Committee of Experts on the Transport of Dangerous Goods
and on the Globally Harmonized System of Classification
and Labelling of Chemicals

Sub-Committee of Experts on the Transport of Dangerous Goods

Forty-first session

Geneva, 25 June – 4 July 2012
Item 3 (a) of the provisional agenda

Listing, classification and packing:
Proposals of amendments to the list of dangerous goods of Chapter 3.2

               Neutron radiation detectors

                   Transmitted by the Dangerous Goods Advisory Council[1]

               Introduction

1.         Neutron detection is a key component in the identification of illicit nuclear materials (e.g., plutonium) passing through ports of entry and borders of a country. Radiation detection systems can be employed to scan freight containers or perform searches using portable radiation detectors. Additional applications for neutron radiation detectors include nuclear reactor monitoring, neutron-based cancer treatments, cosmic ray research, neutron spallation, non-destructive testing and health physics applications. Since 2009, a shortage of Helium-3 gas commonly employed in neutron detectors has necessitated the use of alternative technologies. One such technology employs boron trifluoride (BF₃) as the neutron detection medium. The effectiveness and safety of this technology has been demonstrated over the last 70 years in the applications listed.  In spite of the important safety and security role these devices play, the small quantity of toxic gas present at atmospheric pressure often causes delays in their transport. The problems seem unwarranted in light of the low risk posed and DGAC submits this paper to provide a basis for discussion on how transport of these devices may be facilitated.

2.         Neutron radiation detectors described in this proposal are hermetically sealed electron tube devices that contain non-pressurized BF₃ gas that functions as the detection medium. They have been transported worldwide for over 70 years. With more than 250,000 BF₃ sensors in service worldwide in the nuclear power and radiation protection industries, there is no known incident of a BF₃ leak in transport.

3.         Considering their role in preventing nuclear terrorism, as well as their importance in other health and safety applications, it is essential that BF₃ based neutron radiation detection systems and detector system components can be rapidly deployed worldwide.

               Discussion

4.         A number of safety features are inherent in the design and construction of neutron radiation detectors, the component of radiation detection systems containing BF₃:

-        The gas is non-pressurized with the pressure at the time of filling kept at 105kPa absolute at 20^oC or below;

-        The amount of gas is relatively small.  The largest radiation detector systems contain not more than 55 grams of gas;

-        Radiation detectors are extremely rugged, having a minimum burst pressure of 1800 kPa. Under requirements of the United States Department of Transportation neutron radiation detectors must be packed in strong outer packagings that are capable of withstanding a 1.8 meter drop test without leakage;

-        The detection systems and neutron radiation detectors transported as components are packaged with an absorbent material that is capable of absorbing all of the gas contained in package. A study by Brookhaven National Laboratory shows the absorbent material to be highly effective in absorbing the gas should it leak from the radiation detector under use or transport conditions; and

-        Radiation detectors are hermetically sealed. Each unit is helium mass spectrometer leak tested to a 1 x 10^-10 standard cc/sec leak tightness before filling. 

5 In the case of land transportation in the United States of Americaand Canada, these devices are authorized for transport under permits. Under ADR/RID, it is understood that they fall under the equipment exemption in section 1.1.3.1(b) so that these regulations do not apply.

6 A recent amendment to be incorporated in the 2013-2014 ICAO Technical Instructions will permit air transport on cargo aircraft as UN 1008 BF₃ under a new Special Provision. While this will somewhat ease air transport problems, air transport will continue to prove difficult owing to the refusal of many air carriers to accept any Division 2.3 goods.

7 In the case of sea transport, while these devices can be transported under UN 1008, it is the practice of some carriers to require a freight container containing toxic gases to be used exclusively for that purpose. As such, it is sometimes necessary to dedicate an entire freight container for use in transporting one radiation detector. As is the case with air carriers, some ocean carriers refuse to ship Division 2.3 goods, creating serious logistical problems. The need for permits and approvals further complicates transport.

8 The transport difficulties brought on by the Division 2.3 hazard classification appear unwarranted in view of the small risk these devices pose and contrary to the shared objectives of safety and security. DGAC would welcome a discussion on alternative approaches to transporting these devices. One solution could be to permit these devices as UN3363 Dangerous Goods in Apparatus. While UN3363 is limited by SP 301 to substances that are permitted as limited quantities, this could be overcome by a new special provision. To provide a basis for discussion and provide a better understanding of the requirements contemplated, the proposal below is provided. The proposal includes elements from the new ICAO TI special provision to be included in the 2013-2014 edition.

9 To provide a better understanding of radiation detectors and systems, DGAC plans to provide an additional informal paper prior to the meeting.

               Proposal

10.       DGAC proposes the following:

Introduce in the glossary two new terms:

Neutron radiation detectoris a hermetically sealed electron tube transducer that converts neutron radiation into a measureable electric signal. The gas in the device is the neutron detection medium.  

Radiation detection system is an apparatus that contains neutron radiation detectors as components.

Add a new special provision XXX against UN3363 to read as follows:

XXX         Neutron radiation detectors containing non-pressurized BF₃ gas in excess of 1 gram and radiation detection systems containing such neutron radiation detectors as components may be transported under this entry, provided:

(a)    The pressure in each neutron radiation detector does not exceed 105 kPa absolute at 20^o C;

(b)    The total amount of BF₃ in neutron radiation detectors per outer packaging or per radiation detection system does not exceed 55 grams;

(c)    Each neutron radiation detector is of welded metal construction with brazed metal to ceramic feed through assemblies. The burst pressure of detectors is not less than 1800 kPa;

(d)    Each neutron radiation detector (including multiple detectors as, for example, in a device) is contained in a sealed plastic liner with sufficient absorbent material to absorb the entire gas contents; and

(e)    Each neutron radiation detector is packed in a strong outer packaging capable of withstanding a 1.8 meter drop test without leakage and each radiation detection system is packed in a strong outer packaging unless neutron radiation detectors are afforded equivalent protection by the radiation detection system.

Neutron radiation detectorscontaining not more than 1 gram of BF₃, including those with solder glass joints, and radiation detection systems containing such detectors where the neutron radiation detectors meet and are packed in accordance with the above conditions, are not subject to these Regulations.

                    

 

联合国危险货物运输专家和全球化学品统一分类和标签制度专家委员会

危险货物运输专家分委员会

第四十一次会议

日内瓦, 2012年6月25日-7月4日
议程第3 (a)项

列表、分类和包装：
对修订3.2章危险货物列表的提案

 

               中子辐射探测器

                   由危险货物咨询委员会(DGAC)提交[2]

               介绍

1.         中子探测是鉴定非法核材料（如钚）通过入境口岸和国家边界的关键部分。辐射探测系统可以通过扫描货运集装箱或使用便携式辐射探测器进行搜索。中子辐射探测器的其它应用还包括核反应堆监测，中子癌症疗法，宇宙射线的研究，散裂中子，非破坏性测试和健康医学应用。2009年以来，中子探测器常采用的氦-3气体短缺，因此有必要使用替代技术。以三氟化硼（BF₃）作为中子探测介质的技术就是其中一种。该技术的有效性和安全性已在过去的70多年有记载的应用中得到证实。尽管这些设备在安全和安保方面扮演重要的角色，但它们会在大气压力下释放少量的有毒气体，从而往往会造成其运输的延误。考虑到其构成的风险低，这一问题似乎很不合理，DGAC提交本文作为讨论如何便捷地运输这些设备的基础。

2.         本提议中所述的中子辐射探测器为密封的电子管设备，内含非加压的三氟化硼气体作为探测介质。在过去70多年里，这些设备在世界各地进行运输。超过250,000 个三氟化硼传感器服务于全球核电和辐射防护行业，从未发生过运输过程中三氟化硼泄漏事故。

3.         考虑到它们在防止核恐怖主义以及在其它健康和安全应用方面的重要作用，这种基于三氟化硼的中子辐射检测系统及检测系统组件能快速应用于世界各地是十分必要的。

               讨论

4.         中子辐射探测器的设计和结构中固有一些安全功能，内含三氟化硼的辐射探测系统组件：

-        气体为非加压，灌装时绝对压力保持在20℃下105kPa或更低；

-        气体量相对较小。最大的辐射探测器系统内含气体量不超过55克；

-        辐射探测器是非常坚固的，其最小爆破压力为1800千帕。按照美国运输部的要求，中子辐射探测器必须装在牢固的外包装内，该外包装能够承受1.8米跌落试验并无泄漏；

-        检测系统和中子辐射探测器以组件方式运输的，其包装内应有能够吸收包装内所有气体的吸收材料。布鲁克海文国家实验室研究表明，吸收材料能有效吸收辐射探测器在使用或运输条件下泄漏的气体；和

-        辐射探测器是密封的。灌装前，每个单元均采用氦质谱仪进行1×10^-10标准cc/秒的密封性检测。

5 在美国和加拿大陆地运输的情况下，这些设备经获批准后可授权运输。根据ADR/RID，这些设备属于第1.1.3.1（b）部分中的豁免设备范畴，所以这些规定并不适用。

6 最近即将纳入2013-2014年ICAO技术细则的一项修正案，将允许货机在一项新的特殊规定下空运UN 1008三氟化硼。虽然这会在一定程度上缓解空运问题，但由于许多航空承运人拒绝接受任何2.3项货物，其空运仍将十分困难。

7 在海运情况下，这些设备可以按照UN 1008进行运输，实际操作中一些承运人需要专门为此使用含有毒气体的货物集装箱。正因为如此，有时必须用整个集装箱来运输一个辐射探测器。和航空承运人一样，一些远洋承运人拒绝运输2.3项货物，这造成严重的物流问题。许可证及批文的需要进一步将其运输复杂化。

8 因2.3项危险性分类所带来的运输困难，考虑到这些设备引起的小风险显得并不合理，同时也违背了安全与安保的共同目标，DGAC乐于进行关于这些设备运输的替代办法的讨论。一种解决办法是允许这些设备按UN3363仪器中的危险货物处理。但UN3363被SP301规定为用于允许限制数量运输的物质，这可以通过新的特殊规定来解决。为了提供一个讨论的基础并对预期要求有更好地了解，提出以下提议。该提议包括将要加入2013-2014年版ICAO技术细则的新特殊规定的部分内容。

9 为更好地了解辐射探测器和系统，DGAC计划在会议召开前提供一份非正式的补充文件。

               提议

10             DGAC提出以下几点：

术语表中引入两个新的术语：

中子辐射探测器是一个将中子辐射转换成可测量电信号的密封电子管传感器。设备内的气体是中子探测介质。

辐射探测系统是包含中子辐射探测器并将其作为组件的仪器。

对UN3363新增的特殊规定XXX如下：

XXX内含非加压超过1克的三氟化硼气体的中子辐射探测器和包含中子辐射探测器作为组件的辐射探测系统，可在本条目下运输，需满足：

(a)    20℃时，每个中子辐射探测器内的绝对压力不超过105 kPa；

(b)    每个外包装或每个辐射探测系统内的中子辐射探测器中三氟化硼总量不超过55克；

(c)    每个中子辐射探测器均为金属焊接结构，并用铜锌合金金属陶瓷填充各部件接口间隙。探测器的爆破压力不低于1800 kPa；

(d)    每个中子辐射探测器（包括多个探测器，如在设备里）均装在一个密封的塑料内衬里，该内衬含有足以吸收所有气体的吸收材料；和

(e)    每个中子辐射探测器均装在一个牢固的外包装内，该包装能够承受1.8米跌落试验且无渗漏，每个辐射探测系统也应有牢固的外包装，除非辐射探测系统能给予中子辐射探测器同等的保护。

中子辐射探测器如内含的三氟化硼不超过1克，包括那些用玻璃焊接密封的，和含有这种中子辐射探测器且按照上述条件包装的辐射探测系统，不受本规章限制。