Материал: Крючков Фундаменталс оф Нуцлеар Материалс Пхысицал Протецтион 2011

PIT planning

Onsite physical inventory taking is an extremely responsible procedure which requires stringent work planning. “Failing to plan is planning to fail” is the best adage to describe the significance of the PIT planning.

The PIT commission shall estimate the volume of the PIT work and develop the PIT plan. The PIT plan shall describe in full the sequence of all operations with NM to be done, the facilities to be employed and the respective deliverables. The PIT plan shall include the following important parts:

∙breakdown of NM by types;

∙selection of NM for accounting and verifying measurements;

∙grouping of passive NM by strata and calculation of the random sampling volume for each stratum;

∙sequence of measurements and required instrumentation;

∙operation of working materials to record measurement results and preparation of reports;

∙a complete time profile of the work performance;

∙persons in charge of work stages.

The PIT plan constitutes a voluminous package of documents. Early experiments in the field made by the Kurchatov Institute proved PIT planning to be a responsible and time-taking procedure. Thus, the documents that described all procedures of the initial physical inventory taking for one bulk (HEU) handling facility formed a volume of several hundreds pages. Each facility unfortunately requires generation of its own procedural documentation based on generic regulations. One important note in this connection is that a model document has been issued by Rostekhandzor of Russia to provide a general guidance for the PIT preparation and implementation (Methodical Recommendations on Implementing Nuclear Material PIT at Nuclear Facilities and Nuclear Material Storage Points (RB-026-04, Moscow, 2004)). This general guide serves as the basis for each facility to generate procedural documentation of its own.

Enterprise preparation for physical inventory taking

After the order to implement the physical inventory taking in the MBA is received (before the PIT starts), the required arrangements shall be undertaken. These shall include preparation of documentation, nuclear material, process components and instrumentation for the PIT.

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All NM in operation is given the form to be convenient for the inventory taking. For example, packages with NM shall be positioned so that the inspection of seal prints, the reading of seals’ factory numbers and batch numbers and so on would not be hampered.

NM that requires accounting measurements of the quantities and compositions thereof shall be placed separately from the other. Labels shall be prepared to designate the material that has been inventoried.

The equipments and service lines shall be cleaned.

Preparation of documentation shall include the making of the inventory listing (IL) as of the PIT time and checkout of same against the rest of documentation. When this is checked out, the custodian shall compare the data on the items shown in the IL against the physical inventory listing (PIL) data from the previous PIT, the inventory change report (ICR) and the initial information on the items (certificates, invoices, measurement records, etc.).

Metrologists shall check the availability of all the instruments to be used for measurements during the physical inventory taking.

Sequence of physical inventory takings

Site PIT techniques and procedures depend on the type of the process and the quantity and the type of NM in the MBA and are specified in the PIT plan. However, there are a number of general conditions to be noted. These are namely as follows:

∙For the period of the PIT, the MBA to be inspected shall have NM shipment, receipt and write-off operations and formation of new items suspended.

∙Measurements should be done during the inventory taking based on the developed time profile and subject to the specified sequence of measurements.

∙The nuclear material inventory taking work in the MBA shall be carried out by not less than two persons simultaneously.

∙The inventory taking shall involve the custodian’s control of nuclear material.

The physical inventory work requires the reconciled IL for NM within the MBA to start. Using this listing, the WITC shall check the conformity of the physical inventory to accounting data:

a) Checkout of the attributes of the items within the MBA (presence of the IL items and the integrity thereof):

∙items with NM in the MBA are checked for being actually present;

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∙location;

∙items are examined for external defects and TIDs are inspected for the absence of breaks;

∙IDs of the TIDs and the items are reconciled (using a scanner if there are barcode labels);

Measurements of the attributes are assumed to confirm the declared data

if:

∙the items with NM are at such locations as indicated in accounting records;

∙the items do not have external defects;

∙the TIDs are not broken;

∙the barcode information matches that in the accounting records.

Measurements of NM attributes are normally done for all items in the MBA.

b)Verifying and accounting measurements. Measurements shall be performed at key measurement points using instruments intended for verifying and accounting measurements.

c)The quantity and accuracy of discard, if any, shall be estimated.

Verifying measurements (audits) shall be performed to check the

availability and conformity to accounting data within the item material measurement error limits. Verifying measurements shall be performed for passive nuclear material, as well as for active NM that was subjected to accounting measurements prior to the current inventory taking and have been under access controls since. Verifying measurements shall seek to identify defective items. Defective items are understood as items with characteristics other than conforming to accounting data.

Verifying measurements shall include checks of the following NM parameters:

∙net weight;

∙product volume;

∙element and isotope concentrations;

∙NM mass in the product.

The parameters for the last two positions are normally checked by nondestructive assays.

Where checks find the difference of the measured value and the accounted quantity being other than falling beyond the 99% confidence interval, the accounted value of the said characteristic is assumed to be confirmed. Otherwise, the item that contains this NM shall be considered defective. In this case, the anomalous discrepancy obtained shall be

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analyzed and investigated and accounting measurements of the NM shall be performed.

Where access controls have been applied to NM, verifying measurements of the material shall be performed on a sampling basis using sample size statistical calculation techniques. The volume and type of verifying measurements shall be specified in the PIT program.

Accounting measurements. The inventory taking includes accounting measurements for the characteristics of active NM that have not been performed prior to the inventory taking.

Based on the work results, the WITC shall prepare the nuclear material physical inventory listing (NM PIL), the material balance report (MBR) and the inventory taking statement. The WITC shall report all discrepancies (deficiencies, surplus, wrong writes-off or registrations of material used in processes, etc.), as detected in the course of the work, to the enterprise administration.

The inventory taking shall be finished with the material balance closing, and the inventory difference (ID) and ID determination error estimations for each NM type. If no anomaly in the nuclear material accounting and control is established by the PIT, the documented inventory of nuclear material in the MBA shall be taken as the inventory of nuclear material in the MBA as of the beginning of the next material balance period.

Finalization of physical inventory taking results

NM PILs, inventory taking statements with the WIC findings and recommendations, as well as material balance reports (MBR) shall be prepared as the result of the PITs.

1)The items measurement results shall be entered on the PIL. This lists data for each item in the MBA as obtained by accounting measurements (given errors). Similarly to the IL-list, the PIL-list shall have the items entered thereon grouped by types, strata and batches.

2)Preparation of the material balance report (MBR). Each NM in the MBA shall have a separate MBR prepared for it, this to represent the NM balance with a breakdown by facilities. The MBR shall be prepared based on the PIL from the previous and the current inventory takings and the ICR over the current MBP. Separate columns in the MBR shall show the booked NM inventory, the NM quantity increase and decrease for the MBP reported on and the final physical inventory of NM.

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The data in the MBR shall be given for each item (stratum) in such sequence as would match the PIL and the ICR. The NM quantities in each item (stratum) and errors shall be entered by lines so that the MBR columns had the material balance components aligned in the MBR columns.

The ID value shall be determined as the algebraic sum of all items in the MBR. The MBR shall give the calculated error σID. The MBR shall be signed by the chairman and the members of the WITC.

3) The inventory taking statement shall contain the conclusion with respect to the conformity or nonconformity of the NM physical inventory to the IL data. The ID quantity and the estimated range of its permissible values shall be presented. Entries on the detected anomalies (if any have been found by the inventory taking) shall be made, the inventory taking commission to formulate recommendations for these to be removed. The anomaly established by the WITC shall be described in details in the memorandum enclosed with the PIT document package. The statement shall be signed by the chairman and all the commission members who took part in the inventory taking. The statement shall be made available to the custodian for examination.

PIT cost. Initial PIT problem

Physical inventory takings are an extremely costly process. For example, the US Department of Energy that has in control six national laboratories and some three dozens more nuclear industry facilities, including assembly and disassembly plants at Pantex, a commercial nuclear production facility in Hanford and others, spends millions of US dollars annually on physical inventory takings. This takes place in the conditions when US nuclear industry has large quantities of material held currently in containers which are sealed and inspected periodically or continuously. This spending is allocated when not all material is subject to measurement and the initial inventory takings date back to a long time ago.

Russian spending on PITs, with the initial physical inventory takings being required and NM inventories being no less immense than in the USA, can hardly be overestimated.

An initial PIT requires all nuclear material to be measured. There are many organizations in Russia that need initial physical inventories to be taken. The experiments made by the Kurchatov Institute [2] have proved that initial inventory takings for only two of its facilities are expected to take nearly one year of work. This brings to life a great deal of problems with the total labor expenditures the initial physical inventory taking at

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