ML20030D343
| ML20030D343 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 08/26/1981 |
| From: | Hukill H METROPOLITAN EDISON CO. |
| To: | Stolz J Office of Nuclear Reactor Regulation |
| References | |
| RTR-NUREG-0737, RTR-NUREG-737, TASK-2.F.2, TASK-TM LLL-246, NUDOCS 8109010206 | |
| Download: ML20030D343 (10) | |
Text
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Metropolitan Edison Company Post Of fice Box 480 N
Middletown, Pennsylvanic 17057 Writer's Direct Dial Number August 26,1981 L1L 246 g\\ D Office of Nuclear Reactor Regulation 4
'e Attn:
John F. Stolz, Chief
'g N
~~~j Operating Reactors Branch No. 4 gr 9
U. S. Nuclear Regulatory Commission 4
j Washington, D. C.
20555 7
p-12
Dear Sir:
Three Mile Island Nuclear Station, Unit 1 (TMI-g i
Operating License No. DPR-50 Docket No. 50-289 Inadequate Core Cooling (l1.F.2)
.NUREG 0737, Section ll.F.2 requires an evaluation of additional instrumentation which might be used to detect the existence of or approach to inadequate core cooling.
It also requires that the evaluation include reactor water level indication.
In response to this requirement, GPUN has been conducting an evaluation of such Instrumentation to determine its usefulness and practicality.
Our evaluation has included both in-house activities and participation in Owners Group activities. The purpose of this letter is to summarize briefly these activities and their current status, and to outline our planned program.
Activities We believe we have been focusing our efforts on a long term problem that requires very carefully considered judgments.
The status of our efforts has been the subject of extensive documentation and oral testimony including the l
Atomic Safety and Licensing Board (ASLB) hearing on January 21 and 22, 1981 and l
documentation of prc. filed testimony of September 15, 1980, March 19 and 20, 1981, testimony discussed by representatives of NRC through cross-examination bef ore l
the ASLB, Amendment 21 to the TMI-I Restart Report dated October 3,1980, and meetings before the Advisory Committee on Reactor Safeguards (ACRS) on November l
29 and December 4, 1980 and June 25 and July 10, 1981.
t l
We have already achieved a significant improvement in this TMI-2 Lesson Learned l
Item through the use of additional and modifled instrumentation and procedures that have been verified by detailed analysis by both our staff, B&W, and the NRC
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metropohtan Edison Con'pany is a Member of the General Pubhc Utsties System j
. statt. This is 71so supported by the ACRS Chairman's letters of December 12, 1980, June 9, 1981 and July 11, 1981 on this subject. Thus, our efforts support a deliberate process necessary at this stage to assure a proper decision.
This deliberate process follows the normal engineering method of development of functional criteria, identification of alternatives, and selection of the preferred system prior to detailed engineering, procurement and installation.
This approach is the same as that supported by an NRC staff witness appearing on this subject (see TMI-1 ASLB Tr. 15956-15959).
One major thrust of our evaluations has been an attempt to understand the basic criteria for the additional Information.
We used as a starting point the criteria given in NUREG 0737. We found, however, as discussed below, that these must be supplemented in order to arrive at a definitive set of criteria which could be used as a basis for existing or additional instrument selection. To this end, we participated in the work sponsored by i-he B&W Owners as well as our in-house evaluations.
The intent has been to determine which additionalinstruments might be used to detect, confirm or diagnose the existence or approach to an ICC condition, to determine which portion of the operating crew (e.g., control panel operators, shift supervisors, STA, etc.) would use the Information, and to define what actions would be taken or avoided based on the information.
In parallel with the development of criteria we have also undertaken an evaluation of available or proposed instruments which might be utilized. We have participated in the B&W Owner's Group evaluation as well as performing our own in-house evaluation.
In addition, because of the continuing unanswered questions, we have initiated an independent review by an outside consultant, Dr.
Vijay Dhir of UCLA, to define the advantages and disadvantages of existing and proposed sy.tems and to consider whether additional, alternative new approaches exist which warrant examination.
We have furthermore agreed to consult in a proposed program expansion by Penn. State University to continue development of neutron detectors as a method of measuring reactor vessel water level.
l Status j
The status of our evaluations to date was presented to the TMI-1 Subcommittee of the Advisory Committee on R( : tor Safeguards (ACRS) at their meeting on June 25 I
and 26, 1981.
At that time, we pointed out that we have identified possible uses for water level or related information.
One possible use would be to determine whether venting the hot legs was necessary or desirable, and to guide any such venting operations.
Another possible use for example, would be in conjunction with the existing saturation meters to determine whether HPI flow could be reduced or termina ted. We understand from our most recent discussions with you that these types of applications are consistent with the criteria as defined in NUREG 0737.
The specific requirement of NUREG 0737 that instrumentation should " provide an unambiguous, easy to interpret, indication of inadequate core cooling (ICC)"
l appears to be more complicated to meet. We have used the term ICC to refer to l
those core conditions at which the limits of 10 CFR 50.46 would be exceeded. It i
l
7
. thus represents a non-mechanistic condition beyond the design basis.
Its significance in the present operating procedures is that if such conditions are being approached (as indicated by the core thermocouple readings), the operator is directed to take extraordinary measures in order to improve core cooling.
The problem with using water level to Indicate the existence of approch of ICC is that water level and its rate of change with time vary enormously for ditferent size leaks and leak locations. For lar e breaks the level drops even s
more quickly and results in temporary uncom.ry of the core and would be of little value.
The attached figure 1, shows 1he calculated water level for different size small breaks.
For all of these leak sizes and locations, however, the emergency core cooling systems will function to ensure that ICC does not occur.
We have to date found no method by which water level information during the initial blowdown and ret lood phase of a real accident could be singularly interpreted to indicate that the emergency core cooling systems were not functioning as intended and/or that inadequate core cooling (as wa define it) was being approached. We plan to continue this evaluation.
With respect to currently available hardware systems, we are in the midst of detalled discussions with the NSSS vendors regarding their recommended systems.
We have not yet received the results of our consultant's study, and have reached no conclusions to date.
Program As exhibited in figure 2, the GPU Nuclear program for resolution of the inadequate Core Cooling Instrumentation / Water Level (Item 11.F.2) consists of a further evaluation of the three major areas:
1.
The uses which can be made of the instrumentation systems to detect water level, inventory, etc. being proposed by CE, W, and B&W.
2.
The adequacy of presently or soon to be available instrumentation (Reactor Vessel Differential Pressures, Heated Thermocouples, and RC Hot Leg Level) proposed by the NSSS Vendors (Westinghouse, Combustion Engineering and Babcock and Wilcox).
3.
The new ideas being developed throughout the industry (Penn State University - Neutron Monitoring and a study by Dr. Vijay Dhir on ICC - Water Level Instruments).
The evaluation period includes meetings and discussions with vendors and consultants to develop an integrated summary leading to a technical recommendation on inadequate core cooling instrumentation including evaluation of water level during the month of October.
By November a submittal to NRC concerning our technica; recommendation will be made.
If preliminary selection decisions are made in advance of these dates, the NRC will be so informed, and appropriately revised schedules will be subsequently provided.
. Conclusion GPUN is continuing its evaluation of possible instrumentation in accordance with our current understanding of the requirements of NUREG 0737 as c ut t ined below above.
Furthermore, GPUN believes that the program delineated abcve represents reasonsble progress, is responsive to the ACRS, and will result in rt.3olution of this issue with the staff.
Sincerely, ff_# bl' L-H. D. Hukill Director, TMI-1 enclosures cc:
H. Denton B. H. Grier L. Barrett H. Silver i
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NRC/GPUN Activity Chronology 7/79 NRC Published NUREG 0578 - TMI-2 Lessons Learned Task Force STATUS REPORT AND ~HORT TERM RECOMMENDATIONS a Item 2.1.3.b. Instrumentation for Detection of ICC in PWR's and BWR's.
7/79 GPU Submittal Restart Report Section 2.1.1.6 address'ed Instrumentation to Detect Inadequate e
Core Cooling.
(Several revisions followed.)
10/30/79 NRC (Denton) Clarification Letter of NUREG 0578 Item 2.1.3.b. - Required "The evaluation is to include e
reactor vessel water level indication",
e Also list several additional criteria which RV level or any other instrument would have to meet.
11/7/79 GPU Submitted Restart Report Amendment 5 e Responded to NRC question re ICC (See RR, Sup. 1, Part 1, Q. 39, 39a, 39b).
11/28/79 GPU Submitted Restart Report Amendment 6 e Responded to NRC question re ICC (See Sup. 1, Part 1, Q 17).
12/79 -
Several inforr.1 meetings with NRC re open items inc. ICC.
5/80 6/80 NRC issues TMI-l Restart SER (NUREG 0680).
9/5/80 NRC (Eisenhut) letter on additional requirements from TMI-2 Accident.
9/15/80 GPU files testimony in Response to Intervenor Contentions on ICC Instrumentation.
e Detailed discussion of position.
Sponsored by panel of GPU Engineering and Operations, and B&W ECCS Unit Supervisor.
~
Based largely on B&W Owners Group sponsored report dated e
8/15/80.
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Chronology - Page 2 9/24/80 NRC (Eisenhut) sends letter re SUREG 0578 Item 2.1.3.b. - ICC Rejects B&W Owner's position that no additional instruments e
required.
Specifically calls for RV water level instrument.
e 10/3/80 GPUN submits Restart Report Amendment 21 Formally provides B&W Owners Study on Instrumentation for e
ICC Detection (See Sup, 1, Part 2, Q 95).
10/31/80 NRC published NUREG 0737.
Provides additional requirements for ICC instrumentation e
short and long term (See Item II.F.2.)
11/29/80 ACRS TMI-l Subcommictee Meeting GPUN/NRC both present status of work / positions e
12/1/80 Nhc Staff files testimony Responds to Intervenor contentions re ICC and address e
CPUN position.
(Testimony was originally due 9/15/80, same as GPU.)
12/4/80 ACRS Full Committee Meeting CPUN/NRC summarize positions.
e 12/11/80 ACRS Letter on TMI-l Restart ACRS views unambiguous indication of water level in RV e
should be given further consideration beyond restart.
12/22/80 NRC Staff files second set of tes:imony re ICC.
Supplements early testimony in attempt to support case e
before trial.
l 1/21-22/81 ASLB Hearing Session Initial litigation of ICC by NRC/GPUN.
e ASLB invites further testimony particularly re the e
question of necessary vs. desirable and reasonable progress.
O Chronology - Page 3 1/23/81 GPUN submitted in response to NUREG 0737 Item II.F.2 summarized / referenced GPUN testimony and e
submittals as current position.
2/28/81 GPUN letter on ICC Procedure Submittals.
3/11/81 NRC Staff third testimony filing (D. Ross)
Provided positions on importance based on recent events, e
Summarized status of other PWR responses on II.F.2.
e 3/19-20/81 ASLB Hearing Session re ICC NRC witness cross-examined extensively on necessity vs.
e desirable; status of other owners.
e Our view cf crocs-examination ASLB heard that RV level is desirable but not known to be necessary; mar.y other owners have not made any progress or no more than GPUN.
4/81 NRC publishes TMI-l SER Sup. 3 e Item 2.1.3.b. - ICC, Staff provides new criteria for reasonable progress.
Criteria never mentioned in dis-cussions or hearings.
6/4/81 All Parties to ASLB Hearings file Findings of Fact /
Conclusions of Law e GPUN summarizes collective efforts /foture plans.
Still supports initial position but do note open minded atti-tude to supp;rt additional work, e NRC restates testimony, ignores answers made during cross-examinativa which undermine direct testimony.
Cemnonwealth of PA - support position that unless fully e
understood, RV 1cvel should not be added to TMI-1 at this time.
6/25-26/81 ACRS TMI-l Subcommittee Meeting GPUN/NRC update status / positions.
e 7/10/81 ACRS Full Committee Maeting CPUN/NRC summarize positions.
e
~
Chronology - Page 4 7/11/81 ACRS TMI-l Letter e ACRS suppcrts continuous long term work by GPU and NRC.
References 6/9/81 ACRS letter to Dircks re specific e
questions that must be addressed by Staff to insure water level /ICC properly considered.
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