mean.population = 1000
sd.population = 100
sample.size = 30
pvalues = rep(0,100)

for (i in 1:10000)
{
sample1 = rnorm(sample.size,mean.population,sd.population)
sample2 = rnorm(sample.size,mean.population,sd.population)
results = t.test(sample1,sample2)
pvalues[i] = results[3]$p.value
}

hist(pvalues)