IE Circular No. 79-18, Proper Installation of Target Rock Safety-Relief Valves


                            September 6, 1979 

MEMORANDUM FOR:     B. H. Grier, Director, Region I 
                    J. P. O'Reilly, Director, Region II 
                    J. G. Keppler, Director, Region III 
                    K. V. Seyfrit, Director, Region IV 
                    R. H. Engelken, Director, Region V 

FROM:               Norman C. Moseley, Director, Division of Reactor 
                      Operations Inspection, IE 

                    ROCK SAFETY-RELIEF VALVES 

The subject IE Circular is transmitted for issuance on September 10, 1979. 
The Circular should be issued to all holders of a power reactor operating 
license or construction permit. 

The text of the Circular and draft letter to the licensees and permit 
holders are enclosed for this purpose. 

                                   Norman C. Moseley, Director        
                                   Division of Reactor Operations 
                                   Office of Inspection and Enforcement 

1.   Draft transmittal letter 
2.   IE Circular No. 79-18 

CONTACT:  C. J. DeBevec, IE 

(Draft transmittal letter for Circular No. 79-18 to each holder of a power 
reactor operating license or construction permit.) 

                                                     IE Circular No. 79-18 


The enclosed Circular No. 79-18 is forwarded to you for information. No 
written response is required. Should you have any questions related to your 
understanding of the recommendations on this matter, please contact this 


                                        (Regional Director) 

IE Circular No. 79-18 

                                                 Accession No: 7908200385 
                                                  SSINS No. 6830 

                              UNITED STATES 
                          WASHINGTON, D.C. 20555 
                            September 10, 1979 

                                                      IE Circular No. 79-18 


Description of Circumstances: 

As a result of NRC monitoring of operating experiences involving the Target 
Rock safety-relief valve, two potential problems have been identified. One 
potential problem is that the performance of the valve has been found to be 
impaired by either excessive or insufficient insulation around the valve 
body when installed in its service environment. The other potential problem 
is that improper assembly of the modified valve can result in inoperability 
of the remote air actuator. 

The Target Rock safety-relief valve is a dual purpose valve in that 
overpressure response is provided by pilot valve action and automatic 
depressurization (ADS) is provided by a remote air actuator. Valve operation
has been found to be affected by the amount of insulation placed around the 
valve body. A previous IE Bulletin No. 76-06 was issued on July 21, 1976 as 
a result of operating experiences where excessive insulation was installed 
on the valve. The excessive insulation caused excessive heat to be retained 
producing a higher temperature environment for the elastomeric diaphragm 
which resulted in accelerated deterioration of the elastomer. Failure of the
elastomeric diaphragm, makes the valve inoperable in the power-operation 
mode (i.e.,manual and ADS). Subsequently, a silicone-nomex diaphragm was 
developed by the manufacturer to provide a longer life in high temperature 
environments. In addition, the IE Bulletin explicitly required that 
insulation be installed in accordance with the manufacturer's 

A recent licensee event report from the Monticello facility identified a 
potential problem resulting from insufficient insulation (i.e., just 
opposite of the condition addressed by IE Bulletin 76-06). During the 
performance of special testing of the response to safety-relief valve 
operation, a valve was discovered to be exceeding its design delay time for 
opening. Subsequent inspection and testing of the valve revealed that 
insufficient insulation may cause condensation to accumulate in the pressure 
venting ports which then results in delaying the opening of the main disk. 
This slower response time is significant with respect to primary system 
overpressure and similar transient response analyses. Although the reported 
event at Monticello involved the three-stage Target Rock safety-relief 
valves, the requirements for proper amounts of insulation are similarly 
applicable to the two-stage Target Rock safety-relief valves. 

The second potential problem was recently experienced at the Hatch facility.
The licensee event report indicated that improper assembly of the modified 
design two-stage valve resulted in preventing the air actuator to function. 

IE Circular 79-18                                     September 10, 1979 
                                                       Page 2 of 2 

During the changeover to modify these valves from the previous three-stage 
type to the current two-stage design, two valves were inadvertently 
reassembled with the air-actuator angularly displaced. This misalignment 
restricted the air flow via the air inlet port thereby preventing the 
safety-relief valve from functioning in the air actuation-mode. The 
misalignment was noted and corrected prior to the return of the reactor to 

Recommended Actions for BWR Licensee's Consideration: 

All holders of operating licenses for BWR facilities employing Target Rock 
safety-relief valves should be aware of the potential problems described 
above. It is recommended that this matter be reviewed at your facility in 
the following respects: 

1.   Verify that the installed Target Rock safety-relief valves include the 
     silicone-nomex diaphragms which have the superior time-temperature-
     environment characteristics and that these diaphragms are periodically 
     replaced in accordance with the most conservative recommendations of 
     the reactor vendor or valve manufacturer. 

2.   Verify that the thermal insulation on the valve is installed in 
     accordance with the valve manufacturer's recommendation. 

3.   Verify that procedures are adequate to assure proper assembly of the 
     air actuator, pilot and main disk in accordance with the vendor's 
     installation instructions for the two-stage valve. 

This Circular is being forwarded for information to all BWR facilities with 
construction permits and to all other power reactor facilities with an 
operating license or construction permit. No written response to this 
Circular is required. If you need additional information regarding this 
matter, contact the Director of the appropriate NRC Regional Office. 

Enclosure:  List of IE Circulars 
  issued in the last 
  6 months 


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