ML19262A040
| ML19262A040 | |
| Person / Time | |
|---|---|
| Site: | 07000036 |
| Issue date: | 10/12/1979 |
| From: | Partlow J NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS) |
| To: | Eskridge H ABB COMBUSTION ENGINEERING NUCLEAR FUEL (FORMERLY |
| References | |
| NUDOCS 7910260176 | |
| Download: ML19262A040 (4) | |
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OCT 19 1SL3 SGML:RLJ 70-36 Combustion Engineering, Inc.
ATTN: Mr. H. Eskridge, Supervisor Nuclear Licensing Safety and Accountability Route 21 A Hematite, Missouri 53047 Gentlemen:
This is in reference to your letter of June 4,1979 regarding proposed License Condition 4.3 and 4.5 of Amendment MPP-3 to License SNM-33.
Reference is also made to the additional data supplied by your "r. R. Froma to our Mr. C. E. Emeigh during the July 1979 INMM meeting held at Albuquerque, New Mexico regarding our proposed License Condition 4.3.
We have concluded that the submittals regarding your ganma counter calibration procedures do not present sufficient details to enable us to complete our review. The attachment to this letter has our ccmments and identifies the scope of further information needed in order for us to finalize our conclusions in regards to your gamma counter calibration procedures.
t Our appraisal of the data submitted in Section 4.2.3.1 (and the appropriate sub-sections) of your plan required by 10 CFR 70.57(c), and the additional information contained in your June 4,1979 letter regarding calibrated analytical glassware have not been concluded. We will forward our conclusions to you at a later time.
To expedite our review, we wish to visit with you at your facility to discuss our attached comments and to observe the procedures and practices regarding the foregoing topics. We will be in contact with you in regards to our proposed visit.
Sincerely, O
N Ja#sh.Partlow, Chief MaSrial Control and Accountability ticensing Branch Division of Safeguards
Enclosure:
As stated 215 106 cc:
Combustion Engineering - Windsor Mr. H. V. Lichtenberger 7910260I7(
COMBUSTION ENGINEERING - HEMATITE GAMMA COUNTER - CALIBRATION PROCEDURE NRC/MCL REVIEW COMMENTS 1.
Section 3.4.3.1 of CE's FNMC Plan comr.its to segregating solid waste into four categories--namely, " rags," " paper," " combustibles," and "non-combus tibl es. Section 4.2.3.1 of the Plan commits to NDA calibrations using " standards representing the geometry and matrix density for each basic type of material." Section 4.2.2 of the Pl:a states that, as a minimum, two standard measurements per week will be performed for each measurement system. Apparently (based on the arguments submitted), CE does not realize that a commitment has been made to make two "NDA-rags" standard measurements per week, two "NDA-paper" standards measurements per week, etc., even without License Condition 4.3.
The last paragra,ph of CE-Hematite's Section 4.2.4.1 should be replaced as follows, to be in accordance with Item 2 on Page 28 of the Material Control Licensing Review Criteria for Mat'erial Measurement Control Plans (10 CFR 70.57' "A bias calculation shall be made for each measurement system and all resulting biases shall be used in the Inventory Difference (i.e., ID or MUF) bias correction, except for the following situations:
(1) bias calculations are not performed and hence no bias correction is applied for measurement systems utilizing a ' point calibration in which a measurement value(s) for a unknown, o'r group of unknowns, is derived from standard measurements performed along
'with the unknown measurements.
(2) the calculated bias of any measuremen,t system need rot be utilized in the ID bias correction whenever such bias is less than:
(a) the uncertainty of the standard referehce material involved in the centrol standards used to estimate the bias, or (b) the uncertainty on the control standard's assigned value provided such uncertainty is less than.05%.
(3) any bias that exceeds its associated limit of error shall not,e included in the ID bias correction since these will be reflected in corrections to the material accounting data."
It should also be noted that Section 4.2.4.1 (Bias) of CE's FNMC Plan commits to determining measurement bias, which inturn requires represe r control standards.
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From the " Gamma Counter Impact nccountability" table, it is shown that for the inventory period ending June 25, 1979, 0.1% of shipments and 1.0% of inventory were established by NDA measurements. This corresponds to 65 Kg U and 80 Kg U respectively, or a total of 145 Kg U.
If this 145 Kg quantity is overstated due to an unknown (i.e., undetected) bias of say 50%, the resulting impact on uranium element ID (i.e., MUF) would be that such 10 would be understated by 48 Kg. Needless to say, a 48 Kg error in the U element ID value can hardly be regarded as insignificant.
An undected bias of 50%, although not likely, is certainly possible if:
(a) the initial calibration curves were derived from standards that were not representative of the process waste materials being
- measured, (b) recalibration of most of the initial curves has not been perfomed since October 1974, and (c) at least 16 standard measurements (over the calibration range) are not performed for each calibre. tion curve.
3 CE's June 4,1979 submittal states that the use of a single standard is adequate to confirm that the initial calibration-is still valid. This assumes that any shift in the calibration would either have the same slope as the initial curve, or if it didn't, the shif ted curve would still intersect the "Y" axis at the same point as in the initial curve.
Such an assumption is not valid, however. Hence, at least two points (fairly separated) on the curve need to be checked before one can make any conclusions about the validity of a previously established curve.
4.
It is not clear whether or not CE is calculating a bias correction from the Pc 73 standard measurement data or claiming that NDA control standard measurements are not needed (for bias estimation) because any such bias correction would not have any significant. impact on Inventory Difference.
Nevertheless, even if the bias associated with gama counting measurements has no significa.nt impact on ID, it is necessary to make control standard measurement (utilizing representative standards) over the range of calibration. From such standard measurement data, an estimated bias is to be calculated and its effect en ID determined. Likewise, the same is to be done with all other measurement systems and the net total effect on ID detemined and reported to the NRC.
It should be noted that even though each individual bias is statistically insignificant (and hence, no adjustments are made to item labels, records, etc.) such biases are to be utilized in applying a net bias correction to a plant ID value so as to obtain the best estimate of ID.
~215 106 1
5.
The five gama counting calibration curves (provided by R. Fromn during the INM14 meeting) all flatten out (i.e., slope of curve decreases) at the upper end of the calibration range. Measurement values falling within these upper regions should not be used for accountability purposes because of the high probability of error. For example, in calibration curve No. 6, a 5% counting error (or bias) at the 20,000 cpm level (i.e., an error of 1000 cpm) would produce a 4 to 5 gram U-235 error which corresponds to a relative error of about 15% in the U-235 measure-ment.
6 The following table, which we generated from the five calibration curves supplied by R. Fromn, shows the considerable variation in count rate due to variations in matrix, uranium material form, gt.cmetry, and enrichment.
Hence, the need for truely representative calibration arid control standards is clearly demonstrated.
Grams _ U-235 Vs. Various Counting Rates Curve No.
5000 com 10,000 com 15,000 cpm 20,000 com 6
2:8 7.0 14 31 8
2.4 5.8 '
11 21 12 2.7 7.7 19
> 50 13 3.2 7.0 10 21 14 3.9 8.4 14 19 o
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