Int. J. Pres. Ves. & Piping 34 (1988) 315-330

Some Reflections on Attitudes and Mind-Sets Concerning Pressure Vessel Failure in Nuclear Reactors

Gustaf Ostberg

Department of Engineering Materials, University of Lund, Box 118, S-221 00 Lund, Sweden

A BSTRA C T

Most people would probably agree that the value of the work done by a person holding a professional appointment depends heavily on that person's mind-set or attitude. Often it is precisely attitude that is regarded as offinal importance .for the quality of a particular professional responsibility. Guaranteeing safety is one kind of responsibility. It should therefore be both justified and urgent to consider prevention of pressure vessel failure .from the point of view of attitudes that could lead to mistakes when evaluating various risks. This essay brings together the results of man), years' reflection on decisions taken in questions touching on pressure vessel failure. The starting point is the knowledge that pressure vessel .failure, with grave consequences, really can occur. The aim is to call attention to the importance that can be attached to mind-sets, partly with regard to risk-taking in this context, and partly in terms of continuous thinking and research about pressure vessel failure. The importance of a better understanding of mind-set is not restricted to the technical level, where one should certainly take mind-set into account. Above all, improved conceptions of mind-set can influence the extent of preparedness once the possibilio, of pressure vessel failure is recognized. Another advantage is that research into pressure vessel failure will be more realistic, which should result in greater safety. In addition to certain attempts to examine the universal applicabili O, of some earlier evaluations of shortcomings in metallurgy and testing techniques, a thorough examination of the problems of mind-set with the help of available competence from other quarters is proposed.

315 Int. J. Pres. Ves. & Piping 0308-0161/88/$03-50 © 1988 Elsevier Science Publishers Ltd, England. Printed in Great Britain

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AIM

The report on the Three Mile Island reactor accident delivered by the so- called Kemeny Commission appointed by President Carter in the USA in 1979 contained among its conclusions some observations about the importance of 'mind-set'. The term referred to the way people had adjusted their mental faculties in areas significant for reactor safety. Shortcomings in such adjustments were regarded as a decisive cause of the accident at Three Mile Island.

The attention paid to mind-set in its original sense did not last long. As early as 1980, at the conference in Stockholm, Sweden, on reactor safety arranged by IAEA, mind-set had faded into the oblivion of the unmentionable. Today there are few people who can recall that this concept was ever even mentioned in connection with reactor safety.

Even less hard-to-grasp phenomena of a non-technical nature that can have decisive importance for nuclear power safety have been paid steadily decreasing regard in the discussion and research in this area. In this contribution, dealing with the problem of mind-sets about pressure vessel failure, my purpose is to criticize this anomaly, which I regard as a serious one. My present arguments may be seen as a follow-up to a similar paper a couple of years ago. 1

The Chernobyl accident has given me particular cause to ponder pressure vessel failure in the context of mind-set. Depending on the circumstances, in particular the estimated integrity of the containment, such a failure can be expected to produce a sudden and rapid discharge of radioactivity which, with regard to preparedness and consequences, would largely resemble what happened in Chernobyl. In the discussions that have been held since the Chernobyl accident, it has time and again been maintained that Swedish reactors, thanks to their stronger containment, would be exempt from sudden, rapid and significant discharges of radioactivity. If one were to count the number of times it has been admitted, in public debate, that a pressure vessel failure can occur, and compare that with the number of declarations to the contrary, one would probably find that the ratio of pessimistic to optimistic expressions of opinion is rather more like 1:100 than 1 : 10.

Since the overall view of pressure vessel failure seems not to have appreciably improved in the years that have passed between Three Mile Island and Chernobyl, I think it is high time to call attention to mind-set as a major contributing cause of the dangerous lack of consciousness about the risks associated with pressure vessel failure.

Thus the ultimate objective of my reflections on mind-sets about pressure vessel failure is partly to contribute to better preparedness in the face of this

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kind of reactor accident, and partly to influence research on pressure vessel failure so that it will be more realistic. The final product ought to be increased safety.

A T T I T U D E S ABOUT MIND-SETS

In order to clarify what I mean by mind-sets in the context of the risks of pressure vessel failure, I will cite a number of examples. I do so without pretending to expertise in all the areas where the concept of mind-set can be expected to belong, such as philosophy, psychology, sociology, etc. Still, in all modesty, I will say that on various occasions over the years I have talked with specialists in these disciplines about the phenomenon to be discussed here. It is against the background of the responses I have received to the examples to be cited that I have come to the conclusion that mind-set can be a suitable point of view for considering opinions and behaviour. (There are other keywords and concepts that could also provide useful points of departure for reflections on inadequate consciousness of the risks of nuclear power, such as mentality, ethics and paradigm. I am quite ready to discuss the entire issue in such terms, but refrain from doing so at present in consideration of the announced and restricted scope of my contribution.)

One additional query about the method of illuminating this kind of problem by means of examples is: What general validity can be ascribed to particular observations? In the natural sciences and technology it is, of course, customary to repeat procedures in order to demonstrate the correctness of one's observations. It can therefore be offputting for some people to give serious consideration to the kind of occasional manifestations of opinions or behaviour that often form the basis for interpretations and explanations of phenomena outside the strictly defined areas of technology and the natural sciences. In order to anticipate objections of that sort, I should like, for the sake of brevity, to refer to descriptions of this problem area in non-technological or natural-scientific thinking. 2

As further proof that one should not neglect manifestations of mind-set, even if one is a natural scientist or a technologist, I refer to our ordinary, everyday outlook on attitudes. Presumably it is a rare individual who, when judging a complicated matter on the basis of uncertain evidence, fails to take into account the attitude of the person who submits the problem for his or her decision. This applies not least to decision-making on high political levels. My own experience with such decision-making is that politicians of statesman rank are extremely prone to proceed on the basis of the attitude of the advisor they turn to. This importance of attitude should, I trust, be one reason for paying particular attention when reading what follows here.

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EXAMPLES OF MIND-SETS

The general outlook on demonstrating something by means of examples, as presented in the previous section, may have adequately served as an introduction to the cases I will adduce in what follows. At the same time, I willingly state that exemplifying in this situation is risky, and not only for myself--something I have experienced thoroughly on previous occasions; the repercussions have been palpable.

The more general risk I would point out is that an example may be too hastily dismissed from the very outset as a freak occurrence, stamped by unusual circumstances. The fact of the matter is quite the opposite. The mind-sets that these examples express are by no means exceptional but, rather, typical and prevalent. Thus what I can illustrate in this way is (unfortunately) of universal applicability.

In order to indicate the mind-set feature in each example, I have supplied suggestions for interpretation immediately after the quotation. At the end of this section I will return to a more general contemplation. It should perhaps be pointed out that every one of these examples is taken from my personal experience in dealings with authorities and companies, and in my role as an ordinary receiver of impressions from the mass media.

1. 'Pressure vessel failure has such disastrous consequences that it simply must not be allowed to happen. Therefore we've selected the strongest of all pressure vessel steels for the containers to guarantee that a pressure vessel failure can never happen.' This simplified version of a standpoint on the pressure vessel failure problem was predominant during the period when we still lacked so-called fracture mechanics methods for determining the probability of failure. The statement may be said to express a mental Maginot Line against conditions that one cannot control.

2. 'The problem with the Barseb~ick nuclear power station is that the plant is so located that it is visible to so many people, rather than that many people may be exposed to the effects of a pressure vessel failure.' It would seem that the opinion underlying this statement by a pressure vessel manufacturer is that (a) people's fears are unjustified and harmful, and (b) technologists both know better and are qualified to determine what risks are acceptable.

3. 'If the question of locating a nuclear power plant at Barsebfick came up today in the wake of Chernobyl, I would not reject it on technical grounds. It's possible that psychological considerations might speak against it, but then it would be a matter to be decided by the Government and Parliament. ' The import of that statement has been repeated both by a person who was responsible for the basis of the earlier decision on Barsebfick as a location, and by a participant (from the utilities) in a TV debate after Chernobyl. It is an expression both of the opinion that people's uneasiness is basically

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unwarranted and therefore should not be a determining factor, and of the standpoint that there is a demarcation line between the ethical consider- ations and responsibilities of technologists, on the one hand, and politicians on the other.

4. 'Anyone educated in the natural sciences knows that an ordinary nuclear power station cannot explode unless somebody blows it up.' Phrased somewhat differently, this was presented as a criticism of the mass media by a number of scientists well established in the academic world. The statement is an expression of the demand for confidence in technology, provided that it is governed by scientists.

5. 'No other welded constructions are subjected to such exacting quality control as reactor vessels.' This statement was part of an apology from a manufacturer that the inspection of reactor vessels was too burdensome. The implication, in terms of mind-set, is that the speaker was not aware that reactor vessels should be more carefully inspected than other technical components, considering the consequences of a failure.

6. 'Getting hung up on the difficulty of detecting every little crack in a reactor vessel is just plain refusal to realize and accept the fact that every technical process has its flaws.' Since this was said by a person with managerial responsibility for this aspect of reactor vessel inspection, the statement can be interpreted as an indication that the speaker has adopted a position too far removed from the problem of pressure vessel failure probability and its consequences.

7. 'Cracks that are missed during one inspection will be picked up by another inspector later on.' The remarkable thing about this (statistically speaking, abstruse) confidence in repeating a procedure with presumed shortcomings is that the statement was made by a prominent scientist in the field of technology, who has apparently been persuaded all too easily of the efficacy of inspection.

8. 'Inspection is carried out with the aid of the acoustic signals generated by cracks in pressure vessel materials during operating conditions.' This assertion was made a number of years ago by a prominent representative for technical expertise at a large public meeting on reactor safety. Even today, acoustic emission has not achieved the level of reliability which at that time was no more than wishful thinking. The most charitable interpretation is that the expert was speaking in good faith.

9. 'There is no reason to anticipate the evacuation of this city in the event of a reactor breakdown.' An official spokesman responsible for evacuation planning made this assertion on TV; he had earlier been informed of what would happen during a serious pressure vessel failure, and its aftermath. The statement is understood here as an expression of the desire to 'avoid upsetting the public'.

10. 'There's no point in discussing inconceivable events at an IAEA

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conference.' That reaction to a suggestion I had submitted belies a general unwillingness to reconsider details in the current safety system.

11. 'Proposing studies of how decision makers handle information about low-probability pressure vessel failure is a manifestation of religiosity.' That statement by the energy commissioner of a large Swedish city is understood here as a distancing ploy, in effect saying 'No thank you!' to studies of non- technological or non-'scientific' phenomena, triggered by a general uneasiness when confronted by input from the behavioural sciences.

12. 'It is inappropriate to raise questions about (in)competence in the field of nuclear power.' That statement, by a representative of an agency responsible for the technical functioning of reactors and for research, expresses anxiety about looking into sensitive matters because of the possibility that inadequacies may be revealed.

13. 'The kind of crack propagation we have been asked to investigate has not come up during previous deliberations on failures in reactor pressure vessels. So there's no way it can be a serious problem.' This statement is an expression of the confidence that research always proceeds from certainty to certainty, that deviations from the expected result never occur, and that there is never reason to reconsider. Those who study decision-making customarily refer to devotees of this position with terms like 'security seekers'.

14. 'Creep cracking in reactor vessels is a well-known phenomenon.' This statement obviously runs contrary to the implication of the previous one, although they occurred on the same occasion. To begin with, it contradicts what had been presented by various experts in support of the proposal for research in question, and yet the alleged state of affairs was offered as an argument against an investigation of the cracking in question. The relevance of this statement in the context of mind-set lies in its being an expression of the inclination to dismiss anything that might disturb the sense of security found in the apprehension that everything is under control. Apparently one assumes that the burden of proof rests on whoever suggests that a risk exists--otherwise give people the benefit of the doubt.

15. 'Of course I saw a tumour while I was removing the appendix, but there was no reason for me to comment on the tumour- -my assignment was to perform an appendectomy.' 'We like to call in Specialist X--he gives us the answers we want to hear.' The first statement is a paraphrase; the second is a simplification, but not a distortion. Both indicate the restricted way in which investigative assignments in the area of preventing reactor pressure vessel failure are sometimes handled. The mind-sets of these speakers may be said to have been stamped by the expectations of the people around them.

16. 'My assignment is to investigate and ascertain metallurgical changes (ageing) in the steel during its use in a reactor pressure vessel. It's not my

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business to call attention to the consequences of a pressure vessel failure or even to go into the matter at all.' This far-from-unusual conception can, of course, find support in formal job descriptions, but in fact it is an expression of an inclination to delimit and restrict responsibility.

17. 'This problem of insurance against failure in a reactor pressure vessel consists of a number of aspects; some of them can be dealt with quantitatively with the aid of calculation methods, while others can only be judged qualitatively. Considering this difference, it is in principle primarily the former aspects on which one should concentrate. The others should be ignored, since they cannot be expressed quantitatively.' Such more-or-less unspoken principles are an expression of a narrow scientific attitude which can indisputably be supposed to predominate over a more balanced judgement that is also willing to consider qualitative methods.

18. 'Our company does not assume addit ional responsibility or guarantees for the research assignment. Hence we do not answer for the future application or interpretation of results, nor for the completeness or accuracy of results, nor for the client's interpretation of results, and consequently not for the client's application of results.' This is a proviso in a tender for a research project on technical safety which is presumably based on a similar clause in an agreement on the delivery of merchandise. One can suppose that the prototype is the stipulations normally found in agreements in the USA, where the legal compensation liability is more exacting than in Sweden.

19. 'It may be that the company's management and its technical advisors think that the proposed study of the quality of the firm's products is justified, but we union members have always maintained that no such kinds of investigations into our behaviour should take place.' This position testifies to a rejection syndrome regarding evaluation of professional competence, the very competence that is otherwise usually held up as a guarantee of quality.

20. 'Of course, we think that the proposed investigation of non- destructive examination of reactor pressure vessels is interesting and worth doing but, in consideration of our business relationship with the industry in question, we cannot provide financial support for the proposal. ' This pronouncement by a firm that was consul ted--a firm that, in principle, is interested in acquiring better information about the possibility of pressure vessel fa i lure--demonstrates the power of the informal liaisons in the commercial system in which reactor vessels are included.

21. 'Can you trust a person connected to nuclear power technology who publicly admits that there may be cracks in Swedish reactors?' This is not a literal quotation, but rather a paraphrase of an actual question. Such statements can be explained with reference to demands for or thodoxy and

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uniformity of opinions, which hardly have anything to do with a desire to ascertain and report the risks of nuclear power.

Throughout, these examples indicate mind-sets that question the justification or the legitimacy of worrying about pressure vessel failure. In certain examples (1-4) this deprecation is expressed in the view that technologists and scientists are completely in control of safety, and that they ought to be considered the ones who should basically determine whether the risks are acceptable or not.

Some examples (5-9) testify to a conciliatory attitude in the face of technology's shortcomings, which could indicate that one actually is not as concerned about safety as the public might have reason to expect of people in positions of responsibility.

Some (9, 10) of these dismissive pronouncements can be interpreted as expressions of a disturbing sense of inadequacy to deal with the difficulties that one basically realizes do exist.

One particular cluster (11-14) of examples of mind-sets, when confronting the kind of problem represented by pressure vessel failure, are those that reject studies and more thoroughgoing inspection of pertinent questions. These examples testify to a certain insight that the problem may exist, but simultaneously they show an unwillingness to admit that current technology or professional competence may not be adequate for dealing with the problem.

The next four examples (15-18) refer, of course, to mind-sets about research, but their real implications are about the will really to care about the ultimate significance of the problems in question from the point of view of safety. They reveal pronounced shortcomings in the ability to accept responsibility.

The last three examples (19-21) can be said to reveal mind-sets stamped by a 'socially' conditioned closing of the ranks when confronted by something that is perceived as a threat.

MIND-SETS ABOUT NON-MECHANICAL MATTERS

Differing perceptions of the occurrence and consequences of pressure vessel failure can arise because of discrepancies among various kinds of technologies. The following experiences are submitted by way of example.

The first case concerns segregates in steel ingots used for manufacturing pressure vessels. 3 The occurrence of such segregates is partly statistical, which must be considered when analysing the probability of failure.

The trouble is that understanding statistics of segregates requires insight into their origin from a metallurgical point of view. Therefore, in order to be

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able to study the spatial statistical distribution of segregates, one must employ--and rely on--metallurgical expertise. If, however, one is of the opinion that failure safety is altogether a matter exclusively within the realm of continuum mechanics in the usual sense, it is probably hard to take adequate account of the metallurgical dimension. It seems as though the concepts of metallurgy are so alien to those of continuum mechanics that the two disciplines are often regarded as being too different to be assimilated in a failure analysis.

In the second case we have the probability that large cracks in a pressure vessel escape detection during non-destructive examination--so-called 'defect detection'. 4 The basis for our apprehension of this probability is one single study of subjectively based estimates of the possibilities of defect detection. The reason that we do not have--and never will have--another kind of basis is the demand of the statistical approach for a large amount of data, in this case observations of undetected cracks. Not one among all the investigations that have been made (or are planned) in regard to the technique of non-destructive testing has provided (or will provide) a sufficient number of observations. To maintain otherwise--which some- times occurs--is playing fast and loose with one's knowledge. This is par- ticularly pertinent when one makes pronouncements about the technique that has been applied to existing reactor vessels.

The problem with defect detection statistics is that they are different from other contributions to probabilistic fracture mechanics because their basis is of a subjective nature. Experience so far indicates two things. Most people not only refrain from questioning the only study of subjective estimations that has been conducted. They also renounce suggestions for examining these subjective estimations in order to improve their basis.

What these two cases have in common is that failure phenomena that cannot be unilaterally accommodated in the conceptual boundaries of one or a few scientific disciplines run the risk of being handled badly when safety estimates are conducted, supposing that no considerations are permitted other than those that are perfectly obvious in the first place. Such corrective broadmindedness requires a certain experience, the acquisition of which, it would seem, involves both education and special ability.

THE HUMAN ASPECTS OF MIND-SET

Of course, the very occurrence of a failure implies that there is a piece of material which no longer retains its form or tolerates stresses as intended. Consequently the material often attracts attention and becomes regarded as a conceivable cause of the failure. Thus the material as such automatically

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assumes the leading role in the course of events. This is why one so easily overlooks the weighing of different factors contributing to the failure, a balancing of factors that is essential for understanding the interplay between the material, with its particular characteristics, and the various kinds of stress to which it has been subjected.

There are certainly many reasons for the lack of insight about and understanding of the need for a comprehensive view of such complex processes as accidents in nuclear reactors. One of the reasons for such lacks in the case of pressure vessel failure seems to be a notion that every discipline among the technical sciences has an independent intrinsic value. The implication is that one can obtain a complete and accurate solution to every complex problem by pushing the submission of evidence hard enough with the aid of only one single discipline. When so immature an approach to looking at the total picture is presented as I have done just now, it may seem exaggerated. Unfortunately this is about what actually happens in reality.

It is often maintained in a general connection that our technology increasingly requires technologists who have the comprehensive view and broadmindedness. This applies not least to materials engineering, but the reality looks different from the desired picture of well-considered judgements of materials problems. In fact, to concentrate only on the more general inquiries made into materials engineering, it is rather the opposite that characterizes our way of handling materials questions. It therefore appears almost to be the intentional goal to avoid considering material in its total context, and instead to look for one or another particular aspect on which attention may be focussed. Consequently specialists are usually appointed as evaluators and investigators, more to represent their disciplines than to address themselves to some sort of comprehensive view. Integrating the results into conclusions that might correspond to the diversification and complexity of technology is left to Providence.

The conditions that have been presented here are well known to everyone who has been interested in and worked with research and development as human phenomena. Regrettably one must acknowledge that most tech- nologists find themselves in an unfortunate position when it comes to dealing with one-sidedness. Most of them dissociate themselves from viewpoints of the kind presentedhere. Philosophy, psychology, sociology and politicizing are regarded by technologists as not belonging to their sphere.

Maybe the best move is to forget about trying to effect a conversion by means of re-education. The solution may rather lie in the conclusion arrived at by the former director of a Swedish research organization: What technologists need to do is read more Shakespeare. Or why not Hans Christian Andersen~s 'The Emperor's New Clothes', for example? The conclusion is indeed instructive. I ought to acknowledge that this suggestion

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was once made by, of all people, Edward Teller. I absolutely agree with h im--an agreement purchased with my own costly and painful experience.

MIND-SETS AND ORGANIZATIONS

To open this section on the importance of organizations for mind-sets, I hasten to point out that what is about to be said is not based on great personal expertise in organization theory. It is only a presentation of various thoughts that have their origin in observations of certain organizations concerned with safety--observations which I have had the good fortune to discuss with recognized experts on administration and organization.

If one describes how organizations in the field of safety are seen to behave by such specialists, their reactions are usually expressed in the terminology we associate with discussions of bureaucracy. Above all they point to the uniformity of interpretations of how organizations work which prevails in typical bureaucracies. This uniformity is usually opposed to the administration's endeavour to focus activities on certain goals. Such ritual behaviour by the employees of a bureaucracy has other negative results; it can, for example, lead to a gap between the organization and the public it is supposed to serve. One soon loses sight of the original reason for being given a particular task. What becomes important instead is the organization's own life and way of living. Rules develop for facilitating a kind of inner rationality rather than an outer efficiency.

The significance of all this as regards safety is the difficulty it creates for improving one's ability to handle the problems of the outside world. In the experiences gathered from investigations and analyses of nuclear power safety, there are plentiful examples that such difficulties are so great that they impede even very conscious and determined outside efforts to effect changes.

Short of a total dismembering and reconstruction of organizations, it appears that the only alternative is seeing to it that their size is kept as small as possible. This will limit the possibilities of an organization to develop into a fully fledged bureaucracy in the pejorative sense.

The reason for stressing bureaucratic organizations in this discussion of mind-sets is that the way such organizations work creates employee mind- sets that are significant not only for the work on safety problems within an organization but also for the way these problems are treated by those who depend on the organization. The best conceivable intentions of the direct or indirect client, here with regard to pressure vessel failure, have very little chance of being realized in all quarters unless they are shared and approved by the bureaucratic organization as a whole.

In my opinion, the results of an organization theory-based analysis

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of the importance of bureaucracy for the crucial mind-sets about pressure vessel failure prevention imply, above all, that one must take these relationships into consideration when evaluating the effect of various proposals and measures. One can of course find certain examples of what this means in more concrete terms, but the general influence of bureaucracy on the work being done on safety in nuclear technology remains to be examined. Good use should be made of the attempts that have been initiated.

Further studies of bureaucratic organizations' treatment of risks should eventually lead to the question of what risks we can satisfactorily contain with the help of our customary safety procedures. Can we tackle the pressure vessel failure problem in all its phases? Are conscientious efforts to reduce the probability of occurrences of pressure vessel failure as dubious as the organizational preparedness for the consequences of such a catastrophe?

ATTITUDES ABOUT CONSEQUENCES

The usual way to analyse a risk is to divide the accident in question into probability and consequence. Then these phenomena are treated separately. This treatment is most often conducted by different people and by different institutions.

From the conceptual viewpoint it is natural to let probabilities and consequences be independent of each other. If, however, one considers such aspects of risk analyses as cannot be treated without the human factor-- attitudes and value judgements--then the tidy division into probabilities and consequences becomes more doubtful.

Pressure vessel failure, in my opinion, belongs among the kinds of risk that must be treated in the context of a psychological connection between probabilities and consequences. That is because there are uncertainties in the basis for estimating probabilities and risks that cannot be bridged without human decision-making. Consequently there is also reason to call attention to the connection between, on the one hand, the method of conducting probability estimates of pressure vessel failure accidents and, on the other hand, the interpretation one makes of their consequences. My impression is that heretofore there has been far too little sensitivity for and consciousness of this connection in analyses of pressure vessel failure probability.

The situation seems to be different for other kinds of accident, e.g. aeroplane crashes, with low probability but catastrophic consequences. One would, of course, be justified in speaking of inadequate anticipation in the context of such accidents. The term 'inconceivable events', which I have used

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in reflecting on reactor safety, was coined in the field of air traffic safety. Nevertheless it would seem likely that one is conscious of the consequences of a plane crash when analysing its probability.

In the area of pressure vessels, however, it has proven to be necessary to point out time after time that a sudden failure can often result in the deaths of human beings. When the subject arises of a major reactor accident, where the containment breaks and radioactivity is suddenly dispersed throughout the area around the nuclear plant, it is not unusual for people to turn away in revulsion from descriptions or pictures of the consequences. During a certain period on Swedish TV there was a logo announcing news about reactor accidents: one saw a radioactive cloud above a reactor. So strong was the reaction from certain quarters that this picture is no longer allowed. Now the pendulum has swung so far that TV debates about the Barseb/ick nuclear plant are sometimes introduced with pictures of people bathing on the neighbouring beaches.

Most people seem to feel that photographic montages of disasters in ordinary reactors that suggest similarities to atomic explosions are exaggerated and misleading~despite Chernobyl. The fact is that there are no better representations of the imaginable consequences of a pressure vessel failure than sketches. This is, to me, an indication of mind-set about the 'experiencing' of such a catastrophe. In the long run, this mind-set can be a major barrier to safety measures and preparedness against such sudden, rapid and enormous discharges of radioactivity. What I have in mind is not some kind of terrorizing propaganda, but rather what is known in a more general context as 'imaging'. What that implies is the subject of the special section which follows.

WHY ALLOW OURSELVES TO BE CAUGHT OFF-GUARD?

The Chernobyl accident has given rise in Sweden to a good deal of probing into our protection against radioactivity. Many measures have been proposed for rectifying the shortcomings revealed after this disaster. On the other hand, very little consideration has been given to the reasons why we were vulnerable to such a surprise in the first place.

It can be fairly asserted that we have been rather well aware of the risks posed by Soviet reactors of the Chernobyl type for a long time. Yet we were surprised, caught off-guard, in the sense that we were not sufficiently well prepared when the accident occurred. How could this be? Why had not our awareness of the risks of the Soviet reactors renewed and influenced our planning and preparedness?

If we raise this question in the context at hand, it is natural to point at

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mind-sets as a major contributor to our surprise. Of course, there may be additional reasons for the sorry state of our preparedness, but one cannot avoid considering the matter from the point of view of mind-set.

With reference to all the examples of mind-sets about pressure vessel failure set forth in an earlier section, it would not seem necessary at this point to delve further into the implications of mind-set in the context of pressure vessel failure. What I would like to focus on, however, is that one attitude of special importance in this particular connection is the cool reception often encountered by so-called 'intelligence'. This refers not to espionage but rather to the search for information and insights that fall outside standard conventional procedures.

This kind of intelligence is in fact carried out on a large scale by companies and certain public organizations, where there is great concern to avoid falling victim to surprises that have disastrous consequences. There is a methodology for intelligence, and it can thus be regarded as a systematic activity with rules and principles.

Attempts by myself and others over many years to gain a hearing for intelligence and its role have shown, however, that the greatest difficulty lies in the deprecatory mind-sets of individuals and organizations. Hence such mind-sets are also dangerous in the context of preparedness against something as awesome as pressure vessel failure.

It is a short step from this rejection of intelligence to the psychological effect of an unpleasant surprise. To contain this presentation within reasonable limits, I once again avail myself of another paper. 5

DISCUSSION AND CONCLUSIONS

Some people may think I have gone a bit too far with my compilation of phenomena bearing on mind-sets about the risks connected with pressure vessel failure. The fact is, however, that there is a good deal more with which I have not concerned myself here--for example, expressions like 'If Cabinet Minister X onlyl knew... '. Also omitted here are the attitudes and mind-sets of today's students at the institutes of technology which point forward to the important future outlook on pressure vessel failure.

The mind-sets about pressure vessel failure which have been illustrated and commented on in this presentation can be discussed with regard to such things as their philosophical, psychological and sociological ramifications. Aside from the fact that this would probably lead too far afield from the purpose of the discussion to which this paper is a contribution, a thorough treatment of these aspects of the mind-sets presented would require more expertise than I can mobilize at present. Therefore I confine myself here to

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stating that there should be much of value, for estimates of the risks associated with pressure vessel failure, to be gained from a more thorough analysis of mind-sets, as well as of related phenomena and concepts like mentality, paradigm, ethics, etc.

The following discussion, however, is devoted to the conclusions that can and should be drawn now, partly regarding pressure vessel failure with its present risks, and partly regarding future developments. The general conclusion concerning the risks we have to deal with at present is that decision-makers outside the nuclear power establishment itself must be aware that the basis for their judgements can be influenced by mind-sets like those presented here. Exactly what cautionary limitations may result from such awareness is difficult to predict before this contribution has been discussed. It may be that mind-sets are something that has already been taken into consideration in estimating the risks of pressure vessel failure. My guess, however, is that decision-makers, like the public in general, can be somewhat more thoughtful than heretofore when looking more narrowly at pressure vessel failure risks. A study I have recently concluded, 6 with others, into the way decision-makers process information about low probabilities should result in certain contributions to the understanding of mind-sets, assuming that further funding is approved.

It should also be valuable to achieve greater clarity about the probabilities of pressure vessel failure in those respects that have previously been less well illuminated as a consequence of prevailing mind-sets. I refer here to knowledge about the effectiveness of defect detection and the influence of segregates in pressure vessel steel. On both of these points (my queries up to and including the writing of this contribution have unveiled no correspond- ing initiatives elsewhere) plans of approach have been drawn up.

Most important of all, however, is trying to influence the mind-sets of everyone who has any influence in the area of pressure vessel failure. This is a task requiring the contributions of professionally competent people with experience of similar problems in other areas. Such competence is available from such consultants, among others, as are engaged in management and personnel development.

In conclusion, I will emphasize that it is by no means self-evident that a contribution touching on mind-sets and attitudes and the like has to emanate from previously existing organizations addressing safety in the field of nuclear power. In terms of the subject at hand, in fact, one would be quite likely to encounter the problem sometimes called 'blowing up a balloon from inside'.

If the measures proposed here are taken, the first achievement will be to improve preparedness in the event of a reactor accident resulting from pressure vessel failure. Moreover, an increased consciousness of the

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implications of mind-sets in this connection can result in more realistic research. That, in turn, should enhance the prevention of pressure vessel failure.

A C K N O W L E D G E M ENTS

I thank the Swedish Nuclear Power Inspectorate for a grant in support of the translation of this paper, and the Southern Sweden Power Supply Company (Sydkraft) for a travel grant to facilitate its presentation.

R E F E R E N C E S

1. Ostberg, G., On the trustworthiness of safety assessments for nuclear pressure vessels, Int. J. Pres. Ves. & Piping, 25 (1986), pp. 257-66.

2. Cook, T. D. & Reichardt, C. S., Qualitative and Quantitative Methods in Evaluation Research, Sage Research Progress Series in Evaluation, Vol. 1, 1979.

3. Ostberg, G., Comment on the paper by F. Nilsson: The influence of A segregates on the risk of fracture in a feed-water nozzle, Proc. Int. Symp. on Reliability of Reactor Pressure Components, Stuttgart, 21-25 March 1983, Int. Atomic Energy Agency, Vienna, 1983.

4. Ostberg, G., On the risk of failure of nuclear pressure vessels, 6th Int. Con/i on Fracture, New Delhi, 4 10 December 1984, Vol. 5, pp. 3533 40.

5. Ostberg, G., On imaging surprises, Contribution to appear in abridged form in the proceedings of a workshop on Surprising Futures and the Sustainable Development of the Biosphere, arranged by the International Institute of Applied Systems Analysis (IIASA) and the Swedish Council for Planning and Coordination of Research (FRN), Friibergh Manor, Sweden, 13-17 January 1986.

6. (~stberg, G., Rydnert, B. & Ofverbeck, P., How decision-makers deal with low probabilities, Report to the Energy Research Commission, Sweden, project No. AES 1313 2, 1987-01 19.