[WPEC SG21: Assessment of Neutron Cross-Section Evaluations for the Bulk
of Fission Products]{.underline}

> 43-Tc-99 Review

Pavel Oblozinsky, BNL, March 18, 2004

### **1. General**

### 

### **Properties**

Unstable nucleus, T~½~ = 2.11 x 10^5^ y, one of the most important
fission products.

### 

**EXFOR data**

Solid data set is available, including total, capture, (n, p) and (n,
α). Few data for (n, 2n) and (n, n') at 14 MeV.

### **Evaluations**

-   **ENDF/B-VII** year origin 1999 (resonances) and 2001 (fast region),
    by BNL-

> KAERI collaboration, submitted for inclusion to ENDF/B-VII,
> <http://www.nndc.bnl.gov/csewg_members/eval/n-99Tc.html>

-   **ENDF/B-VI** year of origin 1999 and 1978, resonance part
    re-evaluated in 1999

> by BNL-KAERI, fast region evaluated in 1978 by Schenter et al

-   **JEF-2** year of origin 1982, author Gruppelaar and Menapace

-   **BROND-2** year of origin 1984, author Ignatyuk and Kravchenko

-   **JENDL-3** year of origin 1990, by JNDC FP Nuclear Data Working
    Group

-   **CENDL-3** year of origin 1998, by Zhuang Youxiang et al, CNDC

### **2. Thermal and resonance region**

**ENDF/B-VII**

-   Taken from ENDF/B-VI, release 8.

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-   Problem with reduced scattering radius R', problem fixed in merging
    with fast region evaluation to reproduce recent experimental total
    cross sections by Gunsing (2000) \[1\].

**ENDF/B-VI**

-   New evaluation by Mughabghab et al (1999), incorporated into
    ENDF/B-VI, release 8 in 2001.

-   RR region: MLBW formalism, update of BNL-325 using new data measured
    at Geel and Saclay in 1997, up to 991 eV.

-   UR region: 991 eV -- 140.51 keV (1^st^ excited level)

**JEF-2**

-   Taken from BNL-325 (1981).

**JENDL-3**

-   RR region up to 4.219 keV, MLBW formula used, taken over from
    JENDL-2 with some modifications.

-   UR region in the region 4.219 keV -- 100 keV.

**CENDL-3**

-   RR region (below 4.219 keV) taken from JENDL-3.2

-   URR region (4.219 keV -- 100 keV) taken from JENDL-3.2

**Recommendation/Conclusion**

**ENDF/B-VII is recommended**, it is the most recent evaluation done by
Mughabghab et al.

### 

### **3. Fast neutron region**

#### ENDF/B-VII methodology

-   Up-to-date methodology, based on the code EMPIRE, all important
    reaction mechanisms taken into account.

-   Spherical optical model, HF statistical, multi-step and
    pre-equilibrium models. Direct contribution to low lying (n, n')
    levels by DWBA (code ECIS).

-   (n, tot) data by Gunsing (2000) \[1\] below 150 keV taken into
    account.

-   Fine tuning of parameters to reproduce (n, p) and (n, α) data at 14
    MeV.

#### ENDF/B-VI methodology

-   Based on evaluation done in 1971, with a few updates by Schenter et
    al in 1978

##### JEF-2 methodology

-   Based on RCN evaluation (1978) with some later updates.

#### 

#### JENDL-3 methodology

-   Methodology fairly up-to date, all important effects taken into
    account.

-   Above 100 keV spherical optical model and statistical model code
    CASTHY, pre-equilibrium component added from PEGASUS code, used for
    MT=1, 2, 4, 51-91 and 102.

-   Reactions MT=16, 103, 107 etc calculated using modified PEGASUS
    code.

-   Direct & semi-direct capture estimated and normalized to 1 mb at 14
    MeV.

-   Elastic and inelastic angular distributions calculated by CASTHY,
    other channels considered isotropic.

-   (n,2n), (n,p) and (n,) normalized at 14 MeV to specific data or to
    systematic values.

#### Recommendation/Conclusion

ENDF/B-VII is the most up-to-date evaluation, **ENDF/B-VII is
recommended**.

**Table 1**. Thermal cross sections, resonance integral and one-group
capture values for Tc-99.

+------------------+-------+---------+--------+-----------+----------+
| **\              | #     | #       | # E    | #         | # O      |
| Source**         | Total | Capture | lastic |  Resonanc | ne-group |
|                  |       |         |        | e Capture |          |
|                  | **(ba | **(     | **(b   |  Integral | #        |
|                  | rn)** | barn)** | arn)** |           |  Capture |
|                  |       |         |        | *         |          |
|                  |       |         |        | *(barn)** | **(barn) |
|                  |       |         |        |           | \[3\]**  |
+------------------+-------+---------+--------+-----------+----------+
| # E              | #     | # 5.76  | #      | #         |          |
| NDF/B-VI (2001)  | 20.0  |         |  311.0 | 6.262E-1  |          |
+------------------+-------+---------+--------+-----------+----------+
| JEF-2            | #     | #       | # 3.52 | # 304.3   | # 6      |
|                  |       |  19.12  |        |           | .400E-1  |
+------------------+-------+---------+--------+-----------+----------+
| # JENDL-323.06   | # 1   | # 3.42  | #      | #         |          |
|                  | 9.64  |         | 312.0  | 5.920E-1  |          |
+------------------+-------+---------+--------+-----------+----------+
| BROND-2          | #     | # 19.1  | # 3.5  | # 304.3   | #        |
|                  |  22.6 |         |        |           | 6.522E-1 |
+------------------+-------+---------+--------+-----------+----------+
| CENDL-3          | #     | # 19.64 | # 3.42 | # 311.1   | #        |
|                  | 23.06 |         |        |           | 5.907E-1 |
+------------------+-------+---------+--------+-----------+----------+
| Mughabghab       |       | 20(1)   |        | 320(20)   |          |
| 2003\[2\]        |       |         |        |           |          |
+------------------+-------+---------+--------+-----------+----------+
| BNL-325 (1981)   |       | 20(1)   |        |           |          |
+------------------+-------+---------+--------+-----------+----------+

**Table 2**. Summary of resolved and unresolved resonance region for
Tc-99.

+---------+-----+---------+----------+---------+----------------------+
| **Li    | **  | **First | **RRR\   | # URR   | **Remarks**          |
| brary** | Yea | Author\ | **       |         |                      |
|         | r** | **      |          |         |                      |
+---------+-----+---------+----------+---------+----------------------+
| ENDF/B- | M   | \< 991  | # 99     | New     |                      |
| VII1999 | ugh | eV      | 1 eV- 14 | eval    |                      |
|         | abg |         | 0.51 keV | uation, |                      |
|         | hab | MLBW    |          | taken   |                      |
|         |     |         |          | from    |                      |
|         |     |         |          | END     |                      |
|         |     |         |          | F/B-VI. |                      |
+---------+-----+---------+----------+---------+----------------------+

#### References

1.  F.Gunsing, A. Lepretre, C.Mounier and C.Raepsaet, \"Neutron
    resonance spectroscopy of 99-Tc from 3 eV to 150 keV\", Phys. Rev.
    C61 (2000) 054608.

2.  S.F. Mughabghab, Thermal neutron capture cross sections, resonance
    integrals and g-factors, Report INDC (NDS)-440 (IAEA, Vienna,
    February 2003).

3.  H. Gruppelaar et al, Status of pseudo-fission-product cross sections
    for fast reactors, Final Report of Subgroup 17, Report NEA/WPEC-17,
    ECN-R-98-014 (NEA, Paris, 1998). Recalculated systematically for all
    211 FP and all 5 evaluated libraries by I. Sirakov (BNL, 2002), see
    <http://www.nndc.bnl.gov/sg21/nucl/acs/accs.htm>.