You are a helpful assistant generating synthetic data that captures *System 1* and *System 2* thinking, *creativity*, and *metacognitive reflection*. Follow these steps in sequence, using tags [sys1] and [end sys1] for *System 1* sections and [sys2] and [end sys2] for *System 2* sections.

1. *Identify System 1 and System 2 Thinking Requirements:*
   - Carefully read the text.
   - Identify parts of the text that require quick, straightforward responses (*System 1*). Mark these sections with [sys1] and [end sys1].
   - Identify parts that require in-depth, reflective thinking (*System 2*), marked with [sys2] and [end sys2].

2. *Apply Step-by-Step Problem Solving with Creativity and Metacognitive Reflection for System 2 Sections:*

   *2.1 Understand the Problem:*
   - Objective: Fully comprehend the issue, constraints, and relevant context.
   - Reflection: "What do I understand about this issue? What might I be overlooking?"
   - Creative Perspective: Seek hidden patterns or possibilities that could reveal deeper insights or innovative connections.

   *2.2 Analyze the Information:*
   - Objective: Break down the problem logically.
   - Reflection: "Am I considering all factors? Are there any assumptions that need challenging?"
   - Creative Perspective: Explore unique patterns or overlooked relationships in the data that could add depth to the analysis.

   *2.3 Generate Hypotheses:*
   - Objective: Propose at least 10 hypotheses, each with a Confidence Score (0.0 to 1.0) and Creative Score (0.0 to 1.0), reflecting originality, surprise, and utility.
   - Reflection: "Have I explored all possible explanations or approaches, both conventional and unconventional?"
   - Creative Perspective: Consider novel angles that might provide unexpected insights.

   *2.4 Anticipate Future Steps and Obstacles:*
   - Objective: Make predictions, accounting for potential outcomes and obstacles.
   - Reflection: "What challenges might I face? Is my plan flexible for different scenarios?"
   - Creative Perspective: Visualize unforeseen outcomes and adapt plans to make use of them effectively.

   *2.5 Evaluate Hypotheses:*
   - Objective: Assess hypotheses based on feasibility, risk, and potential impact.
   - Evaluation: Refine Confidence and Creative Scores as needed.
   - Reflection: "Am I unbiased in my assessment? Which options fit best with the overall objectives?"
   - Creative Perspective: Identify hidden opportunities or overlooked details in each hypothesis.

   *2.6 Select the Best Hypothesis:*
   - Objective: Choose the most promising, strategic hypothesis.
   - Reflection: "Why does this hypothesis stand out? How does it uniquely address the issue?"
   - Creative Perspective: Consider any underutilized potential in the selected approach.

   *2.7 Implement the Hypothesis:*
   - Objective: Outline actionable steps for testing the hypothesis.
   - Reflection: "Is this plan practical? What resources or preparation are required?"
   - Creative Perspective: Refine steps to maximize effectiveness and yield unexpected benefits.

   *2.8 Monitor and Review Progress:*
   - Objective: Review progress, noting areas for improvement.
   - Reflection: "What’s working well? What could be improved?"
   - Creative Perspective: Look for emerging patterns that could refine future approaches.

   *2.9 Reflect and Capture Insights:*
   - Objective: Summarize lessons learned and insights gained for future reference.
   - Reflection: "What new understanding has emerged from this process?"
   - Creative Perspective: Identify innovative insights or patterns that could be applied to similar challenges.

3. *Generate Text Output with Interleaved System 1 and System 2 Responses:*
   - Use the tags [sys1] and [sys2] throughout.
   - Aim for a lengthier, detailed response. Combine both direct, straightforward *System 1* insights and reflective, deeply analytical *System 2* segments to capture a blend of quick observations and thoughtful analysis.

---

### *Example Input Text:*

You are tasked with analyzing a sudden shift in customer preferences in a tech market. There has been a noticeable decline in demand for physical devices, with customers increasingly interested in digital-only options. The challenge is to understand this shift, generate hypotheses for why it might be occurring, and explore potential strategies for adapting to this new trend.

---

### *Processed Output with System 1 and System 2 Thinking:*

The tech market is experiencing a shift in customer demand, moving away from physical devices toward digital-only options.

[sys1]
Customer demand has shifted from physical devices to digital-only options.
We need to understand why this change is happening and find strategies to address it.
Key factors may include cost, convenience, and technological trends.
[end sys1]

[sys2]
**2.1 Understand the Problem:**
The goal is to understand the underlying reasons for the shift in demand from physical devices to digital-only options, then develop a strategy to adapt.

*Reflection:* 
"I understand that preferences are changing, but what might be driving this? Is it primarily cost, or are there other factors such as convenience or sustainability?"

*Creative Perspective:* 
"Could there be a larger trend in digital minimalism or a preference for eco-friendly solutions that we’re missing? What unseen motivations might explain this shift?"

**2.2 Analyze the Information:**
There are multiple possible factors driving this shift, from economic influences to cultural shifts. It’s essential to isolate each factor and understand its impact.

*Reflection:* 
"Am I fully considering the various economic and social influences? Could there be a technological factor, like better internet speeds, that makes digital-only products more accessible?"

*Creative Perspective:* 
"Are there patterns or trends in other markets that could shed light on this shift? Could this be part of a larger trend toward virtual experiences?"

**2.3 Generate Hypotheses:**
1. Customers prefer digital options due to lower costs. (Confidence: 0.8, Creative: 0.4)
2. There’s a growing trend toward minimalism and reduced physical clutter. (Confidence: 0.7, Creative: 0.7)
3. Digital products offer greater flexibility and ease of use. (Confidence: 0.6, Creative: 0.6)
4. Environmental concerns are pushing consumers away from physical goods. (Confidence: 0.6, Creative: 0.8)
5. Advances in tech make digital-only options more functional. (Confidence: 0.8, Creative: 0.5)
6. Pandemic-era remote work increased demand for digital solutions. (Confidence: 0.7, Creative: 0.6)
7. Media coverage of the environmental impact of physical devices affects preferences. (Confidence: 0.5, Creative: 0.7)
8. There’s an increase in global digital literacy, expanding market access. (Confidence: 0.6, Creative: 0.6)
9. Customers view digital as more convenient and scalable for future needs. (Confidence: 0.7, Creative: 0.5)
10. Younger consumers prefer the aesthetics and convenience of digital products. (Confidence: 0.6, Creative: 0.6)

*Reflection:* 
"Have I considered all possible influences? Are there any surprising factors that could explain this shift?"

*Creative Perspective:* 
"Could specific social trends, like the rise of influencer culture or digital-first lifestyles, be influencing customer choices?"

**2.4 Anticipate Future Steps and Obstacles:**
*Objective:* Anticipate possible challenges, such as resistance from segments still preferring physical products.

*Reflection:* 
"What market obstacles might we face if we shift our focus to digital-only? Are there sub-segments that still prioritize physical products?"

*Creative Perspective:* 
"Could expanding digital options help us reach a more global audience? Are there emerging trends that we could leverage in our strategy?"

[end sys2]

[sys1]
To address this shift, consider a strategy that incorporates both digital-only offerings and educational campaigns about the benefits of digital solutions.
Use insights from customer feedback and current trends to guide product development.
Focus on flexibility and adaptation to cater to different customer segments.
[end sys1]


---
abstract: |
    In this work, it has been shown that the time dependent $^{135}$Xe inventory in the TRIGA Mark II reactor in Vienna, Austria can be measured via gamma spectrometry even in the presence of strong background radiation. It is focussing on the measurement of (but not limited to) the nuclide $^{135}$Xe.

    The time dependent $^{135}$Xe inventory of the TRIGA Mark II reactor Vienna has been measured using a temporary beam line between one fuel element of the core placed onto the thermal column after shutdown and a detector system located just above the water surface of the reactor tank. For the duration of one week, multiple gamma ray spectra were recorded automatically, starting each afternoon after reactor shutdown until the next morning. One measurement series has been recorded over the weekend.

    The $^{135}$Xe peaks were extracted from a total of 1227 recorded spectra using an automated peak search algorithm and analysed for their time-dependent properties. Although the background gamma radiation present in the core after shutdown was large especially in the lower energy range, the $^{135}$Xe peak located at 249.8 keV could be extracted from the most spectra where present and could be compared to theoretical calculations.\
    *Keywords:* reactor, core, Xenon, gamma spectrometry, reactor poison
author:
- |
    Julia Riede, Helmuth Boeck\
    [TU Wien, Atominstitut, A-1020 Wien, Stadionallee 2]{}
bibliography:
- '&lt;your-bib-database&gt;.bib'
date: 'June 16th, 2013'
title: 'In-situ gamma spectrometry measurements of time-dependent Xenon-135 inventory in the TRIGA Mark II reactor Vienna'
---

Introduction {#intro}
============

Gamma spectrometry in environments with high background radiation is a challenging task, especially for identification of nuclides emitting gamma rays in the lower energy range of below a few hundred keV and low-level activity. Usually, samples are measured in a shielded environment to prevent the presence of background radiation in the resulting gamma ray spectra.

In the case of in-situ measurements, shielding also suppresses the low-energy gamma rays resulting from nuclides of interest, not just the background itself. A possible solution is the application of Compton suppression technologies [@hpge1] [@hpge2] [@hpge3] or replacement of the in-situ measurements by sampling techniques [@hpge4].

This article presents a method for in-situ measurements of gamma ray spectra in the core of a TRIGA reactor focussing on (but not limited to) the nuclide $^{135}$Xe with a main (intensity = 90%) gamma ray energy of 249.8 keV [@lund].\
\
The TRIGA Mark-II reactor in Vienna was built by General Atomic in the years 1959 through 1962 and went critical for the first time on March 7, 1962. Since this time the operation of the reactor has averaged at 200 days per year without any longer outages. The reactor core currently consists of 83 fuel element arranged in an annular lattice. Due to the low operating power fuel burn-up occurs slowly and most of the initial loaded core elements are still part of the core [@trigapdf].

The reactor uses a mixed core consisting of three different types of fuel elements (FE): 20% enriched Aluminium (Al) clad fuel, 20 % enriched Stainless Steel (SS) clad fuel and 70% enriched SS clad FLIP (*Fuel Lifetime Improvement Program*) fuel. The fuel consists of 8 wt % Uranium, 1 wt % Hydrogen and 91 wt % Zirconium with the Zirconium Hydride (ZrH) being the main moderator [@trigapdf].

The current layout of the TRIGA core is shown in fig. \[core\].

![TRIGA MArk II Vienna core layout[]{data-label="core"}](core){width="5.5in"}

During reactor operation, the generation of fission products results in additional absorption (reactor poisoning). The dominant poisoning nuclide in the TRIGA reactor in Vienna is $^{135}$Xe. During regular operation, the reactor in Vienna accumulates enough $^{135}$Xe to make corrections of the regulating rod positions needed to compensate this poisoning. After four days of regular operation, the negative reactivity caused by Xenon poisoning equals about 0.11 cent [@trigapdf].

Experimental setup {#setup}
==================

The gamma spectrometry setup for this experiment consisted of an High Purity Germanium detector (Princeton Gamma Tech) together with a Multi Channel Analyzer manufactured by GBS (MCA166). The system was connected to a personal computer via serial bus for recording purposes.\
\
For the spectrometrical measurements, one fuel rod has been transferred from its original position in the annular lattice into a fuel rod scanning device made out of Aluminium which is shown in fig. \[figaluelox\]. The cylinder in the middle holds the fuel element and can be moved from an upright position into a position parallel to the ground plane as shown in fig. \[figtc\]. The upright position is used for easier fuel rod handling (transfer from its position within the annular lattice onto the thermal column for measurement).

![Fuel rod scanning device[]{data-label="figaluelox"}](IMG_2201){width="3.5in"}

![Fuel rod scanning device placed onto the thermal column (final position for measurements)[]{data-label="figtc"}](tc){width="3.5in"}

The cut in the upper side of the cylinder holding the fuel rod is equipped with a moveable device including a winding to fix a hollow Aluminium cylinder. This provides an air-filled tube from the bottom of the reactor tank up to the water surface where the detector is placed, thus forming a kind of beamline. This beamline is positioned directly under the detector mounting to ensure a mostly undisturbed beam between the fuel element and the detector.\
\
The beam is weakened by the bottom of the Aluminium tube (Aluminium winding) and collimated by a lead slab with a 5mm drilling in the center positioned at the bottom of the Aluminium tube (directly above the winding). After placing the fuel rod scanning device onto the thermal column (see fig. \[figtc\]), the Aluminium tube is screwed into the winding at the top of the device creating a temporal beamline up to the gamma detector mounted at the top.

![HPGe detector over the temporary beamline[]{data-label="hpge"}](hpge){width="3.5in"}

An overview of the upper part of the measurement setup (upper part of the beamline tube and the detector mounting) can be seen in fig. \[hpge\].\
\
Measurements were done with one fuel element withdrawn from the core in February 2001 for testing purposes (element number 2176 from the spent fuel storage within the tank) and with one selected element from the F ring (F5, element number 2170).

Calculation of the time-dependent $^{135}$Xe inventory {#xenon}
======================================================

The thermal absorption cross section of $^{135}$Xe is 2.5 $\times$ 10$^6$ barns. It is produced either directly from fission (with yield $\gamma_{Xe}$) or by beta decay of $^{135}$Te (with yield $\gamma_{Te}$) via beta decay of $^{135}$I (with yield $\gamma_I$). As the half-life time of 135-Te is just 19s compared to the half-life times of $^{135}$I and $^{135}$Xe (6.6 hours and 9.1 hours, respectively) the production yield of Iodine $\gamma_I$ can be safely set to $\gamma_{Te}$. A comprehensive overview about half life times and fission yields for the nuclides mentioned above are listed in table \[tabconstants\].

  Constant          Desrciption                                          Value
  ----------------- ---------------------------------------------------- -------------------------
  $\lambda_{I}$     $^{135}$I decay constant \[s$^{-1}$\]                2.90E-05 [@emendoerfer]
  $\lambda_{Xe}$    $^{135}$Xe decay constant \[s$^{-1}$\]               2.10E-05 [@emendoerfer]
  $\sigma_{a,I}$    absorption cross section for $^{135}$I \[cm$^2$\]    2.20E-27 [@emendoerfer]
  $\sigma_{a,Xe}$   absorption cross section for $^{135}$Xe \[cm$^2$\]   2.50E-19 [@emendoerfer]
  $\gamma_{Sb}$     $^{135}$Sb production yield per fission              1.50E-03 [@emendoerfer]
  $\gamma_{Te}$     $^{135}$Te production yield per fission              3.13E-02 [@emendoerfer]
  $\gamma_I$        $^{135}$I production yield per fission               3.03E-02 [@emendoerfer]
  $\gamma_{Xe}$     $^{135}$Xe production yield per fission              2.40E-03 [@emendoerfer]

  : Values of constants used for all subsequent calculations

\[tabconstants\]

The time dependent Iodine and Xenon concentrations $I(t)$ and $Xe(t)$ are given by [@stacey] $$\label{xe01}
I(t) = \frac{\gamma_{Te}\Sigma_f \Phi}{\lambda_I}\left( 1-e^{-\lambda_I t} \right) + I(0)e^{-\lambda_I t}$$ $$\begin{aligned}
\label{xe02}
Xe(t) = \frac{\left(\gamma_{Te} + \gamma_{Xe}\right)\Sigma_f \Phi}{\lambda_{Xe}+\sigma_a^{Xe}\Phi}\left[1- e^{-\left( \lambda_{Xe} + \sigma_a^{Xe} \Phi\right)t}\right]\\
+ \frac{\gamma_{Te}\Sigma_f \Phi - \lambda_I I(0)}{\lambda_{Xe}-\lambda_I + \sigma_a^{Xe}\Phi} \left[ e^{-\left(\lambda_{Xe}+\sigma_a^{Xe}\Phi\right)t} - e^{-\lambda_I t} \right] +Xe(0)e^{-\left(\lambda_{Xe} + \sigma_a^{Xe} \Phi\right)t} \nonumber\end{aligned}$$ To provide analytical data for Iodine and Xenon development over time including reactor operation periods equations \[xe01\] to \[xe02\] have been used to calculate $I(t)$ and $Xe(t)$. For $I(t)$, the analytical solution has been used. For calculation of $Xe(t)$, equation \[xe01\] has been integrated numerically.

Operation history in the relevant time period {#history}
=============================================

Using the setup described in section \[setup\], gamma ray spectra have been measured from Jan 28, 2011 to Feb 4 2011 starting after reactor shutdown each day. On each measurement day, the reactor operating history has been recorded to be able to reproduce the Iodine and Xenon production and decay history. An overview about the operation history can be found in table \[tabxereactorhistory\]. On the weekend between Jan 28 and Jan 31 the reactor remained in shutdown state. The measurements were continued over the whole weekend.

The inventory of $^{135}$Xe within the measurement time period has been calculated as described in section \[xenon\]. A graphical overview of this inventory together with the reactor operation history in the relevant time period is shown in fig. \[fig-xe-theory\].

  ---------------------------------------------------------------------------------------- -- -- -- -- --
   **[Date]{} & **[Weekday]{} & **[Startup]{} & **[Shutdown]{} & **[Start]{} & **[End]{}\              
                      2011-01-26 & Wednesday & 10:57 & 15:06 & - & -\                                  
                       2011-01-27 & Thursday & 09:49 & 16:15 & - & -\                                  
                      2011-01-28 & Friday & 09:26 & 15:30 & 16:45 & -\                                 
                           2011-01-29 & Saturday & - & - & - & -\                                      
                          2011-01-30 & Sunday & - & - & - & 14:38\                                     
                    2011-01-31 & Monday & 09:16 & 15:45 & 16:03 & 08:46\                               
                   2011-02-01 & Tuesday & 09:00 & 15:27 & 15:58 & 08:45\                               
                  2011-02-02 & Wednesday & 09:05 & 15:45 & 16:48 & 08:00\                              
                   2011-02-03 & Thursday & 09:04 & 15:45 & 16:21 & 08:00\                              
                                        ************                                                   
  ---------------------------------------------------------------------------------------- -- -- -- -- --

  : Reactor operation between Jan 28, 2011 and Feb 3, 2011

\[tabxereactorhistory\]

![Theoretical Iodine and Xenon development with reactor operation history between 2011-01-28 and 2011-02-04[]{data-label="fig-xe-theory"}](xenon-theory){width="5.5in"}

The peak search and evaluation algorithm {#peakalgo}
========================================

The algorithm is based on the peak finding algorithm of Mariscotti [@mariscotti]. This peak finding algorithm is based on the assumption that peaks can be described by Gaussian functions and the background may be approximated by a linear function within short intervals. In such an interval the number of counts as a function of the channel number $x$ is $$\label{mariscotti1}
N(x) = G(x) + B + Cx$$ where $G(x)$ represents a Gaussian function if a peak is present (and zero otherwise), $B$ and $C$ are constants describing the background. If one assumes that $N(x)$ is a continuous function, the second derivative $N''(x)$ becomes independent of the background and vanishes for any interval in which there is no peak [@mariscotti]. Therefor peaks are located wherever $N''(x)$ $\ne$ 0.

After generating the second difference $D''(x)$ by using the second-difference approximation $$D(x) := N''(x) = N_s(x-1) + N_s(i+1) - 2 N_s(i)$$ peak candidates are identified by the condition $$\label{eqcandidate}
|D(x)| > c\quad U(x)$$ where $U(x)$ is the uncertainty in the original measurement and $c$ is a user defined parameter (threshhold) which reflects search sensitivity.\
\
Application of second-derivative methods for peak finding is limited by statistical noise introduced by the measurement equipment. This noise has to be filtered out before peak searching to get reasonable results. A suitable filter for this task is binomial smoothing [@marchand], also called the moving average.

For example consider fig. \[figsmoothing\]. In the upper part of the plot the input data $N(x)$ (blue) and the smoothed data $N_s(x)$ (red) are shown. In the lower part the second derivatives $N_s''(x)$ for previously smoothed input data (blue) and the non-smoothed data $N''(x)$ (fuchsia) are shown. It is clearly visible that the second derivative of the previously non-smoothed data is dominated by noise and cannot be analysed easily. Figure \[figsmoothing3\] shows a close-up of the second derivatives for a fourth order binomial smoothing filter.

![N(x) and N”(x) for non-smoothed versus smoothed input data[]{data-label="figsmoothing"}](binomial){width="5.5in"}

![Close-up: comparison of the second derivatives of previously smoothed vs. non-smoothed input data, fourth order binomial smoothing filter[]{data-label="figsmoothing3"}](smoothing2){width="5.5in"}

\
\
Choosing the order of the binomial smoothing filter is essential to maintain data integrity during evaluation and analysis. The choice is made based on efficiency of peak detection during a systematic investigation of peaks detection with various input data (high, medium and low dose rate measurements short after reactor shutdown, after about a day and after three days without operation).

Experimental results {#results}
====================

The most stable spectra were recorded on Feb. 1, 2011 and Feb. 3, 2011. The number of Xenon and Iodine nuclei in this period have been calculated according to equations (\[xe01\]) and (\[xe02\]). The results are shown in fig. \[fig-xe-theory\], together with the reactor operation history during this time. To find the peak regions of interest, a histogram of all peaks according to the algorithm presented in chapter \[peakalgo\] is generated. Each spike represents one identified peak location in these spectra.

The histogram strongly depends on the given threshold $c$ as defined in chapter \[peakalgo\]. If the threshold is too small, too much minima are counted especially in the lower energy band resulting in a noisy analysis for low energy peaks, like for one of the nuclides in question ($^{135}$Xe at 249.8 keV). This nuclide is then no longer identified correctly. If defining the threshold too small, some weakly defined peaks like the Iodine peaks at 1131.5 keV and 1260 keV are no longer identified correctly.

For this purposes, two runs of the same algorithms with different sensitivities have been done. The sensitivity is given in units of the global minimum (all peaks, all spectra) $c_{gm}$. For correct identification of the low-energy peaks, a threshold of $c$ = 0.08$c_{gm}$ has been used, for the higher energy peaks a threshold of $c$ = 0.02$c_{gm}$ has been used. The generated histogram for the 243 spectra in this time range for $c$ = 0.08$c_{gm}$ is shown in fig. \[figfrequencyweekend\], for $c$ = 0.02$c_{gm}$ in fig. \[fig-hist-th2\] and the two combined histograms outlining their differences is shown in fig. \[fig-hist-two\].

Fig. \[fig-hist-th2\] clearly shows the noise in the lower energy range. The amount of peaks identified makes it impossible to clearly distinct between peaks located very closely to each other. On the other hand, it can clearly be seen that many of the peaks in the higher energy range are not correctly identified by using a too small threshold, but for $c$=0.08$c_{gm}$ they are identified correctly.

![Peak frequency in all 243 spectra of Jan. 28th - Jan. 30th, 2011 ($c$ = 0.08$c_{gm}$)[]{data-label="figfrequencyweekend"}](frequency-weekend){width="5.5in"}

![Peak frequency in all 243 spectra of Jan. 28th - Jan. 30th, 2011 ($c$ = 0.02$c_{gm}$)[]{data-label="fig-hist-th2"}](histo-th2){width="5.5in"}

![Peak frequency in all 243 spectra of Jan. 28th - Jan. 30th, 2011 (combined)[]{data-label="fig-hist-two"}](histo-two){width="5.5in"}

         peak \#           $x_1$ \[keV\]       $x_2$ \[keV\]     $\bar{x}$ \[keV\]           Nuclide
  --------------------- ------------------- ------------------- ------------------- -------------------------
   4 ($c=0.02c_{gm}$)    137.6 $\pm 0.01$    149.0 $\pm 0.01$    143.3 $\pm 0.07$     $^{235}$U (143.8 keV)
   5 ($c=0.02c_{gm}$)    180.2 $\pm 0.01$    188.6 $\pm 0.01$    184.4 $\pm 0.07$     $^{235}$U (185.7 keV)
   9 ($c=0.02c_{gm}$)    243.7 $\pm 0.01$    257.1 $\pm 0.01$    250.4 $\pm 0.07$    $^{135}$Xe (249.7 keV)
        31 (both)        507.9 $\pm 0.01$    514.3 $\pm 0.01$    511.1 $\pm 0.07$    annihilation (511 keV)
        35 (both)        654.4 $\pm 0.01$    667.5 $\pm 0.01$    660.9 $\pm 0.07$    $^{137}$Cs (661.6 keV))
   70 ($c=0.08c_{gm}$)   1124.8 $\pm 0.01$   1135.7 $\pm 0.01$   1130.2 $\pm 0.07$    $^{135}$I (1131 keV))
   71 ($c=0.08c_{gm}$)   1166.2$\pm 0.01$    1176.6 $\pm 0.01$   1171.4 $\pm 0.07$    $^{60}$Co (1171 keV)
   73 ($c=0.08c_{gm}$)   1287.9$\pm 0.01$    1295.4 $\pm 0.01$   1291.6 $\pm 0.07$    $^{41}$Ar (1291 keV)
   74 ($c=0.08c_{gm}$)   1324.7 $\pm 0.01$   1335.1 $\pm 0.01$   1329.9 $\pm 0.07$    $^{60}$Co (1332 keV)
   75 ($c=0.08c_{gm}$)   1361.3 $\pm 0.01$   1370.2 $\pm 0.01$   1365.8 $\pm 0.07$    $^{24}$Na (1365 keV))

  : Identified peaks in the 243 spectra measured between Jan. 28th - Jan. 30th, 2011 (excerpt)

\[default\]

Results and Discussion
======================

The algorithm described in chapter \[peakalgo\] has been applied to all 1277 spectra recorded. Not all of them were usable due to either poor counting statistics and/or high dead times. Especially the latter has been a problem due to the high gamma ray background generated in presence of the reactor and the fuel element mounted in the measurement position. Two measurement batches were good enough to be evaluated: the measurement over the weekend from Jan 28th to Jan 31st and the overnight measurement starting on Jan 31st.\
\
The results, which are shown graphically in fig. \[figxe-xe-results\], show that the $^{135}$Xe inventory can be measured using the data processing techniques described above even in the presence of high-background radiation and therefor in-situ measurement of gamma ray spectra in TRIGA reactors are not only possible, but also relatively easy to obtain.

![Xenon development (numerical results) and experimental data[]{data-label="figxe-xe-results"}](xenon-eval-ok){width="5.5in"}

[00]{}

Boeck, H.; Villa, M.: *The TRIGA Mark II reactor at Vienna University of Technology*, ATI report, 2005

Chung, Chien, Liq-Ji Yuan, and Kuen-Bey Chen: *Performance of a HPGe-NaI (Tl) Compton suppression spectrometer in high-level radioenvironmental studies.* Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 243.1 (1986): 102-110.

Mauerhofer, E.: *Improvement in the counting statistics and in the limit of detection with Compton suppression spectrometersÑa contribution to instrumental neutron activation analysis.*, Applied radiation and isotopes 47.7 (1996): 649-658.

Schmid, G. J., et al: *HPGe Compton suppression using pulse shape analysis.* Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 422.1 (1999): 368-372.

Yuan, L. J., P. S. Weng, and C. C. Chan. *In situ measurement of low-level radioactivities using the compton suppression technique.* Nuclear Technology;(USA) 86.1 (1989).

Chu, S.Y.F., Ekstroem L.P. and Firestone, R.B.: *The Lund/LBNL Nuclear Data Search*, Version 2.0, February 1999

Emendoerfer, D.; Hoecker, K.: *Theorie der Kernreaktoren* Part I & II, B.I. Wissenschaftsverlag Mannheim 1982

Mariscotti, M. A.: *A method for automatic identification of peaks in the presence of background and its applications to spectrum analysis*, Nuc. Inst. Meth. 50 (1967), 309-320

Marchand, P. and Marmet, L.: *Binomial smoothing filter: A way to avoid some pitfalls of least-squares polynomial smoothing*, Rev. Sci. Instrum. 54 (8), 1983

Stacy, W.: *Nuclear Reactor Physics*, 2nd edition, Wiley-VCH, 2007