ML19309D294
| ML19309D294 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 03/31/1980 |
| From: | Jordan W, Little L, Smith I Atomic Safety and Licensing Board Panel |
| To: | NRC OFFICE OF THE EXECUTIVE LEGAL DIRECTOR (OELD) |
| References | |
| NUDOCS 8004100222 | |
| Download: ML19309D294 (7) | |
Text
Bd 3/31/80 UNITED STATES OF AMERICA NUCLEAR REGULA'IORY COMMISSION O
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ATOMIC SAFETY AND LICENSING BOARD I
DOCKETED Ivan W. Smith, Chairman URO di Dr. Walter H. Jordan 7:
APR y ggg Dr. Linda W.
Little 9'
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In the Matter of
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Docket No. 50-289
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METROPOLITAN EDISON COMPANY
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(Three Mile Island Nuclear
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Station, Unit No. 1)
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MEMORANDUM AND ORDER TO NRC STAFF REGARDING CLASS 9 ACCIDENTS (March 31, 1980)
By its supplemental filing of March 21, 1980, the NRC staff has further responded to the board's inquiry of what specific accident sequences, not previously analyzed because they previously may have been regarded as outside the design basis (e.g.,
a Class 9 accident), should now be considered in the analysis of the acceptability of returning TMI-1 to operation.
The board is dissatisfied with the staff's supple-mental response.
It is unfortunate that there is apparently a continuing failure in communication as to what information the board is seeking.
By this order, we are attempting for the third time to elicit an answer which is responsive to our inquiry.
We need to be informed by the staff what critical accident sequences the staff will analyze in order to assure that the proposed short and long term actions necessary and sufficient to provide adequate protection to public health and safety have been taken.
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.Section II of the staff's supplemental response is entitled Discussion of Accident Scenarios and Preventive and Mitigative Measures.
The staff has provided, by example, by references to other documents, and by attachments, a listing of preventive and mitigative measures being considered to date as part of the actioq plans in response to the TMI accident.
However, the board has not been provided with a specification and description of any of the postulated accident sequences for which the preventive and mitigative measures discussed in the action plans or elsewhere are being considered.
The staff's supplemental response, at pp. 5 -7, refers generally to the staff's consideration of " scenarios",
" combinations", " initiating events... and subsequent failures,"
" examples of scenarios", " representative" scenarios, etc.
We are attaching copies of those pages of the staff's response with the relevant words and phrases underlined.
We direct the staff, within fifteen days from the date of service of this order, to:
1.
Specify and describe each of the accident sequences (or other similar terminology employed) which the staff apparently is con-sidering under the umbrella of the very general references in the underlined portions of the attached pages 5-7 of its supplemental response; or 2.
Explain why the staff can not or will not specify/ describe the accident sequences, i
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. If the staff believes it is inappropriate for this board to make this inquiry, for jurisdictional or other reasons, it is invited to tell us so, and explain why, within ten days from the date of service of this order.
The staff may seek relief from us, including a request for certification to the Commission.
In taking this action we have considered the Commission's recent Memorandum and Order in the Black Fox proceeding.
Public Service Co. of Oklahoma (Black Fox, Units 1 and 2),
CLI-80-8, March 21, 1980.
That Order confirmed the staff's view that it did not have to inform the Commission of in-dividual cases where the staff did not think the environmental consequences of Class 9 accidents need be considered.
In this proceeding, it is evident from the staff's response and supplemental response that accident sequences which previously were not considered as part of the design basis acceptability of TMI-l are, in fact, now being considered.
Furthermore, our inquiry is not directed towards a comparison of whether the environmental risk from such (a Class 9 accident at e
. TMI-1), if one occurred, would be substantially greater than that for an average plant."
Black Fox, supra, slip 02 at p.3.
TIIE ATOMIC SAFETY AND LICENSING BOARD
& lJ & h Tus Linda W.
Little h
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/klf Walter II. Jordan 4
M van W. <Smi th, Chairman
Attachment:
As stated Bethesda, Maryland March 31, 1980 l
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A h to II.
DISCUSSION Of acIDENT SCENARIOS AND PREVENTIVE AND MITIGATIVE MEASURES Since the TMI-2 accident, special attention has been drawn to severe core accidents, including core melting (so called " Class 9" accidents).
The Staff has therefore proposed to the Commission that additional efforts be made to mitigate the consequences of such events.
Task II.8 describes activities ongoing within the NRC in the area of degraded or melted cores.
It should be noted that Items II.B.1 (reactor coolant system vents), II.B.2 (plant shielding to provide access to vital areas and protect safety equip-ment for post-accident operation), and II.B.3 (post-accident sampling) are included in the Order (Item 8:
Category A recommendations as specified in Table B-1 of NUREG-0578).
Items II.B.6 (features to cope with core melt accidents in reactors at sites with high population densities) and II.B.7 (containment inerting) are not in the Order.
Other items eventually decided to be applicable to the generic class of reactor or containments represented by TMI-1 will be applied to that plant on a schedule consistent with other operating reactors.
During the deliberations of the NRC groups and of the other organizations that have reported the results of their reviews,U the TMI-2 scenario and related specific and generalized scenarios were considered, including numerous 8f Af ter the accident at THI-2, offices within and organizations outside the NRC reviewed the safety of nuclear power plants in order to reduce the probability of a TMI-2 accident or other similar accident in the future. Within the NRC, these efforts were focused in the Bulletins i
and Orders (880) Task Force, the Lessons Learned Task Force, the Special Inquiry Group (Rogovin), and the Advisory Committee on Reactor Safeguards (ACRS).
Outside the NRC, the President's Commission on the Accident at Three Mile Island (Kemeny Commission), various industry groups, and several Congressional committees have worked and are still working toward that end.
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variations on initiating events and subsequent failures.
Specific design and procedural changes were recommended to make these initiating events and subsequent failures less likely and to improve measures to deal effectively with and to mitigate the consequences of these scenarios even if they were to occur.
In addition, recommendations were made in the areas of management and technical competence, operator and other staff training, quality assur-ance, staffing, health physics, maintenance, and emergency preparedness.
These recommendations were necessary to improve plant safety in general and to address TMI-2 related scenarios.
As a result, further efforts were required of the licensees and reactor vendors to improve the analysis of transients and, accidents as well as the procedures for handlirg such events.
With the exception of the items discussed in the Kemeny and Rogovin reports, which were published af ter the Order, the recommendations of these groups were considered for inclusion in the Staff recommendations to the Commission for incorporation into its Order regarding the TMI-1 license suspension.
The recommendations of the Director of NRR were identified as the eight i
l short-term and four long-term requirements in the Commission's Order.
i The scenarios considered may be summarized as those clear and close analogs j
of the TMI-2 accident that involve combinations of initiating events including feedwater transients and-small break LOCAs, and subsequent failures including loss of auxiliary feedwater, loss of all feedwater, loss of ECCS, and small break LOCAs.
Some of these combinations could result in inadequate core
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. cooling and possible subsequent serious core damage or core melting with substantial hydrogen generation and significant release of radiation.
The following are examples of scenarios examined:
1.
Loss of feedwater plus loss of auxiliary feedwater plus a stuck-open PORY plus a loss of HPI (this scenario corresponds to the TMI-2 event without operator action to restore safety systems or to close the PORV).
2.
Small break plus loss of all ECCS (HPI and LPI).
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3.
Loss of feedwater plus loss of all auxiliary feedwater.
4.
Small break plus loss of all feedwater.
These scenarios were chosen to be reoresentative of those that result from combinations of the initiating events and failures discussed above.
The first two scenarios, which involve multiple failures, would be expected to lead to substantial core damage or core melt.
The third and fourth scenarios, also involving multiple failures, are not likely to result in core damage since the high pressure injection system can be used to assure core cooling.
It As required by Item 8 of the Order, specifically 2.1.9 in NUREG-0578, further analyses by the licensee are continuing for small break LOCAs, inadequate l