Today In History

US President Franklin Roosevelt signed an Executive Order for the establishment of the War Relocation Authority, which led to the internment of Japanese-Americans during WW2. (Source)

US Army General MacArthur arrived at Kooringa, Australia by train and discovered there would be no army waiting for him to reinforce the Philippine Islands. Source.

Eight B-26 Marauder bombers took off from Port Moresby, Australian Papua at 0900 hours; one of them would return to base due to engine trouble. The remaining seven attacked Vunakanau airfield and Lakunai airfield near Rabaul, New Britain, causing minimal damage. As the bomber crews returned to base, they reported a sighting of a fleet carrier (most likely mis-identified Kasuga Maru), causing the commanders to scramble to prepare a major strike against the target ...

On a passage from Buenos Aires, Argentina for New York, United States via Rio de Janiero, Brazil the 7,417-ton neutral Argentinian motor tanker Victoria with linseed oil was spotted 200 kilometers east of Hampton Roads, Virginia, United States by the German submarine U-201 under command of Adalbert Schnee. A torpedo was launched from the submarine which struck the Victoria on her port side between No.s One and Two holds. The master of the tanker immediately ordered the engines stopped and a distress call to be made, however as the ship seemed not to be settling the crew remained on board. An hour later at 0145 hours Schnee ordered another torpedo to be fired which also struck on the port side near to the bridge, he then surfaced and only then saw that the tanker was a neutral vessel. He immediately reported the mistake to the Commander of Submarines of the wolfpack, who ordered him to submerge and leave the area. The crew abandoned ship after the second hit in two lifeboats which were shortly thereafter separated by wind in the darkness. The distress signal had been picked up by the American Minesweeper USS Owl (AM 2) which was towing the oil barge YOG-38 to Bermuda. She arrived after seven hours and inspected Victoria at dawn; the tanker was lying on an even keel with two gaping holes in her port side. She seemed to be salvageable so a boarding party of eight men was transferred to the tanker and they worked the whole day to start the diesel engines, but the rough seas prevented an engineer that was needed aboard could be transferred during the afternoon. Consequently the men had to remain aboard the next night ... =0px

Squadron Leader John Dering Nettleton of No. 44 (Rhodesia) Squadron RAF was gazetted for the Victoria Cross award for leading a bombing run on German factories in Augsburg, Germany on 17 Apr 1942 ...

On this day 35 years ago, there was an accident at the Chernobyl NPP, at approximately 01:23, two thermal explosions occurred at the fourth power unit of the Chernobyl NPP, which completely destroyed the reactor.

This accident was the result of criminal inaction by the Soviet authorities, because the reasons that led to the explosion of the reactor were known 11 years before the Chernobyl accident.

So one of the main causes of the accident was the "final effect".

An error in the design of the control rods was dangerous. To control the power of the nuclear reaction, rods containing a neutron-absorbing substance are introduced into the core. When the rod is removed from the core, water remains in the channel, which also absorbs neutrons. In order to eliminate the negative impact of this water, graphite extruders were located under the rods in the RBMK. But with the rod fully raised, a column of water 1.5 meters high remained under the extruder. (Reduced by 1.5 meters, the extruder was used for economic reasons - it made it possible to reduce the height of the reactor room).

When the rod moves from the upper position, the absorber enters the upper part of the zone and introduces negative reactivity, and in the lower part of the channel the graphite extruder replaces water and introduces positive reactivity. At the time of the accident, the neutron field had a dip in the middle of the core and two maxima - in its upper and lower parts. With this field distribution, the total reactivity introduced by the rods during the first three seconds of movement was positive. This is the so-called "Final Effect", as a result of which the operation of the emergency protection in the first seconds increased power, instead of stopping the reactor immediately.

As for the criminal without the action of the Soviet authorities, on November 30, 1975, a similar incident with the Chernobyl accident took place at the Leningrad NPP, there was a local leakage of radiation, later it was determined that the cause of the accident was the same "final effect".

Thus, for more than 11 years, the Soviet authorities did nothing to prevent a possible accident, and the "final effect" of the rods was eliminated after the accident by modernizing the reactors.

eternal memory of the heroes-liquidators of the consequences of the accident ....