Information Notice 2019-06, Potential Over-Pressurization of High Specific-Activity Alpha-Emitting Radioactivity Sources
| ML19073A203 | |
| Person / Time | |
|---|---|
| Issue date: | 08/14/2019 |
| From: | Andrea Kock, Chris Miller Office of Nuclear Material Safety and Safeguards, Office of Nuclear Reactor Regulation |
| To: | |
| Lintz M | |
| References | |
| IN-19-006 | |
| Download: ML19073A203 (4) | |
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR REACTOR REGULATION
OFFICE OF NUCLEAR MATERIAL
SAFETY AND SAFEGUARDS
WASHINGTON, D.C. 20555 August 14, 2019 NRC INFORMATION NOTICE 2019-06: POTENTIAL OVER-PRESSURIZATION OF
HIGH SPECIFIC-ACTIVITY ALPHA-
EMITTING RADIOACTIVITY SOURCES
ADDRESSEES
All holders of and applicants for a specific byproduct materials license under Title 10 of the
Code of Federal Regulations (10 CFR) Part 30, Rules of General Applicability to Domestic
Licensing of Byproduct Material." All Radiation Control Program Directors and State Liaison
Officers.
PURPOSE
The U.S. Nuclear Regulatory Commission (NRC) is issuing this information notice (IN) to inform
addressees about the possibility of significant pressure build-up in high specific activity alpha- emitting sources, such as americium-241 (Am-241) or plutonium-240 (Pu-240), caused by
radiolysis and production of hydrogen. This IN requires no action or written response on the
part of an addressee. The NRC is providing this IN to the Agreement States for their
information and for distribution to their licensees as appropriate.
DESCRIPTION OF CIRCUMSTANCES
A 5 mL flame-sealed borosilicate glass ampoule was used to store an aqueous radioactive
reference source containing 1.5 mCi (55.5 MBq) of Am-241. The source was stored sealed for
12 years. During that time, sufficient hydrogen gas was generated from radiolysis to over- pressurize the glass ampoule and cause it to fail. Contamination and potential for personnel
radiation exposure resulted from the source failure.
BACKGROUND
In August 2017 a 5 mL glass ampoule, which contained 1.5 mCi (55.5 MBq) of Am-241 when
sealed on 15 July 2005, ruptured in the laboratory of an NRC licensee. The licensees
investigation determined that alpha decay of the Am-241 source produced sufficient hydrogen
gas (H2) during that time to result in an internal pressure of 25 atmospheres (atm) within the
source ampoule. The mechanism for production of H2 was the radiolysis (dissociation) of water
molecules within the sample matrix into hydrogen and oxygen ions. Radiolysis occurred due to
ionization of the charged alpha particles moving through the matrix water, and the subsequent
recombination of hydrogen ions produced H2 gas.
DISCUSSION
The flame-sealed borosilicate glass ampoule is a commonly used long-term storage container
for liquid radioactive reference standards. This container has been used and distributed by
standards laboratories since at least early in the 20th century. This glass ampoule is expected
to be strong enough to contain 2 atm pressure, and is believed by the licensee to be adequate
to contain 5-6 atm. The rupture of this high-specific activity source was the first occurrence of
this problem for the licensee, with ampoule pressure increasing continuously from time of
sealing in 2005 until the failure of the glass in August 2017 at approximately 25 atm internal
pressure.
The licensee described long-standing experience with the borosilicate glass ampoule as a
standard reference material configuration, which provides useful capabilities to researchers
because it can be opened and re-sealed by flame-sealing. The scientific staff also has
expressed reluctance to consider alternative source containers because of the past historical
precedent of its use and long-standing experience with the glass ampoule.
Original Source characteristics:
Am-241, 1.5 mCi (55.5 MBq) on 15 July 2005 Specific activity 3.433 Ci/g (127 GBq/g)
Volume = 5 mL
Chemical Form: AmCl3 in 1M HCl
Source activity as of 8 Aug 2017 (approximate date of failure):
Am-241, 1.3 mCi (47.6 MBq) in 4.48 mL
CONCLUSION
If absorbed into the body, alpha-emitting radionuclides can produce large doses to target organs
(bone surfaces in the case of Am-241). In this case, the contamination resulting from the failed
ampoule was not immediately detected. Personnel exposures occurred over the course of
several days before the contamination was identified, creating the potential for inadvertent
additional exposures of other personnel due to spreading contamination. In addition to potential
radiation exposure, adverse impacts to laboratory operations occurred during the assessment of
the event and in recovery. Assessment of the actual internal doses from exposure required
months of follow-up bioassay sampling and analysis.
GENERIC IMPLICATIONS
Similar sources with these high specific-activity characteristics have been available since the
1990s, so it may be only recently that sufficient time has elapsed time to generate the observed
internal hydrogen gas pressure. Therefore, it is timely and important for any licensee
possessing similar sources to anticipate the possibility of over-pressurization and of failure of
source containers not designed to withstand sufficient pressure buildup.
Limited Information is available for one additional similar event, which occurred at the
International Atomic Energy Agency (IAEA) Seibersdorf Austrian Research Center Laboratory
on August 3, 2008. The IAEA event involved a high specific-activity Pu-240 reference source
which was sealed in 1993, therefore creating roughly a 15-year period of hydrogen gas buildup. This IN is being published to alert potentially affected licensees about the over-pressurization
and subsequent container failure of a high-specific activity alpha-emitting source and to
sensitize others who may possess similar high specific-activity sources to the hazard.
CONTACT
This IN requires no specific action nor written response. Please direct any questions about this
matter to the technical contact(s) listed below or the appropriate regional office.
/RA/ /RA/
Christopher G. Miller, Director Andrea L. Kock, Director
Division of Inspection and Regional Division of Materials Safety, Security, Support State, and Tribal Programs
Office of Nuclear Reactor Regulation Office of Nuclear Material Safety
and Safeguards
Technical Contacts: Todd Jackson, Region I
610-337-5308 E-mail: Todd.Jackson@nrc.gov
Celimar Valentin-Rodriquez, NMSS
301-415-7124 E-mail: Celimar.Valentin-Rodriquez@nrc.gov
Note: NRC generic communications may be found on the NRC public Web site, http://www.nrc.gov, under NRC Library/Document Collections. NRC INFORMATION NOTICE 2019-06, POTENTIAL OVER-PRESSURIZATION OF HIGH
SPECIFIC-ACTIVITY ALPHA-EMITTING RADIOACTIVITY SOURCES DATE AUGUST 14,
2019 ADAMS Accession No.: ML19073A203 *concurred via email
OFC Tech Editor RI/DNMS/CIRAB RI/DNMS/BC NMSS/MSTB/PM
NAME JDougherty* TJackson* ADeFrancisco* CValentin-Rodriquez*
DATE 03/18/19 08/01/19 08/12/19 07/31/19 OFC NMSS/MSTB/BC NMSS/MSST/D NRR/DIRS/IRGB/LA NRR/DIRS/IRGB/PM
NAME THerrera* AKock* IBetts* MLintz*
DATE 07/31/19 08/13/19 06/18/19 08/13/19 OFC NRR/DIRS/IRGB/BC NRR/DIRS/D
NAME PMcKenna* CMiller*
DATE 08/14/19 08/14/19 OFFICIAL USE ONLY