ML19281A357

Minutes of Subcommittee on Plant Arrangements Meeting Held in Washington,Dc on 781025 to Discuss Review of Task Action Plan A-17, Sys Interaction in Nuclear Power Plant & Zion Station Interaction Study.W/Federal Register Notice

ML19281A357
Person / Time
Site:	Rancho Seco
Issue date:	01/19/1979
From:	Advisory Committee on Reactor Safeguards
To:	Advisory Committee on Reactor Safeguards
References
ACRS-1593, NUDOCS 7903120161
Download: ML19281A357 (27)

Text

{{#Wiki_filter:a ADVISORY COMMITTEE ON REACTOR SAFEGUARDS Ntti:1 F AR nEGULATORY COMMISslON W ASHINGTON. D. C. 20555 flCiG- /s 73 PPA t/z. z), 9 MEETING DATE: 10:25:78 DATE ISSUED: 12:22:78 CORRECTED CY: 1/15/79 CERTIFIED: 1/19/79 MINUTES OF THE SUBCOMMITTEE ON PLANT ARRANGEf1ENTS - 10:25:78 WASHINGTON, D.C. The ACRS Subcommittee on Plant Arrangements met in Room 1046 at 1717 H Street, N.W., Washington, D.C. at 8:30 a.m. on October 25, 1978 to develop information for consideration by the ACRS in its review of the NRC Staff Task Action Plan A-17 Systems Interaction in Nuclear Power Plants, and the Zion Station systems Interaction Study. The notice of this meeting appeared in the Federal Register on October 10, 1978 page 46611. Copies of the Federal Register Notice and the Tentative Schedule of Discussions are attached (Attachment A and B respect-ively). No written statements from the public were received nor were there any requests to make oral statements. No written reports were issued or approved by the Subcommittee at this meeting. Attendees ACRS NRC M. Bender, Chairman J. Angelo S. Lawroski A. Schwencer D. Moeller G. Zech J. Ray D. F. Ross J. Arnold, Consultant J. A. Norberg E. Epler, Consultant J. Olshinski C. Michelson, Consultant J. L. Anderson, Consultant (ORNL) N. J. Palladino, Consultant M. Chiramal J. McKinley, Staff H. L. Ornstein L. Lois J. E. Kohler R. Bellamy E. C. Marinos H. C. Li H. Balut n ' ~ ' ~ -- - .m -- l 790312ogt $0fp..ba b jj_ (1/19/79) P

t. 2-NRC Continued Commonwealth Edison Company H. Schierling C. Reed M. A. Taylor T. R. Tra mm L. B. Marsh W. F. Naughton W. Mill s L. S. Rafner C. Liang J. P. Leider M. A. Fedele, Consultant G. Vellender, Consultant (Fluor) J. Hickman, Consultant (Sandia) T. Roell, Consultant (Fluor) D. D. Carl son, Consul tar.: (Sandia) L. J. Charmoli, Consultant (Fluor) W. R. Cramond, Consultant (Sandia) P. Steptoe, Consultant Public F. Hubbard, CE R. L. Ashley, Bechtel Power F. H.. Rowsome, Bechtel W. H. House, Bechtel R. J. Schomer, PASNY T. J. Sullivan, Consmners Power K. S. Canady, Duke Power L. D. Kenworthy, International Energy Assoc. Ltd. S. T. Stetson, AIF T. Raney, EBASCO R. R. Russell, Houston Elec. Power K. S. Sunder, PASNY G. M. Wilverding, PASNY R. C. Olson, Baltimore Gas & Elec. L. B. Long, Southern Co. Services L. S. Gifford, GE R. Borsum, B&W E. H. Kennedy, CE c

Executive Session Mr. Bender asked the members of the Subcommittee if they had topics they would like to add to the Tentative Schedule for Discussion. Dr. Moeller expressed a desire to hear the NRC Staff's definition of system interaction and any limitations they might place on what they consider to be interactions. He pointed out that the definition of systems interaction seems to apply only to those that have an adverse effect on reactor safety and he wondered if the Staff's review included those interactions that could be beneficial or were followe.d far enough to determine that they were not detrimental. Dr. Moeller was also interested in hearing how the Zion station selected the 67 events that they reviewed. He noted the difficulty he had with the computer printouts of the license event reports and the difficulty in identifying events of interest. When one enters the computer with certain key words, not all the LERs of interest would be printed out on the basis of one or two key words. Mr. Ray was interested in learning if the Staff or the utility considered electrical inductive coupling of systems to an interaction and how this would be accounted for in the study. Mr. Arnold wondered if the Staff and its contractors considered the systems to be in perfect working order or if they considered degraded systems con-ditions. He noted that the technical specifications permit reactor operation with certain degraded conditions where systems are not totally operable or redundant systems are out of service. Mr. Epler suggested that the Committee be alert to the evaluation of the significance of the various types of interactions. He noted one case where the loss of off-site power resulted in the stoppage of the secondary circulating water pumps, following this the natural circulation of the water fromthe cooling towers caused hot water to flow back into the plant causing unexpectively high temperatures in some components. He felt that this inter-action was very significant but would have not been found through the normal review prVcess. Mr. Michelson expressed his concern that the interaction studies were based on normal operating conditions as opposed to emergency conditions within the plant. He also expressed concern for the coupling of non-safety systems through some interaction mechanisms to safety related systems. Mr. Palladino also expressed interest in hearing the NRC Staff's justification for limiting the review to normal plant conditions instead of extending to transients and accident conditions. V

A Mr. Bender extended this and expressed his personal interest in the effect of inadvertant actuation of the fire protection sprays on the performance of other plant systems and if this would have any safety significance. Meeting with the NRC Staff Mr. Bender, Subcommittee Chairman, opened the meeting with a statement re-garding the conduct of the meeting in accordance with the provisions of the Federal Advisory Committee Act and the Governrent of the Sunshine Act. Mr. J. C. McKinley was the designated federal ecployee. Mr. John Angelo, Task Manager for Task A-17 " Systems Interaction" reviewed the status of the effort. The program has stretched out somewhat and the Staff looks forward to completing the initial portions by September of 1979 as to opposed to a target of May of 1979. Phase II continues to be scheduled for 12 months after the completion of Phase I. Mr. Ross took note of what he considered one of the Subcommittee's concerns which was the ability to recognize system interactions after they have occurred. He questioned the ability to foresee interactions before an adverse effect is observed. He recalled from his days of reactor operations an incident where various reactor scrams occurred as a result of the water cooler being plugged in the protection system regulated power supply. Each time the water cooler refrigeration compressor started it caused a dip in the regulated power supply voltage which caused a scram. Mr. Ross solicited the Subcommittee's guidance with regard to the scope of the study they had in mind. He asked specified guidance with regard to the timing or priority of this project as well as the overall definition of the work to be done. Mr. Angelo noted that the Staff realized that a systems interaction study could quickly get out of hand as far as scope of work was concerned. The NRC limited the scope of work to be performed by Sandia as severely as possible with the expectation of still producing something useful. He has interpreted the Committee's concern to relate to things that happen on a da/-to-day basis that could probably cause trouble in a nuclear power plant which meant that the contractor would concentrate primarily on normal plant operations and normal transients. Mr. Jack flickman from Sandia Labs described the program, its objectives and its accomplishments to date. The objectives are (1) develop a method-ology to identify and evaluate systems interactions important to public safety, (2) assess the standard review plan to determinate th~e completeness of the plan ~in the areas of systems interactions and (3) develop a technical base or criteria, procedures, and information requirements appropriate for use by applicants. It is hoped that the first two objectives would be completed within the first 16 months of this study contract. Mr. Hickman defined the Phase I as the development of the methodology, assessment of the standard review plan and a demonstration of the methodology on a selective plant design. Phase II would be to turn the methodology over to V

i the NRC for use as guidance for the applicants. Mr. Hickman pointed out that the goals of the system interaction methodology are to identify the important systems, identify the potential interactions between systems and finally to evaluate these interactions. He described Sandia's approach to achieving these goals (See Slide 1). Part of the analysis will be to identi ?y the commonalities of the various irportant systems. Commonalities might include pipes running between two fluid systems or parts of redundant systems passing through the same compartment. The first question to be answered was "which systems,if they interact, are importarit to the health and safety of the public " The next step would be to model those systems in terms of a fault-tree type nodel and to identi fy the failure modes and commonalities. The third step is to identify how the systems could interact through normal operations or through failures and have an effect on the safety of the design. Mr. Hickman expressed Sandia's intent to develop a methodology and to demonstrate that methodology on a focused set of problems. At the same time it is the intent that the methodology would have a broadea application if one wanted to use additional models. The potential for human errors to affect systems performance was raised and the broader question of the desirability of testing and tha consequences of testing on system performance was also discussed. During further discussions, the Subcommittee and its consultants expressed concern that the Sandia methodology might not identify all of the potentially serious systems interactions. An example cited was that of a non-safety related water system rupturing and flooding a compartment containing safety related equipment. Mr. Hickman felt that situation would be addressed,but that the methodology had not progressed to the point where he could make a positive statement. Mr. Bender suggested that the contractor make a catalog of typical situations that could be used as a basis to determine how the methodology would treat some of these known interactions. Mr. Hickman pointed outwhich aspects were within the scope of the current study and how the methodology would be applicable to areas that were excluded from the current scope. It was noted that fires were excluded from this interaction study. Aside from the economics of having to address fires, the Staff agreed to not to include them since there was a major effort within the NRC Staff to review fire hazards. The Staff believes that fires and other condition 3 and 4 events are being adequately reviewed this time. The Staff does not see this methodology as a replacement for the present review plan. They expect it will confirm that.the present plan is adequate or identify portions of the plan that need to be strengthened.

There was considerable discussion with regard to the plant conditions and the number of challenges that would be made against the various systems. It was noted that the safety of some of these systems is assessed on the bases of the probability of failure as a function of the number of times the system is challenced. In some cases, if the number of challenges approaches the number of the failure probability then the probability becorres greater or if the number of challenges is well below the design value the probability of failures is less. The discussion also touched on the ability to consider degraded conditions. It was presumed, once the fault-trees were constructed, they could be structured to include degraded conditions. Mr. Hickman went on to discuss the kinds of interactions that the Sandia study will address. Basically, there are two types either two systems are in some way connected together with wiring or piping or they share the same space. These could be broadly termed as process coupling and spacial coupling. Mr. Hickman concluded by showing a schedule which shows the completion of the Phase I report in September of 1979 (See Slide 2). Mr. Bender inquired how the study would address activities that were non-operational such as naintenance. An example was given of an arc welding machine *. hat might create a very strong electromagnetic field, operating in the vicinity of an electronic component and affect a control circuit. Mr. Cramond was not sure that the study would be able to identify thi; type of interaction but he felt that the methodology would be applicable to failures of that sort where the human comes in to perform a test or nain-tenance and causes something to fail. Mr. Cramond showed how he expected the fault-tree for this study to be constructed.

tarting at the fur ctional level and working down to the system, subsystem and component level followed by a detailed failure (See Slide 3). Mr. Cramond thought t1e logic diagram could deal with degraded modes such as valves that were mispasitioned.

Mr. Cramond went on to identify a number of causes of component failJTes (See Slide 4). In this analysis a physical conntction can be electrical, mechanical or hydraulic. The Subcommittee discussed the philosophy of the regulatory requirerents ar"f the problem of the applicant that just meets the requirement ani goes no further. To counter this there could be a proliferation of requ'rements which would then further encourage applicants to just meet those that are identi fied. V

. Dean Palladino expressed his concern that regulations that are too specific could discourage the designer from designing a system correctly by forcing him to focus on such narrow issues that he failed to see the broader picture. Mr. Bender pointed out that the proposed system interaction studies would not substitute for the normal tiRC Staf f review processees. Mr. Cramond acknowledged that he wasn't sure that all system interactions would be identified by his fault-trees. But he felt that all of the major types of interactions would be found. It wasn't clear that things like leaking fluids entering junction boxes or structural interactions would be addressed. Mr. Bender recognized that this first attempt would not be all inclusive but simply a matter of developing the methodology. In response to a question, Mr. Arnold learned that the Sandia group performing this study did not include individuals experienced in designing power plants, and he expressed the thought that the benefits to be realized from this study would be greatly enhanced by participation of such individuals. Mr. Angelo pointed out that it was not the fiRC's intent to substitute a new way of reviewing nuclear power plants. Mr. Cramond indicated that it was Sandia's intent that the models be generic and that plant specific systems features would be inserted and any interactions would be revealed. At the conclusion of this presentation, Mr. Angelo noted that the Phase I effort represents about $440,000 over a 16 month period. The Phase II effort would be approximately $200,000 over a 12 month period. Mr. John Anderson from Oak Ridge flational Laboratory described the ORfil study directed at the narrow aspect of the interaction between auxiliary systems and the protection systems including the safeguards systems. The study has not addressed the questions of structural and piping interactions. It has involved less than 1 man year per year of affort and has been going on for about a year and a half. The objective of the study is to identify the harmful interactions, their significance and how to deal with them. It has been limited to the auxiliary control systems which normally include the feedwater pres-surizer level and systems of this sort that are in direct control of the plant. The approach is to evaluate direct interactions not necessarily the subtle ones that come about through operation or mismanagement. It was Mr. Anderson's view that a necessary condition to interaction is a degradation of some sort in one of the systems but not necessarily a complete fail ure. It was his opinion that an interaction between two normal systems could be fixed on some sort of a schedule. The Oak Ridge approach is to examine a partia"l= PWR control system, the B&W Integrated Control System, v----

identify the control variables and the potential failure mdes, evaluate the limiting conditions resulting from failures, determine if they are accurately treated in the PSAR, and identify protection capability. Depending on the outcome of this effort, OR!ll may proceed to boiling water reactors (Browns Ferry) and then on to pressurized water reactors by CE and Westinghouse. Finally, there is a plan to evaluate some o f the more pertinent licensee reports, but there is some question as to whether this will be particularly fruitful since the reports do not lend themselves to a clear identification of systemsinteractions. So far the study has revealed that a failure within the system or a smaller scale affecting one or pernaps two of the control variables tend to be of minor Failures of actuators or more than two parameters tend consequence s. to be more dramatic. However, in most cases the operator has had some capabilities for taking corrective action if he has accurate information avail abl e. Mr. Anderson felt that the availability of the definitive information is probably one of the most significant shortcomings that the study has uncovered. There has been at least two multiple failures of this system. In one of the failures all the signals going to the system were affected, not only did the system have erroneous information but so did the human operator and he could not make a logical decision on how to take over from the automatic system. The OR!ll study will include recommendations to the NRC Staff to assist them in their licensing reviews. One of the re recommendations will cover the subject of adequate operator information during upset conditions. Dr. Moeller noted that his analyses of licensee event reports relating to air cleaning systems found that from 1/3 to 1/2 of the reports related to instruments that show the status of the air cleaning system rather than to failures of the system components themselves. Mr. Anderson illustrated the problem with an axample from operating history. The event resulted from a loss of small portion of power in the control system. An electrical fault occurred and one circuit was wiped out and the power that was lost controlled the selection of signals used in the control system. These signals came from the protection systems and they were derived with a classical buffering arrangement so that they qualified under the separation criteria. They were then laundered by the control system and passed back to the console for the operator to use. The event was a fairly localized power failure but due to the way the signals were laundered the operator lost virtualy all of the control system. Well over 75% of the information on the operator's console was either dead, meaning it was pegged downscale or pegged upscale or it failed midscale, and the operator could not tell if the instrument was reliable or disable. The operator had some misleading indications,and he had some obviously faulty indications. He also had some good indications and he wasn't sure what was good or bad. V

In this particular event the feedwater wat lost. The control system, responding to what it thought were correct signals, caused the feedwater to be reduced essentially zero and the steam generators boiled dry. The plant scrammed on overpower and overpressure when the feedwater was lost. The operator recognized that he had lost feedwater and he took action to initiate feedwater flow with the feedwater pumps still idling. He manually increased the speed of the feedwater pumps which then proceeded to flood the steam generators with cold water causing a reactor pressure drop and initiated the engineered safety features which turned on the auxiliary feedwater and it flooded the entire secondary system with cold water resulting in a 3000 hr. cooldown rate. The initiating event for this incident was a maintenance man replacing a light bulb in a push button on the console. He inadvertently dropped the bulb down the hole and shorted out two contacts precipitating the entire event. (See SMUD letter dated March 31, 1978 - Attachment C).

4. Michelson pointed out that this entire event started in a nonsafety mlated system but was reflected back into the safety related systems, also noted that a partial lost of power is sometimes worst than a total ass of power.

It was agreed that more than redundancy was required in the control systems to correct this problems. Redundancy may require 3 or 4 channel operation. In some case, Mr. Anderson thought, it was useful to process some information through the plant computer in order to indicate trends but he thought to recognize that certain vital pieces of information are necessary during upsets which may include the loss of the computer and that other sources of information should be available. He suggested a design approach which would include mitigating factors in the control systems to prevent these systems from initiating unwarranted safety actions. That is, unnecessary challenges to the protection systems. Although this study is not complete ORNL plans to recommend some design improvements. Zion Station Interaction Study Mr. Zech of the NRC Staff reviewed the events leading up to this study noting that, in its letter of June 17, 1977, the ACRS recommended that Commonwealth Edison should submit to the Staff the results of a study of system interactions relating to the possible failure of safety, nonsafety or that systems will interfer with the plant operator's ability to accomplish shutdown heat removal. Subsequently, on November 10, 1977, the NRC Staff, Commonwealth Edison and the ACRS Subcommittee met to discuss the licensee proposed plans for conducting this review. At that meeting it was agreed that the licensee would concentrate on the review of approximately 9000 licensee event reports that had occurred since 1969. This review was to identify those events that involved undesirable system interactions and that affected the ability to accomplish shutdown heat removal under non-accident conditions. These events were then evaluated to identify those T'""*

. that could have some impact onthe Zion Station and to identify any corrective action that might be warranted. Commonwealth Edison and its consultants, Fluor Pioneer, ultimately culled the 9000 licensee event reports down to 267 which were considered applicable to the Zion station. On June 16, 1978, the licensee submitted a report summarizing the results of its study and making recommendations for corrective actions. Copies of that report have been distributed to the ACRS. The NRC Staff reviewed the licensee's report and concluded that nothing was discovered that would require immediate corrective action and nothing was identified that would require corrective action on a generic basis. The licensee and the NRC Staff are presently evluating the various corrective actions proposed inthe report; some of which have been initiated by the licensee and others are still being considered. Mr. Reed of Commonwealth Edison Company, point out that this study re-presented a truly independent review since Fluor Pioneer, now called Fluor Power Services, had not been involved in the original design and had not been involved in any subsequent modifications to the plant. Mr. Vellender of Comnonwealth Edison reviewed the methodology empicyed in the Zion station interaction study. The first phase was to identify those documented events which might impair or degrade the nonaccidents decay heat removal capability as a result of system interaction. The second phase was to review these events to determine if they could occur at the Zion station. And the third phase was an evaluation of the events to determine what corrective options were available. In the first phase over 9000 events were reviewed to find those that resulted in a degradation or loss-of-effectiveness of any of the following systems : The reactor coolant systems residual heat removal system, component cooling water system, service water system, auxiliary power system, instrument power system, chemical control system, auxiliary feeriwater system and portions of the main steam system. The action which initiated the event could have been a normal control function or an operator induced action. These events were reviewed to determine if an interaction was involved. For example, the failure of an RHR pump to start due to an electrical fault in the motor was not considered to be a system interaction. However, if the motor failure was due to excessive humidity and temperature in the RHR cubical, that was considered an interaction. Maintenance and operational errors on the systems were not considered interactions for the purpose of this study. After the initial selection o f events Fluot Power Services was retained to review the selected events. Each event was analyzed by a multi disciplinary Fluor team to clearly understand how the event occurred. Once a clear understanding was e

i obtained, the Zion station was reviewud to,ee if a similar event could occur there. The scope of most events was greatly broadened to assure an adequate evaluation was made. For example, the investigation of an event related to service water valves being flooded in a pit was not limited to the service water system for the Zion station but it included an investigation of all pits which contained safety and shutdown cooling valves. Another example, was the investigation of water leakage into electrical boxes. For this event the scope included an investigation of all electrical boxes used for safety, shutdown and cooling services. In addition, physical surveys of the Zion station were made in which the physical relationshio between systems was observed and first hand deter-mination was made of any field affects. In addition, the Fluor investigators held a discussion with Zion plant operation, maintenance, engineering and management personnel. When all the data had been gathered, the lead Fluor engineer, in concert with other team members, made an assessment of the possibility of an identical or similar event occurring inthe Zion station. During this review it was noted that there are many alarms and indicators that will inform an operator of the existence of an abnormal condition, including system interaction events. The alarms and indicators include the control room panel gages, meters, recorders, control device indicating lamps, and visual audible indicators or alarms. Other local gages, meter and indicating lamps are also avilable. A particularly important observation was the number of events that might lead to a low temperature overpressurization of the primary system. For this event, Commonwealth Edison had conducted an eariler investigation and had installed equipment to preclude overpressurization of the Zion units. In general it was observed that the majority of the events were related to generic problems which -had been previously studied and for which corrective action had begun or had been completed. ~ ~ ~ Fluor arrived at a number of conclusions, the first was that the generic studies requested by the NRC and the implementation of the resulting recommendations in sur.h areas as fire protection, pipe break control, low temperature primary system overpressure, etc., has resulted in modi-ficiations which substantially reduced the possibility of the occurrence of a majority of events studied. Secondly, Fluor recommends the following investigations or plant nodifications: (a) Following an evaluation of the benefits of J tubes which have been installed in one of the steam generators on unit 2. A determination should be made as to the need for similar modification of the other steam generators. (b) The containment spray pump diesel fuel oil tank vent and fill lines susceptibility to being blocked and covered after a significant snow fall should be investigated or corrected. e

. (c) An investigation should be conducted to determine if ice formation on the diesel generator room air inlet dampers could be detrimental to the operation of the dampers. (d) Before initiating any steam generator maintenance that has the potential to affect the pressure retaining capability of the steam generator tubes, the procedure include require-ment.to check che integrity of the tubes prior to returning the steam generator to operation. (e) A program should be developed to survey electrical boxes containing open terminals, which are used in safety or shutdown systems and which are located in the auxiliary building, steam generator safety valve rooms, pipe tunnels and crib house to determine if they could be subject to the entry o f water. For those boxes in this category the existence or lack of box drain holes should be determined by inspection. If drain holes are not found in these boxes they should be added or some other technique should be used to prevent potential shorting of the terminals by water accumulation. Finally, Fluor concluded that although the study did determine that some systen interactions could occur at the Zion station. These occurrences would not significantly degrade the safety and shutdown systems in the plant and thus would have little or no affect on the public health and sa fety. Mr. Reed stated that Commonwealth Edison feels that this report ful fills its obligation to the Committee and that the study did verify that the current NRC program provides sufficient assurance that the potentials of systems interactions have been precluded. Although, the study was beneficial from a confirmatory standpoint, Commonwealth does not plan to continue the licensee event report reviews or system interactions studies on a continuing basis. Commonwealth is prepared to implement the recommendations of the report with the concurrence of the Committee and the NRC Staff. Mr. Eplerexpir ed further the consequences of the loss of various DC power sources. Mr. Leider from Commonwealth stated that a loss of DC power would result in a reactor scram,and the interaction that had resulted in the earlier diesel fire had been corrected. A number of hypothetical interaction scenarios as well as some historical sc~enarios were discussed, including their applicability to the Zion station or their application generically. Mr. Reed had noted that Commonweal n was initially concerned about attacking this generic problem on the Zion station but as the study was completed the licensee concluded that it had been useful to confirm what they had originally felt was the case. With regard to the method of making the V

, systems interactions study, Commonwealth could think of no better way than to review the past licensee event reports. In response to a question, Mr. Reed stated that Connonwealth does not have a plan for continuing review of licensee event reports. He felt that the NRC Inspection and Enforcement Bulletins and the feedback that the utilities receive from the industry provides adequate information. This does not mean that Commonwealth does not look at the incoming licensee event reports, but only that it does not perform as detailed an analysis of them as did in this study. Mr. Michelson and Mr. Schwencer took note of the need for a more disciplined review of the licensee event reports by the NRC and of the Task Action Plan to address systems interaction. Mr. Schwencer described the NRC handling and distribution of licensee event reports. Mr. Reed confirmed that not only is the Zion station participating in the NPRDS (Nuclear Plant Reliability Data System) but so are all of the other Commonwealth Edison nuclear power plants. He also noted that in about 99 cases out of a 100 by the time the NRC I&E bulletin was issued on an event the utility had heard about it through the nuclear steam supply vendors or through informal contacts with other utilities. He pointed out that the avilability of the power generating stations is of great concern to the utilities and that anything that reflects adversely on this availability is discussed by the various utility executives. AIF Systems Interaction System Studi Grouc In response to a question by Dr. Moeller, Mr. Canady, Chairman of the Systems Interaction Study Group noted that cne of the AIF goals was to orient the NRC Staff's efforts toward looking it what the industry is currently doing. He felt that the architect-engineer!, and the nuclear steam system suppliers are doing a good job in evaluating systems interactions. He felt that the NRC should determine if a problem exists before it develops a solution. Executive Session (0 pen) Mr. Bender suggested that the Subcommittee and its consultants give some thought to the response that should be made to this presentation. He asked if there were any additional suggestions to be made with regard to this particular study effort. Mr. Michelson stated his preference for responding to this question with written comments. e

14 - Mr. Bender suggested tilat the NRC and its contractors attempt to catalog some of the things that are systems interactions questions that could later be used to test whether the methodology being developed is adequately addressing them. He also asked for an assessment o f the extent to which the methodology being developed by Sandia could be followed and how far it should be followed. Mr. Angelo asked for some indication of Committee acceptance of the scope of work being done by Sandia or if there were areas the Committee felt could be addressed further. Mr. Bender expressed his personal view "at as a first cut this was probably as good way as any. He emphasized the importance of making some kind of a representative list of system interactions that could be addressed by the method to show how system interactions affect the probability relationships used in deciding whether something is safe or not. Mr. Angelo pointed out that a representative from Probabilistic Analyses Branch (Mr. Taylor) is working closely with him on the systems interaction study work. Mr. Angelo felt that he had enough guidance from the Subcommittee to proceed with the study work. Mr. Bender reported that the Subcommittee would report to the full Committee what had been learned from today's discussion and that he would try to get some additional reaction from the full Committee. He also indicated that the full Committee might request an abbreviated version of today's presentations. Mr. Angelo did not anticipate any problems funding the interaction study. Mr. Reed noted that Commonwealth has spent approximately $200,000 on the Zion station study. Mr. Zeck requested that this Subcommittee report to the full Committee with regard to the Zion station review. Mr. Schwencer noted that the Committee had asked for a similar study on Indian Point 3 and he asked for Committee comments with study of Zion and its applicability to Indian Point. 3.

. Mr. Bender did not think the Subcommittee was prepared to discuss what the Power Authority of the State of New York (PASNY) should do with regard to an interaction study for Indian Point Unit 3. He noted that the Committee had agreed to accept the approach which Conmonwealth Edison had proposed for Zion as being a good way to start on the problem and he felt that Common-wealth had done a workman like job. He thought the Committee would like to review what has taken place and perhaps offer some comments before giving advice to PASNY with regard to Indian Point Unit 3. Dr. Lawroski reinforced the opinion that a list of events should be compiled by which with the effectiveness of the methodology could be tested. He fel t it should be done promptly in order that an early evaluation of the effective-ness could be obtained. Mr. Hickman felt that the Staff and its contractors could put together a list of questions to test the proposed methodology. Dr. Moeller's personal reaction to the Zion study was that the Fluor report seem to be thorough and they had looked quite extensively at the licensee event reports, but he was disappointed in the conclusions. He did'nt feel that the conclusions came near the quality of the rest of the study. Mr. Ray felt that the Commonwealth effort was a good first cut. Mr. Bender thanked the participants in the meeting and noted that there was a spectrum of view points concerning systems interactions and pointed out that he could not judge at this time what the full Committee might do with the information generated today. He then adjourned the meeting at 2:50 p.m. A complete transcript of the open sessions of this meeting is on file at the NRC Public Document Room at 1717 "H" Street, N.W., Washington, D.C. or can be obtained from ACE Federal Reporters, Ir.c., 444 N. Capitol Street, Wash-ington, D.C. 20001 - (202) 347-3700. F

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• NOT SPECIPICALLY ADDRESSED IN TilIS STUDY.

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COMP nw P PilYSICAL S SPACIAL 9 9 A I C IS I IS h AC. 35 IF g g V O Q Q h I I INTERCONNECTED I I I y ,Ig 4... ,,g...srsrtas INDEPENDENT CAUSAL HARDWARE IIARDWARE Ac, a cgm 53 coH ree com FAILURES FAILUhES a q o ANOTIIER COMMON COMMON COLOCATED SUPPORT INDUCED COMPONENT H E = H u m n.n E~rror ~ SYSTEMS ENVIRONMENTS bLIDE A-e.

I t 46611 NOT]CES Dated: October 3,1978. [7590-01-M] ~ ,,5 intermation; financfaJ data, such HUCLEAR REGULATORY

1. ries; and personsJ information con.

M. RagccA Warnra. COMMIS510N the %, eons.nerviduals nasociated 31th l gi Committee Management ADVISORY COMMITTIE ON REACTOR $AFE. is These matters are othin ex-Coordinator. a, (4) and (6) of 5 USC. 552b(c). GUARDS, $USCOMAUTTEE ON PLANT AR. j M,,mment in the Sunshine Act.y to close meeting: This determina. heing (FR Doc. 78-28320 Filed 10-6-78; 8:45 mm) RANGEMENTS I e as made by the Committee Manaae-The ACRS Subcommittee on Plant ,.. Offseer pursuant to provisions of n , con lo(d) of Pub. L 92-463. The Com- [7555-01-M] Arrangements will hold an open meet-ing on October 25.1978,in Room 1046, l v,e Mnnngement Officer wns delegated $USCOMMITTEE ON REGULATORY BIOLOGY 1717 II St. NW Washington, D.C. haathority to make such determina.gy the Acting Director, NSP. on Feb-OLOGY, C2L1UAR AND MOLECULAR Not-Generic Issue, Systems Interaction in Of THE ADVISORY COMAuTTEE FOR PHY53-20555, to begin its review of the NRC Igf 18.187T. Nuclear Power Plants. Task A-17. and ooy

sted: October 3,1978.

to review the Zion Station Systems In. hHng M. RDECCA WINEER. teraction Study. Notice of this meet-Committee Management In accordance with the Federal Advi-ing was published September 21,1978 g sory Committee Act, Pub. I. 92-463, as (43 FR 42806). i In accordance with the procedures I m Doc.78-28323 Filed 10-6-78; 8.45 am) amended, the National Science Foun. outlined in the FEntur. RzctsTut on dation announces the following meet. October 4.1978 (43 FR 45926), oral or

inU, written statements may be presented

• 335-01-MI by members o the publIC, recordings SescourTrEE oN Rtcel.AroRY BlowoT or will be permitted only during those

.scoMMITTEE ON POPULATION SiOLOGY Yar AnytsctY Con Trtz rom PnstoLocv, portions of the meeting when a tran-AND PHY110 LOGICAL ECOLOGY CzLLULAa aun Mot. tecum Biotoov.

script is being kept, and questions may be asked only by members of the Sub-heing Date and time: October 26 and 27,1978; 8:30 committee, its consultants, and staff. ?. &ccordance with the Federal Advi-a.m. to 5 p.m. Persons desiring to make oral state-j y Committee Act, ns amended. Pub. Place: Room 321. National Science Founda. ments should notify the des!gnated - l . n-463, the National Science Foun-tion 1800 0 Street NW., Washington, FederaJ employee as far in advance as uton announces the following meet-practicable so that appropriate ar-D.C.20550. Type of eneeting-Closed. rangements can be made to allow the Contact person: Dr. Robert B. Sanden. Pro-necessary time during the meeting for cc e rowurrrxx on PorULarloM BloLocT awn gTam Director, Regulatory Biology Pro-such statements. PsrsiotocicA3. EcoLOcY or THE ADv!soaY gram. Roorn 333. National Science Fou* The agenda for subfect meeting 7. Comultiss rom ENVLRoNM1 mal BloLoGY. dauon Washington, DA 20550, tele-shall be as follows: Wednesday, Octo- ? .e/s and time: October 26 and 27,1978; 8 phm 202-6324208. ber 25,1973, 2:30 a.m. until fAe conctu-

• fon of business. The Subcommittee 3

La. to 5 pan. each day. Pumose of subcommittee: To provide advice snar meet in Executive Session, with - rue: Room 338. National Sefence Founda. and recommendations concerning support any of its consultants who may be L:n 1800 0 Street NW., Washington, for research in regulatory biology, present, to explore and exchange their

• ^

I D C.2C550. h of mting Closed. Agenda: To review and evaluate research preliminary opinions regarding mat- ,1 J o;act person: Dr. Donald W. Kaufma!L proposals knd pro)ect as part of the seleo-ters which should be considered haciate Program Director. Populauon tion process for awards, during the meeting and to formulate a

8. ology and Physiological Ecology Pro-Reason for closing: The proposals being're-report and recommendations to the mm. Roorn 306. Nauonal Science Foun.

viesed include information of a propri-full Committee atten. Washington. DA 20550, tele, or confidential nature, including At the conclusion of the Executive etary pone 202-632-7317. technical information; financial data, suca g g g Pupose of subcommittee:To provide advice as salaries, and personal information con-ud recommendations concerning support individuals associated with the cerning foe research in population biology and proposals. These matters are within ex-the Commonwealth Edison Co., and semds: To review an'd eratuate research emotions (4) and (6) of 5 USC. 552b(c), their consultants, pertinent to the r ntological ecology a Government in the Sunshine Act, agenda items. The Subcommittee may Poposals as part of the selection process g8 Authority to close meeting This determina-then caucus to determine whether the g' swards, uon was made by the Comrnittee Manage-matters identified in the initial session i g } "rwd inct nf r o a o m'nt OfficCr Duf5u*nt t Dr VISf* have been adequately covered-and including tion Wdi of Pub. L 92463. The Com* whether the project is ready for f

• ry or confidenual nature s

Whnica! !nformation: financtai data, such m tee Management Oincer sss elegated review by the full Committee. 's salaries and personal informauon con-

• * "Uth TitY t ** k ' 'UCh * ** '" I"**

Further information regarding "C** 3#* " topics to be discussed, whether the I ermaris individuals associated with the D gh**C ^8 rnecting has been cancelled or resche-l 8'coosata These matters are within es. "Dtions (4) and (6) of 5 USC. 552b(c). duled, the Chairman's ruling on re-Omemment in the Sunshine Act. Dated: October 3,1978. quests for the opportunity to present Amortty to close meeung:This determina. oral sf.tements and the time allotted M. REBECCA WWKtIH therefor Can be Obtained Dy a prepaid bon was made by the Comm;ttee Manage-awnt Officer pursuant to provisions of Cbmmifue Mangeme'nt telephone call to the designated Fcd-

• tion totd) of Pub. L 92-453. The Com.

Coordinafor. eral employee for this meeting, Mr. Ntet hianagement Officer ats delegated Robert 1. Wright, Jr., telephone 202-tae authonty to make such determina-p 34 634-3314 between 815 a.m. and 5 p.m., by the Acting Director. NSP, on Pet. e.d.t.

• • 'y 18,1977.

FIDERAL REGISTit, VOt. 43, NO.196-tut 3 DAY, OCTOSit 10, 1973 T Y/NU ? I

46012 NOTICES Dated: October 4,1978. (1) The probab!c effectiveness of the (3210-01-M] JonN C. Hortz. Import relief as a means to promote Adttsory Committee ndjustment, the efforts being made or OVERSEA $ PRIVATE INVESTMENT Afanagement O//icer. to be implemented by the ladustry { 1FR Doc. 78-28556 Pued 10-4-78; 8.45 amj concerned to adjust to import compell-tion. and other considerations relevant (Redelegatten of Authority No. A-78-101 [3190-01-M] to the position of the industry in the i Nation's ceonomy; AUTHCRity c7 omctts OFFICE OF THE SPECIAL (2) The effect of import re!!ef on g ag,,;,,, 4,,% REPRESENTATIVE FOR TRADE consumers and on competition in the By virtue of the authority vested in NEGOTIATIONS domestic markets for such articles; me as Acting President of the Over. (3) The effect of import tellet on the seas Private Investment Corp. (the rtADE PouCY $TAFF CowMTTts international economic interest of the [edbgation o A 0 s.tkie.vien of Public views United States; orty A7-Pursuant to section 201 of the Trade (4) The impact on United States in-OPIC Redelegation of Authority No. Act of 1974, on September 21, 1978, dustries and firms as a consequence of DL/D-(71)7 OPIC Redelegation of 4 any possible modification of duties or Authority No. A-74-10 OPIC Redele. tafes I gation of Authority No. A-75-Il i e td ernation.1 T d other import restrictions which may (!! 703.15, 703.30-703.33), OPIC Rede. Commission (USITC) on the case of result from international obligations legation of Authority No. A-78-13, a Certain Fishing Tackle (Investigation with respect to compensation; hereby redelegate authority as fol. No. TA.20134). The Commission sub-(5) The geographic concentration of lows: l mitted a report containing an affirma-imported products marketed in the tive determination that as a result of their being designated as eligible for United States; THE INSURANCE DEPARTMENT (6) The extent to which the United fr t q' hu ,,tf j[r Oy States market is a focal point for ex-CENEM-p (1) The Insurance Department of artifical baits and flies, provided for in ports of such article by reason of re-item 13t.60 of the TSUS. are being im. straints on exports of such article to, the Corporation is hereby established ported into the United States in such or on imports of such article into, as the department primarily responsi-increased quantitles as to be a substan-i tial cause of scriaus injury, or the third country markets; and. ble for the adrninistration of the Cor. threat thereof, to the domestic,indus-(7) The economic and soefal costs poration's insurance ar.d reinsurance authorities under section 234(a) and ,1 try producing articles like or directly which would be incurred by taxpayers. (f) of the act, 22 U.S.C. Sec. 2194(a) j competitive with the imported arti. communities and workers if import and (ik The Insurance Department i relief were or were not provided. a aded by the Vice President The Commission finds and rec-om. The Office of the Special Represent-g mends that. to prevent ur remedy the serious Injury to the domestic indus-ative for Trade Negotiations chairs the try, it is necessary to suspend for a interagency Trade Policy Committee VICE PRESIDENT roR INstTRANcE structure that makes recommenda-(2) The Vice President for Insurance period of 5 years; the designation of is hereby delegated the following au-f [gg I b and tions to the President as to what e Igibje action, if any he should 'take on re-thorities-3l o the SU for duty free treatment under the s@mW W 2e UMC under (a) To' authorize and issue contracts i of inswance or reswance conng GSP' thin 60 days of receiving a report section 201(d). In order to assist the risks of the type described in section Wl i Trade Polley Staff Committee in de-234(a) of the act. 22 U.S.C. Sec. g from the Commission containing an veloping recommendations to the 2194(a), in the name and on behalf of g affirmative determination, the Prest. President as to what action to take the Corporation, or to the ext t dent must determine what method j and amount of import reilef he will under sections 202 and 203 of the the Corporation is duly authorized to provide or determine that the provi-Trade Act of 1974, the Committee wel-act as agent in the name and on behalf a } sion of relief is not in the national eco. comes briefs from interested parties of any associadon. corpwadon M nomic interest, and whether he will on the above listed subjec'.s. (Addition

• other entity, to execute and enter into l

direct expeditious consideration of ad-alinformation on this case is available in the name and on behalf of such as-I justment assistance petitions. in USITC report 201-34.) sociation, corporation or other enuty In determinmg whether to provide import relief and what method and Briefs should be submitted in twenty any such contract of insurance or rem-amount of import relief he wiis pro- (20) copies to Secretary, Trade Policy surance, provided that (i) no such con-vide the President must take into ac. Staff Committec, Room 728. Office of tract of insurance shall cover an in-count. In addition to other consider. the Special Representative for Trade vestment, as described in the terms rs., deem relevant, the fol-Negotiations, 1800 0 ~ and conditions of any such contract, at ay Street NW., that exceeds $10.000.000. (11) the maxi-Washington, D.C. 20506. mum contingent liability of the Corpo-To be considered by the Trade ration, or any such association, corpo- 'The Commission determined that snelled Policy Staff Conunittee, submissions rati n c ' other entity, with respect tJ hooks fishing rods and parts thereof, and shoW k reccW in be Nee of W any in vestment insured under snf itshinc rects and parts thereof: provided for Special Representative for Trade Ne-such contract of insurance shall not in items 731.05: 731.15. and 731.20 through 3126. inclusine. of the Tariff Schedules of gotiations no later than the close of exceed $30.000.000, and (111) the mu!- business Priday, October 20,1978. mum contingent liability of the Corpo-(ln btEes ration, or any such association, corpo-rt d o th creased quantitles as to be a substanting-Witt. taw B. Kru.y Jr ration or other entity, with respect to su came of wnous injury, or the threat there.

Chairman, any such contract of reinsurance sha or to the domestle industries producing ar*

Trade PolicySfaf/ Committee. not exceed $30,000.000; l tic en line or directly competfuve with the IFR Doc. 78-28352 Filed 10-6-78; 8:45 am) ea gem e M Imported articles, ing liabilities unocr section 234(aN l e of the act, 22 U.S.C. Sec. 2194(aA FIDERAL RIGl!TIR, VCt. 43, NO.196-TUE5 DAY, OC70Bf t 10,1978 I t e lI I

DETAILED SCHEDULE PLAf1T ARRAtlGEMEllTS SUBCOMMITTEE WASHItiGT0ft, D. C. OCTOBER 25, 1978 8:30 a.m. EXECUTIVE SESSION (OPEN) 8:45 a.m. MEETING WI711 NRC STAFF AND ITS CON'IRACIOR (OPIN) IhTROIUCTION - John Angelo (DP!!) 5 min REPORT ON THE S11]DY OF SYSTEMS IhTEPACTION - Wally Cramond (SANDIA) 1 hr QUESTIONS REPORT ON WORK BEING PERFORMED AT ORN1-Mat Chiramal/ Jack Anderson (DCR) 1/2 hr QUESTIONS 12:00 noen Il]NCH 1:00 p.m. ?!EETING WITH NRC DIVISION OF OPERATING REACTORS AND CO'010hTlEALTH EDISON COMPANY (OPEN) Introduction - Gary Zech (IDR) 10 nin Zion Station Interaction Study - Cordell Paed (Com Ed) I hr QUESTIONS 2:45 p.m. CAUCUS (OPEN) 3:00 p.m. AIUOURN fTTAlNN5NT

A ^ h=~)/S t. ~~ t i G,y..., c ~ } SA;RA.'.MNTO.'. tun 10 pat. UTit.lTY DISTR:07 C 5201 S St ett. !!n 113.7. Sac amant:. tafif:rnia 95213; (MS) 452 In: u f. March ll, 1973

• ^

t- -o Direc:cr o f Regulatory Operations 03 ATTN: Mr. R. H. Engelken IdC !2 q NRC Operations Office, Region V 04' EI.. 7# 1990 N. California Boulevard Walnut Creek Plaza, Suite 202 Ct, - uN I .= Walnut Creek, California 94596 r a _. =. _ ' - =. u Re: Operating License DPR-54 3 -'d Docket No. 50-312 A E Reportable Occurrence 78-1 a

Dear Mr. Engelken:

In accordance with Technical Specifications for Rancho Seco Nuclear Cencrating Station, Section 6'.9.4.1.b, the Sacramento Municipal Utility District is hereby submit:ing a fourteen day followup report to Reportable Occurrence 78-1, which was initially reported to your of fice on March 20,197S. On the date of that initial report, a grocad short in the plan: non-nuclear instrucentation resulted in a reactor trip and subsequent RCS cocidown which exceeded limits set forth in Technical Specifica: ions Figure 3.1.2-2. This followup report will describe the sequence of events surrounding :he incident, detail how the instrumentation loss precipitated the transien:, discuss the analysis perfor=ed on the transien: and its effects on the RCS, and set forth the corrective action that has and will be taken to prevent recurrence and to insure the integrity of plant syste=s. Secuence of Events Prior to the cooldown transien:, the plant was operating at a s:cady state power level of 70 percent, with all four reactor coolan pumps operating and an average reactor coolant sys:es te:pera:ure of 332*?. Shortly before 0425, a control room operator began replacing a burned-ou: light bulb in a back-lighted pushbutton switch on one of the con:rol consoles. The DC pcwer for this switch is provided fro: the "Y" por: ion of the Non-Nuclear Ins:runenta:ica (NN!-Y). To change ou: the light bulb, the light assenbly was pulled ou: fr:n the panel and flipped drun, e>gesing :he bulbs. During :he change, a bulb was dropped into the open ligh: asse:bly cavi:y, crea:ing a sher: :o ground. The current-limiting and undervol: age pro:ection for :he SNI-Y DC power suppli-:s ac:uated durins the curren: sur;e, cut:ing off AC po er to all NNI-Y OC power supplies. Preliminary investiga:icas ?. ave shavn : hat app roxicatel- :wo-:hirds of :he NNI signals -(pressure, terpera:ure, letel, flew, e:c.) vere af fe::ed 7TA'C/fMEN7~ 7 soc 70300 rv \\

Director of Regula:ory Operations March 31, 1978 by the pcuer loss. The' erroneous signals provided both the Con:rol Roos and the Integrated Control System (ICS) with faulty information. The ICS, attempting to natch equipment output with plant requirecents, reduced nain feedus:er flow to zero in response to faulty signals. The reduction in feedwater flew caused RCS pressure to increase, with a reactor trip occurring on high pressure at 0425. In the period following the reactor trip, the operators were still harpered by the lack of instrucentation available and by equipment responding to inaccu-rate signals. For approxi=ately nine minutes following :he trip, pressure slowly decayed in the RCS, recaining at apprcxi:ately 2000 psi. It has been 3 postulated that pressure recained fairly constant during this period due to the cooling provided by =akeup flew into the RCS and to the lif:ing of a Pressurizer Code Safety valve below its setpoint of 2500 psig. An auxiliary feedvater pump had started on the loss of feedwater flow, hcvever, the auxiliary feedwater valves re=ained closed in response to erroneous Once Through Steam Generator (OTSG) startup level signals. These two signals were rendered inoperable by the NNI-Y DC power failure, the "A" steam generator level signal drif:ing to =cro indica: ion over a nine-=inute period while the "3" steam generator level drifced full scale. The actual plant conditions showed that both OTSG's went dry during :his period. When the startup level for t'he "A" OTSG drif ted below the low level setpoint, the ICS opened the auxiliary feedwater valve ad=it:ing water to the shell side of the "A" OTSG. This inflow of water created a heat sink for the RCS resulting in a rapid pressure drop. The operators also cay have, increased the cain feed pump flow at this time, providing another source of feed flow to the "A" steam generator. The rapid drop in pressure took the RCS through the Safety Features Actuation Syste= (SEAS) setpoint (1600 psig). On SEAS signal, both auxiliary feedwater bypass valves opened which began the filling of both s:eas generators with water. Until power was restored to NNI-Y approxi=ately one hour and ten =inutes after the reactor trip, the operators con:inued the injec: ion of auxiliary feedwater that was started on STAS signal. It did not appear that any RCS te=perature indication was reliable, so the opera: ors =aintained RCS pressure as well as possible utilizing the pressurizer level indica: ion and the RCS pressure indication that was available. Con::al was obtained by adjusting high pressura injec: ion flev. The pressurizer hea:ers were act available due to the NNI power loss, preventing their use for pressure centrol. The continuous injection of auxiliary feedwater resul:ed in cc:plete filling of both steam generators, af ter which water began to enter the steam lines. This large heat sink continued to cool off the ACS, although the operators were not aware of sys:em :e:perature. When the pcwer to the NNI-Y OC power supplies was finally res:cred, :he operators realized :he RCS tempera:ure had dropped :o arcund 235*7, which placed the plant in the restricted region of Technical Specifications Figure 3.1.2-2. I= redia:e ac:ica was taken :o re:ura :o :he per=issible

e3 _,..* - : r Director of Regulatory Opers: ions March 31, 1978 operating region, inclu' ding spraying the pressurizer to reduce pressure, keeping three RC?'s operating (pu p combinations were changed) to increase temperature, shutting off auxiliary feedwater flow, and draining the CTSG's. Non-Nuclear Instru=entation power Loss The short caused by the light bulb drew excessive curren: through :he 24-volt EC power supplies which service co=ponen:s in NNI cabine:s 5, 6, and 7. The power for these cabinets is designated NNI-Y, wi:h the power for cabinets 1, 2, 3 and 4 being designated NNI-X. The four power supplies for NNI-Y are opera:ed current-limited w1:h a setpoint of 7.5 a=ps. The subsequent reduction in voltage caused an undervol: age conitor to opera:e, opening the two shun: breakers through which AC power fros inverter D and inver:er J is supplied to the DC power supplies. Loss of these power supplies =eant that every co:penent in cabinets 5, 6, or 7 operating on DC power was not fune:ioning properly. An NNI signal could have been affec:ed two ways be: ween its source and the receiving co:ponent. The signal could be interrup:ed completely due to a contact opening on being deenergized. Because =cs: of the signals are -10 volts to +10 vol:s, this would have resulted in a =id-scale reading or in soce cases a reading anywhere between -10 volts and +10 volts being transmitted to the indicator or sent to the ICS as an ac: cal plant para eter. If a signal conditioning co=ponent (buffer a plifier, square root extractor) was affected, this would have eant that the desired conditioning would nct have been performed on the signal or that the component might not pass the true signal, resulting in erroneous values being sen: to the indicator or to the ICS. Since signal paths in the NNI are not restricted to either the X or the Y cabinets, about two-thirds of the signals passed through at least one co=ponent in cabine: 5, 6 or,7 and were thus rendered invalid. These spurious readings had several ef fects. It was difficult for the operators to ascertain which of their indicators were valid, given the changing plant conditions and the wide varie:y of possible errors : hat were in:roduced. Only a select few parameters were known to be valid readings, and the opera: ors had to control the plant based on tha: in fo r=a tio n. The second effect was : hat spurious signals were fed into the ICS, so equip =en: was operated au: -*-3-=lly, without regard to ac:ual conditions. The first evidence of this was the runback of the main feed pumps :o :ero, which caused the reac:or crip. La:er, the auto =atic actions. involved with adding feedwa:er to :he dry steam genera: ors hindered operator actions and precipi:ated the rapid depressuriza: ion leading to SFAS iniciacion. Power was finally restored :o the NNI-Y when operators realized tha: :he shunt breakers were open. Restoring power re:urned the act-nuclear instru- =entation to opera: ion, perni: ting proper eperator respense to :he plant condi: ion, which at this ti e was outside :he permissible operacing region. e

%n.. i t .i . Director of Regulatory Operations March 31,19 7S Transien t Analvsis There was very little per:anent record of the plant parameters during the transient. A =ajor source of infor ation was the Post Trip Transient Review, which prints out selected cc puter poin:s periodically following a reactor' trip. It was not possible to ex:ensively analy e this and the other data available (recorder outputs, hourly logger typer, e:c.) during the transient. Over a period of several days following the inciden:, engineers were able to trace which signals were valid, deter =ine what equipmen: operated at which times ~, and then interpolate to arrive at a te=perature trace fer the RCS. Ic=ediately following the trip, te=peratures slowly increased while pressure decayed away, caintaining apprcxt ately 2000 psig.. At approxi=a:ely nine =inutes af ter the trip, feedwater began :o enter the "A" stea: generator, resulting in an RCS depressurization leading to SFAS initiation. With the full auxiliary feedwater flow initiated by SFAS, RCS te:perature fell from the high of about 595*F to 285'? in the span of slightly acre :han one hour. This cooldown ra:e of approxi=ately 300*F per hour is well above the permitted rate of 100*F per hour stated on Figure 3.1.2-2. When NNI power was restored with the RCS at 285*7, =easures were taken to bring the plant back within li=its hy increasing te=perature and reducing pressure. To assure that all co:ponents of the plant were not da: aged by the transient, available infor=ation on the RCS pressure and terperature, OTSG pressure, te=perature and level, feedwater flev ( ain and auxiliary), pressurizer level and other relevant paraceters were trans:itted to :he reactor vendor, Babcock and Wilcox, for analysis. On March 23, the District received a response fra: B&W indicating that their analysis was co=plete. Af:er evaluating the effects of the transient on the reactor vessel, the reactor coolant piping,, the pressurizer, the OTSG's, the fuel asse:blies, :he RCP's and seals, aad :he control rod drive techants:s, it was reco:: ended that Rancho Seco be per=it:ed to return to power, under certain specified conditions. The analysis was subtitted to the Office of Nuclear Reactor Regulation, and on Farch 24, they agreed that Rancho Seco could return to opera:ica, providing the conditions centioned in :he 35% let:e were fulfilled. When the Dis trict receives the co:ple:e analysis from 3&W, a copy will be forwarded to the NRC Regional Of fice. Corrective Action The 12:ediate correc:ive actica taken f llowing :he rapid cooldcun was to return the plan: to the permissible opera:ing regica of :he Technical Specifica: ion figure. The unit was then kept shutdown while data was ga:h> red and sent to 35% for 2nalysis, and further invas: iga: ions in:o :he inciden; were cade at the planc. The F.2nage:ent Safety Review Co==i::ee hcid a =eeting on the subjec: on March 21, and issued several direc:ives. A cc =it:ee of three engineers fro: the elec:rica', rechani:al and nuclear disciplines was

v T Direc:or of Regula:ory opera: ions March 31, 1978 appointed to deternine 'the circu= stances leading to the shutdown, to deter ine if the emergency shutdown systems are adequa:e or whether some redesign is indicated, to evaluate :he significant para:eters involved in the ecoldown to determine if any component da:sge had occurred, and :e reco= end corrective actions. The findings of this ec==1ttee will be relayed to the NRC Regional Office when they are available. The PRC was directed to review the circunstances connected with the incident, and to review the 35W recce:endations which were forthcosing. The PRC was to recoc=end a re: urn to pcuer if they agreed that the recoc=endations were acceptable. If any disagreements developed, no return to power was permit:ed until the >5RC reviewed the =atter and determined appropriate action. 'Upon receipt of the 35W reco==endations, the PRC reviewed them cnd requested that a special test procedure and a casualty procedure be written to assure ce=pliance. PRC concerns about the following i:e=s also had to be sa:isfied prior to scar:up: 1. A question was raised concerning possible dacage to steam lines from the injec: ion of water, so the lines were checked for any defor=ations. 2. A 2255 psig leak test was perfor=ed on the RCS to insure integrity. 3. The overvoltage trip setpoints on the NNI DC power supplies were increased from 27 volts to '29 volts to prevent spuricus trips. The special test procedure addressed the condi: ions i= posed by 35W, such as reactor caneuvering limits for the first s:artup, increased surveillance of the loose parts moniters for a week, an operability check of on-line and redundant NNI instrucentation, and daily surveillance of tha primary and secondary radioche=istry for a week :o check for leaking cocpenents. The casualty procedure was written to provide required opera:or actions for restoration of NNI power following a trip similar :o that experienced. The PRC also co==itted to having a procedure written by April 7 giving opera: Or instructions if NNI power cannot be res:ored. Current S tatus Following SRC's review of the 35W analysis of the ::ansient, they agreed that a return to power was acceptable if :he 35W rece :endations were followed. On Friday, March'20, :he rea::or was taken critical, and the initial power ascension was begun. The ene-veck surveillance prcgrams required by 35W are still progressing, and the S!? will be reviewed up:n cc:pleti:n. The s:artup was normal, and no unusual circurs:ances developed tha: would indica:e damage to reac:or syste:s as a resul: of :he ::ansien:. Respec: fully, 1 <7 a . j h C. E.&u /f". v J. J. Sk:ticce Assistan: General 1:anager JJM:FTE:sc and Chief Engineer

i h TE NestI3 s30 N ov. 7 /976 msTueuTro To r,cRS EENTES M. 6ende/, chai/ir:an PInnl Arranc,ctn>nli Jube ominittee. ce/;5 mee/ing cl /he Piand Arranyernen/s Al /hc .%bcur,nitice. Ihe in >t nc-licn P/nn. n-n was ene al lhe iiems <eviccJed. D7e ecrnrnenla lc lclltW weIl be c/ infere>l aho it. Jhe Rrws and we>la,jhe'ese s ubccina), fless The Tnsj & hon Plan. /icu]>icn d. <cn/n&1s Jhe Lilcwinc,: En'?"tlEE?'Is?ac D:e ptoblein /c beresolved by/hi3 /o3h HOV 131978 is Ic eslohlish a.syslemo-liL process k ^" # 9MW2i i i3i4N nnpocl en vnn.'l' #'"cos o-lherplant sysle !si l2 _T Revisicn i cilhe Task Relien Plan re,slales lhejucblevi: Tlie probleni Ic he resclved is 40 idenlil'y wirere lhe preseni desi}n, anal is and review p p<ccedures rnay ncJ aneplobh acccon/ k/ polen/iall9 adverse sys-lem infe;roclisns recornmend Jhe reyv/alcr oc/dn /hal sho t Id be fal<en le rec li[y eliciencie.s in lhe peccedures." d B lhe langua7e c/ I?ev. o,lhe Tasi iuculd be y expec led le develcp procedures where b n Inr7e 7 von lil1 y o{.inferaclicas ivov/d be oxpo. sed by iie review prc cess. l //rraimwr D

R//ho uq h -lhii is a. cominendo h/e o h,'ecl ve. 77' i> even,ncre impor-lon/ -/hn.l tt bu3Is he erlobinhed Jc di,pcse c l in~/eracl ions, be>)h reoI o ad pv}en-lid I, wh,ch o e c nIveadq Je nown /c enis-). The >'eviseil In ng uag e :een>s

4. sa y lho) lhe -lnsk wlIl cleol ol>c tedh r.Jesigr, pvo c lit e s rluch hn re produc ed ih es e ven I a nd pu den //a I n 1evo c libnt, i

/1 is lherelc, c evc < / h u h:le Jc, idenh/ some ev i,Ji; p<chlern a<en 3 ond Io int vaye ~heI he.1he lnsk u.,, lr,4 n i r e.scluJic n cJ en sliac7 pic bleurs. silsmpi le esin bl,sh a bn > 15 fo < Som e decjo ee o J se,sicin i,derodi,l>n i > u, m, e i o'o >!e, ;w eve < er lne in>pm / en sn fel w, n depend Ic th car p,c h,, n. /; / el Jhe resull.,3 deg ree c ) decp adolion c/ occu,ronte o,ui j.,.oleclih,,. Th s wa s > e c c9 n. 2 e d n o, !., l '> e 7.o ~ Ic / i., de<elopo>ei.,J p, cyto,n n,id,vollie/ )han 14,v;7 e w;/t, / picho b;I;lier <>nd (coseovent es, rJesign p< nclic es we> e > dup} ed je n ocid io der n:-lrons. Y ese tn, > be slo.!e,) I li i,, ,o e i e, n n,

d. / 'c w s,

i l g,,,,l vej be p,, v,, e,j n. Pa vd ec t icn o.u,, <ce ra Jo SaiI I-c/ l're.saine renici?.or a s l!> e res ull . sing e (cn>f) fniIvre, /nsl> vmenla oI a l herelc,,e mv>J nud be shoved, bi /v c;en e/al, J he evenl wh,el, r);3a hle s o r deqrodes p<c-lecl ion musl ncl also '<n use picdeclibn lo be needed,

c. The aclkr, of one projec/sve halu e, e.;,c.Jire, realc> spu,1cus, should,.-l n /cida ble, no J analher prodecl& e <>cidn k h e n eeded. en use These principles wove nol un&ersall adopled b y Jhe developmenJn l reacle/ prog,oins, howe /e/ Jhes e en<ly ren c lcrs incIvded con-Inis smenl {eislv<es a hich f rovided adr),*bienn) r/ep]h cd r}elense. 3hculd helh <virlrci and pialec.)&n inil,dhe res vid wcv/d be con loinerl, Idowere/ ns renclef ceres incrense.d in size, if beconie ren IQ.ed Jhal n. mollen cor e couId noJ he ccndoiner) n nd Jhc delen3e Jhe prodecdian sysdena. As a resv// depended <>nlirel on ob RTw5 eoneern s, in; liga da,9 oolvies J ho e been pwpas eA ~l'ic h would, o,s Snilure lo se rom, <esJo< e J h e l exo,nyte Jhe u.nsling o us e sysdenis defense in elep h, As h on wdh adec, unde yiess v,e relie J ond }se assuroisie o J promp t aux. feedwa ley In:liolicia, wovid b e a ble k klerade Ja e inosi serere dvansiend I. e., /oss c.J Leedwnler, Josi os Jhis problem seemed L be o) Jhe poi,,I nsed dhe RESA/L 4/4 cl resolu-l ton, lue sdincy ho us t pic /,rjeginled Predeclion Sysdem wherein Jhe insdev<nen/s and loylc ler con-lrol, prolecdkn. nnd ESF ha/e been Sir 19 e Sys]enh f4cre specibc o ll -lh e incorpornled inlc n / / P3 inclades /he ESF feolu<e, Feedwn )e/ J.soJnlibn. Jhe Renclor siwl</own, and Avx Feedwnlev idrlinllon. Tisis

mviles on inderor/ nan whici, is polenfialI. n>cie sc> riot <s ihni, lhe siinv//aneous lailese c l <cnIv,.c I o n<>l,)rclecli cr1. The concern wc vid be the spu ncvs an]lialicn c( Feedwale/ Isolalkn,(an nnlic;,.a-lei) 7;-ainien)) Icgelhov a a lh -lhe y u in;lin le.smo, a nd nc x reeclu <> le,', i,, lhis l ina I>,1;I snanner-lhe lhvee /creh cs / delenw in dep/h, te nlvc /, reaclm' ih u }c/c k a t, a nd A Tw 5 nii li} old io woul<] he de[co-led isa a sing /c even], Il is an/cresllny lo cci,sidev /he siqn,Nc ant e c / lhis. Il had been prepcsed tho) Independen), dNe> s c .s h t. ldc u su,rlenn he oppliid as del' nse agonusl e Jaila, e /c sc, ani, hc we<W /he <eg vl>ied i idepen<)onc e ci docers e sy slenn a culd be diflit ell L cl> Join and k denicnsl< ale. ns an nllernaln e 4 !'e A Tw 5 inilq nlic n >y5] ems w we p<cpcsed which, ccnsis fin 9 eSsendinll9 c,1 added <ol, el <apo< i/, nicoid oc m heven /15 due<ie and th e<c k /c in dcpenden /. Ne u. h9 Jhe i,ucqc <alic n c I ccnl<cI, rea c h/ shu idc u. o ons A 7w s mili} a Ikn inIc sn og h syslen>, a e n> e a back a l sy c o <e c ne,

Allhet:c h lhere ion be ne &c e.bl a > le lhe .sericusness c / Jhe ccn5cc,vences c { lhe Inll1fe c/ lhis Sysler71, we nte erili7ely wilhoul atuidanc e as le ihe p<c,hvb;lil c/ iis cec vwonec. The syslem y anc> c pi c c es sc > s and di} ila l schlu a > e inc lu de s Sc / w hie l, w e lins e oc expe> ienc e ten >pos a ble St-liie ene /In.d ten /u, q ef expenen< e w.lh convenlic. n>( ha, dw a <e o rid Iec hniej ves, we con, hc w <>vw poslvic> lc o nicc honi> n, Js, /nilure sv97esled b exirlih q expevient e, wherein und 2 p, c9, oins wa vId, i7, cvvc r, he in s e r led,Un Ihe un d l Inleg <a led Pi clec /d n 5, l ea 7., 7 T/u s reprewn/5 a ruevend piol>lem ii, n hk h 41,e lh v ec In, pi s e i ele le>>s e i,i <lc,3 /J, h<> ve be ei, l,uc,pcraled ;nic lhe I,de9<nled padeclic,, s,s leni. uis en ihc defense in dep/h, which rush,no vil reddes is, indep enden) di?ers e se,.s4pms,is <cinbined u,la ex siny te sys l em,ii becon;es di ((ic vll le dernons /va le Ih.,I Jhe dej)]h c/ defense is maininined. hinsnicch as n. ha3n k, resolulicn oJ Jhis problem is ure,on/ly needer) the <jucslic,a co uld s erve os a lest prchiern lu c'en /ve> le the <>flec-lG'eness cl Jhc pecposed 15 / pen In lwo elibn 7 nielhado hg y.

n//hou9 h lhe inechamsm for foiIva o/ Jhe iPS is uncertain, Jhere can be no douhF as le Jhe sere,,/'l cl +he cvasec,vene es.12 / Jhe oJhe< ena e>l Jnc.3,peclev,n,, Jhe probab;hl ond mechan;uns a cu<<en) problem where'm Jo/ /rs!evocitur1 c ye well es-fohlished bu lhe conseguemts he i/ luslya bed f.> Jhc c><enh ren)a s n u n' e(loin. Thi s ca r1 ad 14 Bile.hinsert arvinl2o'on tuhere liw t h olo Non of loJJ od onc d.C. hv.5 cavs ed Subs la nkio $ equependrN dumoc? a nd ehyod:,lic. a nd o f Jhe.sarn e li,n e ca s > e d et s vo,v ci residva! nea l reinova l copa behl y

• ln bo]n ea'Cnbb sys-l erns wesc beinq -lcsled c /

serviced. In one insJonce lhe opvolvt in; led le -lerminade Jhe des) and as a resuil Jhe ha lleg cha,ge was exhausded) in Jhe olhet, ]hc operalc/ htminoled Jhe opera-lior, bu) openc'd Jhe wienc; cucud h<cakor, Jhereb tioinlig 4he dc bus, y /n bo)h e<en/s dhe opevole/s we<c una ble k a cire<J ciainage. In cric cose lhe hn fleiy u.?.n allowed lo become corr,plelel discha/cf ed because c) y e hdeep<eJ woming symplo, lhe opo<oleis inabild l /,, Ji>e olhe/, Jhe annunckolo/ which wcold idenhly 4 i,e 1,oubte, deyended or, d. c. fe < 14s aperaJ&n,

In bodh cases -lhe noc/c/ scromined al/hcugh nel b design indeirl. In one case il was 4he y foil-sale charoc}erislic. of Jhe scrain betr>l<er5j in lhe c/he>, lhe underfre7vence; relop, aWeh de pend on r). c., ca used 4he main ci/culnhng pum?5 Ac Inp, Th e loss of d c. on hch mom; of lhe plan l$ sysdems clepend, by cn usinej.s crom, in ) vin e a.us ed 4hese 5ysden)s lo be needeJ /er residual head removal. ln hcJh even}s cuben Jhe reoc lc/ sc vommed, one o((.sibe n.c. source suas losh, nnd because el Jhc ; nab;h k cpera-le cravd breobus w t-lkcvl d.c., one diese! genua h/ in ea ch ens e becorne u,ia., n a la ble. Becau.s e cf inal>tllly le cpe< ole cucuil haenkes, s equ,pmen] damag e resulled. In one inse 4he Jua bine bearings were los] because o f mo b;I;l le darenneci l l,e mop eval >le d. c. d vi ven o, I ump, n no reslove Jhe f o.c. pu,ng, In Jhe 0-lhe/ cose Jhe dies el enen k/ g wn.s vnse/ les} nnd in oge<a lion o / lhe J,,'ne, Becavse of inab;hh k dOconnecd the genevolov, ;f a ttempded k d<ive lhe main generalc/ os ~ moi < and was des /vcyed in Jhe a llein,>l Ts

. in bc}h cases correclNe measu<es have been appikd h prevenJ repehlibn a5 clama7e la ef uslMenb. ln bclh cases dhe feo v/23 whthh caused }he unin} ended and une;ipecler) scrom remain uncorrecled. Add;/iinal equipenend for residuni head removal vernamed opemble lhus meelincy Jhe single failure requiremend, so lho) no basis exisIs /cv reyui<incj remedhI mensures - b lhese evends lhe conseguences of a single hwnan eucr have been magni /Nd he, lhe mleracbcns. N is liket Jhod if all of Jhe pcssible inderaclions we<e Anown, such en euhen c-lher sysdems are vndes' /esi n.lJhe same din,e,or when adddiona/ operndo/ e rors are tommiffec), r il mic;hl beccme apparen} /hnd opph2adicn ol lhe single faiIure crilcricn iuovId be inade9uale and,u.~,Ihcvi la km; in/c acccr d Ihese inle/nc/kns, prc/>o b;Iislic. nssessmen}s wouIr) he invaho!, Neve again il wculd be use/s/ Jo leslJhe pc>rlormanc e c-( lhe lideroclien melhcriclop by a Hemp-linc to idenhl allpon)b;lihes nhe/c /cas o-l a d.c. bus y tuov/d cause a seram, and oIso lo idenlif ollpossibil.las y wh ere lo ss 0-f d. c. wo uld de<j m de residc o l h en -l remoraI capo hilil. /nasmuch a 5 many olen/ioI y p i;rleroclibn3 are tuell hidden, Jhii rov /d be a chollenge to the p<oposed melhadolo79

Cne erample of a hidden m ec h a ni s <n ,tc < infero clibn is Jh e in ler/cck., dis cc<ered a i c sle/ y c<eek n fder.severai tjenes of operadicn, wh,2 h hnd ils condo c l.s o n lhe morable pc<lihn al a cirevil h<en lier' and nhick preronded opern-lIcn el Ihe redundo n l } rain nhen lhe circuil brenhe/ was ra cL ed c.A c(,cct,libn. The in/er/ce h wa s inJended 5 a pre <es,) cpera /ibn o { bcJh trains aJ Jhe so<ne l enl J,;ne, bs) wdk lhe b een ker ro cked cul, had h linm1 becam e in oporo ble-Si}n; /n /l Jhe S<cwns Fer pdci l<ghJ circuils, en fo;/s,e, ca used Jh e cacv;l h vea k ers lo he <noinlained in -lhe dripped tend llicn. Th e circo l arranc, emend con 3 'in/ ended on/ ha n:s use a lhe chilil k J r,p on demand. /n beJJ, kslantes 4h e inl era c-lidn3 resulled l<cm welI hidden and unsuspec-led n, ensures in/ ended k p<clecl equipmend, a nd w e<e dis cc rered cn ly when poik<rnoine wn 5 d erna nd or) u n d o / un us v a I c i/c om slo n c es, In summary, i/ is p<cposed Jhn ihe idendificalibn el oddificnoI in-leroclions would be use fvI,4hnd Jhe idendi(icoliin of hidden and vnSuspeclrr/ rneclianiJnn,incJudonj in Ievocli6ns wi}h lhe operolo/, wov/d be even rnere vie /vl. Nousere/, in considerali6n 0 f Ihe in/erocli6n]

alread known lo extil, cl Jhe staded o bjecli&es of Jhis Task Acliin Plan, lh e m od irnpula n-l wc uld "Ic reccininend lhe requ/al cry acliin /ha4 should be be -la k en 4c rechl de fre.icirci es in J h e, orc ceidvves ',' AHo c hed nie eSJa ys o n fail Sa fe a nd Jhe Sin g le t=syc/. whic h ma.g h e c / senw us e in ccnn e e di bn wdh J n e h,4e/c c-l1bn Prc7rnn,. b b./h f n S

/Wov s The Siny e Eryc / nn Es.saeg. l l Much a Nen-l/en ha.s been g ven /c /he nng e i lhe single failure represen/eci failure. Onjinall of no mote }han a regoiterr7en/ Jor rede ndanct ccmyc neah,nci o evilerion, and appIna bje pn'ncipa lc oclive cc,nponen/s and Jheir in/erccnneclibns. /vorn Jhe pas.sive <cinfonen/s iveve excIvded Man os wco "/he bot /cm ol' requiremend Jcr redundance 4he pile." (The hct/cm cJ Jhe pile had le he ir.,fa//thie I Toda cr, n hen sc > aunned, Jhe roda wo uId n ll So Il ou. 4 his applies fr> Jhe inleytil c/ Jhe presswe vessel y which mv34 nel fen l). The si,,9 e foi/ure crilenon / hna been elevaled from a simple reyv;/ emend k/ redundonc e, k. helir a n>>~ nan u en a nd a rno viinarr, recjuiremen/ lc( ony sty -lem w)lhev/ rega<d k> s probn h:ltlies c/ fregvency c/ challenge /4 is wav/hwhile lhal we kok, for a ehange, J aJ Jhe Sing e E< rot', 771e faticwing ing/c Errors l i / taused fuel dainage c< mellmy n eo//g <eoc ovs. RECEIVCD ADVISORY COMM13EE ON 't^cto" 5^'Ecu^xas u.s. su NRx Fa v//'l tornmvn/ca/idn NOV 131978 /- p//e 7'eJ//n7 E 6/7 -/ Tes//n3 A$g,9gsyii:34M.[ l2 rj 5 woesene& by opera k< e<ro<- wTtt JL1 Penersil5 sJ LavvenJ Pe<versi/5 Bonvs oporaJent w<ane; va Ive desi} n inadey cou;

t In /cdcys plan /s we have had no <c<e mell eveni bu) hate seen 4he conse7ventes c/ a single human erro/ rnnqnilled cul of propotlidit b, syslem respons es and isrlero clibn>, fome e,carnples : N. f3. (Ichina on l u sh &re b e o n l) g a les I

d. c. b.is - ) e 3 di f><{

I hn dieseI genera los Jcsi d.c.hv2-leslth t y 2&,, res.s eI 1ove I pro teclior, y owered sys J em [e1dih dangerous j l z B r c ~,, s Fe<<3 hye 4esdi;,c Te.slitig s necessc2n and a re7 cloicy requiveinenf i bwl can ilself be hazardou; s A gren/ money erron ho<e been comm,'lled while conducling les/s and Jhe passibililies nye lih>;/les.s. Mnny are /n ker> }he Scim h cl opercrl ions on J he ivrong componenl cr drair,, or mcre receal19 on Jhe w<cn7 9eneraliiuj uni l, and ho/C Sc (a (, been reladiVe19 harmless, Dunng ~ fesllncg howeser' dhe pli)nl orindikidual sysdems may be in a 9 <assl9 oll-normoI con-fiejusolior, svch JhnJ et sing /c error ran Jn}7er a. cascade clunan.!icq>aled evenis, very !,hely l leading c addilicnol human error.s ns n. resuld of confusion anni confliclih o/ g mislead > n 9 slodus ]n iarmodion, The Zion Inicroclion.5ludy Irsi et surpv}ssig eleven over pressuriendion evenis which occurved wilh lhe reorice

a ccId and waler.schd, annt w,lh varicv3 ies4.s or mainIrmance operadicn3 beif conducled, probabl5 wilhovd proper ccrordin allon, efperhaps wi/hovl understandi )he pcssibilil o-linferaclibn, The zien.slud y cweve<, foiled h y lo call a flenlicn lo lhe significance el manu interocli6ns. 01 lhe evenis riescribed in }he Wo/3 /978 /e//ef Ic M Bendev, 9 lhe Brc.uns Fem, live a nd I he 2ihn on1 diesel 7 en era iv/ live were noled, and ont lhe in He, }n one, dehoil, Tiie 2icn du m ma. Ieanl pecdeclicri 3yidern des llncj evenJ wa s nc/ noled. In ihol eronl lhe cpernlng.s/n H wa s vou wo <e c4 i 1he.sericusness cf Ihe silva liin aIlheog h /he s slein wa.1 in y gren d dnorde/ Scr an ex/ ended penod, 7~ is is somewhisJ h s ;miIc, / la Jhe Sn n Cocfre p:lc1 Iqh 4 oven), nhn h e>I.so wa s aci vecc9niz.ed b Jhe libn Sivd y q 14 wovid be woflhwhile,a-/ / ens) os on exercise lo examke a few poss;bil;lies wherein w,lh vonbv.s sysienn Undergoin bt'sY 6f moindenor)re, a Jihe, /e Erecy", pcssib) acicmponled b, on exle/nni oren), co ulol prodvre uno ccep a bit l Yesv))s fi4l Quad Olies lheplanlvn5 oppfnloc)(of 0]rnoSh 2N hous,3 wih ene haHei ducha rg ed a llowing o mpie d irn e 4/ on independen] pren)) This exercise mi}hl be tendvideol a.s a,,o v) c J Jh e.s.s -lem.s indevoclion r+ogra m, y // is yu;le passisle IhaJ humon er,o/ a v <>' q n leslidq is a dominand failvie rnechonism in n eed al n fienJian.

1:. r. t. nicy 5,13 76 Es.say on Fal l S n-fe. The value of fail. Safe desicjn has been much over valed. There ore hines e.uhen on in/<usion caused by a failsafe ocluolibn, vert; c(len. spun *cus and unwonled, can he unhandu. Al clher -limes il can lac down rig hi dangerota, 777e nst?E ecre exarnp e, n lailsofe spunbus dumpinq l clu m p is o n of Jhe enliVe mollen core in/a lhe dump Jank could be vn,)lenson] and exj)ensive, Unde /some moindenonce cond; liens il ecuid he dangerousI /elhal, illus4 rales 77,e zicn irrleroclicn Study h*s}s eleven overpres3urizalien very well. The sdudy 4hi3 evonds which occurred wiIh Iho reocdc/ ccici and wader sclic), // is rolher surprisinc;. hv4 il seems -lhal no prodecl tan ac)oin3-l -/hi1 WQS f YoVided. O[ ]he eleven evends. len occurred on wesling ause h reacicts and one on er c e vn;1. In adddibn k Jhe lack of proleclion, Jhe followinc7 also condvibuled : avnscEE.i?mt 0

a. The s1sdems durin9 wa]er solial #/ent/i m e m s m cu m s u.s."

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3. Sa(c.ly nijeclibn was in;lia-leci,

~ vervj l:kek ns a rese14 of foiI sale cic lua-lion;, Corr /vollers and volves can /ni/ cppn, closed er in place, p foifure in one aspec/ con be advan]ngeous in one n>cde od operalion of har mlul in ano /her, 7763 is egeolh, J<ue kr prodecdion.syslenis where holl> iris /ruinen/s and aclua-lors are vsvall des >}ned h fail sale, 5 regardless of 4he consegoentes aJ. spun'av3 nc/valion, H opprors lha} Jhese enatlers we<e 1 7 /en no considem-l ion in regard Jo walersold/ ofcrodion. IJ wouId Jherekte seein no</h while lo e><nmine Jh e Irnpo cl, and /he value, o f fa j l sa {e desi n ct plan} wide has).s,which could be done ns cri

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3 Over pressuviz.alian Ewnl1 )Nho'Ie 0,o e/0 lr h c in 4h e (c id -Wale /-s c iial (c nnll4 tc n. Vendo/ AE I. bL uc<c Leddown volves cIcscd Lon c S ~ jn > )<uincnI oit. RHR Jy 0lCrn nelaled 2 W .5 4 L Te < c,c m '/ relles va lve, 3 y uEsc n p it sy s lern ;s c la.J e,) valve, c / va lies inadve,Jooll. cle.se : Solel Injec lron Inilwle,) ??? 4 n.1 54 k: y 3 w DetInlcI l edin e, ricwn }hleol, Op em Ic / e rrt r. Cold wa le/ egfondeol inSG 7CE Bechiel /4 s abc<e As abase Sw ve+c th ohcie as oho <e 9 w FPI 4.e ldo wn vo l e clos ed Insivurn en ) +esdin'g. Io yi BecIdel Condrc) valie cIcsed a n 0, ea k e/ -{v,jpeol Ic.ss of powe/ ny ue4c charp;m tol<e cpuned onJ Les.s eI insIoli. Loldown to Ive closed

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b !(!MNIIhDM'MIA M N - - n grouping them in one area of the assembly. Specific units can be GENERAL INFORMATION-Stacoswitch products are designed and signed with heat rise as a specific consideration, though at the expense rninufactured to meet exacting specifications of Original Equipment of other factors. Contact factory for design assistance, Manufacturers who demand dependability, attractive appearance, and LIGHTING-Stacoswitch maintains a fylly equipped and certified light caximum value from their products. Combining imaginative engineer. laboratory. Tests are performed in compliance with National Bureau ing with manufacturing know-how Stacoswitch offers the most versatile Standards and military specifications, including MIL-S-22885 MIL-C-and reliable circuit control components available. 25050. MIL-L-25467, MIL-P-77880, and Fed STD. No. 3. Among the Stacoswitch's full line of Lighted Pushbutton Switches and. Indicators light laboratory capabilities are brightness, color, contrast, reflectance provide a wide selection of circuitry control capabilities and display ang!e of observation, high intensity (sunlight readability and contra screen combinations. it costs no more to specify the very finest. Design and LED measurement. All measurements and equipment calibration and performance features, durability, cost savings and realistic delivery are traceable to the National Bureau of Standards. schedules all combine to make Stacoswitches ycur best buy. When you Stacoswitch units accept T-1-% midget flange base incandescent compare total cost., purchase installation, and maintenance.,you lamps, M25237 or equivalent, with design voltage ranging from 1.3 can't beat Stacoswitch. 28 VOC, and neon lamps for operation on 115VAC. Pushbutton tempera-QU ALITY CONTROL - Stac: switch, as a part of its operation, maintains ture is directly related to brightness and power consumption of the a cuality Control Department which encompasses a:1 of the functions lamps se!ected to provide the required color and brightness. A reduc required to attain the company's high quality objectives in every fevel of temperature can be achieved by reducing the power consumed by t of production, as well as requirements of the most discriminating cus' lamp, if lower brightness is acceptable. Within the parameters of th tomers. The inspection system and documentation used to control the selected lamp, display calcrs, and legend style, color and brightness quality of products manufactured conforms to all requirements of MIL-within a customer specified range can be furnished. 1-45208A. As an approved manufacturer of Qualified Products List LOAOS-Switch load ratings are a function of a number of variabfes. (GPL) parts Stacoswitch's program is regularly monitored by the appro-Life, temperature, duty cycle, and type of load, whether resistive or priate Defense Department Agencies. inductive, are among the considerations. Cata!cg ratings are intended SEISMIC QUAllFICATtDN -For contret applications in installations as an optimum rating, considering all factors. A!! catalog ratings include where seismic activity may require the extra margin of reliability,a safety margin of 150% of rated loads under prescribed conditions. Stacoswitch has tested and qualified the Series 1M,1MR,40,40R,2S, 2R, and 60 Switches. Seismic qualification tests were conducted.in Switches are capable of switchmg an open circuit load of 10 times the and T.V.A. 2200 Appendix "C, rated resistive. accordance with 1.E.E.E. 344-1975 Switches were subjected to a search for resonance in each of the three The basic switch modufe used in all Stacoswitch 4-lamp switches is a U.L. recognized component listed under File No. E50237. It is impos-major orthcgonal axes over a frequency range cf 1 to 35H2 at an ap. plied double amplitude of 1.0 inch up to a limiting value of 0.3g peak. sible to supply U.L Listings under all possible configurations. Contact Sweep rate was one octavs per minute. Resenance, defined as trans. factory for assistance on specific listing requirements. missibility greater than 1.5, was not detected. Switches were also sub, For evaluation of contact ratings refer to the following chart showing jected to high sinus 0idal vibration in the B-C axis and the B-A axis, both life / load switching capacities: in phase and 180 degrees out of phase. Testmg was performed over _.m..c_ u.. l 1 N the frequency ran;e cf 1 to 35 Hz at an at:pl:ed dcubf e amptitude of 5.0 i t = " "I I i inch up to a limiting value of 3.0g peak. During a!i high level sinusoidal I i I I I vibration testing the switches were monitored with t contact chatter-

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I t . % ' "l l transfer detector. No chatter or transfer was noted. At the conclusion u. i l ,'l. of tests a thuou;h examination reveated no dama;e or adverse effects. j } g Lamps were likewise monitored during the tests. No lamp sai!ures I } l g i gij-l occurred. MATERIALS-Plastic body of the basic switch / indicator rnodule is ij; j j i l I } j I made of a premium grade gfass fi!!ed thermec!astic polyester. This !.r. {j

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NN material offers high impact strength, dielectric strength and insulation i t i ~~ i y resistance. U.L. recognized, the plastic is fire resistant and flame re-t i tardent. Thcugh resistant to many commen sc! vents and cleaning solu-i 3 tions it is recommended that isopropyl alcohol is used for cleaning. ' " ~ g Edtrix housing assemblies and switch housings are made of aluminum g for high structural strength combined with fight weight. Black anodized a-finish on all non-shielded units provides ccrresion resistant surface. c,cu. nn v ov P,Fl/EMI shielded units have a conductive chem-film irridite finish that I I d,cm.'oc,.c m. I is equally corrosion resistant. " "? I Contact matenals are high conductivity precious metal a!!cys, gold i i u-i l plated. Switch moving contacts are not based on over-center springs. t l i U. g -"l No sprin;s are used as conductors, eriminating a!! prob! ems cf anneal-

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I ing and loss of spring pressure. } Pushbutten plastic color chips provide contro!!ed color diffusion and ( excellent resistance to high temperature. Face plate has high structural [; q .i.,,g i strength and hardness to resist surface scratches. Stainless steel push-j.. 5 i: = =. to. button housing provides structural strength and heat sinking capability. 1 I-A HEAT-Materials used in Stacoswitch units provide excellent resist-( i '*.= tog ance to h;gh temperatures. For comfort of human interface the switch can be operated in most conditions with up to two lamps continuous i duty. In matrix assembles wt ere significant temperature potential i '= =.to.o i exists external cooling or heat sinking may be required to maintain I I I comfortable pushbutton surface temperature. Reduced build-up of heat ~ ~ ~ 1 " " u7-a "r ov ~, ~ where continuous lamp duty is required can be achieved by dispersing* " *

• c,c these switch or indicator statiord throughout the matrix rather than 4

i bU Ll'GHTED PUSHBUTTON SWITCH / INDICATOR 4 ., ~,. -?, a ~

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• Easy to install-Easy to maintain l
• Puts more switches in a smaller space
• Save panel space-Reduce weight i

? I The Stacoswitch 1M/1MR Matrix System is comprised of 15 lighted plug-in displays and pushbutton switches...all 1% mounted in a common housing;The compact design of the housing assembly puts all switches in one area, saving 3 precious panel space while providing an uncluttered and -% g; 1 1_. more eye-appealing display design. 9 '9 " Slotted hole" flanges joined to the housing tube structure I 7 ' ~- make mounting of the matrix assembly to a standard panel quicle and easy. A single panel cutout is all that is required m. .T: -., ,~~ ly to install the total system. I Standard receptacle terminals, solder or wire wrap, provide ... _]i... ] single plane, behind the system wiring. No wiring of switch plug-in module means they can be removed and replaced independently from the systemswtringg.MO_sc..94Md/'3E9 I

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-9 e+ Woww w% M,*vt ~ The 1M'MatrirSystems' accepts;the2 square Modetr40MM. + .~ ' M 7 ^.. ~ ME switch / indicator modules and-the: Series.40 Pushbutton/:D#- f -N-Display Screens. The--1MR Matri* System accommodate's ~ the rectangular Model 40MR switch / indicator modules and.

? _ N.. -c C the Series 40R Pushbutton/ Display Screens 5 '.4--r.tMW9.-l.y.+m e i-9WS?

,a. g. ^ ~ "$. 5$ .. g. g==e@g@g,:.-..,. f. . h ' A.' $ *)? ?';... - ,G, i $1e = '5 $82 k.5?IN' '.$.Y, '+<~ ~ %5' % :e WQ ,..-..,.+.,.g:,.t.n, nv~- g ...:, e. - r. 'M g, M %.h.$ ^73$'. Tfk. N -d es ) <W' ..?ElT.?.::t 1 ^ .- =Q g -P74 y-C, - - a p>: Q p .g - : f.} f ... L7. b - J~ J.<. / ..e o f,

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~.z:?y ys (' n = W V Y;v T r~; " ~~'i v ~ m. w.;. 1 o , x"*"Specifying a STACOSWITCH IMllMR Lighted Pushbutton Sicitch Matrix is e -p.. ~. mi r~ -- --~~~~ .- : " w.,,. ..,.uw.n. - .-i s m m '. 1* '.m. pyNe ' N M.%u:m.w 1MR = RECTANGULAR l t., 1, 1M = SQU ARE~. How to Specify Matriz Components b rs ' The components required to fabricate a MATRIX system are specif i 1 j j 1 J 1 ] matrix of all components is identified. These components are: [ i .1. Tne Pushbutton/ Display Screen module. ~ 1 [ & 2. The switch or indicator modv%. .~ } j . 3. The housing assembly. J s ,+ _ 3 = ..~ ~: 4 7..'. .-a-.. +. -. ~.....:. -. dan L u: :,w.:. u _. e-.v _e.w.. 3 .....-...~-7 ,4 m....,__ -_w..g ~ r,-- ... my s '*.. ~.. p.s t -f. m.g., _a +- THE SERIES 40/40R PUSH 8UTTON/D! SPLAY SCREENS. 384 display options plus took alike appearance for use in same panels wh N Y(*( f~ W s. / j a a l - 0,2 %, . ordering information. s v, .G~$'[.[c i ^ N, SERIES 40R)Y[t.m d a &$[oSERIES 40 -~ .j 3.g . _.q ,-r,.g g.; e.ge..-. . _,g ,.. s, .c-... ..sgacg A p ge _ ;g., p. y

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!MMb "M h ~ +mw ~ Q '[/".*hM 8 [THE'MCCEtF4CM/40MR: PLUG-IN SWITCH /lNDICMOR %,."D"' Solenoid-held?E"" Latchdown action and?"I'" Indicat M '- t ' ~ ' % J.- ' W 4PDT"and.seafing are standard optionse Refer to'the 40M/40MR Suritet'/ ~ Wif.s -!.f.?. Indicator sections for ordering information. " "Z/.: M ~. A ODEbOMlb f r d IN b s_.. -w n ~,. = E 40 r - %:,3 w </ g n..,,,,. A c' g.- w,WW$$$h $5[].?C.5&,.. -?$ & ,3 -Mt.w :s 2,.:. 2 s3r i .,N fS' ~ ' Wv.%* -W M Gf..=. m M ' +-_ ' x' . -qs~n,.2..sm-4.r

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5 . -. dis c W. W; t-c c. 'I ~ - THE~ SERIESitM/1MR RECTANGULAR HOUSING ASSEMBLIESA com / e and extractierrof the. Switch / indicator modules and Pushbutton/ Display s. screens fror:Lthe panel front with no ' lind panet" wiring disruption. A o tnd mounting arrant,.:nents are myriad of standard display configuratic, k available.W.W. :. - - { SINGLE ROW MATRIX A SINGLE ROW ATRIX 8hMN hwn.aba.wd.-._. _ t., A.u _.;,d[$$ m. ,M s. p,iy 4 L,_..a.. ._., ;pyi rw:p3. -m.g3 .<w fA ~ff } y~.05.' '.'-$ gyr. n',r-c.p.v.q~~ - =~.. - ,..QQWQ

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T .,.l.,- SOLDERLESS. TERMINATIONS AVAILABLE. w. ..A =. ; bl<l 4 . y4-. .cgg:.cr.s,y. ,,) h n -.> w ma .,1-%. p - . ca. 2 y g _._. g. n.> ;. f.c.;9 % ){ g .q,., .p. .m

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, Receptacles fit bot' matrix types -IM (Square) and 1MR (Rectangular). J. 3.s. m *w +~ - %.1..g -. -ug;,w, aegu. .; ag,,scw,ym,pgg. 7 ppg. .o. ,..g,y ggg.g,., +

.=_ h N IN lll @ IIdlk l l@ ell 11 I I m SWITCH /INDICATD11-The Series 40R is a rectangular version of f. the square Series 40, covered'on pages 7-8, and offers the same design features and advantages. Identical switch mechanisms ar] used in both series: the only difference is the Series 40R is rec-W

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tangular while the Series 40 is square. Units are manufactured to

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^$- A - meet or exceed all applicable Military Specificatons M22885, and are Seismic Qualified under I.E.E.E. Standard 34419 9i t T.V.A. Appendix "C". ~~ f P V c4 in addition to the indicator only, used as a warning light, the (gyh} AGE switches are availabre with choice of momentary or alternate . if. AC POWER action with either 2PDT or 4PDT contact arrangement and either ~ common or split lamp ground. Optional RFI/EMI shielding is also OfF l available. Mounting is simple and secure. Spacer collar on mount-s ON ing sleeve allows switch / indicator to be mounted either flush t the front panel or extended, as shown in the photograph below, for use with edge-lit or similar overlay panel. DISPl.AY PUSH 8UTTON-The rectangular Series 40R Display Pushbutton is used with the Series 40R Switch / Indicator, and must be ordered separately. It provides the same display options as the Series 40 Display Pushbuttons as described on page 9, plus a larger frontal area to accommodate longer legends. Pu button can be supplied with a captive bail which allows the push- ~ button to be removed. without use of tools, from the front of the panel for refamping, yet retaining it to the mating switch /indica at all times. In the event the pushbutton is to be removed entirely gAC05WITgg 1 from the panel the bail can be quickly disengaged, and as quickly reengaged for reinstalfing the pushbutton. Pushbutton is also available with common tamp ground or split lamp ground in four h SERIES ggg ~ choices of lamp arrangement. If split lamp ground is required both pushbutton and switch / indicator must be so ordered. Pus button accepts four T-t-3/4 lamps to be ordered separately. See listing on page 25. N ,a w' Imusummum x; ;. .I, A _2 M d s kf S .wwaa _x g g f2%%w $g $5&lA?lM&ghy$ ~ _w_ RSN2 & $$$ g "Bi'5Eh?E55 15

~.e1 STACOE!CG -3rd.. 83E8 ?D 'USHBU' 'Ot/DL8'E SCREYS i<w -+. * .., k [^" i E e For Series 40 Switch / g s y 1, J Indicators and Model NOT STACO 1" M0, 40M Switch / indicators READY ig i r h g,,> y for 1M Lighted Pushbutton Switch GO , OM.ACTf,

. 2 Matrix System f*

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~, Display Options SYS G0 ON r 1 ALT ' ACT OFF +7 o _m,2 -w 4+ -.. _ -. - gg .3 .' ?. Mt.. ... -,. ~ a-4 'Y P'Oh h .S ' l'. .Wf r

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=7g~ 1-~~~<-~ I ._.d' Series 40 Pushbutten/ Display Screens are used in both

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wT'th..@c., ' ~ ' ~ the Model.40 Switch / Indicators and the Series 1M 'O' lighted Pushbutton Switch Matrix System. Individual mount switches and matrix system assemblies can be j . a<%9 - .- @ Sq .;r - TYPICAL PUSHBUTTCN ASSEMBLY incorporated on the same control panels for look alike display appearance. [PUSHBUTTCN HOUSING FACEPt. ATE configurations and color combinations. Eight display screen styles utilizing vertical and horizontal split com-I ~ H'0 EN binations enable one to four levels of information to be 35 5/D S displayed individually or s,imultaneously within each LEGEND PLATE switch light station. NCOLOR FILTERS. Choice of six legend colors and eight legend illumina-tion display styles provide the design engineer with the t DISPLAY SCREEN display versatility to meet the most exacting demands. OlviDER Stacoswitch's high temperature lens combinations o GASKET allow complete, controlled color diffusion flexibility 9 n eMency Rr cMcal " l' II LAMP BOARD ~ . ASSEMBLY lighting areas, such as high or low amb;ent light, or i c 2 high glare light conditions, option high contrast legend l KEYING PIN fisplays and non-glare face plates provide optimum i {g re dability. l 1 f ]

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