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Japan Nuke issues..
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<blockquote data-quote="Hobbes" data-source="post: 1484643" data-attributes="member: 3371"><p>Terrific. All we have to do is fix people. <img src="/images/smilies/image096.gif" class="smilie" loading="lazy" alt=":hithead:" title="Image096 :hithead:" data-shortname=":hithead:" /></p><p></p><p></p><p>But that's not what the investigation concluded.</p><p>These are the conclusions from the investigation into TMI:</p><p></p><p>A. CAUSES OF THE ACCIDENT </p><p></p><p>1. Malfunctions in plant equipment - initiated </p><p>the accident at Three Mile Island, but they alone </p><p>did not cause the uncovering of the core or the </p><p>severity and duration of the accident. Feedwater </p><p>transients such as the one that initiated the March </p><p>28 accident occur routinely at nuclear power </p><p>plants. They result from a variety of minor equip- </p><p>ment malfunctions or from human error such as </p><p>experienced at TMI. 3 </p><p></p><p>Routine transient.-; can evolve into serious acci- </p><p>dents if complicated bv human factor deficiencies </p><p>and other deficiencies in training, in control room </p><p>design, in instrumentation and equipment, in </p><p>emergency procedures and in plant design. The </p><p>psychological stress experienced by plant person- </p><p>nel during a crisis is a further complicating factor. </p><p></p><p>All of these factors can serve to confuse plant </p><p>personnel and to render them unable to respond </p><p>to a minor accident effectively. At TMI, these fac- </p><p>tors caused a minor event to evolve into a serious </p><p>accident. </p><p></p><p>2. Plant operators and managers inappropri- </p><p>ately overrode the automatic safety equipment </p><p>actions that were the immediate cause of the un- </p><p>covering of. and severe damage to, the reactor </p><p>core. 4 However, it is inappropriate and unfair sim- </p><p>ply to blame these personnel for the Three Mile </p><p>Island accident. It should be emphasized that the </p><p>utility, the reactor-vendor, the architect-engineer </p><p>and the XRC were responsible for deficiencies in </p><p>training. 5 in control room design. 6 in instrumen- </p><p>tation and equipment, 7 in plant design, 8 and in </p><p>emergency procedures. 9 These deficiencies were the </p><p>underlying cause of the accident. </p><p></p><p>Many of these deficiencies resulted from insuffi- </p><p>cient attention by the utility, the reactor-vendor, </p><p>the architect-engineer and the XRC to human fac- </p><p>tors in nuclear plant design and operation. 10 These </p><p>human factor problems were l^eyond the control </p><p>of the operators on duty during the accident and </p><p>were so serious that they had consequences equiv- </p><p>alent to those that could be caused solely by major </p><p>mechanical failures and design defects. </p><p></p><p>3. Several major weaknesses in the design of </p><p>TMI-2 contributed to the difficulties faced by </p><p>plant operators and managers in understanding </p><p>plant behavior, in stabilizing the plant, and par- </p><p>ticularly hi preventing radiological releases to the </p><p>environment. 11 In some cases they involved equip- </p><p>ment designed for use in an accident that failed </p><p>to fulfill its intended purpose on March 28. 12 In </p><p>other cases, design had focused on normal operat- </p><p>ing conditions; instrumentation and equipment </p><p>needed or useful under the emergency conditions </p><p>at TMI had not been provided or were inadequate </p><p>to the task. 13 These design weaknesses are of con- </p><p>cern because of their possible generic safety </p><p>implications. </p><p></p><p>Design weaknesses in the emergency-related </p><p>equipment included : </p><p></p><p>A system of some 1.200 alarms, of which </p><p>several hundred went off in the first minutes. </p><p>Operators said they had concluded prior to the </p><p>accident that the alarms would provide little, if </p><p>any. immediate assistance in diagnosing a major </p><p>transient or in assigning priorities to accident con- </p><p>ditions. 14 After the accident, operators said the </p><p>alarms were "not very helpful" 15 and "got in the </p><p>wav." </p><p></p><p>A computer printer that was, as anticipated </p><p>by the operators, of little help because it failed to </p><p>keep pace with the sequence of alarms 17 and be- </p><p>came severely backlogged. 18 </p><p></p><p>A radiation monitor that was intended to be </p><p>a key indicator of a loss-of-coolant accident </p><p>(LOCA) but apparently did not sound on March </p><p>28. Prior to the accident it may have been mis- </p><p>calibrated, and on the first day it may have become </p><p>disabled by the steam and water resulting from </p><p>the LOCA." </p><p></p><p>The failure of the containment building to </p><p>seal automatically on initiation of high pressure </p><p>injection, resulting in the automatic pumping of </p><p>radioactive water from the containment into the </p><p>unsealed auxiliary building. 20 </p><p></p><p>Design weaknesses related to equipment that was </p><p>needed in the emergency, but was unavailable or </p><p>inadequate to the task, included : </p><p></p><p>The lack of a direct indicator to show whether </p><p>the pilot-operated relief valve (PORV) was open </p><p>or closed. 21 </p><p></p><p>Indicators of conditions in the reactor coolant </p><p>drain tank (pointing to a LOCA) that were not </p><p>directly visible to plant operators from the main </p><p>console in the control room. 22 </p><p></p><p>The lack of strip chart recorders for reactor </p><p>coolant drain tank conditions, without which it </p><p>was difficult for operators to reconstruct trends in </p><p>the tank's temperature, pressure and water level. 23 </p><p></p><p>The lack of instrumentation to measure water </p><p>level in the reactor vessel directly. Instead, opera- </p><p>tors had to rely on water level in the pressurizer </p><p>as an indirect indicator that proved unreliable </p><p>during the accident. 24 </p><p></p><p>The inability to maintain isolation of the con- </p><p>tainment building when use of the let-down system </p><p>was required to cope with the accident. 28 </p><p></p><p>The inability to seal off the pathways between </p><p>the auxiliary building and the environment to pre- </p><p>vent releases of radioactivity to the environment </p><p>after operators overrode containment isolation in </p><p>order to use the let-down system. </p><p></p><p>Instrumention that was designed only for nor- </p><p>mal operating conditions and could not provide </p><p>readings for the extreme conditions produced by </p><p>the accident. 28 Thus control room personnel could </p><p>not monitor those extreme conditions directly. 27 </p><p>Since these misleading readings influenced actions </p><p>taken to control the accident, the limited range of </p><p></p><p></p><p></p><p>the instruments was a particularly significant </p><p>weakness in plant design. </p><p></p><p>In addition, as had happened before during </p><p>early testing of the plant, the "candy-cane" curve </p><p>in the hotlegs trapped steam formed from boiling </p><p>of the coolant. This blockage inhibited natural </p><p>circulation and contributed to difficulties in under- </p><p>standing plant behavior and in stabilizing the </p><p>plant. </p><p></p><p>Had these weaknesses not been present in the </p><p>design of the plant, the operators and managers </p><p>would have been in a better position to understand </p><p>and to respond to the accident.</p><p></p><p>4. The emergency procedures for Unit 2 were </p><p>vague, confusing, incomplete and not fully under- </p><p>stood by plant personnel. 28 They did not provide </p><p>useful guidance to operators and managers in </p><p>identifying and responding to the critical elements </p><p>of the accident in the early hours. 29 </p><p></p><p>Better emergency procedures and better under- </p><p>standing of them by plant operators and managers </p><p>would have facilitated diagnosis and understand- </p><p>ing of the plant's behavior. It should be noted, </p><p>however, that it is impossible to write emergency </p><p>procedures to fit every possible accident sequence. </p><p></p><p>5. There were several weaknesses in the TMI </p><p>operator training program that contributed to the </p><p>difficulty control room personnel had in under- </p><p>standing and responding to the sequence of events </p><p>of the March 28 accident. 30 </p><p></p><p>These weaknesses included : </p><p></p><p>Limited training in multiple-failure acci- </p><p>dents, particularly such prolonged ones as experi- </p><p>enced on March 28 at TMI ; 31 </p><p></p><p>Limited training in the basics of nuclear </p><p>power plant physics and behavior; 32 </p><p></p><p>Failure to instruct operators on conditions in </p><p>which water level in the pressurizer would not be </p><p>a reliable indicator of water level in the reactor </p><p>vessel. Operators had been directed never to let the </p><p>pressurizer fill completely ("go solid") with water </p><p>during plant operation. 33 This direction had been </p><p>based on the concern that a pressurizer "solid" </p><p>with water could limit their ability to control </p><p>pressure in the primary system and could result in </p><p>damage to the plant. 34 </p><p></p><p>Operators and managers would have been better </p><p>prepared to respond to the accident if their train- </p><p>injr had been more extensive in these areas.</p><p></p><p>6. Despite the inadequate training, confusing in- </p><p>formation and problems with instrumentation, one </p><p>operator did diagnose the stuck-open PORV soon </p><p>after he arrived at about 6 a.m. 35 He then di- </p><p>rected that the block valve for the PORV be closed, </p><p>thereby stopping the leakage. 36 In addition, within </p><p>hours after the core was uncovered, at least three </p><p>utility personnel correctly diagnosed that condi- </p><p>tion. 37 One of them was a member of the utility's </p><p>emergency command team. 35 He stated that it had </p><p>been generally recognized that the core may have </p><p>been uncovered for an extended period after 7 </p><p>a.m. 39 Yet statements by other senior managers on </p><p>the utility's emergency command team suggest that </p><p>they never recognized that the core was uncovered </p><p>on the first day of the accident 40</p></blockquote><p></p>
[QUOTE="Hobbes, post: 1484643, member: 3371"] Terrific. All we have to do is fix people. :hithead: But that's not what the investigation concluded. These are the conclusions from the investigation into TMI: A. CAUSES OF THE ACCIDENT 1. Malfunctions in plant equipment - initiated the accident at Three Mile Island, but they alone did not cause the uncovering of the core or the severity and duration of the accident. Feedwater transients such as the one that initiated the March 28 accident occur routinely at nuclear power plants. They result from a variety of minor equip- ment malfunctions or from human error such as experienced at TMI. 3 Routine transient.-; can evolve into serious acci- dents if complicated bv human factor deficiencies and other deficiencies in training, in control room design, in instrumentation and equipment, in emergency procedures and in plant design. The psychological stress experienced by plant person- nel during a crisis is a further complicating factor. All of these factors can serve to confuse plant personnel and to render them unable to respond to a minor accident effectively. At TMI, these fac- tors caused a minor event to evolve into a serious accident. 2. Plant operators and managers inappropri- ately overrode the automatic safety equipment actions that were the immediate cause of the un- covering of. and severe damage to, the reactor core. 4 However, it is inappropriate and unfair sim- ply to blame these personnel for the Three Mile Island accident. It should be emphasized that the utility, the reactor-vendor, the architect-engineer and the XRC were responsible for deficiencies in training. 5 in control room design. 6 in instrumen- tation and equipment, 7 in plant design, 8 and in emergency procedures. 9 These deficiencies were the underlying cause of the accident. Many of these deficiencies resulted from insuffi- cient attention by the utility, the reactor-vendor, the architect-engineer and the XRC to human fac- tors in nuclear plant design and operation. 10 These human factor problems were l^eyond the control of the operators on duty during the accident and were so serious that they had consequences equiv- alent to those that could be caused solely by major mechanical failures and design defects. 3. Several major weaknesses in the design of TMI-2 contributed to the difficulties faced by plant operators and managers in understanding plant behavior, in stabilizing the plant, and par- ticularly hi preventing radiological releases to the environment. 11 In some cases they involved equip- ment designed for use in an accident that failed to fulfill its intended purpose on March 28. 12 In other cases, design had focused on normal operat- ing conditions; instrumentation and equipment needed or useful under the emergency conditions at TMI had not been provided or were inadequate to the task. 13 These design weaknesses are of con- cern because of their possible generic safety implications. Design weaknesses in the emergency-related equipment included : A system of some 1.200 alarms, of which several hundred went off in the first minutes. Operators said they had concluded prior to the accident that the alarms would provide little, if any. immediate assistance in diagnosing a major transient or in assigning priorities to accident con- ditions. 14 After the accident, operators said the alarms were "not very helpful" 15 and "got in the wav." A computer printer that was, as anticipated by the operators, of little help because it failed to keep pace with the sequence of alarms 17 and be- came severely backlogged. 18 A radiation monitor that was intended to be a key indicator of a loss-of-coolant accident (LOCA) but apparently did not sound on March 28. Prior to the accident it may have been mis- calibrated, and on the first day it may have become disabled by the steam and water resulting from the LOCA." The failure of the containment building to seal automatically on initiation of high pressure injection, resulting in the automatic pumping of radioactive water from the containment into the unsealed auxiliary building. 20 Design weaknesses related to equipment that was needed in the emergency, but was unavailable or inadequate to the task, included : The lack of a direct indicator to show whether the pilot-operated relief valve (PORV) was open or closed. 21 Indicators of conditions in the reactor coolant drain tank (pointing to a LOCA) that were not directly visible to plant operators from the main console in the control room. 22 The lack of strip chart recorders for reactor coolant drain tank conditions, without which it was difficult for operators to reconstruct trends in the tank's temperature, pressure and water level. 23 The lack of instrumentation to measure water level in the reactor vessel directly. Instead, opera- tors had to rely on water level in the pressurizer as an indirect indicator that proved unreliable during the accident. 24 The inability to maintain isolation of the con- tainment building when use of the let-down system was required to cope with the accident. 28 The inability to seal off the pathways between the auxiliary building and the environment to pre- vent releases of radioactivity to the environment after operators overrode containment isolation in order to use the let-down system. Instrumention that was designed only for nor- mal operating conditions and could not provide readings for the extreme conditions produced by the accident. 28 Thus control room personnel could not monitor those extreme conditions directly. 27 Since these misleading readings influenced actions taken to control the accident, the limited range of the instruments was a particularly significant weakness in plant design. In addition, as had happened before during early testing of the plant, the "candy-cane" curve in the hotlegs trapped steam formed from boiling of the coolant. This blockage inhibited natural circulation and contributed to difficulties in under- standing plant behavior and in stabilizing the plant. Had these weaknesses not been present in the design of the plant, the operators and managers would have been in a better position to understand and to respond to the accident. 4. The emergency procedures for Unit 2 were vague, confusing, incomplete and not fully under- stood by plant personnel. 28 They did not provide useful guidance to operators and managers in identifying and responding to the critical elements of the accident in the early hours. 29 Better emergency procedures and better under- standing of them by plant operators and managers would have facilitated diagnosis and understand- ing of the plant's behavior. It should be noted, however, that it is impossible to write emergency procedures to fit every possible accident sequence. 5. There were several weaknesses in the TMI operator training program that contributed to the difficulty control room personnel had in under- standing and responding to the sequence of events of the March 28 accident. 30 These weaknesses included : Limited training in multiple-failure acci- dents, particularly such prolonged ones as experi- enced on March 28 at TMI ; 31 Limited training in the basics of nuclear power plant physics and behavior; 32 Failure to instruct operators on conditions in which water level in the pressurizer would not be a reliable indicator of water level in the reactor vessel. Operators had been directed never to let the pressurizer fill completely ("go solid") with water during plant operation. 33 This direction had been based on the concern that a pressurizer "solid" with water could limit their ability to control pressure in the primary system and could result in damage to the plant. 34 Operators and managers would have been better prepared to respond to the accident if their train- injr had been more extensive in these areas. 6. Despite the inadequate training, confusing in- formation and problems with instrumentation, one operator did diagnose the stuck-open PORV soon after he arrived at about 6 a.m. 35 He then di- rected that the block valve for the PORV be closed, thereby stopping the leakage. 36 In addition, within hours after the core was uncovered, at least three utility personnel correctly diagnosed that condi- tion. 37 One of them was a member of the utility's emergency command team. 35 He stated that it had been generally recognized that the core may have been uncovered for an extended period after 7 a.m. 39 Yet statements by other senior managers on the utility's emergency command team suggest that they never recognized that the core was uncovered on the first day of the accident 40 [/QUOTE]
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