Foram encontradas 60 questões.
Disciplina: TI - Desenvolvimento de Sistemas
Banca: CESGRANRIO
Orgão: Eletronuclear
- Engenharia de SoftwareTestes
- Fundamentos de ProgramaçãoAlgoritmosAlgoritmos de Ordenação
- Fundamentos de ProgramaçãoLógica de Programação
Seja um array composto por 7 números inteiros.
[ 5, 15, 77, 21, 5, 25, 2 ]
Esse array foi usado por um profissional de teste de software para testar uma função que ordena, de forma ascendente, um array de números inteiros. Essa função implementa o algoritmo de ordenação por seleção.
Para avaliar a evolução do array sendo ordenado, o profissional de teste solicitou ao programador que criou a função de ordenação que fizesse uma modificação no código, de modo que o somatório dos elementos do array com índices 2, 3 e 4 seja exibido no console imediatamente antes do incremento da variável ( i ) que controla a execução do comando de repetição mais externo.
Feitas as modificações solicitadas, o código da função passou a ter a seguinte forma geral:
ordena (int vetor[ ]) {
int i = 0;
int tam = length (vetor); // comentário: a função length retorna a quantidade de elementos de um array
while ( i < tam ) {
while ( ) {
// comentário: isso é apenas a forma geral do algoritmo de ordenação
// não é o código completo
}
print ( vetor[2] + vetor[3] + vetor[4] );
i = i + 1;
}
}
O que será exibido no console pelo comando print na 3ª iteração do comando de repetição mais externo?
Provas
A descrição de esquemas de bancos de dados relacionais pode ser feita por meio da seguinte notação:
- Uma tabela possui um nome e um conjunto de colunas, separadas por vírgulas.
- Em uma linha qualquer, os valores referentes às colunas são atômicos e monovalorados.
- Colunas que compõem a chave primária aparecem sublinhadas.
- A notação X → Y indica que Y depende funcionalmente de X (ou X determina Y).
Um banco de dados possui uma única tabela, cujo esquema é o seguinte:

Qual é o número mínimo de tabelas que esse banco de dados deve ter para que seu esquema atenda à 1FN e à 2FN, apenas?
Provas
Disciplina: TI - Desenvolvimento de Sistemas
Banca: CESGRANRIO
Orgão: Eletronuclear
- Fundamentos de ProgramaçãoAlgoritmosAlgoritmos de Busca
- Fundamentos de ProgramaçãoAlgoritmosAnálise de Execução de Algoritmos
- Fundamentos de ProgramaçãoEstruturas de DadosEstrutura de Dados: Array
Seja uma função que realiza uma busca binária sobre um array de números inteiros ordenados. Não se sabe, em princípio, se os números estão ordenados ascendente ou descendentemente. O cabeçalho dessa função é o seguinte:
int busca (int [ ] vet, int elem)
Isto é, a função busca recebe um array de números inteiros (vet) e um número inteiro (elem) como parâmetros, e retorna um número inteiro. Caso exista em vet um inteiro igual a elem, a função retornará o índice desse inteiro no array; caso contrário, a função retornará -1.
O algoritmo de busca binária produz um índice (ind) a cada iteração sobre o array, tendo em vista comparar o elemento que se deseja procurar (elem) com o elemento vet [ ind ]. Isto é:
if ( vet [ ind ] == elem )
return ind;
No comando acima, diz-se que houve uma visita ao elemento vet [ ind ].
Admita que a função busca foi chamada por meio do comando a seguir:
int resp = busca (vet, 50);
Sabendo-se que os elementos visitados foram 54, 17, 33 e 50, nesta ordem, qual array foi passado como parâmetro para a função busca?
Provas
Disciplina: TI - Desenvolvimento de Sistemas
Banca: CESGRANRIO
Orgão: Eletronuclear
- Fundamentos de ProgramaçãoFunções, Métodos e Procedimentos
- Fundamentos de ProgramaçãoTipos de Dados
- Fundamentos de ProgramaçãoRecursividade
- Paradigmas de ProgramaçãoOrientação a ObjetosOrientação a Objetos: Classes e Objetos
Uma linguagem de programação orientada a objetos possui uma classe, chamada String, que é usada para representar cadeias de caracteres. Essa classe possui inúmeros métodos, dentre os quais se destacam os seguintes:
- int length() – retorna um inteiro que representa a quantidade de caracteres de uma string. Por exemplo, ”Brasil”.length() é igual a 6.
- char charAt(int p) – retorna o caractere da posição p de uma string. Por exemplo, “Brasil”.charAt(0) é igual a ‘B’.
- int indexOf(char c) – retorna o índice da string onde se localiza a 1ª ocorrência do caractere c. Caso c não pertença à string, a função retorna -1. Por exemplo, ”Brasil”.indexOf( ’s’ ) é igual a 3.
- String substring(int p) – retorna uma substring contendo os caracteres da posição p até length() – 1. Por exemplo, ”Brasil”.substring(2) é igual ”asil”.
Além das funções anteriores, o operador + foi sobrecarregado para executar uma concatenação quando os dois operandos forem do tipo String. Por exemplo, ”Bra” + ”sil” é igual a ”Brasil”.
A função a seguir tem por objetivo percorrer uma string (str), recebida como parâmetro, e retornar outra string, que deve ter os mesmos caracteres que str, exceto as vogais minúsculas, que devem ser trocadas pelas suas correspondentes maiúsculas.
String troca(String str) {
String min = ”aeiou”;
String mai = ”AEIOU”;
char c;
int pos;
if (str.length() == 0)
return ””; // comentário: retorna uma string vazia
c = str.charAt( 0 );
pos = min.indexOf ( c );
if ( pos != -1 ) { // comentário: != significa diferente
c = mai.charAt ( pos );
// 1
}
// 2;
}
A função acima não está completa. É preciso substituir os comentários // 1 e // 2 por comandos que façam com que a função execute a troca de vogais minúsculas por vogais maiúsculas e retorne a string resultante.
Quais comandos completam a função de acordo com o objetivo definido acima?
Provas
O controle diário da utilização de passes de metrô em uma cidade é feito por programas que utilizam um banco de dados composto pelas seguintes tabelas:
CREATE TABLE PASSE (
NUM INTEGER NOT NULL,
DATA_EXP DATE NOT NULL,
NUM_VIAGENS INTEGER NOT NULL,
PRIMARY KEY (NUM))
CREATE TABLE REG_VIAGEM (
NUM INTEGER NOT NULL,
NUM_ROLETA INTEGER NOT NULL,
DATA_VIAGEM DATE NOT NULL,
FOREIGN KEY (NUM)
REFERENCES PASSE (NUM))
A tabela PASSE contém uma linha para cada passe vendido pela empresa que administra o metrô. A coluna DATA_EXP informa a data de emissão do passe, e a coluna NUM_VIAGENS informa o número de viagens em que o passe poderá ser usado (número máximo de viagens). Este número não sofre alteração ao longo do tempo.
A tabela REG_VIAGEM contém uma linha para cada viagem em que o passe foi usado. A coluna NUM_ROLETA informa a roleta na qual o passe foi inserido, e a coluna DATA_VIAGEM informa a data em que o usuário inseriu o passe na roleta.
Qual consulta SQL permite obter os números dos passes que nunca foram usados, juntamente com os números dos passes que já esgotaram o número de viagens realizadas?
Provas
Disciplina: Inglês (Língua Inglesa)
Banca: CESGRANRIO
Orgão: Eletronuclear
The controversial future of nuclear power in the U.S.
Lois Parshley
President Joe Biden has set ambitious goals for fighting climate change: To cut U.S. carbon emissions in half by 2030 and to have a net-zero carbon economy by 2050. The plan requires electricity generation – the easiest economic sector to green, analysts say – to be carbon-free by 2035.
A few figures from the U.S. Energy Information Administration (EIA) illustrate the challenge. In 2020 the United States generated about four trillion kilowatt-hours of electricity. Some 60 percent of that came from burning fossil fuels, mostly natural gas, in some 10,000 generators, large and small, around the country. All of that electricity will need to be replaced - and more, because demand for electricity is expected to rise, especially if we power more cars with it.
Renewable energy sources like solar and wind have grown faster than expected; together with hydroelectric, they surpassed coal for the first time ever in 2019 and now produce 20 percent of U.S. electricity. In February the EIA projected that renewables were on track to produce more than 40 percent by 2050 - remarkable growth, perhaps, but still well short of what’s needed to decarbonize the grid by 2035 and forestall the climate crisis.
This daunting challenge has recently led some environmentalists to reconsider an alternative they had long been wary of: nuclear power.
Nuclear power has a lot going for it. Its carbon footprint is equivalent to wind, less than solar, and orders of magnitude less than coal. Nuclear power plants take up far less space on the landscape than solar or wind farms, and they produce power even at night or on calm days. In 2020 they generated as much electricity in the U.S. as renewables did, a fifth of the total.
But debates rage over whether nuclear should be a big part of the climate solution in the U.S. The majority of American nuclear plants today are approaching the end of their design life, and only one has been built in the last 20 years. Nuclear proponents are now banking on next-generation designs, like small, modular versions of conventional light-water reactors, or advanced reactors designed to be safer, cheaper, and more flexible.
“We’ve innovated so little in the past half-century, there’s a lot of ground to gain,” says Ashley Finan, the director of the National Reactor Innovation Center at the Idaho National Laboratory. Yet an expansion of nuclear power faces some serious hurdles, and the perennial concerns about safety and long-lived radioactive waste may not be the biggest: Critics also say nuclear reactors are simply too expensive and take too long to build to be of much help with the climate crisis.
While environmental opposition may have been the primary force hindering nuclear development in the 1980s and 90s, now the biggest challenge may be costs. Few nuclear plants have been built in the U.S. recently because they are very expensive to build here, which makes the price of their energy high.
Jacopo Buongiorno, a professor of nuclear science and engineering at MIT, led a group of scientists who recently completed a two-year study examining the future of nuclear energy in the U.S. and western Europe. They found that “without cost reductions, nuclear energy will not play a significant role” in decarbonizing the power sector.
“In the West, the nuclear industry has substantially lost its ability to build large plants,” Buongiorno says, pointing to Southern Company’s effort to add two new reactors to Plant Vogtle in Waynesboro, Georgia. They have been under construction since 2013, are now billions of dollars over budget - the cost has more than doubled - and years behind schedule. In France, ranked second after the U.S. in nuclear generation, a new reactor in Flamanville is a decade late and more than three times over budget.
“We have clearly lost the know-how to build traditional gigawatt-scale nuclear power plants,” Buongiorno says. Because no new plants were built in the U.S. for decades, he and his colleagues found, the teams working on a project like Vogtle haven’t had the learning experiences needed to do the job efficiently. That leads to construction delays that drive up costs.
Elsewhere, reactors are still being built at lower cost, “largely in places where they build projects on budget, and on schedule,” Finan explains. China and South Korea are the leaders. (To be fair, several of China’s recent large-scale reactors have also had cost overruns and delays.)
“The cost of nuclear power in Asia has been a quarter, or less, of new builds in the West,” Finan says. Much lower labor costs are one reason, according to both Finan and the MIT report, but better project management is another.
Available at: https://www.nationalgeographic.com/environment/ article/nuclear-plants-are-closing-in-the-us-should-we-build-more. Retrieved on: Feb. 3, 2022. Adapted.
In the last paragraph, the author states that “Much lower labor costs are one reason, according to both Finan and the MIT report, but better project management is another.” because he believes that
Provas
Disciplina: Inglês (Língua Inglesa)
Banca: CESGRANRIO
Orgão: Eletronuclear
The controversial future of nuclear power in the U.S.
Lois Parshley
President Joe Biden has set ambitious goals for fighting climate change: To cut U.S. carbon emissions in half by 2030 and to have a net-zero carbon economy by 2050. The plan requires electricity generation – the easiest economic sector to green, analysts say – to be carbon-free by 2035.
A few figures from the U.S. Energy Information Administration (EIA) illustrate the challenge. In 2020 the United States generated about four trillion kilowatt-hours of electricity. Some 60 percent of that came from burning fossil fuels, mostly natural gas, in some 10,000 generators, large and small, around the country. All of that electricity will need to be replaced - and more, because demand for electricity is expected to rise, especially if we power more cars with it.
Renewable energy sources like solar and wind have grown faster than expected; together with hydroelectric, they surpassed coal for the first time ever in 2019 and now produce 20 percent of U.S. electricity. In February the EIA projected that renewables were on track to produce more than 40 percent by 2050 - remarkable growth, perhaps, but still well short of what’s needed to decarbonize the grid by 2035 and forestall the climate crisis.
This daunting challenge has recently led some environmentalists to reconsider an alternative they had long been wary of: nuclear power.
Nuclear power has a lot going for it. Its carbon footprint is equivalent to wind, less than solar, and orders of magnitude less than coal. Nuclear power plants take up far less space on the landscape than solar or wind farms, and they produce power even at night or on calm days. In 2020 they generated as much electricity in the U.S. as renewables did, a fifth of the total.
But debates rage over whether nuclear should be a big part of the climate solution in the U.S. The majority of American nuclear plants today are approaching the end of their design life, and only one has been built in the last 20 years. Nuclear proponents are now banking on next-generation designs, like small, modular versions of conventional light-water reactors, or advanced reactors designed to be safer, cheaper, and more flexible.
“We’ve innovated so little in the past half-century, there’s a lot of ground to gain,” says Ashley Finan, the director of the National Reactor Innovation Center at the Idaho National Laboratory. Yet an expansion of nuclear power faces some serious hurdles, and the perennial concerns about safety and long-lived radioactive waste may not be the biggest: Critics also say nuclear reactors are simply too expensive and take too long to build to be of much help with the climate crisis.
While environmental opposition may have been the primary force hindering nuclear development in the 1980s and 90s, now the biggest challenge may be costs. Few nuclear plants have been built in the U.S. recently because they are very expensive to build here, which makes the price of their energy high.
Jacopo Buongiorno, a professor of nuclear science and engineering at MIT, led a group of scientists who recently completed a two-year study examining the future of nuclear energy in the U.S. and western Europe. They found that “without cost reductions, nuclear energy will not play a significant role” in decarbonizing the power sector.
“In the West, the nuclear industry has substantially lost its ability to build large plants,” Buongiorno says, pointing to Southern Company’s effort to add two new reactors to Plant Vogtle in Waynesboro, Georgia. They have been under construction since 2013, are now billions of dollars over budget - the cost has more than doubled - and years behind schedule. In France, ranked second after the U.S. in nuclear generation, a new reactor in Flamanville is a decade late and more than three times over budget.
“We have clearly lost the know-how to build traditional gigawatt-scale nuclear power plants,” Buongiorno says. Because no new plants were built in the U.S. for decades, he and his colleagues found, the teams working on a project like Vogtle haven’t had the learning experiences needed to do the job efficiently. That leads to construction delays that drive up costs.
Elsewhere, reactors are still being built at lower cost, “largely in places where they build projects on budget, and on schedule,” Finan explains. China and South Korea are the leaders. (To be fair, several of China’s recent large-scale reactors have also had cost overruns and delays.)
“The cost of nuclear power in Asia has been a quarter, or less, of new builds in the West,” Finan says. Much lower labor costs are one reason, according to both Finan and the MIT report, but better project management is another.
Available at: https://www.nationalgeographic.com/environment/ article/nuclear-plants-are-closing-in-the-us-should-we-build-more. Retrieved on: Feb. 3, 2022. Adapted.
In paragraph 12, the author affirms “(To be fair, several of China’s recent large-scale reactors have also had cost overruns and delays)”, in order to
Provas
Disciplina: Inglês (Língua Inglesa)
Banca: CESGRANRIO
Orgão: Eletronuclear
The controversial future of nuclear power in the U.S.
Lois Parshley
President Joe Biden has set ambitious goals for fighting climate change: To cut U.S. carbon emissions in half by 2030 and to have a net-zero carbon economy by 2050. The plan requires electricity generation – the easiest economic sector to green, analysts say – to be carbon-free by 2035.
A few figures from the U.S. Energy Information Administration (EIA) illustrate the challenge. In 2020 the United States generated about four trillion kilowatt-hours of electricity. Some 60 percent of that came from burning fossil fuels, mostly natural gas, in some 10,000 generators, large and small, around the country. All of that electricity will need to be replaced - and more, because demand for electricity is expected to rise, especially if we power more cars with it.
Renewable energy sources like solar and wind have grown faster than expected; together with hydroelectric, they surpassed coal for the first time ever in 2019 and now produce 20 percent of U.S. electricity. In February the EIA projected that renewables were on track to produce more than 40 percent by 2050 - remarkable growth, perhaps, but still well short of what’s needed to decarbonize the grid by 2035 and forestall the climate crisis.
This daunting challenge has recently led some environmentalists to reconsider an alternative they had long been wary of: nuclear power.
Nuclear power has a lot going for it. Its carbon footprint is equivalent to wind, less than solar, and orders of magnitude less than coal. Nuclear power plants take up far less space on the landscape than solar or wind farms, and they produce power even at night or on calm days. In 2020 they generated as much electricity in the U.S. as renewables did, a fifth of the total.
But debates rage over whether nuclear should be a big part of the climate solution in the U.S. The majority of American nuclear plants today are approaching the end of their design life, and only one has been built in the last 20 years. Nuclear proponents are now banking on next-generation designs, like small, modular versions of conventional light-water reactors, or advanced reactors designed to be safer, cheaper, and more flexible.
“We’ve innovated so little in the past half-century, there’s a lot of ground to gain,” says Ashley Finan, the director of the National Reactor Innovation Center at the Idaho National Laboratory. Yet an expansion of nuclear power faces some serious hurdles, and the perennial concerns about safety and long-lived radioactive waste may not be the biggest: Critics also say nuclear reactors are simply too expensive and take too long to build to be of much help with the climate crisis.
While environmental opposition may have been the primary force hindering nuclear development in the 1980s and 90s, now the biggest challenge may be costs. Few nuclear plants have been built in the U.S. recently because they are very expensive to build here, which makes the price of their energy high.
Jacopo Buongiorno, a professor of nuclear science and engineering at MIT, led a group of scientists who recently completed a two-year study examining the future of nuclear energy in the U.S. and western Europe. They found that “without cost reductions, nuclear energy will not play a significant role” in decarbonizing the power sector.
“In the West, the nuclear industry has substantially lost its ability to build large plants,” Buongiorno says, pointing to Southern Company’s effort to add two new reactors to Plant Vogtle in Waynesboro, Georgia. They have been under construction since 2013, are now billions of dollars over budget - the cost has more than doubled - and years behind schedule. In France, ranked second after the U.S. in nuclear generation, a new reactor in Flamanville is a decade late and more than three times over budget.
“We have clearly lost the know-how to build traditional gigawatt-scale nuclear power plants,” Buongiorno says. Because no new plants were built in the U.S. for decades, he and his colleagues found, the teams working on a project like Vogtle haven’t had the learning experiences needed to do the job efficiently. That leads to construction delays that drive up costs.
Elsewhere, reactors are still being built at lower cost, “largely in places where they build projects on budget, and on schedule,” Finan explains. China and South Korea are the leaders. (To be fair, several of China’s recent large-scale reactors have also had cost overruns and delays.)
“The cost of nuclear power in Asia has been a quarter, or less, of new builds in the West,” Finan says. Much lower labor costs are one reason, according to both Finan and the MIT report, but better project management is another.
Available at: https://www.nationalgeographic.com/environment/ article/nuclear-plants-are-closing-in-the-us-should-we-build-more. Retrieved on: Feb. 3, 2022. Adapted.
According to Jacopo Buongiorno, one of the reasons why it is more expensive to build large nuclear plants in the West is that
Provas
Disciplina: Inglês (Língua Inglesa)
Banca: CESGRANRIO
Orgão: Eletronuclear
The controversial future of nuclear power in the U.S.
Lois Parshley
President Joe Biden has set ambitious goals for fighting climate change: To cut U.S. carbon emissions in half by 2030 and to have a net-zero carbon economy by 2050. The plan requires electricity generation – the easiest economic sector to green, analysts say – to be carbon-free by 2035.
A few figures from the U.S. Energy Information Administration (EIA) illustrate the challenge. In 2020 the United States generated about four trillion kilowatt-hours of electricity. Some 60 percent of that came from burning fossil fuels, mostly natural gas, in some 10,000 generators, large and small, around the country. All of that electricity will need to be replaced - and more, because demand for electricity is expected to rise, especially if we power more cars with it.
Renewable energy sources like solar and wind have grown faster than expected; together with hydroelectric, they surpassed coal for the first time ever in 2019 and now produce 20 percent of U.S. electricity. In February the EIA projected that renewables were on track to produce more than 40 percent by 2050 - remarkable growth, perhaps, but still well short of what’s needed to decarbonize the grid by 2035 and forestall the climate crisis.
This daunting challenge has recently led some environmentalists to reconsider an alternative they had long been wary of: nuclear power.
Nuclear power has a lot going for it. Its carbon footprint is equivalent to wind, less than solar, and orders of magnitude less than coal. Nuclear power plants take up far less space on the landscape than solar or wind farms, and they produce power even at night or on calm days. In 2020 they generated as much electricity in the U.S. as renewables did, a fifth of the total.
But debates rage over whether nuclear should be a big part of the climate solution in the U.S. The majority of American nuclear plants today are approaching the end of their design life, and only one has been built in the last 20 years. Nuclear proponents are now banking on next-generation designs, like small, modular versions of conventional light-water reactors, or advanced reactors designed to be safer, cheaper, and more flexible.
“We’ve innovated so little in the past half-century, there’s a lot of ground to gain,” says Ashley Finan, the director of the National Reactor Innovation Center at the Idaho National Laboratory. Yet an expansion of nuclear power faces some serious hurdles, and the perennial concerns about safety and long-lived radioactive waste may not be the biggest: Critics also say nuclear reactors are simply too expensive and take too long to build to be of much help with the climate crisis.
While environmental opposition may have been the primary force hindering nuclear development in the 1980s and 90s, now the biggest challenge may be costs. Few nuclear plants have been built in the U.S. recently because they are very expensive to build here, which makes the price of their energy high.
Jacopo Buongiorno, a professor of nuclear science and engineering at MIT, led a group of scientists who recently completed a two-year study examining the future of nuclear energy in the U.S. and western Europe. They found that “without cost reductions, nuclear energy will not play a significant role” in decarbonizing the power sector.
“In the West, the nuclear industry has substantially lost its ability to build large plants,” Buongiorno says, pointing to Southern Company’s effort to add two new reactors to Plant Vogtle in Waynesboro, Georgia. They have been under construction since 2013, are now billions of dollars over budget - the cost has more than doubled - and years behind schedule. In France, ranked second after the U.S. in nuclear generation, a new reactor in Flamanville is a decade late and more than three times over budget.
“We have clearly lost the know-how to build traditional gigawatt-scale nuclear power plants,” Buongiorno says. Because no new plants were built in the U.S. for decades, he and his colleagues found, the teams working on a project like Vogtle haven’t had the learning experiences needed to do the job efficiently. That leads to construction delays that drive up costs.
Elsewhere, reactors are still being built at lower cost, “largely in places where they build projects on budget, and on schedule,” Finan explains. China and South Korea are the leaders. (To be fair, several of China’s recent large-scale reactors have also had cost overruns and delays.)
“The cost of nuclear power in Asia has been a quarter, or less, of new builds in the West,” Finan says. Much lower labor costs are one reason, according to both Finan and the MIT report, but better project management is another.
Available at: https://www.nationalgeographic.com/environment/ article/nuclear-plants-are-closing-in-the-us-should-we-build-more. Retrieved on: Feb. 3, 2022. Adapted.
In the fragment of paragraph 7 “and the perennial concerns about safety and long-lived radioactive waste may not be the biggest”, may not be expresses a(n)
Provas
Disciplina: Inglês (Língua Inglesa)
Banca: CESGRANRIO
Orgão: Eletronuclear
The controversial future of nuclear power in the U.S.
Lois Parshley
President Joe Biden has set ambitious goals for fighting climate change: To cut U.S. carbon emissions in half by 2030 and to have a net-zero carbon economy by 2050. The plan requires electricity generation – the easiest economic sector to green, analysts say – to be carbon-free by 2035.
A few figures from the U.S. Energy Information Administration (EIA) illustrate the challenge. In 2020 the United States generated about four trillion kilowatt-hours of electricity. Some 60 percent of that came from burning fossil fuels, mostly natural gas, in some 10,000 generators, large and small, around the country. All of that electricity will need to be replaced - and more, because demand for electricity is expected to rise, especially if we power more cars with it.
Renewable energy sources like solar and wind have grown faster than expected; together with hydroelectric, they surpassed coal for the first time ever in 2019 and now produce 20 percent of U.S. electricity. In February the EIA projected that renewables were on track to produce more than 40 percent by 2050 - remarkable growth, perhaps, but still well short of what’s needed to decarbonize the grid by 2035 and forestall the climate crisis.
This daunting challenge has recently led some environmentalists to reconsider an alternative they had long been wary of: nuclear power.
Nuclear power has a lot going for it. Its carbon footprint is equivalent to wind, less than solar, and orders of magnitude less than coal. Nuclear power plants take up far less space on the landscape than solar or wind farms, and they produce power even at night or on calm days. In 2020 they generated as much electricity in the U.S. as renewables did, a fifth of the total.
But debates rage over whether nuclear should be a big part of the climate solution in the U.S. The majority of American nuclear plants today are approaching the end of their design life, and only one has been built in the last 20 years. Nuclear proponents are now banking on next-generation designs, like small, modular versions of conventional light-water reactors, or advanced reactors designed to be safer, cheaper, and more flexible.
“We’ve innovated so little in the past half-century, there’s a lot of ground to gain,” says Ashley Finan, the director of the National Reactor Innovation Center at the Idaho National Laboratory. Yet an expansion of nuclear power faces some serious hurdles, and the perennial concerns about safety and long-lived radioactive waste may not be the biggest: Critics also say nuclear reactors are simply too expensive and take too long to build to be of much help with the climate crisis.
While environmental opposition may have been the primary force hindering nuclear development in the 1980s and 90s, now the biggest challenge may be costs. Few nuclear plants have been built in the U.S. recently because they are very expensive to build here, which makes the price of their energy high.
Jacopo Buongiorno, a professor of nuclear science and engineering at MIT, led a group of scientists who recently completed a two-year study examining the future of nuclear energy in the U.S. and western Europe. They found that “without cost reductions, nuclear energy will not play a significant role” in decarbonizing the power sector.
“In the West, the nuclear industry has substantially lost its ability to build large plants,” Buongiorno says, pointing to Southern Company’s effort to add two new reactors to Plant Vogtle in Waynesboro, Georgia. They have been under construction since 2013, are now billions of dollars over budget - the cost has more than doubled - and years behind schedule. In France, ranked second after the U.S. in nuclear generation, a new reactor in Flamanville is a decade late and more than three times over budget.
“We have clearly lost the know-how to build traditional gigawatt-scale nuclear power plants,” Buongiorno says. Because no new plants were built in the U.S. for decades, he and his colleagues found, the teams working on a project like Vogtle haven’t had the learning experiences needed to do the job efficiently. That leads to construction delays that drive up costs.
Elsewhere, reactors are still being built at lower cost, “largely in places where they build projects on budget, and on schedule,” Finan explains. China and South Korea are the leaders. (To be fair, several of China’s recent large-scale reactors have also had cost overruns and delays.)
“The cost of nuclear power in Asia has been a quarter, or less, of new builds in the West,” Finan says. Much lower labor costs are one reason, according to both Finan and the MIT report, but better project management is another.
Available at: https://www.nationalgeographic.com/environment/ article/nuclear-plants-are-closing-in-the-us-should-we-build-more. Retrieved on: Feb. 3, 2022. Adapted.
Based on the meanings in the text, the two items that express synonymous ideas are
Provas
Caderno Container