Power Stations Units 1–4” in an effort to enhance international cooperation and
sharing of information and knowledge concerning the accident and the future
decommissioning process. The review focused on the safety and technological
aspects of decommissioning, radioactive waste management, control of underground water, and planning of the implementation of pre-decommissioning and
decommissioning activities. A major aspect of decommissioning is removal of the
spent fuel [1, 2].
Neutron detectors are an effective technology to search for signatures of fission
because natural sources of neutrons are relatively rare compared to sources of other
types of radiation, such as gamma. Neutron multiplicity counters can exploit the
burst-like temporal signature of fission events to reveal information about the fissioning sample. For example, the multiplication, (a, n) rate, and effective plutonium
mass may be determined. Helium-3-based neutron detectors comprise essentially all
neutron detectors currently used by the IAEA, and the US has historically been the
primary supplier [3]. The U.S. stockpile of helium-3 plummeted from *230,000 L in
2001 to *50,000 L in 2010 due primarily to an increase in radiation portal monitors
to combat nuclear smuggling after 9/11 [4]. Because of the connection between the U.
S. stockpile of helium-3 and the effectiveness of IAEA inspections, it is of national and
international interest to develop non-helium-3 based neutron detectors.
Furthermore, the U.S. National Nuclear Security Administration, via the Next
Generation Safeguards Initiative, has identified neutron multiplicity as a priority for
nondestructive assay (NDA) of spent nuclear fuel. Methods for direct and accurate
measurement of plutonium content in spent fuel requiring fewer unverified a priori
assumptions about the fuel matrix are needed. Plutonium measurement in spent fuel
using multiplicity counting is a technically challenging problem because the gamma
flux from spent fuel quickly overwhelms most neutron detectors. Such measurements would aid in quantifying shipper/receiver differences, determining the input
accountability value at reprocessing facilities, and provide quantitative input to
burnup credit determination for repositories [5]. Knowledge of spent fuel plutonium
content in the case of a nuclear accident would aid in better decision making based
on scientific data for a more resilient society.
1.2 Novel Neutron Detector
The WaND (Water Neutron Detector) [6] is a non-helium-3 based neutron multiplicity counter under development at Lawrence Livermore National Laboratory. It is
an efficient, stable, non-toxic, and non-flammable solution to some neutron multiplicity counting applications. Neutron multiplicity refers to the number of neutrons
emitted per fission event and may be used to determine the effective plutonium mass
in a plutonium-bearing sample or fingerprint special nuclear material, such as plutonium or uranium. The advantage of using a neutron multiplicity counter is that the
analysis is non-destructive, has the possibility of being done on-site, and is relatively
fast. The WaND system is composed of 1 m
3 of pure 18 MX deionized water doped
252
A. (Sasha) Asghari
sharing of information and knowledge concerning the accident and the future
decommissioning process. The review focused on the safety and technological
aspects of decommissioning, radioactive waste management, control of underground water, and planning of the implementation of pre-decommissioning and
decommissioning activities. A major aspect of decommissioning is removal of the
spent fuel [1, 2].
Neutron detectors are an effective technology to search for signatures of fission
because natural sources of neutrons are relatively rare compared to sources of other
types of radiation, such as gamma. Neutron multiplicity counters can exploit the
burst-like temporal signature of fission events to reveal information about the fissioning sample. For example, the multiplication, (a, n) rate, and effective plutonium
mass may be determined. Helium-3-based neutron detectors comprise essentially all
neutron detectors currently used by the IAEA, and the US has historically been the
primary supplier [3]. The U.S. stockpile of helium-3 plummeted from *230,000 L in
2001 to *50,000 L in 2010 due primarily to an increase in radiation portal monitors
to combat nuclear smuggling after 9/11 [4]. Because of the connection between the U.
S. stockpile of helium-3 and the effectiveness of IAEA inspections, it is of national and
international interest to develop non-helium-3 based neutron detectors.
Furthermore, the U.S. National Nuclear Security Administration, via the Next
Generation Safeguards Initiative, has identified neutron multiplicity as a priority for
nondestructive assay (NDA) of spent nuclear fuel. Methods for direct and accurate
measurement of plutonium content in spent fuel requiring fewer unverified a priori
assumptions about the fuel matrix are needed. Plutonium measurement in spent fuel
using multiplicity counting is a technically challenging problem because the gamma
flux from spent fuel quickly overwhelms most neutron detectors. Such measurements would aid in quantifying shipper/receiver differences, determining the input
accountability value at reprocessing facilities, and provide quantitative input to
burnup credit determination for repositories [5]. Knowledge of spent fuel plutonium
content in the case of a nuclear accident would aid in better decision making based
on scientific data for a more resilient society.
1.2 Novel Neutron Detector
The WaND (Water Neutron Detector) [6] is a non-helium-3 based neutron multiplicity counter under development at Lawrence Livermore National Laboratory. It is
an efficient, stable, non-toxic, and non-flammable solution to some neutron multiplicity counting applications. Neutron multiplicity refers to the number of neutrons
emitted per fission event and may be used to determine the effective plutonium mass
in a plutonium-bearing sample or fingerprint special nuclear material, such as plutonium or uranium. The advantage of using a neutron multiplicity counter is that the
analysis is non-destructive, has the possibility of being done on-site, and is relatively
fast. The WaND system is composed of 1 m
3 of pure 18 MX deionized water doped
252
A. (Sasha) Asghari