ML19350B221
| ML19350B221 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 03/11/1981 |
| From: | Ross D Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML19350B218 | List: |
| References | |
| NUDOCS 8103200114 | |
| Download: ML19350B221 (15) | |
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UNITED STATES NUCLEAR REGULATORY COM"!SSION BEFORE THE ATOMIC SAFETY AND LICENSING BOARD In the Matter of
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Metropolitan Edison Company
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Docket No. 50-289 (Restart)
(Three Mile Island Nuclear
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Station, Unit 1)
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NRC STAFF TESTIMONY OF DENWOOD F. ROSS, JR.
REGARDING REACTOR WATER LEVEL INSTRUMENTATION (UCS Contention 7, Sholly Contention 6(b) and ANGRY Contention 5(b))
Question 1:
Please state your name and position with the U.S. Nuclear Regulatory Commission.
Answer:
My name is Denwood F. Ross, Jr. My position is Director, Division of Systems Integration, Office of Nuclear Reactor l
Regulation.
l Question 2: Have you prepared a statement of professional qualifications?
Answer:
Yes, a copy of this statement-is attached to this testimony.
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810s200-(Vi
Question 3:
What is the purpcse of your testimony?
Answer:
The purpose of this testimony is to justify the Staff position that reactor water level instrumentation for TMI-1 and other operating reactors is r.ecessary to provide reasonable assurance of no undue risk to the health and safety of the public.
Item II.F.2 of NUREG-0737, " Clarification of TMI Action Plan Requirements" (November,1980) rescheduled and detailed the steps to be taken by licensees and applicants in response to the " additional instrumentation for detection of Inadequate Core Cooling (ICC)," requirement established by the TMI Lessons Learned Task Force in NUREG-0578 (Item 2.1.3.b) and subsequent clarification to that document (the H. Denton letter to All Operating Nuclear Power Plants on
- Discussion of Lessons Learned Short-Term Requirements," dated October 30,1979).
These steps included requirements for documentation, including a final design description of additional instrumentation and displays, to be submitted by all licensees by January 1,1981.
It further required submission of a scimdule for installation, testing, calibration, and implementation of proposed new instrumentation. The stated requirement for installation was January 1,1982.
The staff believes that additional instrumentation to monitor reactor coolant inventory is necessary to provide reasonable assurance that reactors can ope" te without endangering the health and safety ci the public. Our belief has been rein-forced by the two recent incidents for which such measurement capability would contribute to safe operation.
The staff, in previous testimony presented by Laurence E.
Phillips filed on December 1, 1980, cited tie St. Lucie event
(" Report on the St. Lucie 1 Natural Circulation Cooldown on June 11,1980," by E. Y. Imbro, Office for Analysis and Evaluation of Operational Data, USNRC) as an example of need for level instrumentation.
In that event, a bubble was formed in the reactor vessel head and there was an extended period of operator confusion concerning the status of the system. The staff is concerned that events of that nature, where the operator is " blind" with respect to the coolant distribution in the system, place undue stress on the operator and could contribute to unsafe operator actions. Since that testimony, we have another example of a similar situation.
4-A loss of coolant event while in cold shutdown occurred at Sequoyah 1 on February 11, 1981. The loss of coolant occurred through an erroneously open valve that connected the containment spray system to the operating RHR system. The pressurizer level dropped off scale rapidly.
In this event it took ten minutes to reestablish the pressurizer level and 35 minutes to diagnose the event and take appropriate action to refill the system to reach the normal pressurizer level.
The low pressure injection pumps were used to inject water from the refdeling water storage tank (RWST) into the reactor coolant system while the pressurizer level was off scale and the reactor water level was not known. One or two days after the event, the minimum reactor water level was estimated by measuring the boron concentration of water samples taken from RCS, RWST, and containment.
The water level in the reactor vessel would ' nave been indicated directly.and immediately to the operator if the reactor vessel
' level instrument which is being procured for Sequoyah I had been operational.
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v The staff considers level measurement systems necessary for display of additional reactor coolant system (RCS) status information which is needed by the operator for diagnosis of an event or condition both during the course of the event and af ter it has occurred 6 During the event, the operator needs this information either as the basis for initiating emergency actions or as a confirmatory signal to complete the otherwise indicated action. The staff believes that the use of all pertinent status information as input to operator actions is one of the lessons learned from TMI-2. Accordingly, we will require that level information, when that display becomes avai?able, be appropriately incorporated into the emergency procedures for ICC. After recovery from an event, liquid level information can be used to assess whether core uncovery and fuel damage occurred. This is valuable input for decisions concerning the safety implications of restarting a reactor after a transient event with possible core uncovery.
For the thort term, until acceptable water level instrumen-tation can be installed, we believe that the instrumentation deficiency can be compensated by:
(1) the high level of operator awareness due to the TMI-2 accident-(1.e., the operator will be less likely to take imprudent actions due to improper interpretation of available instrumentation);
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. (2) the low probability of occurrence for an event whereby water level instrumentation would serve to mitigate the consequences; and (3) the additional awareness that an instrumentation deficiency exists, corrective measures are in progress, and emergency procedures are interim in nature until the additional instrumentation is provided.
Question 4: We understand that TMI-1 and other B&W operating reactors are taking the position that no additional instrumentation is necessary and are therefore proposing none.
Is that true and is that position acceptable?
Answer:
Yes, that is true. That position is not acceptable to the staff and we believe that we have made this very clear in correspondence (A letter from D. G. Eisenhut (NRC) to R. C.
Araold (Met. Ed.),
Subject:
Lessons Learned Short-Term Requirement 2.1.3.b " Instrumentation for Detection of Inadequate Core Cooling-Additional Infcrmation," dated September 24,1980.)
to Metropolitan Edison Company and to other B&W plant owners which has been previously referenced in testimony before this Board..We expect all plant owners to aggressively pursue the i
design and procurement-of level measurement systems or equivalent instrumentation for. trending the primary coolant inventory
. over the full range to core uncovery. We believe that existing technology for op level measurement systems and for Heated Junction Thcrmocouple (HJTC) systems is such that plant owners can proceed with confidence that such systems, including provisions for the processing and interpretation of data can be provided with functional capability acceptable to the staff. Further, those plant owners who have devoted their resources to satisfying the II.F.2 requirement rather than resisting it expect to meet the scheduler requirements of NUREG-0737.
Questfor,5: -If the staff has identified two level measurement systems which are likely to be acceptable, why does not the staff direct the plant owners to install one of these systems?
Answer:
We do not wish to preclude the consideration of alternate systems which may be selected on the basis of superior functional performance, installation simplicity, safety coacerns associated with the installation, lower cost, or any other factors appropriate to a sound engineering approach to this problem. Further, we recognize that the identified level measurement systems may not be physically adaptable to some reactors without design modifications to the reactor vessel or
. internals which might create unacceptable safety conditions, though no such situation has been identified to the staff to date.
In fact, the supplier of one of these systems (CE), in a recent meeting with the staff, has claimed that their system is adaptable to every operating PMR without requiring additional mechanical penetrations in the reactor vessel. The staff will consider plans for installation of systems requirirg further substantial development or verification effort provided the schedule impact is not unreasonable, the development program is well defined including appropriate contingencies, and the reasons for selecting the less developed system provide acceptable justification for the impact on installation schedule.
Question 6:
Has the staff considered the safety related consequences of a postulated rupture of the instrument tube lines requircd for some level measurement systems?
-Answer:
' Although review procedures usually do not include the analysis of postulated breaks of instrument tube lines because of the small size of the lines, the staff has performed studies in response to an ACRS concern over.the adequacy of ECCS systets to mitigate the consequences of an instrument tube rupture.
' Analyses were performed on a Westinghouse 4-loop PWR with 0.4 inch and 0.6 inch inside diameter instrument lines. The
analyses performed show that the emergency core cooling system (ECCS) can maintain the primary system inventory such that no core uncovery occurs for two small instrument tube line failures, or for one large instrument tube line failure, The analysis indicates that more than three hours are available prior to core uncovery if it is assumed that five small instrument tube lines or two large instrument tube lines fail.
Similar analyses for other FWRs are planned. Vendors have indicated that their high head pumps (coolant charging and/or ECCS) are capable of making up the reactor coolant discharged from at least one instrument tube line failure maintaining the system pressure at or near the shutoff head of the pucps.
Question 7:
The staff, in previous testimony by Mr. Phillips on January 22.1981 (Tr. pp.10,842 to 10,847), has indicated that the technical feasibility of level measurcment systems was a factor in determining whether these systems would be required.
Your testimony indicates that safety considerations relating to physical install 6 tion may be another factor. How does the staff intend to resolve this issue if it is finally determined that the requirement simply cannot be satisfied for technical reasons on a B&W reactor?
Answer:
The staff requirement is for additions 1 instrumentation for detection of ICC. The preferred technique is monitoring of the reactor coolant system inventory.
If the most advanced technology now available for this purpose cannot be applied to B&W reactors for as yet unidentified technical reasons, we will consider a schedule delay to individual :icensees provided that they commit to a definitive program for develop-ment of a different technique for level measurement or an alternate approach to additional instrumentation for detection of ICC. Any such delay would also require licensees to commit to acceptable additional alternative measures to be utilized in the interim that would compensate for the lack of required instrumentation, such as further operator training. However, we simply do not accept the hypothesis that an engineering solution to this problem cannot be accomplished.
If necessary, the staff will consider modification or relaxation of certain specified functional requirements where this will expedite the implementation of an additional instrumentation system which substantially improves the ICC monitoring capability of the reactor under review.
In all cases of schedule deferral, we will monitor the licensee closely to assure that reasonable progress towards the defined goal is maintained.
Question _8: You have indicated that licensees were required to provide documentati0n on their proposed systems for detection of ICC by January 1,1981.
k' hat is the status of other operating PWRs and B&W reactors in particular with respect to the January 1,1982 icplementation requirement of NUREG-0737.
Answer:
For B&W reactors, three of eight reactors (0conee 1, 2, and 3) have promised a near-term decision on the type of system m
selected (Ap, HJTC, or DAVC0 micro-wave system) and the schedule for installation. One reactor (Crystal River 3) has selected a concept (hot leg level instrustentation) but has not yet provided a detailed description and schedule, two (Davis-Besse 1 and Rancho Seco) others are still reviewing currently available systems and have made no decision, and two (ANO-1 and TMI-1) are taking the position that nothing is needed even though they have been informed that this is unacceptable to the staff.
For CE PWRs, three of eight plants are committed to a system though only one expects to be on schedule. Four are still reviewing available options, and one (ANO-2) is taking the position that nothing is needed.
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For Westinghouse PWRs,15 of 27 have committed to systems (mostly ap systems) and expect to meet the schedule for installation. Five other plants are committed to a system with some delay in the installation schedule.
Nine others still have their selection under review and have not committed to a schedule for installation.
Question 9:
Several plants seem to be late and a few have prepared a deviation to 11UREG-0737 requirements for Action Plan II.F.2.
Does the staff intend to enforce the requirements?
Answer:
The staff has just completed a review of the status of the various licensee responses. While the exact mechanism has not yet been determined, the staff intends to take action that will expedite progress on the installation of a level measurement or equivalent system.
Question 10:
Does the staff believe that the licensee (Metropolitan Edison Company) has shown reasonable progress toward compliance with
'the actions recommended in NUREG-0578 and NUREG-0737 with respect to additional instrumentation for detection of inadequate core cooling?
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Answer:
No. The licensee has not responded as requested to our letter of September 24, 1980 to Mr. R. C. Arnold (provide within 30 1
days your commitment to develop a level measurement system),
or to NUREG-0737 (provide a description and other documenta-tion on the system by January 1,1981).
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PRDFESSIONAL QUALIFICATIDN5 DEN 4 DD f. ROSS, JR. L'.,
IMRCH 1980 I ac presently em;1oye: with the U. 5. Nu: lear Re;ulatory Coreissier., within the Office of hu:les-Rea: tor Reg latier., as the Dire:to-cf the Divisio. of Systees Integration. My work address is 7900 Norfolk Avenue, Sethesda, Md.
Tne fun:tional assignments of the Division of Syster.s Integ ation in:1u:e six systems areas (Reactor Systers, Instrument and Control Systers, Auxiliary Syste s, Effluer.. Treat:e. Syster.s, Po-er Syste s, and Containme. Systers) as well as A::ident Evaluation, Radiological Assessme.t. Core Perfor:ance, and Systems Interaction.
Work assignments prior to this present position include:
Acting Director, Division of Proje:t Management Director, Bulletins and Orders Task Force (a post-TP.:-2 g-ou;)
Deputy Dire: tor, Division of Proje:t Management Previously I served as Assistant Dire: tor for Reactor Safety (from 1/76 tc 10/75).
This included supervising the attivities of the Analysis Bran:h, the
. Core Performance Bran:h, and the Rea: tor Systems Bran:h which, together, formed the Reactor Safety group in DSS. The work assig rents performed by Rea: tor Safety included evaluation of emergency core cooling system response, as well as reacter core and prieary coolant system response to transient and other accident conditions.
P00R ORENAL
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Prior to that assignment I served as Branch Chief of the Core Performance Bran:h for about 2-1/2 years.
Other job assignments.since coming to USNR0 (then AE*) in August 1967 include project canager assignments (or afer con-t-ic. :- te) fer several proje:ts, including Threc Mile Island (Units 1 & 2);
I Crystal River Ur.it 3; Oconee 1, 2, and 3; and Quad Cities 1 & 2.
In addition, i se sed on a spe:ial task force re:ie-ing ECC5 performance, including exten:ed se. ice at the ECCS rule-making hearing.
Prior to joining NR ) worked at the General Dynamics nuclear research fa:ility at Ft. k:-tt, Texas for 10 years, including 4 yea s as operations supervis:-
fc-three resea-ch and test rea: tors.
I also worked for 1-1/2 years at the MTR-ETE ope-ations at tne NRTS, Idaho.
I have degrees in Civil Engineering (85,1953); tiathematics (M3,1953); and Nu: lea-Engineering (M51950, and D. Engr.,1974).
P00R ORIGINAL
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