how was it developed ?
In August 1941 Fermi began to plan the building of a sub-critical assembly to test with a smaller structure whether a larger one would work. The pile was built in September 1941 from graphite blocks and tinplate iron cans of uranium oxide.
Chicago Pile-1
Another grant, this time of $40,000, was obtained from the S-1 Uranium Committee to purchase more materials, and in August 1941 Fermi began to plan the building of a sub-critical assembly to test with a smaller structure whether a larger one would work. The so-called exponential pile he proposed to build was long, wide and high. This was too large to fit in the Pupin Physics Laboratories. Fermi recalled that: 
The pile was built in September 1941 from graphite blocks and tinplate iron cans of uranium oxide. The cans were cubes. When filled with uranium oxide, each weighed about . There were 288 cans in all, and each was surrounded by graphite blocks so the whole would form a cubic lattice structure. A radium-beryllium neutron source was positioned near the bottom. The uranium oxide was heated to remove moisture, and packed into the cans while still hot on a shaking table. The cans were then soldered shut. For a workforce, Pegram secured the services of Columbia's football team. It was 
where can the resource for nuclear energy be found It is produced by nuclear fission of uranium and plutonium. what is nuclear power ? It is the use of nuclear reactions that release nuclear energy to generate heat, which most frequently is then used in steam turbines to produce electricity in a nuclear power plant. which was the first nuclear reactor ? Chicago Pile-1 does this power produce any waste ? Yes, spent nuclear fuel is the waste generated. what are different types of waste ? Low-level radioactive waste, is one type of nuclear waste. It is found in the form of contaminated items like clothing, hand tools, water purifier resins, and the materials of which the reactor itself is built. what is nuclear fusion ? It is a proposed form of power generation that would generate electricity by using heat from nuclear fusion reactions. how is the waste disposed off ? There are no commercial scale purpose built underground high-level waste repositories in operation. Presently, waste is mainly stored at individual reactor sites and there are over 430 locations around the world where radioactive material continues to accumulate. the first nuclear reactor you mentioned above where is located ? Stagg Field what was  its significance ? The successful test of CP-1 not only proved that a nuclear reactor was feasible, it demonstrated that the "k" factor was larger than originally thought. It removed the objections to the use of air or water as a coolant rather than expensive helium. It also meant that there was greater latitude in the choice of materials for coolant pipes and control mechanisms.
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Chicago Pile-1 [SEP] Development
In a nuclear reactor, criticality is achieved when the rate of neutron production is equal to the rate of neutron losses, including both neutron absorption and neutron leakage. When a uranium-235 atom undergoes fission, it releases an average of 2.4 neutrons. In the simplest case of an unreflected, homogeneous, spherical reactor, the critical radius was calculated to be approximately: where "M" is the average distance that a neutron travels before it is absorbed, and "k" is the average neutron multiplication factor. The neutrons in succeeding reactions will be amplified by a factor "k", the second generation of fission events will produce "k", the third "k" and so on.