6. MITIGATION AND REMEDIATION OF FOREIGN MATERIAL INTRUSION
6.3. Mitigation of a latent foreign material
With the exception of detection which inherently is the initiator of mitigation activities instead of a directly witnessed (or suspected) current FMI incident and the assessment aspect
which may be more challenging as to reconstruction of a historical event(s) , the mitigation of a past FMI is the same as that of a current FM. Thus, the following sections discuss the same aspects of mitigation that were presented in Section 6.2 in a different order and with particular emphasis on the differences for, and more details on, the detection and assessment of latent FM processes for the mitigation of past FMI(s).
Another additional importance of the mitigation of past FMIs to note is that once a latent FM is detected (i.e. discovered) and subsequently assessed, the mitigation of an unnoticed/unknown past FMI event provide valuable lessons learned towards the improvement of current FMMP. For example, the consideration of following questions and reflecting their answers into the current programme and processes and FMM practices would be beneficial:
— Why and how long has the FM gone unnoticed?
When was it introduced into the SSCs?
Were there any opportunities to discover the FM?
Was there a failure/inadequacy in the current/recent FMMP concerning detection?
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Was there a defect in design for monitoring the impacts and signs of the FM in the SSC?
— Why did the FM intrude into the SSC?
What is the apparent cause?
What were the conditions of work area, people, plant/project, organisation, FMMP?
Could the FMI have still occurred, under the similar conditions, since the implementation of the existing FMMP (for example, could/would the revealed incidents of construction/personal items being left in the work area or systems during early stages of construction have been prevented by the current FMMP and/or the FMMPs that came into effect since)?
6.3.1. Detection
The detection of a latent FM (especially in case of searching for ‘unknown unknown’ as discussed later in Section 6.3.3.2) necessitates different (or additional) approaches and processes than of those for a current FM, which were discussed in Section 6.2.3.
As aforementioned, more than 75 per cent of latent FMs were discovered by luck or coincidence. Unless a structured proactive detection (and retrieval) effort, i.e. a special FOSAR (FOSAD and FORAR) project, is conducted for searching latent FMs in targeted SSCs (or all SSCs which are physically and safely searchable); luck, coincident or self-indication continues to be the primary manner of detection.
6.3.1.1. Coincidental and self-revealing detection
Unlike an FMI event which is directly or indirectly observed to happen during a current activity, there is no observed, reported or recorded FMI for the latent FMs. The chance and opportunity for their detection come from an unrelated plant/project evolution or activity, such as:
— Discovery/encounter of FM in the SSC by the workers, observers, monitors, inspectors during an activity performance that is not part of or relevant to FM detection process;
— Parts, materials are found missing, damaged or defective during disassembly or reassembly of components;
— Absence of any reporting or recording of such issue from the last time (or earlier times) when such SSCs were worked on;
— No known or explained reason for such loss, damage or defect to the subject SSC;
— Unusual and sudden change in the trend or indication of monitored SSC operating parameters (temperature, flow, pressure, vibration, etc.) and sensory indications (e.g.
unusual colour, odour, noise, smoke, leak) from the SSCs;
— Physical damage to a plant SSC for unknown reasons.
6.3.1.2. Programmatic search and detection
Some owner/operating organisations may choose to establish and conduct comprehensive and programmatic searches in and around plant SSCs with an intent and objective to detect/discover possible latent and legacy-latent FMs. Such latent FM search and recovery efforts are typically
triggered due to the recognition of challenges to the plant safety and performance by, for example:
— An event caused by a latent FM, particularly, investigation of which indicates a possibility for existence of similar FMs in the plant SSCs;
— Chronic vintage FMs and past FMM and FMMP defects and deficiencies;
— Series of coincidental discoveries dating back to a specific phase or activity of the project/plant lifetime.
As a result, in accordance with the corporate commitment and policy of a foreign material free operation (or, in some cases, by requests from the regulatory body), the owner/operating organisations decide to undertake a detailed, systematic and structured search, detection and assessment process. This undertaking, which can be termed as comprehensive foreign object search and retrieval (CFOSAR), could be a one-time special project or a permanent and continuous plant/project programme or process.
The CFOSAR projects/programmes require substantial and dedicated efforts and resources (both human and financial) to look for latent FMs in the plant SSCs (that may have resulted from any or all of the factors that resulted in the lack or deficiency of FMM controls and barriers and at any time in the project’s/plant’s past) which, at times, may look like looking for a needle in the haystack. Therefore, in order to make a decision to start a CFOSAR, the boundaries need to be defined to inform the decision makers about the extent of efforts and resources (as well as the schedule) to achieve an adequate level of ‘foreign material free operation’ and ‘no adverse effect of foreign material on safe, reliable and efficient operation’ of the plant.
The matter of the utmost importance for effective and efficient use of efforts and resources and getting expected level of achievement is where to look, which may depend on what to look for. Therefore, for the success and sustainability of CFOSAR efforts, the scope, plans and schedules need to be carefully set based on a graded and/or targeted approach. If such graded and targeted approach is not properly considered and consistently implemented, the CFOSAR initiatives and efforts, even those with a good start, would face increasing burden and strain on the human and financial resources. As a result, the scope and/or goals and expectations of CFOSAR are gradually relaxed or eliminated, which eventually lead to the ineffectiveness, or even abandonment, of the project/programme (as it can be seen in many OPEX with projects/programmes that are initiated with good intentions to improve but are cancelled on the basis of large and increasing scale of efforts compounded by the perception of lacking immediate visible and tangible benefits).
Therefore, it is essential for an effective CFOSAR that the activities, processes and/or SSCs for search and detection are scoped based on a graded approach and associated weighting scale, that is primarily driven by the corporate character and strategy that will determine and apply a value, importance and significance to each activity, process and SSC reflecting, for example (see also Section 4.5):
— Nuclear, industrial and radiological safety impacts and importance;
— Safety, quality and reliability designations, requirements, expectations and effects;
— Plant performance goals and expectations;
— Severity of consequences of potential dormant FM regarding safety, health, economic and financial aspects.
Similarly, the CFOSAR project/programme may target specific SSCs, activities, time or periods in the plant history. For example, it may target any or all of the following:
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— All plant SSCs;
— Items related to safety, items supporting the safety and safety support features;
— Safety Class 1 and 2 SSCs;
— SSCs that are similar to the one found with a latent FM;
— SSCs that were worked on during a certain period where many FMI discovered to occur (e.g. certain multiple activity periods, such as construction, refurbishment, maintenance outage, major plant modification and maintenance);
— SSCs that has never (or recently) been opened or worked on or entered;
— SSCs that has higher probability of, or potential for, leftover and with idle or static points/areas, such as tanks, vents, traps;
— Activities that resemble the activity that assessed to be the cause of specific historical FMI, (including those that are legacy or were abandoned after certain time in operation);
— Activities that were performed under a FMMP that is known to be defective;
— Activities that were performed without a FMMP.
Also, some SSCs can also be eliminated/excluded from the scope, such as those that:
— Have been operated with no unusual trends or indications;
— Have been tested, surveyed, monitored;
— Recently opened, worked on or entered.
However, such elimination of SSCs to be carefully elaborated and well justified based on the design and configuration aspects, as OPEX has shown that:
A latent FMs may exist in SSCs that have shown no unusual indications or trends and/or have been tested, surveyed many times. For example, in case of the discovery of a latent FM in a plant’s containment spray system, it was possible to meet the test acceptance criteria, and the blockage of FM has gone unnoticed, since the system might have redundant paths (or paths with least resistance in the tests that are conducted with air flow). Therefore, passing the test may not mean that there is no latent FM in the SSC.
Regardless of the scope, extent and schedule of search and discover efforts, the ultimate goal of CFOSAR is:
— Remove or evaluate (see Section 7) and assess the impacts of the found foreign material;
— Reflect those findings and learnings into the FMMP to establish measures to eliminate or minimise similar FMM issues in the future.
6.3.2. Notification
Same as the notification process presented in Section 6.2.1, in case of the discovery of a latent FM, immediate notification will be made to the line management (i.e. supervisors/team leaders) and to all involved or relevant plant/project personnel, including to the control room, for prompt assessments and mitigative actions.
6.3.3. Immediate actions
Similar to what was described in Section 6.2.2, upon the immediate notification, a prompt assessment is performed to determine the adversity of the detected/discovered/encountered FM and the immediate actions to be taken for mitigation.
However, in most cases of latent FM, the immediate actions may not be needed and further actions may be deferred to the completion of more detailed investigations and evaluations, unless the prompt operability determination results in the relevant SSC being inoperable and the operability is needed for nuclear, radiological or industrial safety.
There are also some early actions are to be taken when a FM is unexpectedly encountered/discovered, such as determining whether the FM is latent or current by check and verification of (see also Appendix IV for a flowchart for decision making and actions):
— Any ongoing FOSAD activity for a same or similar FM: If there is an ongoing FOSAD, then this discovery would serve as the detection of a ‘current FM’ that is being searched for and the detection of this FM needs to be immediately communicated to the FOSAD team for their FOSAD activities that are in progress. Consequently, further FORAA activities and all evidence need to be turned over to that FOSAR team;
— Any unrecovered FM in similar or same nature: If there is no ongoing FOSAR for the detected/discovered/encountered FM, then it would be necessary to check the maintained lost parts list, typically termed as unrecovered foreign material list or lost parts list, which has the records of FMs that have been missing, undetected, unrecovered, equivocal21 or evaluated (see Section 7 for the evaluation process). This check will verify and confirm whether the FM is one of those that were undetected or unrecovered and it could be classified as a current FM, for which the applicable FORAR or FORAA is to be conducted. (It should be noted that even the FM is in the unrecovered FM list as
‘evaluated FM’, it is necessary to ensure that all the analyses, assumptions, justifications and conclusion of evaluation are still valid and correct, particularly the assumptions and conclusions on the transportability of the evaluated FM. For example, the past evaluation might have concluded that the FM would stay in its place or disintegrate/dissolve/decompose without impacting the SSCs for the rest of plant life.
This conclusion could be invalid if the FM is found to be moved to somewhere else or still intact, which requires a new FORAA).
If the detected/discovered/encountered FM is determined not to be a current FM by these checks and verifications, then it is classified as a latent FM and it leads to the conduct of both new FOSAR and FORAA processes, as shown in the sample process depicted in Appendix IV.
In such cases, since the FM has already been detected, the FOSAD activities may mainly consist of FM characterisation while the FORAR would be a full-blown process following all the methods and tools discussed in Section 6.2.4.
On the other hand, if the detected/discovered/encountered FM is determined to be a current FM, this would add to the review, analysis and assessment that is described in Section 6.2.5 upon further investigation that may discover that current FMMP requirements and expectations have been deficient or were not followed. Such cases could be, for example:
— The FM is listed in the unrecovered FM list but there is no evaluation report (or the existing report is inadequate, particularly as to no evaluation and justification to leave it in the SSCs). In this case, it would be necessary to conduct a detailed assessment of the FMMP itself by a FOPAA (in addition to an investigation under CAP);
21 During the lifetime of a plant/project, there may be some cases where an FMI event is suspected but there is no evidence of FM or FMI determined. Such cases may also be entered in the unrecovered FM list with annotation that the FM is
‘equivocal’ to be on the conservative side.