ML20011F627
| ML20011F627 | |
| Person / Time | |
|---|---|
| Issue date: | 02/27/1990 |
| From: | Beckjord E NRC OFFICE OF NUCLEAR REGULATORY RESEARCH (RES) |
| To: | Morris B NRC OFFICE OF NUCLEAR REGULATORY RESEARCH (RES) |
| References | |
| REF-GTECI-081, REF-GTECI-NI, TASK-081, TASK-81, TASK-OR NUDOCS 9003070057 | |
| Download: ML20011F627 (7) | |
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UNITED STATES NUCLEAR REGULATORY COMMISSION n
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FEB 2 7 1999 MEMORANDUM FOR: Bill M. Morris, Director Division of Regulatory Applications, Office of Nuclear Regulatory Research FROM:
Eric S. Beckjord, Director, Office of Nuclear Regulatory Research
SUBJECT:
GENERIC ISSUE 01, "lMPACT OF LOCKED DOORS AND BARRIERS i
ON PLANT AND PERSONNEL SAFETY" The prioritization of Generic Issue 81, " Impact of Locked Doors and Barriers on Plant and Personnel Safety," shows that the estimated public risk posed by electric door lock failures is small and, therefore, the issue will be DROPPED from further consideration.
The enclosed prioritization evaluation will be incorporated into NUREG-0933, "A Prioritization of Generic Safety Issues," and is being sent to the regions, other offices, the ACRS, and the PDR, by copy of this memorandum and its enclosures, to allow others the opportunity to connent on the evaluation. All consnents should be sent to the Advanced Reactors and Generic Issues Branch, DRA, RES (Mail Stop NL/S-169). Should you have any questions pertaining to the contents of this memorandum, please contact Ronald C. Emrit (492-3731).
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Eric S. Beckjord, Director Office of Nuclear Regulatory Research
Enclosure:
Prioritization Evaluation cc:
T. Murley, NRP, E. Jordan, AE00 W. Russell, Reg. I S. Ebneter, Reg. II A. Davis, Reg. 111 R. Martin, Reg. IV J. Martin, Reg. V
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i Enclosure i
i PRIORITIZATION EVALUATION Issue 81: _ Impact of Locked Doors and Barriers on Plant and Personnel Safety i
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c ISSUE 81:
IMPACT OF LOCKED DOORS AND BARRIERS ON PLANT AND PERSONNEL SAFETY DESCRIPTION Historical Backarc.und In October 1982, the EDO appointed a Safety / Safeguards Committee to review NRC security requirements at nuclear power plants with a view toward evaluating the impact of these requirements on operational safety.
The Committee found that there was the potential for security measures at a site to adversely affect safety and issued its recommendations in a reportc21 to NMSS on February 28, 1983.
In view of this finding, a DL memorandums 42 was issued on May 31, 1983, suggesting that a multi-disciplinary group be convened to perform an integrated assessment of this problem with DHFS in the lead coordinating role; the DL memorandum also suggested that DST prioritize this issue.
Based on the responses to the memorandum, DL reportedens that a consensus supported the creation of the multi-disciplinary group to gather the necessary information and prepare a scope of the issue for appropriate consideration.
This approach was approved c24 and a DL memorandumets to DHFS formally initiated action on this matter.
The multi-disciplinary group held its first meeting on February 28, 1984, and issued a report on June 8, 1984.c2e Inasmuch as a proposed rule (SECY-83-311)c27 specifically designed to address the security barrier issue had been prepared independently and IE Information Notice No. 83-36c28 also had been issued, the work of the group was limited to non-security barriers.
Subsequent to the above work, a main feedwater pipe rupture event at the Surry plant (see Issue 139, " Thinning of Carbon Steel Piping in LWRs") caused the failure of a security card-reader which was located approximately 50 feet from the break point. This failure was caused by intrusion of water and steam that saturated the card-reader.
As a result, key cards could not be used to open plant doors.
The control room doors were opened to provide access to the control room, and security personnel were assigned to the control room to provide access security.
One operator was temporarily trapped in a stairway due to the card-reader failure. The Surry plant is considering installing electric override switches to remedy this problem.
Because of the failure of the security card-reader during the Surry event, the staff determined that Issue 81 should be expanded to include potential electric door lock failures and be reptioritized to examine whether the previous priority ranking (DROP) should be changed.tica Safety Significance The possible failure of locked doors and barriers that may be required for fire protection, radiation protection, flood protection, and administrative controls is of special concern during abnormal or accident situations when emergency conditions may require prompt and unlimited access of the plant operators to safety equipment in order to assure proper plant operation.
However, the task group concluded that the locks and barriers associated with 3.81-1
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these areas could easily be defeated or bypassed in an emergency situation, if necessary, provided there were enough time to take the necessary steps.
This issue is applicable to all operating and future plants.
Possible Solutions An evaluation of each plant's locked doors and barriers might be required and appropriate procedural and hardware changes may have to be made to establish that operator access is unimpeded during emergency, abnormal, or accident conditions and that prompt operator action is possible as required.
PRIORITY DETERMINATION Frequency Estimates Mechanical Lock Failure Frequency:
The task group considered the likelihood of mechanical f ailure of the locks used for doors and barriers in nuclear plants to be in the order of 10 G/ demand.629 Other failure modes based on personnel error (e.g., lost key or wrong key) were estimated to be in the order of 10 3/ demand.
In any case, in the event of a failed lock, steps could be taken immediately to defeat the locks used for these general purposes by physically destroying them with available tools, if necessary, such as drills, crowbars, hammers, etc.
Even in the event that a barrier had to be circumvented by destruction of a surrounding reinforced concrete wall, it was estimated that this would no more than 20 minutes with the proper tools (such as a jack-hammer) which are usually available at plant sites.c2s Electric Lock Failure Frequency:
Given that an electric card-reader system failed in one of the two main feedwater rupture events discussed in Issue 139, we will use a 0.5 probability that electric door locks fail when subjected to environments that may result from pipe ruptures in the vicinity of the card reader controls.
In the absence of such an environment, the operating reliability of the electric locks is expected to be similar to the operating reliability of the mechanical locks.
Non-Recovery Probability: The possibility of non-recovery (the operators cannot bypass the barrier by the above remedial means) within one hour is estimated at 0.01.
As a function of time, the probability of non-recovery can be expressed as P(NR)t * **PN)
- For the purposes of this analysis the probability of core-melt for an accident sequence involving a locked door barrier to equipment and controls was estimated to be 1, if the barrier is not bypassed within one hour.
A parametric evaluation of the core-melt probability as a function of time was evaluated as:
P(CM)t = At", where n < 1, n = 1, and n > 1 The probability distribution as a function of time was given by:
P(D)t = P(NR)g P(CM)t The above equations were simultaneously solved for the point where P(NR)t and P(CM)ktedthatP(D)k intersectedandthederivativeofP(D)hroximately22minutesintothe
= 0 (maxima).
The results itidic increased to 3 x 10 2 ap event. Therefore, he maximum joint probability of non-recovery and core-melt within one hour was estimated to be 3.4 x 10 2, 3.81-2 b
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i' Core-Melt Frequency:
The potential contribution to core-melt frequency from mechanical lock failures considered the product of the core-melt frequency from all accident sequences (typically 10 4/RY), the probability of mechanical lock v
failure (10 3) due to human error, as discussed above, and the maximum joint probability of non-recovery during the accident progression (3.4 x 10 2),
Therefore, the potential increase in core-melt frequency from mechanical lock i
failures was estimated as 3.4 x 10 9/RY.
l The potential contribution to core-melt frequency from electric lock failures is considered to be dominated by accident sequences involving high energy pipe ruptures outside containment.
Such pipe ruptures have caused environmental conditions that result in water / steam intrusions to the card-reader controls e
that short the circuitry (See Issue 139).
Based on Issue 139, main feedwater (MfW) pipe ruptures from thinned carbon steel piping were estimated to yield a potential core-melt frequency of 4.2 x 10 7/RY.
However, since remedial actions are being taken to remedy the erosion of carbon steel piping in secondary systems, those results should be conservative.
Given a 0.5 probability of an electric lock failure for similar pipe rupture events, and the maximum joint probability of non-recovery during the accident progression
-(3.4 x 10 2), the potential core-melt frequency)from electric lock failures is estimated to be (4.2 x 10 7/RY)(0.5)(3.4 x 10 2 = 7 x 10 9/RY. The combined contribution to core-melt frequency from mechanical and electrical lock failures is approximately 10 8/RY.
Consequence Estimate With the public dose estimated at about 5 x 106 man-rem (given failure of the containment), the risk would be calculated to be in the order of (10 8/RY)(5 x 100 man-rem)(28 years) = 1.4 man-rem / reactor, assuming an average remaining reactor lifetime of 28 years.
It is to be noted that the probability estimate of 1 for containment failure is conservative, thus the public dose would likely be lower than calculated above.
Therefore, the estimated risk represents an upper bound for this issue.
Cost Estimate Based on the deliberations of the multi-disciplinary group, the estimated cost to evaluate and make modifications to each plant and its procedures is approximately $1.7M/ plant.c2c This cost is based on the following factors:
(1) A one-time evaluation of existing plant locked doors and barriers
$ 200,000 (2) Resolution of adverse safety findings [ Cost for maintaining keys for a security force of 24 per plant is estimated to be $21,000/ reactor.c27 To provide additional keys for operators (5 per l
shift for 5 shif ts) for a reactor lifetime of 28 l
years is approximately $612,500.
Cross-training 1
of security and operational personnel based on 50 operators and security personnel for 1 day / year / plant, 1
3.81-3 b
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f over the lifetime of_the plant (28 years) is i
assumed to be (1/365)(50)(28)($100,000) =
$1,000,000 i
$391,232]
(3) Ongoing program to ensure future reduction of L
safeguards impact on safety ($10,000/ year for an L
average reactor lifetime of 28 years)
$ 280,000 i
(4) NRC reviews of. plant modifications 200,000 T01AL:
$1,680,000 Value/ Impact Assessment Based on the estimated risk reduction of 1.4 man-rem / reactor and the estimated cost of $1.7M/ plant to effect this reduction, the value/ impact score is given by:
3,1.4 man-rem / reactor
$1.7M/ reactor i
= 0.82 man-rem /$M Other Considerations The priority ranking of this issue is relatively insensitive to reasonable changes in the factors comprising the risk estimate.
On the other hand, a consideration that has not been accounted for in this evaluation is the adverse effect of locked doors and barriers on sick or injured plant personnel.
Locked doors or barriers may delay the timely administering of emergency aid to injured personnel.
This consideration is beyond the scope of this priority ranking.
CONCLUSION Based on the calculated value/ impact score (0.82 man-rem /$M), the estimated i
risk reduction (1.4 man-rem / reactor), the potential reduction in core-melt frequency (10 8/RY) and the other considerations noted above, this issue should be retained in the DROP category for all operating and future plants.
REFERENCES 542. Memorandum for R. Mattson, et al,, from D. Eisenhut, " Potential Safety Problems Associated with Locked Doors and Barriers in Nuclear Power Plant," May 31, 1983.
621. " Report to the NRC Office of Nuclear Material Safety and Safeguards,"
Committee to Review Safeguards Requirements at Power Reactors, U.S.
Nuclear Regulatory Commission, February 28, 1983.
623. Memorandum for H. Denton from D. Eisenhut, " Potential Safety Problems Associated with Locked Doors and Barriers in Nuclear Power Plants,"
December 22, 1983.
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'624. Memorandum.for D. Eisenhut from H. Denton, " Safety-Safeguards Interface,"
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January 16, 1984.
E-625. Memorandum for H. Thompson f rom D. Eisenhut, " Potential Safety Problems Associated with Locked Doors 'and Barriers in Nuclear Power Plants,"
l January 30, 1984.
626. Memorandum for T._Speis from H. Thompson, " Submittal of Potential Generic i
Issue Associated with Locked Doors and Barriers," June 8, 1984.
b 627.'SECY-83-311, " Proposed Insider Safeguards Rules," July 29, 1983.
628. IE Information Notice No. 83-36, " Impact of Security Practices on Safe ie-Operations," U.S. Nuclear Regulatory Commission - June 9,-1983.
629.
Memorandum for the Record from L. Bush, " Probability of Failure of Locks,"
May 24, 1984.
l 1163. Memorandum for T. Speis from K. Kniel, " Treatment of Lessons-Learned from Surry Event as Related to Generic' Issues," March 31, 1987.
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