IA-89-108, Discusses Evaluation of Loss of DHR Events for Escalated Enforcement
| ML20247N919 | |
| Person / Time | |
|---|---|
| Issue date: | 01/18/1989 |
| From: | Lieberman J NRC OFFICE OF ENFORCEMENT (OE) |
| To: | Davis A, Ernst M, Russell W NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I), NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II), NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| Shared Package | |
| ML20247N685 | List: |
| References | |
| FOIA-89-108 EGM-89-01, EGM-89-1, GL-87-12, GL-88-17, NUDOCS 8904060353 | |
| Download: ML20247N919 (4) | |
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(gt#f% fgg UNITED STATES
.[5 g NUCLEAR REGULATORY COMMISSION l j WASHINGTON, D. C. 20555 4 %*****/ #N I 8 ;gsg EGM 89-01 MEMORANDUM FOR: William T. Russell, Regional Administrator, RI !
Malcolm L. Ernst, Acting Regional Administrator, RII A. Bert Davis, Regional Administrator, RIII Robert D. Martin, Regional Administrator, RIV John B. Martin, Regional Administrator, RV FROM: James Lieberman, Director Office of Enforcement
SUBJECT:
EVALUATING LOSS OF DECAY HEAT REMOVAL EVENTS FOR ESCALATED ENFORCEMENT Recent review of the loss of decay heat removal (DHR) capability problem by the Office of Nuclear Reactor Regulation (NRR) has caused a reassessment of the NRC staff's position regarding the potential consequences of DHR events.
Because, in some scenarios, the precursors to core damage (boiling in the core etc.) may occur much sooner after a loss of DHR than previously thought and the implications of such a loss may be more serious, there is a need to look more critically at loss of DHR events from the point of view of enforcement and
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reexamine the severity level of violations a!,sociated with DHR events.
Fresent Technical Specifications are not specific about the amount of time that is allowed to restore DHR after an interruption therefore, citing of Limiting Condition for Operation violations only occurs in a rare case where the licensee took little or no action to immediately correct the problem. Such cases would clearly warrant consideration for escalated enforcement no matter what caused the DHR loss. However, the majority of DHR problems do not involve prolonged losses or losses for which the licensee does not take at least sone action and in the past mest of the cases have been cited as procedural violations at Severity Level IV or V. Because the NRC staff's added concern about DHR events is a relatively recent development, enforcement actions arising out of such events will have to rely for the most part on citing Appendix B violations for lack of adequate procedures or not following procedures, at least for the near future.
Given the potential for core damage and the guidance provided by the NRC, failure of itensees to take aggressive action to assure appropriate procedures, their 4 implementation, and training is of significant regulatory concern and therefore, i:
e;; ee appropriately categorized at a Severity Level III. The following guide- "ll lines which have been coordinated with NRR should be used to evaluate whether i a particular loss of DHR should be considered a Severity Level III matter. Given that the NRC has reassessed the significance of this issue and has provided extensive prior notice to the industry on this subject (particularly events occurring during reduced reactor coolant system inventory operations) in the form of Generic Letters (87-12 and 88-17), Information Notices, meetings with .
various industry groups, and letters to licensed operators, stronger actions 9904060353 090403 Fj h A
Regional Administrators % are appropriate in cases where the guidance was not properly incorporated or employed. As stated above, much of the guidance provided to the industry focuses on losses of DHR during reduced reactor coolant system inventory operation and therefore the guidance provided below is probably most gernane to such situations. However, other types of losses of DHR, such as one caused by an improper design change, can also be evaluated using some or all of the guidelines as appropriate.
It must be emphasized that there is no exact formula for arriving at a Severity Level and the factors discussed below may be weighted differently or not considered at all in any given case. The factors that should be considered are:
- 1. How similar was the root cause of the loss of DHR to the deficiencies addressed in NRC generic guidance such as Generic Letters 88-17 and 87-12?
- 2. Given that a deficiency discussed in the guidance, such as a loss of DHR due to improper reactor coolant system level indication, did occur, how ,
sensitive were the operators to the problem? !
- a. How quickly did they respond? (It is acknowledged that the core decay heat level may not call for instantaneous response, however the failure to correct such a situation quickly simply because the operator does not view it as particularly pressing may indicate a lack of sensitivity to this type of problem).
, b. Did they respond using detailed procedural guidance, and if not, was their training alone adequate?
- c. Given that the operators procedurally treated the " symptoms," did they recognize the problem as a loss of DHR? )
- d. Did they have other available indications not specified in the procedures, that could have been consulted and did they use them?
3 Does the plant have a history of interruptions of DHR? (This may indicate 6 continuing lack of sensitivity to this issue.)
- 4. Were procedures in place to provide operator guidance for alternative DHR options not normally employed? (It should be noted here that there I have been a number of instances where licensees have made after-the-fact arguments about alternative sources of circulation and cooling. Because such sources were not procedurally required it was unclear as to whether the operator in such cases could have aligned such sources quickly enough and whether it was only fortuitous that the sources were not unavailable because of plant status.)
The two example scenarios provided below illustrate certain key actions or inactions that when considered under the guidance provided earlier, would result in the indicated severity level classification. It should be noted that in neither instance is DHR flow lost for an extended peri %f, if it was ever fully lost.
r Regional Administrators 1 1. Because maintenance work needs to be accomplished on a reactor coolant pump seal, reactor vessel water level needs to be lowered to mid-loop. In I preparation for the drain down an auxiliary operator does a full inspection of the tygon tube level indication system and then reports to the control room that he is standing by to monitor level during the drain down. Shortly before level reaches the mid-loop area, the control room secures the drain down to allow the level indicators to stabilize prior to draining the last few inches. Simultaneously, maintenance personnel arrive in the containment in preparation for the seal work and inadvertently place a large box on the tygon hose. Upon resuming the drain down, the control room operator notes a growing discrepancy between the level being reported from the containment and the control room indication. Just as the control room operator terminates the drain down to investigate, the operating DHR pump begins to cavitate. The operator quickly secures the pump, restores RCS inventory and starts the standby pump. The auxiliary operator again performs a walkdown of the tygon hose and discovers and removes the blockage before resuming drain down.
Recommendation: Severity Level IV or V for work control. Although pump cavitation occurred after a loss of adequate level, due to erroreous level indication, proper preparation for the draindown was accomplished and the operators responded quickly and correctly to the event.
- 2. Prior to the drain down to mid-loop an auxiliary operator is stationed to monitor level without first having anyone walkdown the tygon hose. Earlier, g
maintenance personnel had entered containment and inadvertently placed a '
large box on the tygon hose. After the drain down begins, the control room operator notes a growing difference between control room level indication and that being reported from the containment. He secures the drain down and then asks the auxiliary operator about the condition of his indicating hose. The auxiliary operator replies that level seems to be t decreasing more slowly than he anticipated but the decrease has been smooth and he doesn't see any air bubbles. With that information the control room operator decides to continue the drain relying solely on the tygon hose rather than the relatively new control room indicator with which there have been past problems. The control room operator makes this decision despite the fact that at the time, the control room indicator is providing a level reading significantly lower than that of the tygon hose.
After recommencing the drain down, the operating DHR pump begins to 1 cavitate. The control room operator gets a report from the containment that level is still indicated to be well above mid-loop and therefore, i he starts the standby pump and secures the cavitating pump. Almost immediately the standby pump also begins to cavitate. The operator then realizing that level must be too low, takes action to restore level and directs the auxiliary operator to walkdown the tygon hose.
Recommendation: Severity Level III. Proper preparations were not made, the operator made a nonconservative judgment in choosing which level indicator to use, and then when given an opportunity to recognize the mistake he made he chose to start a second pump rather than learn why the first pump was cavitating.
The more a case appears similar to the circumstances, of the generic guidance and the less responsive the operators are, the more likely the case should be
Regional Administrators l 4 considered at Severity Level III. Given the attention this issue is being given by the agency, please discuss all losses of DHR, that occur over the next six months, with OE before issuance of enforcement actions.
I In sunrnary, we need to be examining losses of DHR carefully and where applicable sending a strong message to the licensees that unplanned interruptions of DHR, no matter how short, are unacceptable and cannot be viewed as just a part of doing business. l l
h ' &_ i James Lieberman, Director Office of Enforcement cc: J. Taylor, DEDR0 l L. Chandler, 0GC D. Crutchfield, NRR S. Varga, NRR F. Hebdon, NRR
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