Konstantin Petrzhak

Konstantin Petrzhak (alternatively Pietrzak; Константи́н Анто́нович Петржак; 1907–1998) was a Soviet–Russian nuclear physicist and university professor of Polish origin. He discovered spontaneous fission of uranium with Georgy Flyorov in 1940; in addition, he also aided in Soviet Union's atomic bomb project.

Biography
Konstantin Petrzhak was born on 4 September 1907 in Łuków (Congress Poland, Russian Empire, now in Poland; another source also states he was born in Dombrovo, now Kaliningrad oblast. When Konstantin was 12 years old, he started working as a painter at a glass-making factory in Malaya Vishera (Russia). In 1928, he went to Saint-Petersburg to study at the rabfak of Saint Petersburg State University (then called Leningrad State University). In 1931, he joined a radiology group there. Konstantin Petrzhak completed his diploma under the supervision of Igor Kurchatov and graduated from Saint Petersburg State University in November 1936.

In 1934 he began work at Khlopin Radium Institute in Saint Petersburg (First Radium Institute), headed by Igor Kurchatov. Vitaly Khlopin and Kurchatov were his scientific supervisors. He worked there for the rest of his life. Konstantin Petrzhak wrote his Candidate of Sciences thesis, "study of thorium and samarium radioactivity". under Kurchatov's guidance. Petrzhak presented this paper at the Ioffe Institute.

In 1939, Igor Kurchatov asked Petrzhak and Georgy Flyorov to study uranium fission induced by neutrons of different energy levels, following Yakov Frenkel's theory of fission. Georgy Flyorov and Tatiana Nikitinskaya had already made an ionization chamber to detect heavy particles. Kurchatov asked Flyorov, Nikitinskaya and Petrzhak to increase the sensitivity of the ionization chamber. The team created a multilayer ionization chamber to detect decay products originating from the fission of uranium. The ionization chamber utilized electrodes with a total surface area of about 1000 cm2. The chamber's 15 plates were covered with uranium oxide with approximate surface density of 10–20 mg/cm2. The detector compared particle activity to a background level control. When the source of neutrons was taken away, the detector still found particles. The team made three ionization chambers to prove that the effect was not an error, including a more sensitive chamber with a surface area of 6000 cm2. Despite the instrument's high sensitivity, cosmic rays were still a possible source of particle activity. The team moved to an underground lab in the Dinamo station of Moscow Metro (about 50 m below the earth surface) in an attempt to rule out the effects of cosmic rays. In May 1940, they were confident that they had discovered spontaneous fission. The certificate of discovery stated, "the new type of radioactivity with mother nucleus decays into two nuclei, that have kinetic energy of about 160 MeV". Later, the discovery of spontaneous fission was confirmed by Otto Robert Frisch.

In 1940, Petrzhak was recommended for the top team in the soviet atomic bomb project. He is rumored to have participated in said project.

When the Soviet Union entered World War II, Petrzhak was eligible to serve in the Red Army. Winning the Stalin Prize would exempt him from front line service. In the early 1940s, the Academy of Sciences of USSR nominated him for the award, which he did not receive. Sources disagree on whether Petrzhak volunteered, or was drafted into the army.

Petrzhak served in the military intelligence company of a CIWS regiment first as a junior lieutenant, and later as a senior lieutenant. On 28 June 1941, he participated in the battle of Karelian Isthmus. Later, he fought in Volkhov Front. In March 1942 he was ordered to leave the army and join evacuated Radium Institute scientists in Kazan.

In 1943, Petrzhak studied neutron induced fission of uranium under the supervision of professor Piotr Lukirski. In 1944, Petrzhak proposed a method to determine the number of neutrons present during a nuclear reaction, based on the number of protons. He also participated in the development of technology to extract plutonium from irradiated uranium blocks. Jointly with M. Yakunin, Petrzhak developed methods for the radiochemical determination of plutonium, and found the mean free path of Pu-239 alpha particles. Petrzhak founded a laboratory of neutron physics and nuclear fission at the Khlopin Radium Institute in 1947. He was the head of this laboratory until 1986, when he became a part-time contractor.

In 1949, Petrzhak was appointed a member of the Uranium Commission of the USSR Academy of Sciences. He was one of the founders of the Engineering faculty of the Saint Petersburg State Institute of Technology. Petrzhak founded the Saint Petersburg State Institute of Technology department of nuclear physics in 1949, and remained its chair for 22 years. In 1958, he supervised Vladimir Georgievich Korsakov's diploma work.

Konstantin Petrzhak created an express method to detect plutonium and associated radioisotopes in samples of irradiated uranium. From 1963 to 1976, he published a series of articles on the measurement of photofission. From 1973 through 1984, he took part in measuring induced fission cross-sections of U-238, U-235 and Pu-239 when irradiated by monoenergy neutrons In 1978, Konstantin Petrzhak co-authored a paper (with Yuri Oganessian and others) about synthesis of hassium performed in JINR.

Petrzhak was doktor nauk (since 1948) and a professor. He was never elected an academician or the corresponding member of any academy, but Petrzhak was a member of Nuclear Physics Department of Russian Academy of Sciences. According to SCOPUS, Konstantin Petrzhak has 59 publications with Hirsch index 6. Konstantin Petrzhak published articles on fission products from nuclear reactors until his death in 1998. He died on October 10, 1998 and was buried in Saint Petersburg.

Personal life
Konstantin Petrzhak studied painting. He created paintings throughout his life. He used his skills in painting when he covered the plates of ionization chamber with uranium which later led to discovery of spontaneous fission. He was also an amateur violin and guitar player. Konstantin Petrzhak married Galina Ivanovna Mitrofanova (b. 1918), also a radiochemist.

Awards

 * 1946 Stalin prize (2nd degree; jointly with Georgy Flyorov for discovery of spontaneous fission; $100,000$ Soviet roubles each; )
 * 1950 Council of Ministers Prize (for work on fulfillment of governmental tasks)
 * 1953 USSR State Prize (for work on soviet atomic project)
 * 1953 Order of the Red Banner of Labour (for work on soviet atomic project)
 * 1957 Presidium of Academy of Sciences of USSR Prize