ML17257A493
| ML17257A493 | |
| Person / Time | |
|---|---|
| Site: | Ginna  |
| Issue date: | 07/22/1981 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML17257A494 | List: |
| References | |
| TASK-05-11.A, TASK-5-11.A, TASK-RR NUDOCS 8107270076 | |
| Download: ML17257A493 (3) | |
Text
ENCLOSURE TOPIC:
V-ll.A -
RE UIRENENTS FOR ISOLATION OF HIGH AND LOW PRESSURE SYSTPlS INTRODUCTION Several systems that have a relatively low design pressure are connected to the reactor coolant pressure boundary.
The valves that form the interface between the high and low pressure systems must have sufficient redundancy and interlocks to assure that the low pressure systems are not subjected to coolant pressures that exceed design limits.
The problem is complicated since under certain operating modes (e.g.,
shutdown cooling and ECCS injection) these valves must open to assure adequate reactor safety.
II.
REVIEW CRITERIA The review criteria are presented in Section 2 of EGSG= Report 1285.
III. RELATED SAFETY TOPICS AND INTERFACES The scope of review for this topic was limited to avoid duplication of effort since some aspects of the review were performed under related topics.
The related topics and the subject matter are identified below.
Each of the related topic reports contain the criteria and review guidance for its subject matter.
V-3 V-lo.B VI-4 XV-16 Overpressurization Protection RHR Reliability Containment Isolation Radiological Consequences of Small LOCA Outside of Containment Topic V-ll.B is dependent on the present topic information for completion.
IV.
REVIEW GUIDELINES The review guidelines are presented in Section 7.3 of the Standard Review Plan.
V.
EVALUATION As noted in EGSG Report 1285, Ginna has three systems with a lo'wer design pressure rating than the RCS, that are directly connected to the RCS.
The RHR, SIS, and CVCS system do not meet current licensing requirements for isolation of high and low pressure systems as specified below.
8107270076 Bi0722 DR ADOCK 05000244 PDR
(2)
The RHR system is not in compliance with the current licensing requirements of BTP RSB 5-1 since none of the isolation valves will automatically close if RCS pressure exceeds RHR design pressure.
Also, the outboard isolation valves have no inter-locks to prevent RHR overpressurization, and the inboard valve interlocks are neither diverse nor independent.
The SIS is not in compliance with the current licensing require-ments of SRP 6.3 since the MOVs in the low pressure injection lines have no inter locks to prevent opening and the single check valve in each line is not tested.
(3)
The CVCS is not in compliance with current licensing require-ments for isolation of high and low pressure systems contained in BTP EICSB-3 since the suction and discharge line solenoid-operated valves have no interlocks to prevent system overpres-surization, and the discharge line check valves have no position indication available in the control room.
Because of the severe consequences of a LOCA outside of containment and the lack of assurance that these isolation valves could be closed against significant flow under the resulting environmental conditions, the staff proposed that the RHR isolation valves and the CVCS'uction valves should be modified to satisfy the functional requirements of BTP RSB 5-1 and BTP EICSB-3.
We also proposed installation of position indication on the charging pump discharge valves.
The licensee responded to our proposals in a letter dated June 23, 1981 (attached).
In summary, the licensee has argued that:
Additional interlocks in the RHR system are not required because the valves can not open against the differential pressure across the valves.
Loss of the differential pressure is a leakage constituting a single failure.
(2)
(3)
Isolation of the let down system and the failure of the relief valve (which is not tested) has been shown to be acceptable based on SEP Topic XV-16.
The probability of failure of a charging pump and the two check valves in the discharge path presents an acceptable small risk without further design changes.
However, the staff notes that there is no way, at this time, to
.provide adequate assurance that these valves are seating.
The basis for not requiring interlocks in the low pressure injection system is that, since the contractor's report was published, a check valve test program has been established,,
and thus, the system now satisfies the single failure criterion.
The basis for not requiring interlocks on the CVCS discharge valves is that the check valves in series with the positive displacement pumps satisfy the single failure criterion as long as check position is known (or functionability demonstrated) and the pump capacity is verified periodically.
As previously noted, in our system safety evaluation of SEP Topic V-10.B, it is not necessary to close the RHR valves automatically on increasing reactor coolant system pressure during startup because of the overpressurization protection system.
(See also Topic V-3.)
SEP Topic XV-16 results of a letdown line break outside containment are the basis for not requiring modifications in the letdown sub-system because the radiological consequences satisfy regulatory limits of 10 CFR Part 100.
VI.
CONCLUSIONS Because of the consequences o'f a LOCA outside of containment the staff proposes that the=-charging pump discharge check valves be modified to include position indication or a suitable check valve testing program should be initiated to assure that these valves will seat.
Our basis is that there is no way, at this time, to provide adequate assurance that these valves are seating.