In AWS D1.1 is allows you to disregard the end sections 1.250” of a plate during the interpretation on the radiography film. Is there anything like that in ASME Sec. IX.
Read ASME Section IX, Article 3, QW-302.2 and QW-304.1. These paragraphs provide the requirements for weld coupons -...a minimum 6" length of the first production weld(s)... the entire weld circumference is required for pipe coupons.
The plate performance test coupons may be greater than 6-inches long to compensate for start/stop flaws at the ends of the coupon. The radiograph must cover 6-inches, minimum, of the length of the test weld. In other words, make the test coupon 8-inches long and radiograph the center 6-inches.