Ruling party lawmakers have renewed calls to deploy nuclear-powered submarines on the battlefront, refueling debate about using the advanced weapons against North Korean ballistic missile threats.

The communist state marked its first successful firing of a submarine-launched ballistic missile last week, undermining South Korea’s resolve to neutralize threats via land-based missile defense systems.

“The SLBM launch is a grave threat not only to South Korea, but also to the security of Northeast Asia,” said Rep. Chung Jin-suk, floor leader of the ruling Saenuri Party.

“(The danger from the SLBM) is even more severe than that of a land-based missile launch, because it is more difficult to detect where it has been launched from.”

He urged the government to positively consider having a nuclear sub in Korean waters, along with enhancing defense through strengthening the Seoul-Washington alliance, acquiring the protection of the US nuclear umbrella and installment of the Terminal High Altitude Area Defense system.

Chung’s comments came a day after he and 22 other Saenuri lawmakers released a statement calling for the deployment of a nuclear missile.

Saenuri’s Rep. Won Yoo-chul, one of the more vocal proponents of nuclear-armed defense against Pyongyang, echoed Chung’s comments by saying a nuclear submarine is needed for continuous monitoring against North Korea.

Submarines powered by a nuclear reactor holds an operational edge over their conventional diesel-electric counterparts. Its air-independent and nuclear propulsion allows it to operate for months and at a high speed without having to resurface.

Last week’s SLBM launch, while assessed to be a step away from an actual deployment phase, indicated that the communist state may be closer to completing its SLBM program than South Korean ministry’s initial estimate of 3-4 years.

In a report to the National Assembly on Monday, the Defense Ministry said that the North’s SLBM can be deployed for use within the next 1-3 years. It assessed that it will be a threat to not only South Korea, but also the US mainland.

John Schilling of 38 North, a North Korea-monitoring website, acknowledged that the SLBM program is progressing at a faster rate than anticipated. He said that it may be deployed in “an initial operational capacity by the second half of 2018.”

But some within the military have speculated the deployment to be as early as later in the year, as Pyongyang has a reputation for stationing weapons for actual use without sufficient testing.

The North’s stride in submarine missiles poses a significant threat, as land-based anti-missile systems such as the THAAD is expected to have difficulty defending against missiles fired from behind.

Experts say that an effective measure to defend against the SLBM is to procure capacity to operate submarines for an extended period of time.

North Korea reportedly only has one 2,000-ton Sinpo-class submarine from which an SLBM launch is possible. Military believes it will take some time for it to develop larger submarines.

A Tokyo-based media outlet recently reported that North Korean leader Kim Jong-un has ordered his troops to develop a larger submarine that can fire multiple SLBMs, as Sinpo can only fire one missile.

Park Hwee-rhak, the dean of the graduate school of politics and leadership at Kookmin University, said that having a submarine with advanced capacity would allow Seoul a tactical advantage in the waters. North Korean vessels are based on Soviet-era subs and are limited in their operational capacity.

He mentioned the “hunter-killer submarine” -- also known as attack submarines -- specifically designed to sink other submarines and ships, and used since World War II. Park said operating a similar system would help South Korea to detect and destroy North Korean submarines.

“A nuclear-powered submarine has a capacity to operate underwater for an extended period of time, a powerful sonar system and ability to carry sufficient manpower. Just having a nuclear submarine would restrict the submarine operation of the North,” Park said.

But some have raised concerns that having a nuclear submarine may simply contribute to aggravating the arms race in the region and irk neighboring countries, especially China who has vehemently opposed stationing the US-operated THAAD on the Korean Peninsula.

It may not be just Seoul’s rivals that oppose the concept of a nuclear-powered submarine based in the peninsula.

In 2003, the then-Roh Moo-hyun administration pushed for a project to acquire three nuclear-powered submarines before 2020. But the plan was scrapped within a year.

It was rumored that pressure from Seoul’s biggest ally the US had forced the administration to retract the plan.

The allies have an agreement on peaceful nuclear cooperation, which allows for the enrichment of up to 20 percent of fissile uranium-235 in South Korea after consultation through bilateral commission and written consent by the US. The revision, made last year, opens the door for low-level enrichment to be used for nuclear fuel.

Defense Minister Han Min-koo told Parliament that the ministry will review the necessity of a nuclear submarine, but stated that the military has not reached any decision on deployment.

Meanwhile, the Navy’s 2015-2030 plan has centered on acquiring a “qualitative edge” over Pyongyang, essentially having bigger and better ships and submarines than simply having more.

The number of operational vessels is expected to fall, but the accumulative tonnage of the vessels will be raised from 45,000 to 70,000 tons.

This includes replacing the current PKM patrol boats with larger and more advanced patrol ships via PKX projects, and deploying 2,300-ton and 2,800-ton frigates to substitute the smaller 1,500-ton vessels. A comprehensive upgrade in detection and attack capacity is also slated to take place.

By Yoon Min-sik(minsikyoon@heraldcorp.com)