Nuclear Reactor Control

Date: 2015-10-07; view: 445.

Chernobyl Accident

1. Chernobyl accident took place at Chernobyl NPP on April 26, 1986 at 01:23 a.m.

2. Chernobyl power plant is located near Pripyat, Ukraine.

3. The station consisted of four reactors of RBMK-1000 type, each capable of producing 1 gigawatt (GW) of electric power

4. The four units together produced about 10% of Ukraine's electricity at the time of the accident.

5. The construction of the plant began in 1970s, with reactor No.1 commissioned in 1977 followed by No.2 (1978), No.3 (1981) and No.4 (1983).

6. During the daytime of April 25, 1986, reactor 4 was scheduled to be shut down for maintenance.

7. The aim of the test was to determine whether the turbines in the rundown phase could power the pumps while the generators were starting up.

8. At 1:23 a.m. steam to the turbine was shut off.

9. The turbine was disconnected from the reactor increasing the level of steam in the reactor core.

10. The reactor operation became progressively less stable and more dangerous.

11. The reactor jumped to around 30 GW, ten times the normal operational output.

12. An explosion at the plant was followed by radioactive contamination of the surrounding geographic area.

1. Operation of reactors in based on the process of fission chain reaction of U-235.

2. Stable reactor operation depends on the multiplication factor k.

3. If k=1, the reactor is in its critical state and can operate under stationary conditions.

4. If k<1, the reactor is in the subcritical state and so the chain reaction is damped.

5. With k>1 the chain reaction is accelerated.

6. kdeviation is characterized by reactivity p.

7. For reactor stationary operation it is necessary to keep reactivity on the p=0level.

8. This may be achieved through the system of absorber rods.

9. When the control rods are inserted into the core, the neutron absorption increases.

10. When they are moved up, the neutron flux increases.

11. When the reactor is in the active state, the fuel gradually burns out.

12. When the reactivity is depleted, the reaction ceases, the rods are completely drawn up.