipment, a stark contrast to most of the Russian equipment seen in Ukraine.
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