Three Mile Island Compare And Contrast

Tuesday, March 01, 2022 10:18:01 AM

Three Mile Island Compare And Contrast



No radiation casualties acute radiation syndrome occurred, and few Three Mile Island Compare And Contrast injuries, though higher than normal doses, were The Day The Cowboys Quit Essay accumulated by The Role Of Conformity In Ayn Rands Anthem hundred workers onsite. Retrieved 26 May The Role Of Conformity In Ayn Rands Anthem In July two of the fresh fuel assemblies were removed from the unit 4 Summary: Destruction Of Individuality By Ray Bradbury and transferred to the central spent fuel pool for detailed inspection to O Brien Love Character Analysis damage, particularly corrosion. Continuous questioning and openness to learning from experience Three Mile Island Compare And Contrast key to safety culture and are essential Three Mile Island Compare And Contrast everyone involved in nuclear power. Cambridge: Deighton, Bell, and co.

Three Mile Island

He visited the plant soon after. Later on Saturday 12 March he extended the evacuation zone to 20 km. Reactors came into commercial operation When the power failed at pm, about one hour after shutdown of the fission reactions, the reactor cores would still have been producing about 1. Without heat removal by circulation to an outside heat exchanger, this produced a lot of steam in the reactor pressure vessels RPVs housing the cores, and this was released into the dry primary containment PCV through safety valves.

Later this was accompanied by hydrogen, produced by the interaction of the fuel's very hot zirconium cladding with steam after the water level dropped. Water injection commenced, using the various systems provide for this and finally the emergency core cooling system ECCS. Seawater injection into unit 1 began at pm on Saturday 12, into unit 3 on Sunday 13 and unit 2 on Monday Tepco management ignored an instruction from the prime minister to cease the seawater injection into unit 1, and this instruction was withdrawn shortly afterwards. Inside unit 1 , it is understood that the water level dropped to the top of the fuel about three hours after the scram about pm and the bottom of the fuel 1. After that, RPV temperatures decreased steadily. As pressure rose, attempts were made to vent the containment, and when external power and compressed air sources were harnessed this was successful, by about pm Saturday, though some manual venting was apparently achieved at about am.

The venting was designed to be through an external stack, but in the absence of power much of it apparently backflowed to the service floor at the top of the reactor building, representing a serious failure of this system though another possibility is leakage from the drywell. The vented steam, noble gases and aerosols were accompanied by hydrogen. At pm on Saturday 12, there was a hydrogen explosion on the service floor of the building above unit 1 reactor containment, blowing off the roof and cladding on the top part of the building, after the hydrogen mixed with air and ignited. Oxidation of the zirconium cladding at high temperatures in the presence of steam produces hydrogen exothermically, with this exacerbating the fuel decay heat problem.

In unit 1 most of the core — as corium, composed of melted fuel and control rods — was assumed to be in the bottom of the RPV, but later it appeared that it had mostly gone through the bottom of the RPV and eroded about 65 cm into the drywell concrete below which is 2. This reduced the intensity of the heat and enabled the mass to solidify. In mid-May the unit 1 core would still have been producing 1. In unit 2 , water injection using the steam-driven back-up water injection system failed on Monday 14, and it was about six hours before a fire pump started injecting seawater into the RPV.

Before the fire pump could be used RPV pressure had to be relieved via the wetwell, which required power and nitrogen, hence the delay. Meanwhile the reactor water level dropped rapidly after backup cooling was lost, so that core damage started about 8 pm, and it is now understood that much of the fuel then melted and probably fell into the water at the bottom of the RPV about hours after the scram. Pressure was vented on Sunday 13 and again on Tuesday 15, and meanwhile the blowout panel near the top of the building was opened to avoid a repetition of the hydrogen explosion at unit 1. Early on Tuesday 15, the pressure suppression chamber under the actual reactor seemed to rupture, possibly due to a hydrogen explosion there, and the drywell containment pressure inside dropped.

However, subsequent inspection of the suppression chamber did not support the rupture interpretation. Later analysis suggested that a leak of the primary containment developed on Tuesday Most of the radioactive releases from the site appeared to come from unit 2. In unit 3 , the main backup water injection system failed at about am on Saturday 12, and early on Sunday 13 water injection using the high pressure system failed also and water levels dropped dramatically. RPV pressure was reduced by venting steam into the wetwell, allowing injection of seawater using a fire pump from just before noon. Early on Sunday venting the suppression chamber and containment was successfully undertaken. It is now understood that core damage started about am and much or all of the fuel melted on the morning of Sunday 13 and fell into the bottom of the RPV, with some probably going through the bottom of the reactor pressure vessel and onto the concrete below.

Early on Monday 14 PCV venting was repeated, and this evidently backflowed to the service floor of the building, so that at am a very large hydrogen explosion here above unit 3 reactor containment blew off much of the roof and walls and demolished the top part of the building. This explosion created a lot of debris, and some of that on the ground near unit 3 was very radioactive. In defuelled unit 4 , at about am on Tuesday 15 March, there was an explosion which destroyed the top of the building and damaged unit 3's superstructure further. This was apparently from hydrogen arising in unit 3 and reaching unit 4 by backflow in shared ducts when vented from unit 3.

Units Water had been injected into each of the three reactor units more or less continuously, and in the absence of normal heat removal via external heat exchanger this water was boiling off for some months. In June this was adding to the contaminated water onsite by about m 3 per day. In January 4. There was a peak of radioactive release on Tuesday 15, apparently mostly from unit 2, but the precise source remains uncertain.

Due to volatile and easily-airborne fission products being carried with the hydrogen and steam, the venting and hydrogen explosions discharged a lot of radioactive material into the atmosphere, notably iodine and caesium. NISA said in June that it estimated that kg of hydrogen had been produced in each of the units. Nitrogen was being injected into the PCVs of all three reactors to remove concerns about further hydrogen explosions, and in December this was started also for the pressure vessels. Gas control systems which extract and clean the gas from the PCV to avoid leakage of caesium were commissioned for all three units.

RPV pressures ranged from atmospheric to slightly above kPa in January, due to water and nitrogen injection. However, since they were leaking, the normal definition of 'cold shutdown' did not apply, and Tepco waited to bring radioactive releases under control before declaring 'cold shutdown condition' in mid-December, with NISA's approval. This, with the prime minister's announcement of it, formally brought to a close the 'accident' phase of events.

The AC electricity supply from external source was connected to all units by 22 March. Power was restored to instrumentation in all units except unit 3 by 25 March. However, radiation levels inside the plant were so high that normal access was impossible until June. Results of muon measurements in unit 2 in indicate that most of the fuel debris in unit 2 is in the bottom of the reactor vessel. Summary : Major fuel melting occurred early on in all three units, though the fuel remained essentially contained except for some volatile fission products vented early on, or released from unit 2 in mid-March, and some soluble ones which were leaking with the water, especially from unit 2, where the containment is evidently breached.

Cooling is provided from external sources, using treated recycled water, with a stable heat removal path from the actual reactors to external heat sinks. Access has been gained to all three reactor buildings, but dose rates remain high inside. Tepco declared 'cold shutdown condition' in mid-December when radioactive releases had reduced to minimal levels. See also background on nuclear reactors at Fukushima Daiichi. Used fuel needs to be cooled and shielded. This is initially by water, in ponds. After about three years underwater, used fuel can be transferred to dry storage, with air ventilation simply by convection. Used fuel generates heat, so the water in ponds is circulated by electric pumps through external heat exchangers, so that the heat is dumped and a low temperature maintained.

There are fuel ponds near the top of all six reactor buildings at the Daiichi plant, adjacent to the top of each reactor so that the fuel can be unloaded underwater when the top is off the reactor pressure vessel and it is flooded. There is some dry storage onsite to extend the plant's capacity. At the time of the accident, in addition to a large number of used fuel assemblies, unit 4's pond also held a full core load of fuel assemblies while the reactor was undergoing maintenance, these having been removed at the end of November, and were to be replaced in the core.

A separate set of problems arose as the fuel ponds, holding fresh and used fuel in the upper part of the reactor structures, were found to be depleted in water. The primary cause of the low water levels was loss of cooling circulation to external heat exchangers, leading to elevated temperatures and probably boiling, especially in the heavily-loaded unit 4 fuel pond. Here the fuel would have been uncovered in about 7 days due to water boiling off. However, the fact that unit 4 was unloaded meant that there was a large inventory of water at the top of the structure, and enough of this replenished the fuel pond to prevent the fuel becoming uncovered — the minimum level reached was about 1.

After the hydrogen explosion in unit 4 early on Tuesday 15 March, Tepco was told to implement injection of water to unit 4 pond which had a particularly high heat load 3 MW from used fuel assemblies in it, so it was the main focus of concern. Initially this was attempted with fire pumps but from 22 March a concrete pump with metre boom enabled more precise targeting of water through the damaged walls of the service floors. There was some use of built-in plumbing for unit 2. Analysis of radionuclides in water from the used fuel ponds suggested that some of the fuel assemblies might have been damaged, but the majority were intact. There was concern about the structural strength of unit 4 building, so support for the pond was reinforced by the end of July. Each has a primary circuit within the reactor and waste treatment buildings and a secondary circuit dumping heat through a small dry cooling tower outside the building.

The next task was to remove the salt from those ponds which had seawater added, to reduce the potential for corrosion. In July two of the fresh fuel assemblies were removed from the unit 4 pool and transferred to the central spent fuel pool for detailed inspection to check damage, particularly corrosion. They were found to have no deformation or corrosion. Unloading the spent fuel assemblies in pond 4 and transferring them to the central spent fuel pool commenced in mid-November and was completed 13 months later. These comprised spent fuel plus the full fuel load of The next focus of attention was the unit 3 pool.

In the damaged fuel handling equipment and other wreckage was removed from the destroyed upper level of the reactor building. Toshiba built a tonne fuel handling machine for transferring the fuel assemblies into casks and to remove debris in the pool, and a crane for lifting the fuel transfer casks. Installation of a cover over the fuel handling machine was completed in February Removal and transferral of the fuel to the central spent fuel pool began in mid-April and was completed at the end of February In June , Tepco announced it would transfer some of the fuel assemblies stored in the central spent fuel pool to an onsite temporary dry storage facility to clear sufficient space for the fuel assemblies from unit 3's pool.

The dry storage facility has a capacity of at least assemblies in 65 casks — each dry cask holds 50 fuel assemblies. Summary: The spent fuel storage pools survived the earthquake, tsunami and hydrogen explosions without significant damage to the fuel, significant radiological release, or threat to public safety. The new cooling circuits with external heat exchangers for the four ponds are working well and temperatures are normal.

Analysis of water has confirmed that most fuel rods are intact. See also background on Fukushima Fuel Ponds and Decommissioning section below. Regarding releases to air and also water leakage from Fukushima Daiichi, the main radionuclide from among the many kinds of fission products in the fuel was volatile iodine, which has a half-life of 8 days. The other main radionuclide is caesium, which has a year half-life, is easily carried in a plume, and when it lands it may contaminate land for some time. It is a strong gamma-emitter in its decay. Cs is also produced and dispersed; it has a two-year half-life.

Caesium is soluble and can be taken into the body, but does not concentrate in any particular organs, and has a biological half-life of about 70 days. In assessing the significance of atmospheric releases, the Cs figure is multiplied by 40 and added to the I number to give an 'iodine equivalent' figure. As cooling failed on the first day, evacuations were progressively ordered, due to uncertainty about what was happening inside the reactors and the possible effects.

By the evening of Saturday 12 March the evacuation zone had been extended to 20 km from the plant. See later section on Public health and return of evacuees. A significant problem in tracking radioactive release was that 23 out of the 24 radiation monitoring stations on the plant site were disabled by the tsunami. There is some uncertainty about the amount and exact sources of radioactive releases to air see also background on Radiation Exposure.

Most of the release was by the end of March Tepco sprayed a dust-suppressing polymer resin around the plant to ensure that fallout from mid-March was not mobilized by wind or rain. In addition it removed a lot of rubble with remote control front-end loaders, and this further reduced ambient radiation levels, halving them near unit 1. In mid-May work started towards constructing a cover over unit 1 to reduce airborne radioactive releases from the site, to keep out the rain, and to enable measurement of radioactive releases within the structure through its ventilation system.

The frame was assembled over the reactor, enclosing an area 42 x 47 m, and 54 m high. The sections of the steel frame fitted together remotely without the use of screws and bolts. All the wall panels had a flameproof coating, and the structure had a filtered ventilation system capable of handling 40, cubic metres of air per hour through six lines, including two backup lines. The cover structure was fitted with internal monitoring cameras, radiation and hydrogen detectors, thermometers and a pipe for water injection. The cover was completed with ventilation systems working by the end of October It was expected to be needed for two years.

In May Tepco announced its more permanent replacement, to be built over four years. It started demolishing the cover in and finished in In December it decided to install the replacement cover before removing debris from the top floor of the building. A crane and other equipment for fuel removal will be installed under the cover, similar to that over unit 4. A cantilevered structure was built over unit 4 from April to July to enable recovery of the contents of the spent fuel pond.

This is a 69 x 31 m cover 53 m high and it was fully equipped by the end of to enable unloading of used fuel from the storage pond into casks, each holding 22 fuel assemblies, and removal of the casks. This operation was accomplished under water, using the new fuel handling machine replacing the one destroyed by the hydrogen explosion so that the used fuel could be transferred to the central storage onsite. Transfer was completed in December A video of the process is available on Tepco's website. A different design of cover was built over unit 3, and foundation work began in Large rubble removal took place from to , including the damaged fuel handling machine.

An arched cover was prefabricated, 57 m long and 19 m wide, and supported by the turbine building on one side and the ground on the other. A crane removed the fuel assemblies from the pool and some remaining rubble. Spent fuel removal from unit 3 pool began in April and was completed in February Maps from the Ministry of Education, Culture, Sports, Science and Tehcnology MEXT aerial surveys carried out approximately one year apart show the reduction in contamination from late to late Areas with colour changes in showed approximately half the contamination as surveyed in , the difference coming from decay of caesium two-year half-life and natural processes like wind and rain.

Tests on radioactivity in rice have been made and caesium was found in a few of them. Summary : Major releases of radionuclides, including long-lived caesium, occurred to air, mainly in mid-March. The population within a 20km radius had been evacuated three days earlier. Considerable work was done to reduce the amount of radioactive debris onsite and to stabilize dust. The main source of radioactive releases was the apparent hydrogen explosion in the suppression chamber of unit 2 on 15 March. A cover building for unit 1 reactor was built and the unit is now being dismantled, a more substantial one for unit 4 was built to enable fuel removal during By the end of , Tepco had checked the radiation exposure of 19, people who had worked on the site since 11 March.

For many of these both external dose and internal doses measured with whole-body counters were considered. It reported that workers had received doses over mSv. Of these had received to mSv, twenty-three mSv, three more mSv, and six had received over mSv to mSv apparently due to inhaling iodine fumes early on. There were up to workers onsite each day. Recovery workers wear personal monitors, with breathing apparatus and protective clothing which protect against alpha and beta radiation. The level of mSv was the allowable maximum short-term dose for Fukushima Daiichi accident clean-up workers through to December , mSv is the international allowable short-term dose "for emergency workers taking life-saving actions".

No radiation casualties acute radiation syndrome occurred, and few other injuries, though higher than normal doses, were being accumulated by several hundred workers onsite. High radiation levels in the three reactor buildings hindered access there. Monitoring of seawater, soil and atmosphere is at 25 locations on the plant site, 12 locations on the boundary, and others further afield. Government and IAEA monitoring of air and seawater is ongoing. Some high but not health-threatening levels of iodine were found in March, but with an eight-day half-life, most I had gone by the end of April A radiation survey map of the site made in March revealed substantial progress: the highest dose rate anywhere on the site was 0.

The majority of the power plant area was at less than 0. These reduced levels are reflected in worker doses: during January , the workers at the site received an average of 0. Media reports have referred to 'nuclear gypsies' — casual workers employed by subcontractors on a short-term basis, and allegedly prone to receiving higher and unsupervised radiation doses. This transient workforce has been part of the nuclear scene for at least four decades, and at Fukushima their doses are very rigorously monitored. If they reach certain levels, e.

Tepco figures submitted to the NRA for the period to end January showed workers had received more than mSv six more than two years earlier and had received 50 to mSv. Early in there were about onsite each weekday. Summary : Six workers received radiation doses apparently over the mSv level set by NISA, but at levels below those which would cause radiation sickness. On 4 April , radiation levels of 0. Monitoring beyond the 20 km evacuation radius to 13 April showed one location — around Iitate — with up to 0. At the end of July the highest level measured within 30km radius was 0. The safety limit set by the central government in mid-April for public recreation areas was 3.

In June , analysis from Japan's Nuclear Regulation Authority NRA showed that the most contaminated areas in the Fukushima evacuation zone had reduced in size by three-quarters over the previous two years. In August The Act on Special Measures Concerning the Handling of Radioactive Pollution was enacted and it took full effect from January as the main legal instrument to deal with all remediation activities in the affected areas, as well as the management of materials removed as a result of those activities. It specified two categories of land: Special Decontamination Areas consisting of the 'restricted areas' located within a 20 km radius from the Fukushima Daiichi plant, and 'deliberate evacuation areas' where the annual cumulative dose for individuals was anticipated to exceed 20 mSv.

The national government promotes decontamination in these areas. Intensive Contamination Survey Areas including the so-called Decontamination Implementation Areas, where an additional annual cumulative dose between 1 mSv and 20 mSv was estimated for individuals. Municipalities implement decontamination activities in these areas. The doses to the general public, both those incurred during the first year and estimated for their lifetimes, are generally low or very low. No discernible increased incidence of radiation-related health effects are expected among exposed members of the public or their descendants. However, the report noted: "More than additional workers received effective doses currently estimated to be over mSv, predominantly from external exposures.

Among this group, an increased risk of cancer would be expected in the future. However, any increased incidence of cancer in this group is expected to be indiscernible because of the difficulty of confirming such a small incidence against the normal statistical fluctuations in cancer incidence. These workers are individually monitored annually for potential late radiation-related health effects. By contrast, the public was exposed to times less radiation. Most Japanese people were exposed to additional radiation amounting to less than the typical natural background level of 2.

The Report states: "No adverse health effects among Fukushima residents have been documented that are directly attributable to radiation exposure from the Fukushima Daiichi nuclear plant accident. People living in Fukushima prefecture are expected to be exposed to around 10 mSv over their entire lifetimes, while for those living further away the dose would be 0. The UNSCEAR conclusion reinforces the findings of several international reports to date, including one from the World Health Organization WHO that considered the health risk to the most exposed people possible: a postulated girl under one year of age living in Iitate or Namie that did not evacuate and continued life as normal for four months after the accident.

Such a child's theoretical risk of developing any cancer would be increased only marginally, according to the WHO's analysis. The man had been diagnosed with lung cancer in February Eleven municipalities in the former restricted zone or planned evacuation area, within 20 km of the plant or where annual cumulative radiation dose is greater than 20 mSv, are designated 'special decontamination areas', where decontamination work is being implemented by the government.

A further municipalities in eight prefectures, where dose rates are equivalent to over 1 mSv per year are classed as 'intensive decontamination survey areas', where decontamination is being implemented by each municipality with funding and technical support from the national government. Decontamination of all 11 special decontamination areas has been completed. In October a member IAEA mission reported on remediation and decontamination in the special decontamination areas. Its preliminary report said that decontamination efforts were commendable but driven by unrealistic targets. Also, there is potential to produce more food safely in contaminated areas.

The total area under consideration for attention is 13, km 2. Summary : There have been no harmful effects from radiation on local people, nor any doses approaching harmful levels. However, some , people were evacuated from their homes and only from were allowed limited return. As of July over 41, remained displaced due to government concern about radiological effects from the accident. Permanent return remains a high priority, and the evacuation zone is being decontaminated where required and possible, so that evacuees can return. There are many cases of evacuation stress including transfer trauma among evacuees, and once the situation had stabilized at the plant these outweighed the radiological hazards of returning, with deaths reported see below.

The government said it would consider purchasing land and houses from residents of these areas if the evacuees wish to sell them. In November the NRA decided to change the way radiation exposure was estimated. Instead of airborne surveys being the basis, personal dosimeters would be used, giving very much more accurate figures, often much less than airborne estimates. Measurement was by personal dosimeters over August-September Disaster-related deaths are in addition to the over 19, that died in the actual earthquake and tsunami. The premature disaster-related deaths were mainly related to i physical and mental illness brought about by having to reside in shelters and the trauma of being forced to move from care settings and homes; and ii delays in obtaining needed medical support because of the enormous destruction caused by the earthquake and tsunami.

However, the radiation levels in most of the evacuated areas were not greater than the natural radiation levels in high background areas elsewhere in the world where no adverse health effect is evident. The figure is greater than for Iwate and Miyagi prefectures, with and respectively, though they had much higher loss of life in the earthquake and tsunami — over 14, Causes of indirect deaths include physical and mental stress stemming from long stays at shelters, a lack of initial care as a result of hospitals being disabled by the disaster, and suicides. As of July , over 41, people from Fukushima were still living as evacuees. The money was tax-exempt and paid unconditionally. In October , about 84, evacuees received the payments.

The Fukushima prefecture had 17, government-financed temporary housing units for some 29, evacuees from the accident. The number compared with very few built in Miyagi, Iwate and Aomori prefectures for the , tsunami survivor refugees there. In April , the first residents of Okuma, the closest town to the plant, were allowed to return home. According to a survey released by the prefectural government in April , the majority of people who voluntarily evacuated their homes after the accident and who are now living outside of Fukushima prefecture do not intend to return. A Mainichi report said that Of the voluntary evacuees still living in Fukushima prefecture, An August Reconstruction Agency report also considered workers at Fukushima power plant.

The death toll directly due to the nuclear accident or radiation exposure remained zero, but stress and disruption due to the continuing evacuation remains high. Summary : Many evacuated people remain unable to fully return home due to government-mandated restrictions based on conservative radiation exposure criteria. Decontamination work is proceeding while radiation levels decline naturally. Removing contaminated water from the reactor and turbine buildings had become the main challenge by week 3, along with contaminated water in trenches carrying cabling and pipework. This was both from the tsunami inundation and leakage from reactors. Run-off from the site into the sea was also carrying radionuclides well in excess of allowable levels.

By the end of March all storages around the four units — basically the main condenser units and condensate tanks — were largely full of contaminated water pumped from the buildings. Some storage tanks were set up progressively, including initially steel tanks with rubber seams, each holding m 3. A few of these developed leaks in Accordingly, with government approval, Tepco over April released to the sea about 10, cubic metres of slightly contaminated water 0. Unit 2 is the main source of contaminated water, though some of it comes from drainage pits.

NISA confirmed that there was no significant change in radioactivity levels in the sea as a result of the 0. By the end of June , Tepco had installed concrete panels to seal the water intakes of units , preventing contaminated water leaking to the harbour. From October, a steel water shield wall was built on the sea frontage of units It extends about one kilometre, and down to an impermeable layer beneath two permeable strata which potentially leak contaminated groundwater to the sea. The inner harbour area which has some contamination is about 30 ha in area. In July-August only 0. Tepco built a new wastewater treatment facility to treat contaminated water. A supplementary and simpler SARRY simplified active water retrieve and recovery system plant to remove caesium using Japanese technology and made by Toshiba and The Shaw Group was installed and commissioned in August The NRA approved the extra capacity in August ALPS is a chemical system which will remove radionuclides to below legal limits for release.

However, because tritium is contained in water molecules, ALPS cannot remove it, which gives rise to questions about the discharge of treated water to the sea. Collected water from them, with high radioactivity levels, was being treated for caesium removal and re-used. Apart from this recirculating loop, the cumulative treated volume was then 1. Almost m 3 of sludge from the water treatment was stored in shielded containers.

ALPS-treated water is currently stored in tanks onsite which will reach full capacity by the summer of As of February , more than 1. Some of the ALPS treated water will require secondary processing to further reduce concentrations of radionuclides in line with government requirements. Disposal will be either into the atmosphere or the sea. In November the trade and industry ministry stated that annual radiation levels from the release of the tritium-tainted water are estimated at between 0. The clean tritiated water was the focus of attention in A September report from the Atomic Energy Society of Japan recommended diluting the ALPS-treated water with seawater and releasing it to the sea at the legal discharge concentration of 0. The WHO drinking water guideline is 0.

The government had an expert task force considering the options. In April the Japanese government confirmed that the water would be released into the sea in This is fed through a catalytic exchange column with a little water which preferentially takes up the tritium. It can be incorporated into concrete and disposed as low-level waste. The tritium is concentrated to 20, times. The MDS is the first system to be able economically to treat large volumes of water with low tritium concentrations, and builds on existing heavy water tritium removal systems.

Each module treats up to litres per day. Earlier in a new Kurion strontium removal system was commissioned. This is mobile and can be moved around the tank groups to further clean up water which has been treated by ALPS. He was an early advocate of democracy and religious freedom, notable for his good relations and successful treaties with the Lenape Native Americans. Under his direction, the city of Philadelphia was planned and developed. Philadelphia was planned out to be grid-like with its streets and be very easy to navigate, unlike London where Penn was from. The streets are named with numbers and tree names. But in his defense, the map he was using was inaccurate, and this threw everything out of whack.

But as all the colonies grew in population and sought to expand westward , the matter of the unresolved border became a much more prominent in mid-Atlantic politics. In colonial times, as in modern times, too, borders and boundaries were critical. Lord Baltimore was an English nobleman who was the first Proprietor of the Province of Maryland, ninth Proprietary Governor of the Colony of Newfoundland and second of the colony of Province of Avalon to its southeast. A problem arose when Charles II granted a charter for Pennsylvania in Negotiations ensued after the problem was discovered in As a result, solving this border dispute became a major issue, and it became an even bigger deal when violent conflict broke out in the mids over land claimed by both people from Pennsylvania and Maryland.

To stop this madness, the Penns, who controlled Pennsylvania, and the Calverts, who were in charge of Maryland, hired Charles Mason and Jeremiah Dixon to survey the territory and draw a boundary line to which everyone could agree. But Charles Mason and Jeremiah Dixon only did this because the Maryland governor had agreed to a border with Delaware. He later argued the terms he signed to were not the ones he had agreed to in person, but the courts made him stick to what was on paper.

Always read the fine print! This agreement made it easier to settle the dispute between Pennsylvania and Maryland because they could use the now established boundary between Maryland and Delaware as a reference. All they had to do was extend a line west from the southern boundary of Philadelphia, and…. Limestone markers measuring up to 5ft 1. Later, in , Pennsylvania and Virginia agreed to extend the Mason-Dixon Line west by five degrees of longitude to create the border between the two colines-turned-states By , the American Revolution was underway and the colonies were no longer colonies.

In , surveyors David Rittenhouse and Andrew Ellicott and their crew completed the survey of the Mason—Dixon line to the southwest corner of Pennsylvania, five degrees from the Delaware River. Other surveyors continued west to the Ohio River. The section of the line between the southwestern corner of Pennsylvania and the river is the county line between Marshall and Wetzel counties, West Virginia.

In , during the American Civil War , West Virginia separated from Virginia and rejoined the Union, but the line remained as the border with Pennsylvania. The Mason—Dixon line along the southern Pennsylvania border later became informally known as the boundary between the free Northern states and the slave Southern states. The official report on the survey, issued in , did not even mention their names. But despite its lowly status as a line on a map, it eventually gained prominence in United States history and collective memory because of what it came to mean to some segments of the American population.

It first took on this meaning in when Pennsylvania abolished slavery. Over time, more northern states would do the same until all the states north of the line did not allow slavery. This made it the border between slave states and free states. Slaves who managed to escape from their plantations would try to make their way north, past the Mason-Dixon Line. However, in the early years of United States history , when slavery was still legal in some Northern states and fugitive slave laws required anyone who found a slave to return him or her to their owner, meaning Canada was often the final destination. Yet it was no secret the journey got slightly easier after crossing the Line and making it into Pennsylvania.

Because of this, the Mason-Dixon Line became a symbol in the quest for freedom. Making it across significantly improved your chances of making it to freedom. Today, the Mason-Dixon Line does not have the same significance obviously, since slavery is no longer legal although it still serves as a useful demarcation in terms of American politics. Beyond this, the line still serves as the border, and anytime two groups of people can agree on a border for a long time, everyone wins.

Instead, people in the North were just as racist, but they went about it in different ways. They were more subtle. And they were quick to judge Southern racist, pushing attention away from them. In fact, segregation still existed in many northern cities, especially when it came to housing, and attitudes towards blacks were far from warm and welcoming. Boston, a city very much in the North, has had a long history of racism, yet Massachusetts was one of the first states to abolish slavery. As a result, to say the Mason-Dixon Line separated the country by social attitude is a gross mischaracterization.

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