A number of inoperable Maritime Self-Defense Force (MSDF) shipborne missiles have been found, with the eventual cost of repairs still unknown as the missile parts' warranties have expired, the Mainichi Shimbun has learned.

The issue with the short-range RIM-162 Evolved Seasparrow missiles was discovered during a Board of Audit of Japan check on parts for the weapons, a source close to the matter told the Mainichi. However, the problem "will have no direct impact on national defense," an MSDF official said.

The MSDF's Aegis vessels -- which could be called on to shoot down ballistic missiles -- are equipped with the anti-aircraft and anti-missile Seasparrows for self-defense.

According to publicly available Defense Ministry documents, the Japanese government spent a total of some 101.1 billion yen on Seasparrow parts in the 10 years ending fiscal 2015 (not counting fiscal 2014). The domestically produced parts are shipped to the MSDF, which assembles them into missiles. The missiles are then tested for operational fitness before being loaded onto Aegis vessels.

The supply contract warranty states that if a fault is found within a year of the parts' delivery, then the MSDF can bill the maker for the cost of repairing or replacing it regardless of the cause.

According to a source close to the situation, during the Board of Audit's examination of Seasparrow parts delivered over the past several years, inspectors found that assembly facilities at the MSDF's Sasebo and Yokosuka bases did not have sufficient skills to put the missiles together. As a result, parts have remained in storage beyond the warranty period without ever being tested for operability.

The total cost of missiles that now cannot be loaded onto MSDF vessels apparently approaches 1 billion yen, and it is unknown how much repairs will add to the bill.

The MSDF has stated that it will "endeavor to implement appropriate improvement and maintenance measures so that no similar problems occur in the future," and pledged to assemble and test the Seasparrows before the part warranties expire.