每天早晨，数百个装满冷冻海产食品、蔬果干、东方药物和保健食品的箱子逐一经过类似机场安检的程序，但所用光子束或电子束强度更高。这就是过去20年在原子能机构支持下实施的食品辐照计划。
越南胡志明市——每天早晨，越南胡志明市有数百个装满冷冻海产食品、蔬果干、东方药物和保健食品的箱子排放在一个储藏室里，等待逐一经过类似机场安检的程序，但所用光子束或电子束强度更高。这就是过去20年在原子能机构支持下实施的食品辐照计划。
不同剂量的食品辐照将确保：根类蔬果不发芽或过早成熟；杀死寄生物，对香料进行净化处理；消灭沙门氏菌以及造成肉类、家禽和海产食品腐坏的真菌。
1999年，在原子能机构和联合国粮食及农业组织（粮农组织）帮助下，越南首次引入了这一程序。自那时起，便打开了辐照产品的广阔市场，大大提高了各公司出口食品的能力。食品辐照技术已臻至成熟，成了该国食品工业的一大支柱，是提高该国农业竞争力的重要促进因素。
越南原子能研究所辐射技术研究与发展中心电子束部主任Cao Van Chung说：“1999年，我们的食品辐照年处理能力为259吨，到2017年，这一数字已增至1.4万吨。这表明对我们工作的需求在真正激增。今天，我们是全国辐射技术领域的领先机构之一，在食品辐照方面处于龙头地位。”
这些发展之所以成为可能，得益于两种辐照方法的引入。1999年引入的伽玛辐照器利用混凝土屏蔽室内的辐射源产生电离能量，但2013年开始使用电子束辐照器。电子束辐照器不依赖放射源，而是采用直线电子加速器等专业设备产生的高电荷电子流。食品从不与放射性物质接触，辐照既保证了食品质量，又增强了食品安全性，同时不会有放射性残留。
Chung说，虽然这两种方法的辐照过程相同，但各具独特的互补优势。伽玛辐照器采用高大的铝箱，可容纳多种尺寸的产品，箱子环境吊装在架空单轨系统上的放射源穿过辐照室。产品需要经过两轮辐照，以确保包装产品的每一面都经过处理。
另一方面，电子束辐照器两侧都有电子束，这使得辐照过程比使用伽玛辐照器快三倍，因为产品所有部分都能一次性得到照射。但电子束辐照器大小有限，最大箱子尺寸为60×30×50厘米，重量为15公斤，对于较大、较重的产品则必须采用伽玛辐照。
这些机器并排工作，一周七天，一天24小时，只在越南新年期间停工。
在引进伽玛辐照器和电子束加速器之前，海产食品、水果和蔬菜等食品防腐都采用传统方法，包括装罐、冷藏和冷冻以及使用化学防腐剂，效率低下，限制了制造商的产品出口能力。
原子能机构技术合作计划支持采购了这些辐照机器，还提供了工作人员培训和专家咨询。越南是原子能机构在这方面提供支助的40个国家之一。
装满食品的高大铝箱在等待伽玛辐照器的辐照。（照片来源：E. Marais/原子能机构）
越南原子能研究所辐射技术研究与发展中心在1999年成立时仅20名员工，发展到今天已有79名员工。除食品辐照服务外，还为医药产品和巴氏消毒食品提供辐射灭菌服务，并将研发产品商品化，如农业用植物保护剂以及医用金纳米凝胶和银纳米凝胶等。
该中心还开展辐射技术领域的研究与发展，并提供该领域的培训，同时也与国际伙伴合作，研究进一步改进辐照技术的方法。
This growth has been possible thanks to the introduction of two irradiation methods. A gamma irradiator introduced in 1999, which uses ionizing energy from a radiation source shielded in a concrete room, and an electron beam (EB) irradiator has been in use since 2013. EB irradiators do not rely on a radioactive source, using instead streams of highly charged electrons produced from specialized equipment such as a linear electron accelerator. The food never comes into contact with radioactive material, and the irradiation both maintains the quality and increases the safety of the food while leaving no residual radioactivity.
While the process of irradiation for the two methods is the same, each brings distinct and complementary advantages, Chung said. The gamma irradiator uses tall aluminum boxes, which can accommodate a broad range of product sizes, and the boxes are moved through the irradiation chamber around the radioactive source suspended on an overhead monorail system. Products require two rounds of irradiation to ensure all sides of the packaged product have been treated.
The EB irradiator, on the other hand, contains double sided beams, which makes the irradiation process three times quicker than the use of the gamma irradiator, because all areas of the product can be irradiated in a single round. However, the EB irradiator has a limited dimension, with a maximum box size of 60x30x50 cm and weight of 15 kg, so for larger and heavier products gamma irradiation must be used.
The machines work side by side, running 24 hours a day seven days a week, only stopping over the Vietnamese New Year period.
Before the introduction of the gamma irradiator and EB accelerator, spoilage prevention of food products such as seafood, fruits and vegetables was carried out using traditional methods including canning, refrigeration and freezing and chemical preservatives, which due to lower effectiveness, hindered the manufacturers’ ability to export their products.
The irradiation machines were acquired with support from the IAEA’s technical cooperation programme, which also supplied training for staff and expert advice. Viet Nam is one of 40 countries that the IAEA is supporting in this area.
Tall aluminum boxes filled with food products await irradiation using the gamma irradiator. (Photo: E. Marais/IAEA)
VINAGAMMA has grown from 20 employees when the Center was set up in 1999 to 79 today. Besides food irradiation services, it provides radiation sterilization of medical products and pasteurized foodstuffs, and commercializes its research and development products, such as plant protectors used in agriculture and gold and silver nanogels used in medicine.
The Center also carries out research and development and provides training in the field of radiation technology. It also works with international partners to research ways of improving irradiation technology further.