TF DTRA 2017

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Reviewer summary

While this proposal had an interesting scientific scope, it is limited to only silicon isotopes and thus, 
the discovery of the novel signature would hinge on the relevant silicon cross sections.  However, 
the proposal does not discuss how this information would expand upon already existing data on 
silicon capture cross sections or advance the basic science underlying these measurements.

We propose a series of fundamental measurements to quantify the transmutation of naturally occurring Silicon isotopes for materials near a fission blast in response to Thrust Area 1 Topic G1 of the Broad Agency Announcement (BAA) HDTRA1-14-24-FRCWMD-BAA. The intense neutron burst produced by a fission blast interacts with nearby materials transforming nuclei, through neutron capture, into elements that are either radioactive or in the form of stable isotopes that do not exist in large quantities naturally. Instead of passively detecting the radiation released by radioactive nuclei, we would quantify through interrogation the transmutation of nuclei in Urban materials that have been in the vicinity of a nuclear blast. To further understand the fundamental processes leading to the creation and propagation of the above signatures, we propose a series of experiments that will irradiate candidate materials using neutrons and then quantify the limits of detecting the transmuted elements. We would argue that an accurate measurement of the transmuted elements can be used to estimate the yield of a fission blast.

Concrete is a common construction material that would likely be near a nuclear blast. Silicon is one element we propose to initially investigate given that it makes up almost thirty five percent, by mass, of the concrete used in construction. Si-28 has a natural abundance of 92% as compared to Si-29 which has an abundance of 4%. Neutrons from a nuclear blast can transform Si-28 into Si-29 through neutron capture. Interrogating concrete using high energy (MeV) photons would excite the Si-29 nucleus causing it to emit signature photons (nuclear resonance fluorescence ) that can be measured in a short time period (hours).

neutron cross-section from [ IAEA Atlas of Neutron Cross Sections] pg 16

Si-28 NeutronXsect1997.pngSi-29 NeutronXsect1997.pngSi-30 NeutronXsect1997.pngSi-31 NeutronXsect1997.pngSi-32 NeutronXsect1997.png

The neutron energy distribution from a fission (gun-type) weapon. One can expect at least 10^22 neutrons per kiloton to have an energy less than 1 MeV.

conservatively estimate neutron absorbtion cross section to be 1 mbarn.

assume neutron flux of 10^11 n/s/cm^2

density of concrete 2.3 g/cm^3

Silicon makes up 34% of concrete by weight

molar mass silicon = 28.05 g /mol

[math]R = n V \Phi \sigma(\theta) = \left ( 0.34 n_{Si} \right ) V \left ( 10^{11} \frac{n}{cm^2 s}\right ) \left ( 10^{-27} cm^2\right) = 1.6 \times 10^{6} \frac{V}{s \cdot cm^3} [/math]

[math]n_{Si} = \frac{N_A}{M} \rho= \frac{6 \times 10^{23} atoms/mol}{28.05 g/mol} 2.3 \frac{g}{cm^3} = 4.9 \times 10^{22} \frac{1}{cm^3}[/math]

neutron capture on Silicon

N. Ranakumar, E. Kondaiah, R.W. Fink Neutron activation cross sections at 14.4 MeV for Si and Zn isotopes Nuclear Physics A, 1968, pp. 679-683

A.M.J. Spits, A.M.F. Op Den Kamp, H. Gruppelaar Gamma rays from thermal-neutron capture in natural and 28Si enriched silicon Nuclear Physics A, 1970, pp. 449-460

J.W. Boldeman, B.J. Allen, A.R. de L. Musgrove, R.L. Macklin The neutron capture cross section of natural silicon Nuclear Physics A, 1975, pp. 62-76

for neutron energies above 100 MeV

Neutron total cross sections at intermediate energies R. W. Finlay, W. P. Abfalterer, G. Fink, E. Montei, T. Adami, P. W. Lisowski, G. L. Morgan, and R. C. Haight Phys. Rev. C 47, 237 (1993) – Published 1 January 1993

Pulsed-beam time-of-flight techniques are used in a transmission measurement with a continuous spectrum of neutrons to determine neutron total cross sections with good precision up to 600 MeV. Neutrons are produced by spallation of the 800 MeV proton beam from the Los Alamos Meson Physics Facility accelerator incident on a thick, heavily shielded tungsten target at the Weapons Neutron Research facility at Los Alamos National Laboratory. Transmission measurements were completed for fifteen elements with 9≤A≤209 and three isotopically enriched samples of Ca40, Zr90, and Pb208. Principal features of the experiment are the intensity and time structure of the neutron source, tight collimation of the neutron beam line, good geometry, rapid cycling of the samples, stable electronics, and a small, fast neutron detector. Errors due to counting statistics were generally less than 1% for each of several hundred energy bins for each target. The measurements represent steps in the development of a neutron-nucleus optical potential at intermediate energy and important input for the clarification of isovector effects in the nucleon-nucleus interaction. The data also provide insight into the long-standing discussion of mean free paths of the nucleon in the nucleus.

S.F. Mughabghab, M. Divadeenam, N.E. Holden, Neutron Cross Sections, Vol. 1, Part A: Z=1-60, (Academic Press, NY, 1981)

  Only 2 measurements exist for neutron-induced emission spectra above 20 MeV for 28Si. New data have been published by the Louvain group at the 1997 Trieste conference for 63 MeV Si(n,xz) double-differential spectra (z=p,d,a ejectiles). Additionally,  Haight et al. of Los Alamos have preliminary data for Si(n,xp),  for neutrons up to 50 MeV, including emission spectra at four angles.
L.C. Leal, N.M. Larson, D.C. Larson, D.M. Hetrick, "Evaluation of 28,29,30Si up to 1.8 MeV," Nuclear Data for Science and Technology, Int. Conf., Trieste, Italy, May 19-24,  1997

RFP Info


apply using


Basic & Applied Sciences (703) 767-2999 (Dave Petersen???)

Funding Opportunity Number: HDTRA1-14-24-FRCWMD-BAA



In accordance with Section 4.2.1, the requirement for abstract pre-coordination is waived for Topics G1-G19; these topics do NOT require pre-coordination of an abstract prior to the submission of pre-application white papers.

The pre-application white paper deadline for Topics G1-G19 is 1 February 2017. NOTE: An amendment to this BAA will be posted on 2 February 2017 removing Topics G1-G19. PRE- APPLICATION WHITE PAPERS FOR THESE TOPICS MUST BE SUBMITTED BY 11:59 PM (MIDNIGHT) EST ON 1 FEBRUARY 2017. White papers may not be considered if they are received after this deadline. Responses to Topics G1-G19 must address only basic research. Basic research is the systematic study directed toward greater knowledge or understanding of the fundamental aspects of phenomena and of observable facts without specific applications toward processes or products in mind. It includes all scientific study and experimentation directed toward increasing fundamental knowledge and understanding in those fields of the physical, engineering, environmental, and life sciences related to long-term national security needs. It is farsighted, high payoff research that provides the basis for technological programs.2

4.2.1. The predominance of efforts, including all submissions to the thrust areas and most submissions to topics posted in Attachment 1, must be coordinated with the relevant technical point of contact (POC) for the appropriate thrust area prior to submission of a pre-application white paper; an e-mail for the DTRA technical POCs for Thrust Areas 1-7 are provided in Section 7. Coordination of research ideas and efforts must be accomplished via these email addresses, except in cases where a topic specifically states that pre-coordination is not required, and includes submission of an abstract (recommend less than 250 words) of the proposed project/effort or a paragraph description of the proposed project/effort to the email address in Section 7 and a reply email from the relevant email address in Section 7 with the disposition to the applicant. Pre-coordination may not be accomplished with email addresses other than those listed in Section 7. DTRA may not review white papers without prior coordination. Please note that attachments to e-mails may not be reviewed.

In general, all topic-specific and general thrust area submissions require pre-coordination in accordance with the guidelines in Section 1.5 and Section 4.2.1. 

send an e-mail to the address below for pre-coordination?
If you ARE submitting to one of the specific topic numbers detailed below, use the applicable Basic Research-Thrust Area N-Topic G1 to G19 package

Basic Research-Thrust Area 1-Topic G1: Early Time Signatures of a Nuclear Attack Award Amounts for this topic are anticipated to be between $150,000 and $350,000 per year (total dollar value = direct and indirect costs). Larger value efforts (i.e., $350, 000 per year) that are university led, include multiple PIs (at either a single or at multiple organizations), and provide training opportunities are encouraged. In all cases, the proposed award value should be clearly substantiated by the scope of the effort. Proposals from Young Investigators will be considered for this topic. Young Investigator proposals should be clearly marked as such and include a scope of work commensurate with a $100,000 award (total dollar value = direct and indirect costs). Young Investigators are defined as individuals who are currently employed by a U.S. accredited degree-granting college or university who received a Ph.D. or equivalent degree within five (5) years of the date of the pre- application white paper submission. Pre-application white papers and proposals from Young Investigators will be given preference. The preferred award structure for this topic is a base period of three (3) years with up to two (2) additional years as possible options. However, pre-application white papers and proposals that outline scope and effort for only the base period and do not propose options are also acceptable. Pre-application white papers and proposals that outline scope and effort for different base period and option combinations may also be considered; however, note that pre-application white papers and proposals that outline scope and effort that exceed a total of five (5) years will not be considered. Background: Following a nuclear attack, a variety of complex nuclear and chemical processes occur that envelop the bomb materials, the surrounding air, and the local environment. Understanding these processes provides insight into the device composition and origins, useful for post-detonation nuclear forensics. The emission and detection of prompt signatures (optical, gamma, shock wave, etc.) can give valuable information before the material collection and analysis process has begun. However, interpreting these signals can be difficult due to limits in knowledge of the fundamental processes leading to their creation and propagation. DTRA is responsible for research and development efforts for post-detonation nuclear forensics within the DoD. In this topic, DTRA seeks basic research to understand the formation and propagation of prompt signals as well as the identification of new signatures that occur during the early interactions of a nuclear detonation with the surrounding environment. Possible research areas could include air chemistry, nuclear or non-nuclear interactions of the blast with surrounding materials (particularly urban materials) or nuclear data associated with relevant nuclear reactions. Impact: The development of advanced post detonation forensics addresses DTRA’s C-WMD need to enable: prevention of future detonations; identification of those responsible; and improvement in response and recovery efforts. A better interpretation of early-time interactions would provide situational information quicker, inform material analysis and guide a more efficient response. In addition, an understanding of surrounding air chemistry, signature transport and the underlying nuclear reactions helps to better inform modeling and analysis efforts. Objective: This topic seeks research to study the early-time signatures (from T=0 to several hours) of a nuclear blast and their propagation in the surrounding environment. We seek to better comprehend the air chemistry and nuclear effects that result in the production and propagation of prompt signatures (speed of light, speed of sound). Additionally, this topic seeks to uncover new signatures, resulting from the blast’s effect on nearby materials, that haven’t been explored previously because of constraints in accessing detonation sites. These signatures would potentially be measureable for a period of several hours after the blast. The research should identify and characterize these signatures, but not focus on developing a specific detection scheme. Possible research areas may include, but are not limited to:

Experimental and modeling studies of air chemistry and urban effects including: 
  1. Radiation transport
  2. Optical transport
  3. Dynamic particle chemistry and physics
  4. Non-equilibrium dynamics

Nuclear data experimental measurements. Data of particular interest include:

  1. Fission product yields
  2. Prompt-fission gamma yields  Material interactions
  3. Activation of urban materials
  4. Characterization of material morphology


[math]{182 \atop 74} W_{108}[/math] || 26.5 [math]{183 \atop 74} W_{109}[/math] || 14 [math]{184 \atop 74} W_{110}[/math] || 30.6 [math]{186 \atop 74} W_{112}[/math] || 28.4

neutron capture on W-186

[math]{186 \atop 74} W_{112} + n \rightarrow {187 \atop 74} W_{113}[/math]

beta decays after 24 hours.

[math]{187 \atop 74} W_{113} \rightarrow {187 \atop 75} Re_{112} + \beta^-[/math]

66% of the time the beta decay leaves Re-112 in the 5/2- excited state with then decays to the 5/2+ ground state by emitting a 685 keV photon, a 480 keV line is also dominant when there is a transition from the 5//2- state to the lower 9/2- excited state 206.252 keV above the 5/2+ ground state. Other photon energies are emitted but the dominant photon lines are at 685 and 480 keV. 16.9% of the time the beta decay to the Re-112 , 5/2+ ground state directly.

[math] {187 \atop 75} Re_{112}[/math] has a 33 year half life

measure the isotopic concentrations after neutron absorption using PAA

neutron knockout

[math] {187 \atop 75} Re_{112} + \gamma \rightarrow {186 \atop 75} Re_{111} + n[/math]

results in a state that undergoes beta decay 92.5% of the time and EC decays the remaining time emitting photons the dominant one having an energy of 137 keV

neutron capture on W-182

[math]{182 \atop 74} W_{108} + n \rightarrow {183 \atop 74} W_{109}[/math]

long enough half life to be considered stable

measure the isotopic concentrations after neutron absorption using PAA

proton knockout

[math] {183 \atop 74} W_{109} + \gamma \rightarrow {182 \atop 73} Ta_{109} + p[/math]

results in a state that undergoes beta decay 100% of the time after 115 days with gammas emission of 68 and 1121 keV. there are two meta stable states of Ta-109 that IT transition and emitt phontons of energy 16 keV after 283 msec and 520 keV after 15.84 minutes.


Si-29/Si-28 using ICP-MS

One drawback to standard-sample-standard method of mass bias correction is that it is slow. The combination of 5 min of rinse before measurement of a blank prior to each analysis and then 22 min of sample introduction time before roughly 15 min of sample measurement means that the collection of data for one 29Si/28Si ratio, be it sample or standard, requires ∼40 min. Thus 2 hours is required to complete one set of standard-sample-standard determinations. This is much greater than the period required for standard-sample-standard analysis on dual-inlet isotope ratio mass spectrometers (where the cycle may be completed multiple times in just a few minutes). This time period is also much greater than that previously utilized on MC-ICP-MS machines for measurement of isotope ratios of other elements, such as calcium [Halicz et al., 1999].!divAbstract

Nuclear resonance flourescence (NRF) and photon activation analysis (PAA) are two tools that may be used to quantify isotopic ratios. NRF may be performed on time scales of hours while PAA's time scale depends on the half life of the isotope of interest.

Si-28 1st energy level = 1779.03 keV

Possible sources are

Energy || relative intensity || decay mode || half life || Isotope

1779.0 3 1.38 7 e+b+ 32.4 m 3 107In 1779.02 21 0.344 16 e+b+ 15.2 m 7 114Te 1779.05 3 1.91 11 b- 1.217 s 5 81Ga

Si-29 1st energy level is 1273.387 keV

Possible sources are

Energy || relative intensity || decay mode || half life || Isotope

1273.3 4 0.151 25 e+b+ 40.1 m 20 121Xe 1273.367 12 1.549 10 e+b+ 4.140 s 14 29P 1273.367 12 90.6 6 b- 6.56 m 6 29Al


neutron knockout of Si-28 takes 17 MeV and goes to Si-27 which emitts a 511 keV with a half life of 4.5 seconds

proton knockout of Si-29 takes 12 MeV of energy and goes to Al-28 which emits 1779 keV gamma with half life of ~2 min

Concrete has 6 elements and a density of 2.7 g/cm^3

Element Atomic Weight (A) Atomic Number (Z) Proportion by Weight
H 1.0079 1. 0.004
O 15.9994 8. 0.509
Al 26.981539 13 0.034
Si 28.0855 14. 0.345
Ca 40.078 20 0.070
Fe 55.8474 26. 0.038

GEANT4 code

a = 1.0079*g/mole;
  G4Element* elH  = new G4Element(name="Hydrogen",symbol="H" , z= 1., a);
  a = 15.9994*g/mole;
  G4Element* elO  = new G4Element(name="Oxygen"  ,symbol="O" , z= 8., a);
a = 26.981539*g/mole;
  G4Element* elAl  = new G4Element(name="Aluminum",symbol="Al" , z= 13., a);
a = 28.0855*g/mole;
  G4Element* elSi  = new G4Element(name="Silicon",symbol="Si" , z= 14., a);
a = 40.078*g/mole;
  G4Element* elCa  = new G4Element(name="Calcium",symbol="Ca" , z= 20., a);
a = 55.8474*g/mole;
  G4Element* elNi  = new G4Element(name="Iron",symbol="Fe" , z= 26., a);

Previous studies

according to

"From measurements and calculations we concluded that in ordinary concrete the residual radioactivity is predominantly due to trace elements presence. These isotopes are Sc-46, Zn-65, Mn-54, Co-60, and 1Eu-152. All these isotopes are produced from thermal neutron capture reactions, except Mn-54, which is produced from fast neutron reactions. "

Prompt gamma neutron activation analysis of bulk concrete samples with an Am-Be neutron source Khelifi, R.. Applied Radiation and Isotopes Volume: 51 Issue 1 (1999) ISSN: 0969-8043 Online ISSN: 1872-9800

Gamma Spect from concrete using NAA

Using an Am-Be source

from Advances in Applied Science Research, 2011, 2 (4):613-620,Neutron Activation Analysis of Cement Bulk Samples M.Ali-Abdallah, N.A.Mansour, M.A.Ali*, M. Fayez-Hassan*

two, 2Cui Am-Be sources were used to irradiate concrete for a period of 30 (?) days. Suggests that the average neutron flux was [math]3.7 \times 10^3 n/s/cm^2[/math]

GammaSpectFromNAAofConcrete 2011.png

observed lines from Mn-56, Sr-87m, Na-24, and Al-28.

Using Cf-252

Used a 4.9 ug source of Cf-252

File:NAA Using Cf252 Dahing 2015.pdf

Saw Silicon lines at 3.54 MeV and 6.38 MeV using XRF?

Saw Calcium line at 3083 keV using NAA.

neutron capture on Si-30

Si-30 is only 3% of the naturally occurring Silicon isotopes

[math]{30 \atop 14} Si_{16} + n \rightarrow {31 \atop 14} Si_{17}[/math]

beta decays 100% of the time with a half life of 157 minutes. About 0.05% of the time a 1266 keV photon can be emitted when the beta decay left the Phosphorous in the 3/2+ isomer state that transitions down to the 1/2+ ground state of Phosphorous.

[math]{31 \atop 14} Si_{17} \rightarrow {31 \atop 15} P_{16} + \beta^-[/math]

Si-28 is 92% of the natural abundance, can it absorbs a neutron and become an excited state of Si-29 which will decay to the stable ground state of Si-29 frequently enough to be a signature?

Silicon NRF

File:Ryan Vtech 1963.pdf

Silicon PAA

From pg 171 of Segabade work

[math]{29 \atop 14} Si_{15} \rightarrow {28 \atop 13} Al_{15} + p[/math] , half life is 2.2 min, Activity ratio w.r.t. Nickel after 1 hour of irradiation = 3.6, Egamma = 1779 keV

[math]{30 \atop 14} Si_{16} \rightarrow {29 \atop 13} Al_{16} + p[/math] , half life is 6.6 min, Activity ratio w.r.t. Nickel = 1.5, Egamma = 1274 keV